Weather FAQ

Answers to Your Weather Questions

Alt Earth Questions

I don’t know if this is something you can answer, but I was wondering how the weather patterns on earth would change if it rotated about twice as fast. I heard that the centrifugal force would pull the water to the equator, would something similar happen to the air currents? How do you think this would affect the temperature and weather? - Zoe

Thank you for your fun question! This is the sort of question professors LOVE to add to their exams.

If Earth rotated about twice as fast (with a 12-hour day instead of a 24-hour one), it would have significant effects on weather patterns, atmospheric circulation, and the distribution of temperatures. Here's how the changes could play out:

1. Centrifugal Force and Distribution of Water and Air

- Centrifugal Force: With a faster rotation, the centrifugal force would indeed increase, becoming more pronounced at the equator. This would pull water towards the equator, leading to a bulging effect where sea levels rise at the equator and fall at the poles.
- Impact on Air Currents: Air would also be affected by the increased centrifugal force. The atmosphere would become thicker at the equator and thinner at higher latitudes. This would influence pressure gradients and shift wind patterns closer to the equator, as more air is pulled toward these regions.

SUGGESTED READING:

- The Dynamic Earth: An Introduction to Physical Geology by Brian J. Skinner and Stephen C. Porter.

- Atmospheric Science: An Introductory Survey by John M. Wallace and Peter V. Hobbs - Chapter 3, "Basic Physical Processes in the Atmosphere" (sections on pressure gradients and forces). It discusses in more detail how centrifugal force affects atmospheric circulation.

2. Increased Coriolis Effect

- Stronger Deflection of Winds: The Coriolis effect, which causes moving air to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, would become stronger due to the faster rotation. This means that winds would curve more sharply, resulting in more pronounced and tighter circulation patterns.
- More Jet Streams and Faster Winds: With an increased Coriolis effect, we might see additional jet streams develop, with stronger and faster winds aloft. The existing jet streams could become narrower and more intense, leading to greater atmospheric turbulence.

SUGGESTED READING:

- The Atmosphere: An Introduction to Meteorology by Frederick Lutgens and Edward Tarbuck - Chapter 7, "Winds and Global Circulation." This chapter covers the Coriolis effect and its role in deflecting wind patterns, with explanations on how it strengthens with faster rotation.

- Introduction to Atmospheric Dynamics by David G. Andrews - Chapter 4, "Midlatitude Synoptic Systems" (section on jet streams and their formation)

3. Changes in Atmospheric Circulation Cells

- More but Smaller Circulation Cells: Currently, Earth has three main circulation cells in each hemisphere: the Hadley, Ferrel, and Polar cells. With a faster rotation, these cells could be split into more, smaller cells. For example, the Hadley cells could be narrower and closer to the equator, while additional cells might form in the mid-latitudes.
- Stronger Trade Winds: The trade winds, which blow from east to west in the tropics, could strengthen due to the intensified Coriolis effect, leading to more persistent and intense tropical weather systems.

SUGGESTED READING:

Global Physical Climatology (2nd Edition) by Dennis L. Hartmann - Chapter 6, "General Circulation of the Atmosphere." This chapter explains how the Earth's atmospheric circulation cells would adjust with different rotational speeds.
Climatology by Robert V. Rohli and Anthony J. Vega - Chapter 5, "The Global Energy Balance and Temperature" (sections on large-scale wind systems). It includes discussions on how the Coriolis effect influences trade winds and global circulation.

4. Impact on Weather Patterns

- More Extreme Weather at Mid-Latitudes: The more intense and frequent jet streams could lead to increased weather variability in the mid-latitudes, causing rapid changes between weather conditions. The stronger Coriolis effect could also enhance the formation of cyclones, making storms more frequent and severe.
- Changes in Rainfall Patterns: The shift of atmospheric cells and changes in wind patterns could alter where and how rain falls. Regions that currently experience steady rainfall might see a shift in precipitation patterns, with some areas becoming wetter and others drier. The equatorial region might see more concentrated rainfall, while mid-latitude regions could experience more variability and intense storms.

SUGGESTED READING:

Synoptic-Dynamic Meteorology in Midlatitudes (Volume I, 2nd Edition) by Howard Bluestein - Chapter 8, "Extratropical Cyclones" (section on the dynamics of mid-latitude weather systems). This chapter explains how increased rotational speeds could affect storm formation and variability.
Meteorology Today: An Introduction to Weather, Climate, and the Environment (13th Edition) by C. Donald Ahrens - Chapter 13, "Weather Patterns and Severe Storms." This chapter covers how shifts in circulation can alter rainfall distribution and weather patterns.

5. Temperature Distribution

- More Temperature Variation Between Day and Night: With a faster rotation, days and nights would be shorter, which could lead to reduced time for heating during the day and cooling at night. This might create a sharper contrast between daytime and nighttime temperatures, particularly in regions far from the equator.
- Equator-to-Pole Temperature Gradient: The stronger centrifugal force pulling air and water toward the equator could make polar regions even colder while concentrating warmer temperatures closer to the equator. The result would be a steeper temperature gradient, potentially intensifying atmospheric circulation and weather dynamics.

SUGGESTED READING:

Principles of Planetary Climate (1st Edition) by Raymond T. Pierrehumbert - Chapter 4, "Radiative Energy Balance" (section on rotation and temperature profiles). This discusses how changes in the length of day affect planetary temperature variations.
Atmospheric and Oceanic Fluid Dynamics (2nd Edition) by Geoffrey K. Vallis - Chapter 2, "The Governing Equations" (sections on temperature gradients and atmospheric circulation). This chapter elaborates on how temperature differences drive global weather patterns.

Overall, a faster-rotating Earth would likely have more intense and complex weather patterns, with stronger winds, more pronounced atmospheric circulation, and altered temperature distributions.

I have a question of a more fantastical nature. For a bit of context I'm writing a homebrew Dungeons & Dragons world and currently working on the calendar. I was wondering what would the effects of having two moons have on the land and world as a whole? If possible for you to explain what would a calendar look like for such a world?

An astronomer or exoplanetary meteorologist would best answer this question. Based on my brief understanding of binary lunar systems (and the mythology of ancient cultures - a hobby of mine), this is what I would expect:

1. Tides and Ocean Dynamics

With two moons, tides would be more complex. On Earth, the gravitational pull of our single moon creates predictable high and low tides. Adding a second moon would create an interplay of gravitational forces that could result in:

Multiple tidal cycles: Depending on the relative masses and distances of the two moons, there could be overlapping tides of varying strengths. This might result in extremely high “spring” tides when both moons align or unusual tidal behavior when they are out of sync.
Increased tidal variability: Coastal areas might experience unpredictable or very high tidal ranges, potentially reshaping shorelines and affecting local marine ecosystems.

2. Climate and Weather Patterns

The gravitational effects of two moons could impact atmospheric circulation:

Stronger tidal forces could lead to variations in the atmosphere, potentially influencing wind patterns, pressure, and precipitation. This could create weather phenomena tied to the phases of each moon.
Periodic climate shifts: Depending on the orbital paths of the moons, the combination of their gravitational pulls could contribute to longer cycles of climate change, similar to Earth's Milankovitch cycles, but on potentially shorter timescales.

3. Geological Effects

Tectonic activity: The stress from two sources of tidal forces might increase volcanic and seismic activity. This could shape world-building aspects of your D&D campaign, such as regions known for frequent earthquakes or active volcanoes.
Erosion and landforms: Over millennia, the fluctuating tidal forces could create unique landforms shaped by alternating high and low water cycles.

4. Calendar Systems

Designing a calendar with two moons would require considering their orbital periods. For example:

Phases and eclipses: With two moons, there would be more frequent lunar eclipses or potentially even double eclipses, where both moons align with the sun at different times. The phases of each moon would be independent unless their orbits are synchronized.
Dual lunar months: You might have one moon with a shorter orbital period (e.g., 15 days) and another with a longer one (e.g., 30 days). This could create overlapping cycles where certain dates mark both moons being full, new, or at quarters.
Cultural significance: The alignment of the two moons could be used as special holidays, omens, or seasonal markers. The calendar could be divided based on the phases of both moons, with certain days or weeks designated as festivals or important events when both moons are full or new.

Sample Calendar Concept:

Month structure: If one moon takes 15 days to complete its orbit and another takes 30 days, a single month could be 30 days long with alternating weeks where one moon is full or new.
Week design: You might create two parallel weekly structures, one corresponding to the cycles of each moon.
Lunar events: A calendar could highlight double full moons, which might occur every 60 days (the least common multiple of 15 and 30 days), as major cultural or supernatural events.

These elements could serve as storytelling tools in your D&D world, adding depth to the lore, religion, and daily life of its inhabitants. And the best part? It's YOUR world - it doesn't have to follow our universe's physics!

Cloud Questions

Is it possible to see Noctilucent clouds in Atlanta GA after sunrise or at all since the Atlanta Latitude is about 38? This date July 11, 2024 had an astronomical twilight sunrise of 4:54 AM and a civil twilight sunrise of 6:07 and I thought i saw them about 7:30 am.

Noctilucent clouds are generally only seen just before sunrise or just after sunset, as the sun needs to be below the horizon to light up the mesosphere, up to 50 miles above the earth's surface (way above the troposphere - where we experience most weather phenomena). They can be present during the day, but we won't see them, as they're very thin - we need the contrast of the dark sky and the reflected sunlight to perceive them. The clouds form when water vapor gathers on specks of dust in the mesosphere and freezes, forming ice crystals that scatter the reflected sunlight in a silvery-blue. Generally, noctilucent clouds appear between June and August in the Northern Hemisphere, over the poles and maybe down to a latitude of 45 degrees.

However, with the Aeronomy of Ice in the Mesosphere (AIM) NASA satellite, they've seen noctilucent clouds further from the poles, though I'm not sure exactly how far (likely not below 40N). The AIM project observed these clouds for ~16 years (ending March 2023 when the battery failed), taking observations to understand whether the noctilucent clouds' appearance and frequency are related to climate change and what affects their formation. Scientists will be analyzing this data for decades to come!

I've seen thin streaky cirrus clouds during the early morning hours that appear similar to photos of noctilucent clouds, but I'm at 35 degrees North, so I have never seen noctilucent clouds in person.

My next guess would be gas from a rocket launch from Cape Canaveral, but it appears that the only launch around that time was late on July 11 from Vandenberg (Starlink) - launching at about 10:35 pm your time. The other launch I found was a Chinese rocket that failed on July 10, but couldn't find further details and I'm not sure you would be able to see any remnants of that from your location.

Did you happen to take a photo of the clouds?

These pictures were taken on 9/27/24 about 5 miles south of the summit of Mt Adams in Washington state. There was a thin cloud layer at about 30,000 ft that extended some distance to the west moving quite rapidly to the east. 3-4 miles west of us these anomalies began forming in the cloud layer and most produced a heavy rainfall for a short period of time as they passed over. All of the rain disappeared several thousand feet below each cloud and never appeared to reach the ground. After passing over the thin cloud layer quickly began disappearing leaving only the core of the anomaly. What did we see?

Submitted photos:

You asked about some cloud anomalies you saw near Mt. Adams in Washington state (photos reattached here). They look like good examples of what are called "hole-punch" clouds or "fallstreak holes", and are caused by planes. As a plane ascends or descends through the cloud layer, the exhaust seeds the clouds and causes the fallstreak to form.

Here's a Weather Service link and a Wikipedia link about this phenomenon, you'll see similar pictures on those pages:

https://www.weather.gov/arx/why_fallstreaks

https://en.wikipedia.org/wiki/Fallstreak_hole

Do you have any ideas as to what this blue light was in the sky for 25-35 minutes as a HUGE storm was brewing and started? It was in the same spot in the sky the whole time. Not moving with the clouds or anything. I went inside when the wind greatly increased and switched from north to south as it started raining. After the obvious eye of the storm had passed, I went back outside and it was gone. It was actually very bizarre as there was both constant distant lightning and intense strikes happening, not over head exactly but a mile or two away I could see the lightning bolts. I'm certain this wasn't a spot light too, for many reasons. I wish I had spent more time trying to capture this, but these are essentially what the 6 or so pictures look like. Never moved for at least 20 minutes and didn't show on video.

Submitted photos:

Most likely: lights near the ground / pointed upward (probably not a searchlight, as you mentioned...lots of LEDs are used for measurements and night illumination these days)

Least likely: ball lightning or individual blue jets/starters

Sometimes we'll see reflected/refracted lights from cities on low clouds - blues, greens, and yellows mostly. There's a Paycom center near me with neon green LED lights that can be seen on low-medium level clouds, even from miles away, as the lights are really bright - I've nearly mistaken them for auroras a few times!

Elves, sprites, blue jets, blue starters, gnomes, trolls, and pixies - all known atmospheric discharges above the troposphere last milliseconds to a quarter of a second. If you were observing one of these or several, I would expect the glow to change quite a bit in the 20 minutes. Blue jets ARE known to form over some super active thunderstorms in the Stratosphere (layer just above the Troposphere, where most of Earth's weather occurs).

It's unlikely that it was ball lightning if it was stationary for 20 minutes (I have actually seen ball lightning in person - when I was observing one of the most intense lightning storms I've ever seen - the ball lightning floated along in the air, not stationary for the 2-5 minutes it existed), but so little is understood about the phenomenon because it's incredibly rare.

The photos remind me of some of the super bright astronomy flashlights they use at some telescope parties to point out features to an audience. Or maybe someone was trying to send a bat signal?

Looking up other similar photos, I came across the most likely suspect (depending on where you are): a measurement train that runs generally at night - it shoots a blue light up into the sky to check for wear and tear on overhead lines. See the article from the Bristol Post here. In the US, I also found similar images to yours for folks living near the Fore River Bridge in Massachusetts, which has bright LED lights - sometimes blue (they change them) - that reflect off clouds and fog.

Is there a word or phrase to describe the eerie orange sky that appears after a thunderstorm at sunset? I see these on occasion in the DC area in the summer.

As far as I know, there isn't a specific term dedicated exclusively to the eerie orange sky that sometimes appears after a thunderstorm at sunset, but weather enthusiasts use descriptive phrases such as:

"Post-storm glow": This term captures the unique atmospheric lighting that occurs after a storm, often enhanced by the sun's low angle at sunset.
"Afterglow": While this term is commonly used for the lingering light after sunset, it can also apply to the striking colors that appear in the sky after a storm when the light scatters through lingering moisture and storm clouds.
"Storm light": This describes the distinctive quality of light that occurs when sunlight breaks through clouds or storm remnants, often creating an unusual color palette.

Why It Happens

The intense orange, pink, or even greenish hue is due to Rayleigh scattering. After a thunderstorm, the atmosphere is often filled with moisture and dust particles. When the sun is low on the horizon, its light passes through a larger cross-section of the atmosphere, scattering shorter blue wavelengths and allowing the longer red, orange, and yellow wavelengths to dominate. Additionally, the remaining storm clouds can reflect and amplify this colored light, creating an otherworldly effect like my attached photo - taken near severe storms we had been chasing in March 2008.

I was driving back from McPherson KS yesterday. Weather front moving through temp dropped over the hour from 80 ish high humid to 60's or 50's. Tornado Watch i believe. i was driving back on Hwy 150, about 50 minutes out of town heading back to Kansas City when all of a sudden all 4 windows exterior including back "fogged out" in an instant, like a quick WAVE..looked down temp said 53 on my truck. ran my wipers it was as thick as rain and looked almost like very thick wet frost. It happened again a couple miles down the road. i have been all over the world but never experienced this "instant" frost well above freezing that was like someone throwing it on all my windows at once? Microburst of cold air? Pressure drop?

As a meteorologist who stormchases (these days only when storms are nearby), I've experienced this phenomena several times in my life - including when a ton of hail fell, turning the ground white, and quickly cooling the ground after a storm. I grew up in the Kansas City metro area, so I've seen this around both Kansas and Missouri - the local topography and plant life can also affect how cold some microclimates (tiny areas that differ from the overall main climate type of an area) can be after a storm.

What you encountered was likely the result of a rapid temperature drop combined with high humidity. Here’s a breakdown of why it happened so suddenly and dramatically:

1. Temperature and Humidity Factors

When warm, humid air comes into contact with a surface that's significantly cooler (like your windows), the moisture in the air quickly condenses into tiny droplets. This is similar to what happens when you breathe on a cold window and see it fog up.
The sudden temperature drop you noticed—around 80°F down to the 50s—likely meant the exterior surface of your truck windows got cooler than the surrounding warm air, encouraging quick condensation.

2. Why It Was So Sudden

Weather fronts often bring rapid temperature, pressure, and wind speed changes. The drop to 53°F and the presence of high humidity created an almost "instantaneous" fogging effect on your windows. When the temperature difference and humidity levels reach a certain point, the effect can be very sudden and look like frost or thick fog.

As you drove, you moved through areas where the temperature, pressure, and humidity shifted quickly. Strong winds or microbursts (short, intense downdrafts of air) may have also contributed by pushing cooler air over your vehicle. I'd need access to archived weather data to confirm whether there was a microburst at that time and date.

3. Appearance of Frost-Like Condensation

The condensation likely appeared dense and “frosty” because of how quickly it formed on your windows. It was too warm for actual frost, but the thickness of the fogging effect combined with dusty windows could easily look like frost or frozen moisture, as I can attest from personal experience.

4. Why the Effect Isn't Consistent

In a storm environment, temperature and moisture vary greatly over a short distance, especially when you factor in local hills, trees, crops, etc. Additional humidity can come from the evapotranspiration from plants, especially growing crops, in fields. Temperature changes over a short distance often occur - sun-warmed road patches contrast with cold areas where maybe hail or cooled rain recently fell, for example. I've also seen dips in the road where fog gathered and no fog appeared when we hit the hill peaks, thanks to microclimate (very small-scale) effects.

What would cause a huge ring of clouds around the moon? See attached pictures. Is it because the clouds weren’t dense and the moon was almost full causing enough heat to dissipate the clouds? This was a few nights ago.

thin clouds halo around the moon — *Submitted photo*

Your photo shows the moon surrounded by a luminous halo in the night sky. This type of halo is typically caused by the refraction of light through ice crystals in thin, high-altitude cirrus or cirrostratus clouds. The optical phenomenon results in a circle or arc around the moon that can appear faintly like an iridescence or bright ring.

The halo forms because the ice crystals act as prisms and mirrors, bending the light at a consistent angle (usually 22 degrees), creating a circular appearance. Halos like this can be striking visually and memorable in folklore as a sign of upcoming precipitation, as cirrostratus clouds can sometimes precede a storm system by 24-48 hours.

As for your comment on whether the clouds are dissipating due to the heat from the moon, keep in mind that even high clouds like cirrus are still in the troposphere - the lowest part of our atmosphere - far away from the direct influence of the moon. Contrary to what some may think, the moon doesn’t emit heat itself; it only reflects sunlight. Therefore, the warmth of moonlight isn’t enough to dissipate clouds or influence cloud formation directly.

Folklore Weather Questions

My grandmother used to look at the moon and say if the temperature would be hot or cold. I think she was referring to the declination of the moon. If it was further north then the weather would be colder. If further south then warmer. I can see how the moon can have tidal effects on the atmosphere, but is there any truth to this folklore? - Jim B.

Your grandmother is right that the moon affects Earth's temperature: at Full Moon, the poles can experience temperatures up to a degree Fahrenheit HIGHER than at New Moon (an average of 0.036 F across the globe). We do know that the Moon helps to keep our climate (long-term weather patterns) more stable than if it didn't exist where it is - keeping Earth's seasons fairly stable and predictable (less wobbling of the Earth's tilt that gives us our seasons).

The lunar tidal effects are more noticeable in the ocean than in the atmosphere, especially with the changes of the moon's orbital plane shifting in relation to Earth's equator over a 18.6 year period, greatly affecting how warm water at the ocean surface mixes with the cold water below. Here's one study that looked into weather folklore in the Mediterranean (rainy vs. dry period forecasted by observing the moon's "horns" changing - likely due to the Moon's declination shifts over the 18.6 year period): https://adsabs.harvard.edu/full/2000ESASP.463..555U

The experts to check with are planetary scientists at NASA - in meteorology, we don't often look at how the moon affects weather, as the evidence of major effects is scant so far (the sun has a much stronger influence on Earth's weather, which can make it tougher to study the Moon's more subtle effects)...we are far more focused on what happens in the lowest levels of the atmosphere. But planetary scientists bridge the sciences of meteorology and astronomy - they're more likely to know if moon declination may be used to infer temperature changes on Earth.

I did find a study from University of Washington that found that lunar forces affect the amount of rain - slightly. When the Moon is overhead or underfoot, the overall air pressure is higher due to the Earth's atmosphere bulging toward the Moon's gravity, making it slightly less likely that rain will occur with the decreased humidity that comes with higher pressure in the vertical column. The change is tiny, but measurable, making it useful in climate and weather models, but not strong enough evidence to say that a Moon high in the sky means less chance of rain overall. Here's an article explaining the results: https://www.washington.edu/news/2016/01/29/phases-of-the-moon-affect-amount-of-rainfall/ and the quite technical paper that the researchers published: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL067342

Hurricane Questions

I moved 15 miles WSW of Gainesville, FL. Hurricane Idalia hit right after I got here and I remember hearing that was the first hurricane to hit the Big Bend area in like 50 years. Now a year later we are getting ready for our 3rd hurricane in that area. Does anybody know why? - Shane

There have been about 90 total known tropical depressions, tropical storms, and hurricanes that have gone through the Big Bend Florida area, centered near Perry, Florida -- around 24 hurricanes from the mid 1800s until today. In the past 20 years, there have been 5 hurricanes over the area, including Helene and August's Debby: Idalia (2023), Irma (2017), and Hermine (2016). See the interactive Historical Hurricane Tracks here, where you can list a specific town and see which storms tracked over it.

There are additional hurricanes that went through the Big Bend area, but as you cannot search by informal region on the mapping, you'll need to center the map around a city or town, which may reduce the true number of hurricanes that went through the area.

This year's hurricanes have yet to be added to the map, but I expect they'll be added at the end of the hurricane season.

As the Gulf of Mexico and the Atlantic Ocean continue warming due to rising levels of greenhouse gases (and combine with natural cycles like El Nino Southern Oscillation, among other global air and water circulations), climate models predict more intense hurricanes in these warm waters, especially with increased heavy flooding on coastal regions as sea ice continues to melt. This is exactly what we are seeing now - even the simpler climate models 20-30 years ago predicted much heavier rainfall with climate change (human-induced and natural forces combined).

For more information about hurricanes in the past, please see the National Hurricane Center (NHC) climate page.

I also recommend Hurricanes in a Changing Climate for more about hurricanes, their average frequency, and the increase in heavy rain and flooding. It is a little outdated on the data, but overall, it is helpful conceptually. To better understand expert hurricane forecaster predictions, check out 2024's forecast from May 2024.

What were the Hurricanes between Helene and Milton (eg. I thru L)? [Missed some hurricanes?]

If you check the National Hurricane Center's archives, you'll see the named tropical storms and hurricanes so far: https://www.nhc.noaa.gov/archive/2024/

Hurricane Helene

Hurricane Isaac

Tropical Storm Joyce

Hurricane Kirk

Hurricane Leslie

Hurricane Milton

The archived paths can be found at the National Hurricane Center, but I’ve found this website helpful as well for ongoing hurricane season - it’s produced by a fellow University of Oklahoma School of Meteorology grad.

I don't understand what happened in Asheville North Carolina and the surrounding environs. It's a landlocked mountainous place. Yet, when I see the pictures and videos of the aftermath of the hurricane, it looks like an entire ocean fell on that area. How could that be? Where did that water come from? Do hurricanes lift and carry that much water and over dozens of miles? Asheville is supposedly 100 miles form any shore..? Can you explain what happened?

There are multiple things that combined to make a worst-case scenario for Asheville.

First, a cold front stalled out over the area prior to the hurricane coming onshore. This front combined with tropical moisture moving north ahead of Helene led to a large rain event before the hurricane even made landfall. This rain saturated the ground and filled streams and rivers.

Then, Helene moved in, and the strong winds associated with Helene forced huge amounts of air and moisture up over the mountains. This led to extreme, torrential rainfall due to a phenomenon called "orographic lift".

Here's a good article from North Carolina State University about the rainfall and flooding Asheville experienced.

Are more hurricanes starting in the Gulf of Mexico/Caribbean rather than off the coast of Africa? If so, is it the La Niña/ El Niño effect and /or global warming?

Atlantic and Gulf Hurricanes can form anywhere in the tropics from the western African coast to within the Gulf of Mexico, as shown on the Scijinks site (scroll down below the video to see the relevant graphic).

A hurricane requires specific conditions to form and strengthen. Broadly: warm sea surface temperatures, high amounts of water vapor in the air, and weak upper air winds that allow these “spinning tops” to continue unimpeded by outside winds. There’s not a lot of surface roughness (which can slow down storm winds near the lowest levels of the troposphere) over open ocean compared with land, which is part of the reason tropical storms can get so intense (read: stronger winds within and lower pressure centers) over water. More about the atmospheric layers.

As for frequency of hurricane formation in the Atlantic Basin and Gulf of Mexico, the number is increasing slightly as climate change (a mixture of natural cycles and human-induced warming) occurs.

Atlantic basin storms appear to be less directly impacted by El Niño as ENSO (El Nino Southern Oscillation, which includes La Niña) greatly affects Pacific waters, but there are wind and moisture patterns that affect the Gulf/Atlantic, depending on the mode of strong vs weak El Niño or La Niña - this gets complex. There are also other natural oscillations that can have an impact, but these are still being studied too. For fascinating details on this science and some of the expected impacts, check out the 2021 NOAA Atlantic Season Report:

https://www.cpc.ncep.noaa.gov/products/outlooks/hurricane2021/August/hurricane.shtml

It is the third time a hurricane forms in Campeche coast in Mexico. What are the conditions for this to happen? What made Milton hurricane lose power before going inland, and reduce from a category 5 to a category 3?

Atlantic and Gulf hurricanes can form anywhere in the tropics from the western African coast to within the Gulf of Mexico, as shown on the Scijinks site (scroll down below the top video to see the relevant graphic).

A hurricane requires specific conditions to form and strengthen. Broadly: warm sea surface temperatures, high amounts of water vapor in the air, and weak upper air winds that allow these “spinning tops” to continue unimpeded by outside winds (aka low shear). There’s not a lot of surface roughness (which can slow down storm winds near the lowest levels of the troposphere) over open ocean compared with land, which is part of the reason tropical storms can get so intense (read: stronger winds within and lower pressure centers) over water.
More about the atmospheric layers here.

As for frequency of hurricane formation in the Atlantic Basin and Gulf of Mexico, the number is increasing slightly as climate change (a mixture of natural cycles and human-induced warming) occurs. As far as I can tell, meteorologists today can’t give a specific percentage of each process causing this increase - we have weather and climate models to help us to narrow down the numerous variables in the real atmosphere so we can figure out what has the greatest impacts on formation. The environment is far from stationary (and more complex than our improved models), so what’s true one year may not be the next - that’s why long-term climate pattern research is essential.

What researchers generally agree upon in the Atlantic/Gulf of Mexico:

1. Anything that warms the oceans in this area increases sea surface temperatures and water vapor in the air - so climate warming like we are experiencing has an impact on tropical storm formation on top of natural variability.

2. Storms are likely to become more intense and drop high amounts of rain over areas, with areas on land seeing far more flooding like we saw in North Carolina.

3. The general path of hurricanes hasn’t changed much, but the number of hurricanes HAS increased slightly in the past 40 years. 20 years ago, there were an average of 12 storms each year. Today there are an average of 14 or more storms a year. As with anything in science, we need more decades of modern data to really understand this.

4. The strength of hurricanes appears to be increasing, with fewer Cat 1-3 storms and more Cat 4-5 intensities. By how much exactly, researchers are still studying.

5. Whether we will see more land-falling hurricanes in the future is uncertain, as there are several complex factors in storm paths.

For more technical details on our current understanding about hurricanes and climate, see https://www.gfdl.noaa.gov/global-warming-and-hurricanes. As with many science government groups, they discuss their confidence levels in particular data. This makes it difficult for the layperson - is ___ causing ___ for certain? We prefer to use statistics and confidence levels, as few things in weather are black and white.

As for why Hurricane Milton weakened from Cat 5 to Cat 3: one of the ingredients it needed to remain Cat 5 - low shear - changed. The hurricane encountered higher shear (stronger winds with height that can reduce the storm engine’s efficiency) from nearby frontal boundaries and a strong jet stream aloft before landfall.

Why would Tropical Storm Patty form if sea surface temperatures are in the 70s? I thought a minimum of 80 degrees was required for formation.

Anytime you want to know more about a current (or recent) tropical storm, I recommend checking out this link: https://www.nhc.noaa.gov/archive/2024/ (or when it's 2025, change the year in the link) and navigating to the Discussion links for the storm of interest. I personally like to start at the beginning of the storm to see what the forecasters are thinking from day one - they will describe the storm environment, what's causing the system to grow or die, etc. It's pretty technical, but definitely thorough.

The 9am discussion on November 2 mentions that Patty had non-tropical origins, starting as a low pressure system over cooler water. They also say:

"The low has become detached from fronts and has a shallow warm-core structure, though it remains within a cooler airmass behind a cold front over the eastern Atlantic. Despite SSTs around 21 deg C, instability aloft has allowed the system to sustain some moderate convection that wraps most of the way around its center in geostationary and passive microwave images."

The forecasters mention that sea surface temperatures (SSTs) are low for a tropical storm, but instability allows for enough lift to create condensation and clouds, plus the latent heating that fuels tropical storms. Instability comes from the difference in temperatures between lower and upper levels of the atmosphere - the cooler the temperatures aloft are compared to the surface, the greater the lift.

"Little change in strength is expected today, and Patty is forecast to be a fairly short-lived subtropical cyclone. This is because westerly shear is forecast to increase over the system during the next couple of days, which will likely make it difficult for the system to sustain convection near and around its center."

Here the forecasters mention why they believe that Patty won't become a major hurricane. Fascinating stuff! I learn more from these subject experts every time I read a discussion.

3 am discussion on November 4 mentions:

"Patty has continued producing deep convection since the time of the previous advisory, although the convective structure has recently degraded slightly on the latest infrared images. The infrared satellite images and an 03/2138 UTC ASCAT pass depict a more compact cyclone with a confined radius of maximum winds than earlier in the system's life. Patty is also no longer co-located with the upper-level low that was earlier responsible for its hybrid characteristics. Based on these observations, Patty has made the transition into a tropical storm. The earlier ASCAT pass showed tropical storm force winds as high as 39 kt in the southern semicircle. The initial intensity is therefore held at 40 kt."

I'm guessing that because Patty became smaller (conservation of angular momentum: the ice skater spins faster when she brings her arms in, reducing the radius) and moved away from the cold core low pressure system, it can now take advantage of temperature differences between the sea and higher in the atmosphere. Also, if there's less wind shear (which I would expect as Patty gets further from the upper-level low), the tropical storm can continue to create convection and stay together as a storm.

Tropical Storm Patty initially formed from an upper-level low or cold-core system, which can bring colder temperatures in the upper atmosphere. The contrast between the cooler upper-level temperatures and the relatively warm sea surface can create enough instability for convection (thunderstorm activity) to persist and organize into a tropical system.
This process is more common in subtropical storms, which can transition to fully tropical systems if they acquire enough tropical characteristics, like a warm core, organized convection, and a more symmetric structure.

For more explanation on what's going on, keep reading the discussions - these forecasters specialize in tropical weather and have the most recent knowledge of the subject.

Describe the size, shape, and profile of the storm surge that forms under a tropical storm. As seen from above, is it symmetrical wrt the eye? Does it extend further to the east (N. hemisphere)?

Storm surge primarily depends on the direction of the wind relative to the coastline and the characteristics of the coastline itself. It's usually not symmetrical with the eye or necessarily on one side or the other of the storm east vs. west, though in the US it's usually on the right side of the storm relative to its motion as the storm makes landfall.

Additionally, a weaker storm that makes landfall in an area with shallow water off the coastline and a coastline shape that funnels water into an enclosed area (such as a river or bay) can create a worse surge than a stronger storm that makes landfall in an area with deeper water offshore and a coastline that doesn't funnel the water into an enclosed area.

There are other factors as well -- here is a link to a PDF that has some good information on storm surge.

Storm surge; is it the depth of the incoming water, or how far inland the water will come, as in, more inland than normal?

Storm surge is mostly caused by strong winds that push ocean water up onto land where it normally doesn't go. The depth of a surge and how far it goes inland are determined by a variety of factors.

Modification Questions

Conspiracy theories about government's ability to control the weather have always been with us to some extent but they have gotten louder and more frequent since Helene. I have known since I was young that we have the ability to seed clouds but what that really is isn't more than causing a cloud that would have released the moisture it already contains as rain a little earlier than it would have done so without intervention. Is that still basically where we are at in our attempts to control the weather or have we gone beyond that?

From your expert standpoint in meteorologist history, do you believe that meteorologist scientists in the 1940s had the resources and capabilities to create a weather machine, similar to how astrophysicists had the ability to create nukes during that time? Please explain why and breakdown the science and history as to it

I'm so glad you reached out to meteorologists instead of relying on social and other media sources on this topic!

Meteorologists are continually battling the misinformation not only about weather modification (including alleged chemtrails - what a meteorologist knows as contrails - the condensation of moisture on the small particulates emitted by planes), but also climate change. As you noted, the number of conspiracy theories around everything - especially weather and climate - have exploded, especially as these more extreme events happen, likely due to human-generated activities boosting or overwhelming natural cycles.

Sorry, no weather modification machines and none in the works from what I can tell - it’s purely in the science fiction world at this time. Meteorologists would LOVE to control the weather and be right all the time!

Unless the military is keeping extreme weather modification technologies secret (unlikely, as improved modification could boost economies and food production or reduce the impact of weather hazards like flooding and strong winds), humanity does not currently have anything beyond cloud seeding and other small-scale projects. Like you mentioned, the effects of cloud seeding are minimal and small-scale - and originally came from military weather studies.

As a grad student studying microphysics (the science of precipitation mechanisms), I met and talked with Dr. Roscoe Braham - a legendary meteorologist in the world of weather modification who conducted cloud seeding experiments in the 1940s - and he said that it seems unlikely that major changes in the weather would ensue anytime soon from seeding or any disruptive technology that he was aware of. In an interview with the American Meteorological Society, he described the seeding experiments he did with hurricanes in the 40s:

"Dr. Simpson, and perhaps others, had come up with the thought that if seeding enhanced the vertical motion in conductive clouds, and if you could seed the eye wall clouds of hurricanes, you might enhance the vertical motion, enlarge the eye, spread the energy of the storm out over a larger area, and reduce the intensity of it.

So he had to have somebody to seed the clouds. The Australians had developed airborne burners, units to burn a silver iodide-acetone mixture from an airplane. And they'd used it successfully in seeding some clouds in Australia. The University of Chicago--in fact, my lab in Chicago had a contract from the Weather Bureau to develop measuring instrumentation and cloud seeding equipment to mount on the Air Force WD50’s to seed hurricanes.

We essentially failed. We... The Australian burners could not cope with the heavy rate it was ingesting water in the hurricanes. And we had great difficulty sustaining a burner operation...

...This whole business of weather modification involves complex mixtures of the dynamics of the cloud system and the microphysics that goes on. And these things interact."

Transcript of Oral History Interview of Roscoe R. Braham. (2002). [Interview by S. Cole]. https://opensky.ucar.edu/islandora/object/archives%3A7584(Original work published 2002)

I love the recent film Twisters, but the premise of bombing a tornado to make it dissipate is pure Hollywood. While technology has advanced greatly since WWII - and humans understand how the atmosphere works better than we did then - we appear to be a long way from disrupting or noticeably enhancing severe thunderstorms and hurricanes.

The heat release of a hurricane is equivalent to a 10-megaton nuclear bomb exploding every 20 minutes.

Could we potentially use 10 nuclear bombs to disrupt a hurricane? Maybe - we aren’t sure if this amount of firepower would even do anything to a system already so packed with energy. Research tests from the 50s-70s seem to indicate that our firepower isn’t enough to battle nature this way.

Are bombs practical or less damage than a hurricane? No - the radiation fallout alone would be deadly, so these tests are forbidden by international treaties.

More on this topic and a brief summary of where the idea was originally considered (along with other crazy bomb use ideas).

I live in Delaware and we’ve been having a horrible drought for a couple of months now. Is there anything that can be done to make the rain come or otherwise end this drought?

Droughts can be frustrating, especially when they persist for months as you're experiencing in Delaware. While controlling weather on a large scale isn’t possible with current technology, there are strategies and practices that can help mitigate the effects of drought and potentially influence rain patterns to a limited degree:

1. Cloud Seeding

How It Works: Cloud seeding is a weather modification technique where particles (usually silver iodide or salt) are dispersed into the atmosphere to encourage cloud condensation and precipitation.
Limitations: This method only works if there are already clouds present; it cannot generate rain from a clear sky. The effectiveness varies and is subject to lots of regulation. It's also only feasible in a fairly small location, like a farm.

2. Long-Term Water Management

Conservation Efforts: Communities can conserve water by adding restrictions on non-essential water use, such as limiting lawn watering, car washing, and other activities that consume large amounts of water.
Sustainable Practices: Investing in water-efficient infrastructure, like rainwater harvesting systems and more efficient irrigation for agriculture, can help reduce the impact of droughts.

3. Drought-Resilient Landscaping

Xeriscaping: Using native, drought-resistant plants for landscaping reduces water use and helps maintain green spaces with minimal irrigation. I like using succulents in planters and low-water plants like native flowers and grasses near our house in Oklahoma.
Soil Management: Mulching can help retain soil moisture, making the most of any rain that does fall. Some plants can be used as a green mulch, like clover, keeping moisture from evaporating as much.

4. Weather Patterns and Climate Considerations

Waiting for Pattern Shifts: Sometimes droughts persist due to large-scale atmospheric patterns, like high-pressure systems that block storm paths. These shifts typically change as weather systems evolve, but they aren’t predictable on a short-term basis. ENSO (El Nino Southern Oscillation / La Nina) also influences whether a particular area will receive higher or lower amounts of precipitation in a season, depending on the cycle status and intensity.
Seasonal Influences: The region may have to wait for seasonal changes or storm systems that typically bring moisture, such as late-summer thunderstorms or fall storms.

5. Community and Policy Actions

Collaboration with Weather Services: Local governments and weather agencies monitor drought conditions and help coordinate responses to minimize agricultural and municipal water impacts.
Public Awareness Campaigns: Educating the public about water conservation during a drought helps ensure community efforts are maximized.

Limitations

It’s important to note that despite advances in atmospheric science, making it rain or ending a drought is mostly out of human control, especially on a regional scale like Delaware. While cloud seeding can be used in specific situations, the best approach involves water conservation, responsible management, and preparedness for when natural rain patterns resume.

As droughts become more frequent on Earth, climate adaptation measures, such as updated water resource management policies and sustainable practices, can help communities be better prepared for future dry periods. Humans WILL need to adapt, as the climate extremes appear to be getting worse (advanced climate models predict more droughts AND more flash flooding when rain finally arrives).

Hope this helps to explain what's going on...I wish we could control the weather, but it may never be possible due to the complexity of our atmosphere.

Polar Questions

Did you happen to take a photo of the clouds?

I often see strange swirling systems that are in the Northern Pacific Ocean by Alaska. I was never told anything about the storms and I could never really find an answer to what they are on the internet. They remind me of an odd hurricane in the way that they circulate and I was curious to what they are. The link attached has a screenshot of what I'm talking about.

Polar cyclone or polar low - submitted image

These spinning storms in the Northern Hemisphere are called polar cyclones or polar lows. They spin counterclockwise because of the Coriolis force, which causes moving air to curve due to Earth’s rotation.

What is the Coriolis Force?

Imagine you’re standing on a spinning merry-go-round. If you try to throw a ball straight across to your friend on the other side, the ball seems to curve away from your target. Why? Because as you’re both spinning, the motion of the merry-go-round affects the path of the ball.

Earth acts like a giant, spinning merry-go-round. As the Earth rotates, any moving object, like air or water, gets pushed or curved. This “push” is what we call the Coriolis force. It’s not an actual force pushing on the air – it’s more like a trick of perspective because of Earth’s spin.

Coriolis Force and Weather Systems

In large-scale wind patterns on Earth (see the Polar Cell on that page for the area where polar lows form), the Coriolis force makes air move in a curve rather than a straight line. In the Northern Hemisphere, this force makes air curve to the right, while in the Southern Hemisphere, it makes air curve to the left. The effect is weakest near the equator and stronger as you move toward the poles.

The Coriolis force comes into play with polar lows because it makes the air flow around a low-pressure area in a circular pattern. In the Northern Hemisphere, this air moves counterclockwise around the low-pressure area, creating a spinning motion.

A polar cyclone, sometimes called an "Arctic hurricane," gets its energy from heat transferred from the ocean to the atmosphere. When the warm ocean air meets the cold polar air, the warmer air rises, and moisture in the air condenses into clouds, releasing extra energy (called latent heat). This helps the storm grow stronger (lower pressure = stronger).

Polar cyclones are tricky to predict because they form fast – often within just 24 hours. They usually appear over Arctic or Antarctic seas during winter in each hemisphere: October to April in the Northern Hemisphere and April to October in the Southern Hemisphere.

If you're interested in a more detailed technical explanation of how these form, check out this tutorial from Colorado State.

Pressure Questions

I've tried to do research and understand what causes barometric pressure fluctuations, and obviously the answer will be hot/cold fonts forming and moving, but what I don't understand is how pressure can fluctuate quite a bit in a single day when no weather is changing. Let me give you an example. I live in Oregon at a little over 4000ft elevation. Sometimes (not every year for sure) the pressure fluctuates significantly on a single day; say currently from 30in to 29.8in, and often much more than that on just a typical summer day. I can see a similar fluctuation in Phoenix, AZ, and they're thousands of feet lower and much hotter. Our temperatures are fluctuating 40 Fin a single day right now, and in Phoenix it's around 30 F. What causes this significant pressure change? Is this caused by the extreme changes in temperature?

You're absolutely right about the extreme temperature fluctuations causing the great changes in barometric pressure - pressure changes with differing air density, which is related to temperature (warm air is less dense than cool air). Even on a day with no fronts passing through, barometric pressure generally changes four times daily due to the sun's heating (for a more technical explanation of the four main daily pressure changes, check out this historical article by W. Humphreys 1912: https://www.jstor.org/stable/24520688).

The intensity of the pressure changes are further affected by latitude, season, and altitude: the higher your altitude, the greater the daily pressure change. I would certainly expect that with 30-40F difference in diurnal temperatures there will be greater changes in barometric pressure over your area, possibly leading to more pain.

My mother used to get headaches when it rained. Yesterday, during hurricane Milton ( live in south Florida) I had severe cold symptoms. Runny eyes, drippy nose, sneezing. Today I’m fine. Could the pressure from the storm have caused my cold?

Ah yes, being a human barometer is SO much fun, isn’t it? I’ve always been affected by extreme weather (often low pressure systems) too - from unstoppable hiccups to migraines and joint pain.

It sounds like both you and your mom may have barometric pressure headaches, a type of migraine that can strike during severe weather and when hurricanes (large low pressure systems) pass by.

According to the Cleveland Clinic's page on barometric pressure headaches:

"Symptoms include:

- Facial discomfort or pain around your sinuses.
- Mucus draining down your throat (postnasal drip).
- Teary eyes.

Barometric pressure is also known as the atmospheric pressure being applied against a given area — and in this case, that “area” is you.

Because your nasal and sinus cavities are air channels, any change in that pressure, especially a fall in barometric pressure, affects those areas. This forces fluid into tissues and can cause a disruption in fluid balance - and possibly causing inflammation of these sensitive tissues, leading to cold-like symptoms that disappear after the storm passes."

I’m a meteorologist, not a doctor, but the description seems to fit. Maybe you could check with a local doctor or headache specialist for a real diagnosis?

I'm sensitive to barometric pressure changes - they can cause migraines, nausea and vomiting, ear ringing, and dizziness. This may be partly due to my jaw joints being oddly connected, causing any change in my blood pressure to cause swelling and problems. I've been called a weather witch by many people, because I can predict a storm, when it'll be due, and usually the intensity with eerie accuracy - because of my symptoms when there's a sharp drop in pressure that precedes many notable storms. I find that I get uncomfortable under 1000 MBs and use a local university observatory to track pressure stats. They're an excellent resource but their reporting is limited. Here is their site: https://www.atmosp.physics.utoronto.ca/wstat/index.htm I don't like most weather stations reporting of pressure because they often use aggregate data over a large area and their updates and resources are poor. Since Wednesday, September 25, I have been in barometric hell with non-stop belching nausea and everything else mentioned above. It's the worst episode I've had in just shy of 40 years of life and I'm desperate to understand. Near as I can tell, there's been an absolutely massive low pressure system over my area near Toronto Ontario for days and it's been especially odd since there's been no rain and mostly sunny skies, traits that I attribute to high pressure systems. Hurricane Helene is to the south currently stalled over Tennessee. Rain may come in early Sunday and I hope to god a high pressure system comes immediately behind. We've been in the 990s for days and it keeps dipping by 5 mb or more throughout the day, only for it to crawl back up overnight (not breaking past 998, much less 1000), to get knocked down again. What are we experiencing here, why, and what can I look for to see a glimmer of relief?

I empathize with you, my fellow human barometer (though I love weather witch too). Headaches, dizziness, and pain have been my companions during turbulent seasons like fall and spring for the past 42 years, as the jet stream (and the low pressure systems) overall shifts seasonally. From what I understand, jaw joint connection (especially if the major blood vessels and nerves are involved) can indeed cause some issues due to rapid changes in barometric pressure - I had a craniotomy to remove a large skull tumor near the trigeminal nerve that nearly broke through my ear canal, further sensitizing the area and leading to dizziness when pressure changes.

Probably the best climate for these conditions is the desert, further south, where the weather is more consistent, like San Diego, California. Canada in the fall must be rough for you! It's hard enough for me in Oklahoma, but further north, you experience the earliest clashing of cold polar air and warm, humid air - and often in early fall, the cold air mass doesn't reach us, just a wind shift change, as it mixes with daytime heating at the surface.

While I'd normally say that a university weather station is ideal (especially versus the usual consumer-grade weather stations that many weather enthusiasts use), TAO says that it's located at the top of a building at 61m - the pressure will always be lower compared to the standard max height of 10m for a pressure sensor due to stronger winds as you go up through the troposphere (lowest layer of the atmosphere and where most of our weather occurs). Pressure decreases rapidly with elevation, changing 1.0 millibar (mb) with every 32 feet (~9.8 m) at sea level. I'm guessing that the TAO pressure sensor can be useful for solar and atmospheric studies, but it won't give you the most accurate picture of the weather conditions near the ground where you are.

TAO also says: "Please note that the wind sensor is installed on the south east corner and will be influenced by obstructions on the roof (astronomical domes, radio antenna and building itself)." The pressure data are also not standardized to sea level pressure, so the difference in pressure at the ground vs at the top of the building will probably be more than 6.25 mb on average.

As to why this can cause issues with the accuracy of the pressure readings, check out this in-depth technical article (if you'd like a thorough analysis on pressure instruments, see Chapter 3): http://www.weather.gov/media/epz/mesonet/CWOP-OfficialGuide.pdf Simply, these obstructions can cause turbulence that affects the pressure, potentially dropping the pressure even further and appearing like the pressure is rapidly changing when it may not be fluctuating much in the area at the ground.

I recommend bookmarking your local forecast office weather station or aviation weather observation systems (AWOS) at your airport, which is held to the WMO standards (World Meteorological Organization): https://weather.gc.ca/en/location/index.html?coords=43.655,-79.383

The best weather station for you to check would be one that is ideally sited with no obstructions near you, everything to WMO standards, and recalibrated periodically to the highest standards. Most states and provinces can't afford to do that on a wide scale in a dense station network, unfortunately. I am lucky here in Oklahoma, as we have 120 regularly-calibrated, gold-standard research data weather stations through a joint project by our two state universities: The Oklahoma Mesonet. Even so, there's only 1 station per county, still not granular enough to know the exact conditions at my house. A quick search showed that Toronto has its own Mesonet, but I'm not sure if you live anywhere near a site.

I'm not familiar with Canadian weather data options online and a quick search didn't bring up live surface weather observing station maps like we have in the States, so I'm not sure what other options are near you. I did see climatology/historical weather information at https://climate.weather.gc.ca/historical_data/search_historic_data_e.html, but I'm not sure how long it takes for the information to be uploaded to the site.

As for experiencing low pressure systems with few clouds: that can happen when there's not enough moisture in the lower to mid atmosphere (common during a drought), or not enough lift and instability to boost the surface air where it can cool and condense with height.

Why is there no wind on a hot summers night?

The reason hot summer nights are often calm is because hot temperatures in the summertime typically mean you're under a high pressure system. The center of a high pressure system is associated with light winds.

Other factors include trees, which can block light winds, as well as nighttime inversions (air warming with height) that can prevent winds above the surface from reaching the ground.

That said, there are certain parts of the U.S. where it is frequently windy during the night after a hot day, such as the Great Plains (think Oklahoma, Texas, Kansas, etc.). This is because the jet stream commonly causes a "lee trough" (low pressure) to form just east of the Rocky Mountains, pulling air into the low from surrounding areas. This can happen any time of the year, including during the summer.

Horse Latitude. Can someone please explain what this is? I know it has to do with the equator and the Longitude and Latitude but that's it. Other than throwing horses overboard to lighten the weight on a ship!

The Horse Latitudes are subtropical regions located approximately between 30° and 35° latitude, both north and south of the equator (see the graphic under 3. Global Circulations for the location on the Earth). These zones are characterized by calm winds and high atmospheric pressure, resulting in dry, stable weather.

Here’s why they're so interesting:

1. Calm Winds and High Pressure

In the Horse Latitudes, air that has risen at the equator (in the Intertropical Convergence Zone) cools and sinks around these latitudes. This descending air creates high-pressure zones, leading to calm or very light winds. This area can be frustrating for sailors who depend on wind, as sailing ships could get “stuck” here for days or even weeks due to the lack of breeze.

2. Clear Skies and Dry Conditions

The sinking air suppresses cloud formation, resulting in clear skies and dry conditions. This is one reason why many of the world’s deserts, such as the Sahara in the Northern Hemisphere and the Australian Outback in the Southern Hemisphere, are located along these latitudes.

3. Origin of the Term "Horse Latitudes"

One popular theory of the name's origin is that it dates back to the Age of Sail (16th-19th centuries). When ships became stranded in these calm waters, food and water supplies sometimes ran low. According to legend, sailors would throw horses overboard to save on resources, hence the name "Horse Latitudes." Another theory is that the term derives from an old maritime term for a certain amount of freight or allowance, called a "dead horse," which sailors would ceremoniously throw overboard when they passed these latitudes to mark the end of a period of advance pay.

4. Role in Global Circulations

The Horse Latitudes are a critical component of Earth’s global circulation patterns. They act as a boundary between the trade winds (blowing towards the equator) and the westerlies (moving towards the poles). This interaction affects climate and weather patterns worldwide, shaping subtropical regions and desert zones.

I have been reading some accounts of the Hundred Years War and came across an extraordinary meteorological event that took place just outside of Chartres France in 1360. Known as Black Monday, a sudden and violent storm took place on Easter Monday and wreaked havoc on the English army. So much damage was caused that Edward III concluded it was a message from God and hurried to agree peace terms with the French. My question is - what meteorological conditions would be necessary to cause such storm of thunder, lightning, rain and hail which could kill both men and horses? And have such events ever been recorded since in France or Western Europe?

Ah, yes, the infamous Black Monday severe storms - what a fascinating historical weather event!

Weather records can be found in accounts written by everyone from farmers to military leaders, as severe weather would have greatly impacted life. However, regular, standardized weather measurements weren't available until the 1850s, so we don't know every weather event that happened before, unless it had historical significance. And then we are limited to the testimony of the witnesses - modern satellite and observational data aren't available that far back.

Here's a brief analysis of what could have led to this storm and other similar events in Western Europe:

1. Meteorological Conditions Needed

Cold Front Passage: A sudden, severe storm with hail and intense lightning is often associated with the passage of a strong cold front. When warm, moist air is forced to rise rapidly by an advancing cold air mass, it can trigger severe thunderstorms. The dramatic updrafts within these storms are what lead to intense precipitation, especially large hail. The stronger the updraft, the larger the hail that can form before it falls out of the storm due to its weight.
Atmospheric Instability: For a storm to reach such destructive levels, the atmosphere must be unstable, with significant temperature and moisture contrast between the surface and the upper atmosphere. This instability can cause the rapid development of cumulonimbus clouds, which are responsible for most severe weather.
Moisture Source: The location near Chartres, France, is relatively close to the Atlantic Ocean, which provides a source of moisture-laden air. If a strong flow of warm, humid air moved into the region and met with a cold air mass, it could have fueled a violent storm.
Jet Stream Influence: The position of the jet stream can amplify severe weather, as it provides additional uplift and wind shear. If a powerful jet stream was situated over the region, it could have enhanced the storm’s severity and prolonged its duration.

2. Characteristics of the Storm

Thunder and Lightning: Significant lightning can occur when powerful updrafts within a cloud separate charges, leading to electrical discharges. If the storm had especially strong updrafts, this could explain the numerous reports of intense lightning.
Heavy Rain and Hail: Large hail forms when strong updrafts carry water droplets high into the cloud, where temperatures are below freezing. The droplets freeze, collect more water as they fall and are carried back up by the updraft, growing larger until they become too heavy to be supported and fall as hail. For hail large enough to kill both men and horses, the storm's updrafts must have been particularly powerful - on par with strong storms with baseball to grapefruit-sized hail we sometimes see in the United States plains.

3. Historical Context and Similar Events

Notable Similar Storms: While storms of this magnitude are rare, severe weather events involving hail and intense thunderstorms have been recorded throughout history in France and Western Europe. Notable instances include:
- The Hailstorm of July 1788: This event devastated large parts of France and contributed to food shortages before the French Revolution. The hail was reportedly large enough to destroy crops and injure livestock and people.
- Highest Mortality due to Hail (1888): This hail event was said to have killed as many as 246 people with hailstones as large as ‘goose eggs and oranges’ and cricket balls in Moradabad, India, on 30 April, 1888
- Modern Severe Thunderstorms: In modern times, severe thunderstorms with hail larger than golf balls are occasionally recorded in parts of France and Western Europe, usually associated with summer convective weather patterns. The heaviest documented hailstone in the world fell in Bangladesh in 1986 - 2.25 pounds - and the largest measured hailstone fell in either South Dakota or Nebraska - 18.74 inches in circumference vs. 8 inches in diameter, respectively.

While such catastrophic storms are uncommon, they have occurred and continue to occur in France and Western Europe, often recorded in more recent times with greater meteorological detail (and lots more data!)

Rainbows & Optics Questions

Minneapolis has been in drought through September-October this year. Yesterday around 5:30 pm it was windy, dry and partly cloudy -- around 55 or 60 degrees. Suddenly a full rainbow appeared in the SE sky. It was high, bright and lasted a few minutes. How is this possible on such a dry day?

A rainbow on a dry, windy day may seem unlikely, but there are still a few ways it could happen, even in drought conditions:

Virga: Even on dry days, there can be pockets of localized moisture in the atmosphere. It’s possible that some very light precipitation, such as virga (rain that evaporates before reaching the ground - seen sometimes as vertical streaks), was present. If sunlight hits the moisture at the right angle, a rainbow can form. The partly cloudy conditions suggest there might have been just enough moisture in the air for a rainbow to form.
Irrigation or Other Water Sources: In urban areas, sprinklers, fountains, or other water sources like the 10,000 lakes can create mist or droplets that, if lofted by wind, can form rainbows when the sun hits them.
High Humidity or Fog Drizzle: Sometimes, high relative humidity (with a high temperature in the 50s, a little bit of moisture in the atmosphere from evapotranspiration off crops or over water might be enough) can lead to fog or drizzle formation even when conditions feel dry at the surface. If this occurs with the sun at a low angle (like late afternoon), a rainbow can appear.

The combination of the sun's position, scattered clouds, and just enough moisture could have provided the perfect alignment for a rainbow to appear, despite the overall dry conditions.

the attached files show snapshots of pictures recorded on October 8th 2024 by a webcam placed in the Dolomites (Italy) and published on https://www.meteo-webcam.it/rifugio-locatelli-tre-cime-di-lavaredo/. I am wondering which kind of clouds the ones on the right side of the pictures are and how this phenomenon is generated. Moreover, in the last 3 pictures (second file) two rhomboidal shapes can be seen to the left of the three peaks: is this an optical phenomenon? How does it arise?

Webcam Dolomites View Clouds or Lens Flare — *Submitted photo*

As a photographer and videographer, these “clouds” look like optical artifacts of the webcam to me.

The photos you submitted seem to show light reflections or lens flares caused by the sunlight interacting with the camera lens. These flares often appear as translucent or semi-opaque geometric shapes and can vary in color and size. They are not actual clouds but optical artifacts created by bright light sources in the camera's field of view - see how the bottom “clouds” go over the background?

As for the rhomboidal shape to the left, it too is an optical artifact. Looking away from the sun, following an imaginary sunbeam, you can see the same shape shifted in color to more reddish and further down the beam in location.

Tornado Questions

In Des Moines there was an EF-1 confirmed tornado. I had taken a picture of what I thought was just very dark skies before heading home from work - not aware of rotation, as I was rushing to get home. The direction I was facing and location seems to correlate with where the tornado had initially formed but I wasn’t aware of this until after the fact (5:33 pm 7/15/24, facing NW on 104th, looking toward I-35). There was some green tint to portions of the storm further away from the area I photographed. I do know the NWS did place the area I was facing as the start point for the EF-1 that went through Des Moines. I was curious if anyone could tell me anything about this image I got.

It's hard to tell from the photo alone, even after pulling it into Photoshop to clarify and add contrast to the clouds, as it's hard to see the storm structures clearly. I can't tell you definitively that it IS the tornado, especially with the building and trees covering the ground (which is what I really need to be able to see to confirm a tornado from images), but there is certainly a dark area where there might be a condensation funnel or a rain-wrapped tornado.

Here's the highly edited version of your photo:

I'd say that, based on your research on the NWS tornado track and the image, this very likely could be the weak tornado.

As for the green sky, we see that often in the area where sunlight passes through hail and heavy rain, so I wouldn't expect it to be right next to the tornado, depending on the relative viewing angle.

Water Cycle Questions

I'm a science teacher. When teaching about the hydrological cycle, I'm bothered by the assertion that all water on Earth has always been here. Water is continually decomposed during photosynthesis and created in both respiration and combustion. Perhaps not in relatively great amounts, but humor me, isn't this correct?

You raise an interesting point! While it's true that the vast majority of Earth's water has been here for billions of years, some processes can convert substances into water or decompose water molecules.

Current theories on how Earth got its water billions of years ago:

Outgassing from Volcanic Activity: Early in Earth's history, volcanic activity released water vapor and other gases trapped in the planet's mantle. As the planet cooled, this water vapor condensed and fell as rain, filling oceans.
Delivery by Comets and Asteroids: Some theories suggest that water was also delivered to Earth by icy comets and water-rich asteroids colliding with the planet during its formative years. These celestial bodies may have contributed significant amounts of water.
Hydrogen and Oxygen from Chemical Reactions: Some researchers propose that hydrogen and oxygen from chemical reactions in the early Earth’s environment, including reactions involving minerals, could have formed water as well.

While the exact contributions of these processes are still being studied, it's widely accepted that the majority of Earth's water has existed in some form for a very long time, circulating through the hydrological cycle since then.

During photosynthesis, water is used and then released as oxygen, but the water itself isn't created or destroyed—it's just part of the cycle. Respiration and combustion can produce small amounts of water, but these processes are relatively minor compared to the overall water cycle.

Depending on the age group you teach, this is a nuanced perspective that could help deepen your students' understanding of the hydrologic cycle. So often in early science education, we're taught only the simplest concepts and not the nuances that are important for truly understanding the incredible world we live in.

Wind Questions

Why is there no wind on a hot summers night?

Other factors include trees, which can block light winds, as well as nighttime inversions (air warming with height) that can prevent winds above the surface from reaching the ground.

Hurricane Beryl: 7/2/2024 at 20:00 EST the pressure was 943mb with average sustained winds around 90 mph with gusts in the 130s. This data comes from ICON, GOES16, and STOFS. I see it as a weak Cat2 at best right now. NOAA says it's a CAT4 with 155mph sustained winds. My "nerd on a computer" forecast shows it hitting Jamaica as a very weak Cat1. I'm in a group of weather nerds who are screaming "Deep State Conspiracy" over the historic high Category and forecast on this storm. The last several years of highly over forecasted storms doesn't help. Can you please enlighten us! How does NOAA arrive at these numbers? What information do they have that we don't?

The only thing that NOAA uses to categorize hurricanes is maximum sustained wind speed, based on the Saffir-Simpson scale. There are a variety of ways to measure / estimate maximum sustained winds, but the gold standard is data recorded by the hurricane hunter aircraft as they fly through the storm. This is because the hurricane hunters can take "in situ" vs. "remote" measurements, where "in situ" refers to measurements taken directly from the air inside the storm (such as by a barometer or dropsonde) and "remote" refers to measurements taken from a remote location (such as by satellite or radar).

"In Situ" measurements are considered the most reliable, and the hurricane center will usually rely more on them vs. remote measurements. I took a screenshot of NOAA's NHC discussion about Beryl from last night, where they comment on how the hurricane hunter's measurements are higher than satellite intensity estimates (see highlighted text in the attached image). Discrepancies between measurement sources are common, as each type of instrument has advantages and disadvantages. Typically, forecasters are going to give more weight to hurricane hunter measurements vs. other sources because the hurricane hunters are actually inside the storm.

Regarding the ICON model, I would not suggest relying on the ICON for hurricane intensity analysis / forecasting, as it is not built for that purpose. Weather models that are widely used for hurricane intensity forecasting are high-resolution models such as the WRF, HMON, and HAFS, which can be configured and run for specific purposes, such as forecasting hurricanes. You can see these model runs at the following link under the Hurricane tab -- note that they will all have differences between them, which is normal:

https://www.tropicaltidbits.com/analysis/models/

I was wondering how do you read this graph? Is there a database for wind direction over a year (wind rose or something) for Harlow in Essex? and final question what's the difference between a climate and a microclimate and how do I find the latter?

Submitted chart of annual wind data for a unknown location

I did a reverse image search on Google to find a description of the chart. This is a plot of the percentage of hours in which the mean (average) wind direction is from each of the four cardinal wind directions, excluding hours in which the average wind speed is less than 0 m/s. It appears that the prevailing wind direction in Feb-Jun is from the north (northerly flow) and some NE, while Oct-Jan appears to come mainly from the South and West.

Personally, I'm more familiar with windroses like I've attached below - where it's clear that the prevailing winds are from the E, ESE, SE.

Wind rose example plot of winds coming mostly from the E and SE

As an American meteorologist, I'm not familiar with publicly available data in Europe and Canada (Harlow in Essex is in the UK?). Doing a quick Google search on Met Office data, I found windroses for airports across England: https://www.metoffice.gov.uk/services/transport/aviation/regulated/national-aviation/uk-services/airfield-climate-data

You may want to search climate data from the Met Office like this: https://digital.nmla.metoffice.gov.uk/SO_75a68cd2-cabe-43a8-98bb-3919f51e59a9/ The monthly climate reports will give you much of the information found in the chart but in text form.

Climate refers to the long-term (at least 30 years) weather patterns over an area, while a microclimate is usually a small geographical area that is statistically different from the nearby climate when it comes to precipitation, temperatures, and/or wind. In the US, we talk about many wine-producing regions being microclimates - some vineyards experience cooler temperatures high on a hill, changing the characteristics of the grape as compared with the same grape variety grown in a valley vineyard. Examples of microclimates in the UK are displayed at MetLink: https://www.metlink.org/fieldwork-resource/microclimates/

My local NPR weather announcer/reader each morning gives the marine forecast. He uses the terms for the wind direction, for example, “This morning there will be a east wind changing to northeasterly by the afternoon”. I have written to our storied, pillar of our community an email explaining that is confusing and misusing the term northeasterly”. My Question #1: If the wind is coming from the northeast it is called a northeast wind and not a northeasterly wind, correct? My Question #2: Isnt this “…erly” added to the term northeast implying that the wind is going to the northeast and not correctly naming the wind as a northeast wind - 180* wrong? - Tommy

Answer to Question #1:

The terms "northeast wind" and "northeasterly wind" are interchangeable in meteorology. Both mean that the wind is coming from the northeast and blowing toward the southwest. The suffix “-erly” is traditionally used to indicate the direction from which the wind is blowing. So, a "northeasterly wind" is a wind blowing from the northeast.

Answer to Question #2:

Confusingly, in everyday language, the addition of “-erly” can imply that the wind is blowing toward the northeast. In meteorological terms, the direction specified with or without the “-erly” indicates where the wind is coming from. For example:

Northwest wind or northwesterly wind: The wind is coming from the northwest.
South wind or southerly wind: The wind is coming from the south.

So, when the announcer says "northeasterly," they are correctly describing a wind coming from the northeast.

Thank you for your fun question! This is the sort of question professors LOVE to add to their exams.

1. Centrifugal Force and Distribution of Water and Air

SUGGESTED READING:

- The Dynamic Earth: An Introduction to Physical Geology by Brian J. Skinner and Stephen C. Porter.

2. Increased Coriolis Effect

SUGGESTED READING:

- Introduction to Atmospheric Dynamics by David G. Andrews - Chapter 4, "Midlatitude Synoptic Systems" (section on jet streams and their formation)

3. Changes in Atmospheric Circulation Cells

SUGGESTED READING:

Global Physical Climatology (2nd Edition) by Dennis L. Hartmann - Chapter 6, "General Circulation of the Atmosphere." This chapter explains how the Earth's atmospheric circulation cells would adjust with different rotational speeds.
Climatology by Robert V. Rohli and Anthony J. Vega - Chapter 5, "The Global Energy Balance and Temperature" (sections on large-scale wind systems). It includes discussions on how the Coriolis effect influences trade winds and global circulation.

4. Impact on Weather Patterns

SUGGESTED READING:

Synoptic-Dynamic Meteorology in Midlatitudes (Volume I, 2nd Edition) by Howard Bluestein - Chapter 8, "Extratropical Cyclones" (section on the dynamics of mid-latitude weather systems). This chapter explains how increased rotational speeds could affect storm formation and variability.
Meteorology Today: An Introduction to Weather, Climate, and the Environment (13th Edition) by C. Donald Ahrens - Chapter 13, "Weather Patterns and Severe Storms." This chapter covers how shifts in circulation can alter rainfall distribution and weather patterns.

5. Temperature Distribution

SUGGESTED READING:

Principles of Planetary Climate (1st Edition) by Raymond T. Pierrehumbert - Chapter 4, "Radiative Energy Balance" (section on rotation and temperature profiles). This discusses how changes in the length of day affect planetary temperature variations.
Atmospheric and Oceanic Fluid Dynamics (2nd Edition) by Geoffrey K. Vallis - Chapter 2, "The Governing Equations" (sections on temperature gradients and atmospheric circulation). This chapter elaborates on how temperature differences drive global weather patterns.

Overall, a faster-rotating Earth would likely have more intense and complex weather patterns, with stronger winds, more pronounced atmospheric circulation, and altered temperature distributions.