All Questions
Tagged with weather or meteorology
1,216 questions
90
votes
3
answers
40k
views
Impossible or improbable? Hurricane crossing the equator
No known hurricane has ever crossed the equator. Hurricanes require the Coriolis force to develop and generally form at least 5° away from the equator since the Coriolis force is zero there.
Are ...
- 2,658
47
votes
5
answers
22k
views
Why do snowflakes form into hexagonal structures?
Snowflakes are known to form into pretty hexagonal structures. The image below shows a variety of such structures that are possible (although by all means not an exhaustive list):
What is the ...
- 7,626
35
votes
1
answer
6k
views
What factors determine the number of Hadley cells for a planet?
We know (think?) that Earth has three Hadley cells per hemisphere, but from observing gas giants such as Jupiter, we see that they have many more cells. According to a link from a comment in this ...
- 1,833
32
votes
4
answers
5k
views
How do weather models work?
We use different weather models all the time, such as the ECMWF and the GFS. These models are simply amazing to me.
How do these models work? I know they have to take in various data points - what ...
- 1,920
32
votes
3
answers
4k
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Why does Coriolis determine the rotation direction of a cyclone but not my drain?
It is a common misconception that Coriolis is responsible for the direction the water swirls down a toilet, tub or sink drain. E.g. does a toilet flush the other way in the southern hemisphere? (If ...
- 14.2k
31
votes
6
answers
7k
views
Why aren't weather balloons left in the atmosphere permanently?
I was reading about weather balloons and the articles said that weather balloon flights usually last about two hours. When I looked up why, some articles said that when the balloons get high enough in ...
- 605
31
votes
2
answers
45k
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Why are there no hurricanes in the southern Atlantic basin?
We see tropical cyclones (going by different names e.g. hurricane, typhoon, cyclone) all over the tropics, but it seems that there are never any storms in the southern Atlantic. See this map of ...
- 2,758
30
votes
3
answers
6k
views
Equinoxes and solstices: start of the season or mid-season?
In the United States, the upcoming autumnal equinox is marked on most calendars as the "first day of autumn." Similarly the solstices are commonly called the "first day of summer" and "first day of ...
- 451
30
votes
3
answers
10k
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How would an icicle "grow" upwards?
The other day a friend of my dad's showed him a picture of an icicle that appeared to be "growing" upwards out of a crack in a sidewalk. There were no roofs, overhangs or vehicles parked near by... It ...
- 684
30
votes
2
answers
63k
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At what humidity does it start to rain?
As far as I understand it is perfectly valid for air to have 100% humidity. At that point, all water can still exist in form of vapor, non-condensed.
Does it immediately start to rain if humidity is >...
- 403
29
votes
7
answers
48k
views
Is a complete global flood physically possible on Earth?
Genesis 7:11-20 presents an account of an event which, in 40 days, submerges the entire surface of the earth:
[On] the seventeenth day of the second month — on that day
all the springs of the great ...
- 501
29
votes
3
answers
9k
views
Why are hail storms always brief?
It can rain all day, and it can snow for hours on end, but hail always seems to fall for short periods only. Why don't you get prolonged periods of hail?
- 393
27
votes
3
answers
84k
views
How do I convert specific humidity to relative humidity?
How do I convert specific humidity to relative humidity? What variables are needed (e.g. air temperature, pressure, etc.)?
- 5,435
27
votes
4
answers
4k
views
What is the steepest surface that can hold snow?
I know it depends on the type of snow (dry or wet) and the rougness of the surface. I'm looking for an approximate rule of thumb answer. Assuming a reasonably smooth surface, at what angle it's likely ...
- 373
27
votes
0
answers
583
views
Is it possible for a sting jet to form over a continental landmass?
Sting jets are thought to be responsible for some of the most damaging winds associated with extratropical cyclones in the mid-latitudes. So far they have only been confirmed in the European region, ...
- 2,105
26
votes
3
answers
9k
views
What do weather forecasters mean when they say "50% chance of rain"?
What do weather forecasters mean when they say "50% chance of rain"?
Even more confusing: weather report often says something like "30% chance of rain. >10mm", then the next day "70% chance of rain &...
- 5,435
25
votes
2
answers
2k
views
What is the cause of the jet streams?
Jet streams are fast-flowing currents of air in our earth's atmosphere. An enormous amount of energy is necessary to keep a jet stream going. Where does this come from and why?
- 1,524
25
votes
3
answers
13k
views
Is there an upper bound to the amount of rain that can fall in an hour?
The record for most rainfall in a single hour is 12 inches (30.5 cm), set in Holt, Missouri, in 1947. What is the maximum amount of rainfall that could theoretically occur in an hour?
- 577
24
votes
3
answers
1k
views
How good were climate models of the 1990s at predicting the global temperature trends of the 2000s/2010s?
Was there a significant bias between the ensemble of climate models and the long-term temperature trends?
What about spatial patterns?
- 7,827
24
votes
1
answer
20k
views
Do tornadoes have eyes?
In the movie Into the Storm (2014) near the end, storm chaser Pete sees the eye of a massive tornado.
In 1928 (real life), Will Keller was in his barn when a huge tornado passed through. He reported ...
- 343
23
votes
1
answer
5k
views
Where does wind come from?
Wind is (according to Wikipedia) the flow of gases on a large scale.On the surface of the Earth, wind consists of the bulk movement of air.
What forces would cause such a mass movement of air?
- 1,524
23
votes
2
answers
955
views
How can the average coldest day of the year be before the winter solstice?
There are parts of the U.S. where, on average, the coldest day of the year comes before December 21st. [source]
How can this be? Why would temperatures start rising again even while days are still ...
- 333
23
votes
1
answer
3k
views
What causes 'positive' lightning to be rarer, higher charged, and longer lasting than 'negative' lightning?
Why is 'positive' lightning rarer, brighter, higher charged, and longer lasting than 'negative' lightning? Are there any other unique characteristics to positive lightning that sets it apart from ...
- 2,658
22
votes
5
answers
4k
views
Is there a database of global rainfall time series?
Is there any institute out there collecting time series data of precipitation, and making them accessible online? I need data for a few different locations, but:
Low spatial resolution is fine. For ...
- 405
22
votes
3
answers
72k
views
How to interpolate scattered data to a regular grid in Python?
I have three txt files for longitude, latitude and temperature (or let's say three lists lon, lat, temp) from scattered weather station in the UK. I would like firstly to interpolate these data in ...
- 285
22
votes
2
answers
6k
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What are the major differences between weather models and climate models?
Some weather models include GFS (Global Forecast System) and NAM (North American Mesoscale Model).
Some climate models include CCSM (Community Climate System Model) and the NASA GISS (Goddard ...
- 7,827
22
votes
2
answers
2k
views
Why is there no middle ground between tornadoes and hurricanes?
A tornado has an effective area of destruction about the size of a city block.
A hurricane spans several hundred kilometers.
However, there doesn't seem to be a continuum between the two. Why are ...
- 605
22
votes
3
answers
10k
views
Does rain (temporarily) deplete the surrounding atmosphere of carbon dioxide?
CO2 in the air dissolves into rain water, making them slightly acidic. Is that enough to deplete the surrounding air out of CO2? If yes, how fast does this occur? Is it only with the first drops of ...
- 23.3k
21
votes
6
answers
30k
views
Why doesn't the sun reach its highest point overhead at exactly 12:00 noon?
Many sources state that 12:00 noon is the high-point or mid-point of the sun's path across the sky.
However, for where I am, this is obviously wrong. In my own town the high point of the sun occurs ...
- 313
21
votes
2
answers
6k
views
Does Earth's air leak into space over time?
From my current understanding, Earth's atmosphere and air are held by the balance of two forces: 1. Earth's gravity and 2. Air pressure from air out to space.
Is my understanding correct?
So, do ...
- 1,171
21
votes
4
answers
3k
views
Can the previous weather be computed from the current situation?
If one applies today's state-of-the-art weather forecast computations "backwards", i.e. computing how the systems was X days before the current situation based on knowledge of today's situation, at ...
- 357
21
votes
4
answers
24k
views
What would be the effect of bringing seawater pipes to the Sahara desert?
This is a childhood dream.
What would happen if pipes were installed (similar in principle to the Great Man-Made River, but for seawater) to continuously pump seawater into the Sahara desert.
Let'...
- 311
21
votes
4
answers
26k
views
Where can I get archived hourly temperature data?
I am looking for historical hourly temperature data from many cities in the US what other data sources are there except wunderground?
UPDATE: I will use the data to compare stations from the same ...
- 425
21
votes
1
answer
887
views
What data does a skilled meteorologist look at to predict thunderstorms?
An uneducated layman like me would just look at CAPE numbers and make rough guesses on possible thunderstorms. In a related but non-duplicate question, vertical wind shear is discussed.
If we are ...
- 2,103
21
votes
2
answers
5k
views
How do tropopause folds form and do they have any impact on synoptic scale weather?
What is the process that creates a tropopause fold? Do these features have any significant impact(s) on weather patterns or the atmosphere?
- 2,658
20
votes
7
answers
21k
views
Why doesn't the 71% water of the earth dry or evaporate?
Perhaps a simple question, we know 71% of the earth's surface contains water as oceans. If Earth's age is 4.543 billion years, then I guess it should be decreased with drying or should have been dried ...
- 309
20
votes
5
answers
7k
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Is it true that a butterfly flapping its wings can result in a tornado in a distant location?
I have heard that extreme storm events can be caused simply by a butterfly flapping its wings somewhere in a distant location. Is it true that such a small disturbance in the air in one location can ...
- 7,626
20
votes
2
answers
6k
views
In the northern hemisphere summer, why are places in the north cooler than those in the south?
As the Earth's axis is inclined, during summer in the northern hemisphere places in the north are exposed to the Sun's rays for longer, so days are longer during summer (say in June - Aug). Yet, ...
- 301
20
votes
1
answer
2k
views
What is this "crystal ball" located at a meteorological station?
I found what looks like a "crystal ball" in a meteorological station in the Vlădeasa mountains (Romania). What is its purpose?
- 303
20
votes
1
answer
447
views
How is global weather model skill measured?
The models I have in mind are the major global models such as the Global Forecast System (GFS) and the European Center for Medium range Weather Forecasting (ECMWF).
These models produce numerous ...
- 14.2k
19
votes
2
answers
18k
views
Where is the calmest place on Earth?
I have done some research online, and I've found out that Antarctica has the calmest winds (lowest maximum wind speed) recorded on Earth. However, it is uninhabitable for human life. Other very calm ...
- 1
19
votes
2
answers
7k
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What are the applications of hydrostatic solvers vs non-hydrostatic solvers in numerical weather prediction?
In the atmospheric dynamics research community, many colleagues of mine happen to use atmospheric models that have non-hydrostatic equation solvers, e.g. the UK MetOffice model, and WRF-ARW:
The ...
- 1,817
19
votes
2
answers
40k
views
Transfer precipitation forecast in mm to expected snowfall in cm
What conversion functions exist to transfer precipitation forecast in mm to expected snowfall in cm? Simple rules of thumbs as well as more advanced methods would be of interest.
- 1,681
19
votes
1
answer
7k
views
What is the range of possible atmospheric pressures on the surface of the Earth?
I'm developing an Android app which uses a pressure sensor. Due to storage limitations I have to normalize and scale the atmospheric pressure values. For this I need to know the extreme values of ...
- 293
19
votes
2
answers
310
views
Will tropical cyclones form and be sustained in areas they previously were not due to global climate change?
With global climate change, is it possible that tropical cyclones (as seen in the Atlantic basin for example) are going to form and be sustained in regions where they previously did not, for example ...
- 719
19
votes
1
answer
3k
views
Why do more tornadoes happen late in the day?
According to the graph below, which appears to be sourced from the US National Oceanic and Atmospheric Administration, more tornadoes happen late in the day - why is this?
- 4,611
19
votes
2
answers
10k
views
Why does the Hadley cell descend at 30 degrees latitude?
George Hadley's initial model of the Hadley cell described air as being heated at the equator, ascending, and then moving aloft pole-wards where it would cool and descend. Meanwhile surface air would ...
- 7,626
19
votes
2
answers
394
views
What is the status of meteorological data exchange standards?
How do the web services exchange meteorological data?
One method is transferring NetCDF and GRIB data and hooking them up to your software.
I read here about the possibility of using WFS and WCS. ...
- 731