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Questions tagged [meteorology]

The study of how the earth's atmosphere works, including weather forecasting. Use this tag for questions about the earth's weather. When asking questions specifically about the atmosphere, also include the [atmosphere] tag.

79
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2answers
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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 ...
44
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5answers
11k 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 ...
32
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3answers
4k views

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 ...
30
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3answers
6k views

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 ...
29
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4answers
3k 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 ...
29
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2answers
41k views

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 >...
28
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3answers
6k 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?
26
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1answer
2k 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 ...
25
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3answers
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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 ...
25
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2answers
26k views

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 ...
24
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7answers
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Is a complete global flood physically possible on Earth?

Genesis 7:11-20 presents an account of a precipitation 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 ...
24
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3answers
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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 &...
23
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2answers
2k 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 ...
23
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2answers
1k 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?
23
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3answers
669 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?
23
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1answer
2k 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 ...
23
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0answers
373 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, ...
22
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2answers
747 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 ...
21
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5answers
3k 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 ...
21
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3answers
39k 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.)?
21
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2answers
5k 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 ...
21
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1answer
13k 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 ...
21
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2answers
3k 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?
21
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2answers
3k 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?
20
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6answers
14k 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 ...
20
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4answers
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 ...
20
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2answers
3k views

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 ...
20
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1answer
702 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 ...
19
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6answers
14k 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 ...
19
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5answers
5k views

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 ...
19
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1answer
1k 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?
19
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1answer
969 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 ...
19
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2answers
259 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 ...
19
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1answer
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?
19
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1answer
2k 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?
19
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2answers
14k 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 ...
18
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2answers
5k 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 ...
18
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2answers
4k views

Does the US National Weather Service use Celsius or Fahrenheit?

This tweet from the National Weather Service in LaCrosse, Wisconsin, USA says: We have officially hit -30 here at the NWS La Crosse office as of 520 a.m. The wind chill is -54. Be sure to dress ...
18
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2answers
4k views

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 ...
18
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2answers
555 views

Is this ice cover real - and what circumstances are required to make it?

The title says it all... I assume it requires very slow freezing sheltered from the wind. Undercooled water, maybe? A Reddit thread talks about Delaunay triangulation, but that does not explain how ...
18
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2answers
5k views

Why does the Hadley cell descend at 30 degrees?

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 ...
18
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1answer
354 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 ...
17
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3answers
1k views

How do I explain why the Tibetan plateau is colder than lowlands at similar latitudes?

A common layman explanation for why does it get colder to higher elevations (considering only the troposphere here) qualitatively boils down to The Sun heats the Earth's surface and the Earth's ...
17
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3answers
20k views

Why does the Inter tropical Convergence Zone shift?

I am currently learning at school about the climatic conditions (mainly winds, difference in pressure, Coriolis effect, etc.) that cause and affect the monsoons received by India. One of the factors ...
17
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1answer
799 views

Why do tropical cyclones not tear themselves apart?

A tropical cyclone is the generic term for a hurricane, typhoon, or tropical storm. Tropical cyclones derive their energy from evaporation of water at the ocean surface which ultimately recondenses ...
17
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1answer
457 views

Why are weather kites no longer used (much) operationally?

Figure 1.12 from the IPCC AR5 WG1 report (reproduced below) illustrates the different instruments that have been used for weather forecasting. Most of the methods have been in continuous use since ...
16
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2answers
3k views

Why do clouds sometimes form a ring around the Sun?

Someone shared a video with me in which clouds were forming a ring around the Sun. I took this screen shot of that video: What is the reason behind this?