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Questions tagged [weather-forecasting]

Questions about the application of weather data in meteorology/forecasting.

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29
votes
4answers
4k 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 ...
24
votes
3answers
7k 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 &...
20
votes
2answers
4k 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
votes
1answer
746 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
votes
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?
18
votes
2answers
5k 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 ...
14
votes
1answer
4k views

What is the meaning of -999 degrees Celsius?

I was checking the weather forecast just now, and it is showing that it "feels like -999 °C". I never heard or saw -999 °C before. I searched other weather channels, and they were showing that it ...
14
votes
3answers
15k views

If it rains harder, does it mean the rain's duration will be shorter?

If it rains real hard, is there a chance the rain's duration will be shorter? I think the if the rain in the clouds disperses with such force the rain will be over faster than if it was just a light ...
13
votes
2answers
2k views

How to interpret hourly precipitation forecast?

How should I interpret the hourly precipitation forecasts? Most of the time, when there is rain in the forecast, the maximum Probability of Precipitation (PoP) in the hourly forecast is about the ...
11
votes
2answers
317 views

How do meteorologists grade their past forecasts?

In every professional field, practitioners may come home at the end of the day and say "Yeah! I knocked it out of the park!", or alternatively "Oh, man. Gotta do better tomorrow." What about ...
11
votes
1answer
425 views

What does the term “Snow Interval” mean?

When looking Weather Station readings from the National Weather Service website, what does the term "Snow Interval (inches)" actually mean? 6 hr and 24 hr readings are obvious, but I can't seem to ...
11
votes
1answer
2k views

Intuitive explanation of precipitation amount

I'm trying to learn how to make sense of numbers in a forecast. I can interpret temperature and wind speed, but I don't know what to make of rainfall. What does it mean, for a human, that there will ...
10
votes
2answers
796 views

Can the Bering Sea Rule be used to predict the weather?

Recently, a colleague explained that the recent cold spell in the eastern United States could have been predicted using the Bering Sea Rule. The idea is that 17-21 days after a storm appears in the ...
10
votes
1answer
131 views

Is there a convenient place to get vertical wind shear info for my location?

Now that it's thunderstorm season here in New Hampshire, it would be nice to be able to find out what the vertical wind shear is like at the altitudes that affect thunderstorm formation, to guess ...
10
votes
2answers
398 views

Are weather forecast models more accurate for either high or low temperatures?

The other day our low temperature for the day was ~10 degrees F below our forecast low. I've noticed this before in the winter, especially when temperatures start to go below 0 degrees F (-18 degrees ...
8
votes
3answers
424 views

Predicting school closures with historical weather prediction data?

I'm interested in predicting when the local schools will be closed due to snow and other winter weather. I have a list of school closure dates and a rough sense of the criteria used to determine the ...
8
votes
1answer
102 views

Are the storm cones introduced by Robert Fitzroy still in use?

In 1860 or so, following the tragic wreck of the Royal Charter with the loss of over 400 lives, storm cones were installed in many UK ports, under the direction of Admiral Fitzroy, head of the ...
7
votes
3answers
148 views

Why don't weather forecast models normally take solar eclipses into account?

Since there is a total solar eclipse somewhere almost every year, I would have thought it would be included as a standard option in weather forecast models. However, I've learned that is not really ...
7
votes
2answers
1k views

Help interpreting a wind rose diagram

Can someone comment on technical explanation of the wind rose attached? I can understand the wind is blowing between WNW & SSW with speed of 7-11 km/h. For frequency of 11-16 km/h its blowing ...
7
votes
2answers
679 views

Calculate the latitudes of a Gaussian Grid

I would like to calculate the latitude values of a Gaussian Grid of a size of my choosing. Unfortunately, I didn't find a method or a formula to do so. Where can I find this information? Alternatively,...
7
votes
2answers
755 views

Long-term Wind Speed Forecasting: reality or wishful thinking?

I have been studying/working with Wind Energy for a while and, one of my main responsabilities right now is to search for adequate long-term wind speed forecasting models. However, 2 things strike me ...
7
votes
1answer
185 views

What wind forecast datasets are available for forcing a wave forecast model?

I am trying to set up a spectral wave model for waves forecasting in the Mediterranean. I need the meteorological forecast for this region. I am aware of the ECMWF datasets. But unfortunately, only ...
7
votes
3answers
451 views

Algorithmically Determining the Rainy Season

I have historical precipitation data for hundreds of cities around the world. I would like to algorithmically determine when the rainy season (if exists) is for each location. Are there any algorithms ...
7
votes
1answer
838 views

Statistical weather prediction

Assuming I have time evolution of air temperature, air pressure, wind speed, wind direction, relative humidity and cloudiness, how can I predict weather based on this information? I know that high ...
7
votes
1answer
136 views

I'm still confused about what “probability of precipitation” means

I'm trying to understand what weather forecasts mean more precisely. As I understand it from reading Wikipedia, blogs, etc., the percentage value for rain/precipitation that you see in a forecast is ...
6
votes
6answers
313 views

Are there any weather services that provide hourly forecasts beyond 7 days?

I'm working on a small project and am trying to find a way to get the very extended hour-by-hour forecast for a location. Most services (Darksky, etc.) seem to offer 7-day extended hourly forecasts, ...
6
votes
1answer
166 views

Why do forecast areas on weather.gov appear as twisted squares?

I get my weather forecasts from good ol' NOAA's weather.gov site. On the detailed site weather pages, there's a map that shows the forecast area as a green square (for Boston at least, the square is ...
6
votes
1answer
6k views

Is it typically colder after a storm?

I've heard that it's colder after a storm. I think this is an interesting question, not least because of the implicit comparison: colder than what? A few different comparisons come to mind, and still ...
6
votes
3answers
390 views

Publicly available data set with ensemble forecasts and observations?

I am looking for a publicly available, easy to download, small data set of ensemble forecasts (or reforecasts), with corresponding observations or reanalysis. We are planning to illustrate some ...
6
votes
1answer
149 views

How much further can weather forecasting models go before the limits of Chaos Theory set in?

Refer to a report here that mentions the huge advancement in weather forecasting models since the 1980s: How much better? “A modern five-day forecast is as accurate as a one-day forecast was in ...
6
votes
0answers
79 views

Worldwide weather maps database

I am searching for a database (a free one would be great) that would give me, for any chosen rectangular area on earth, historic data about pressure, sea water temperature, wind (including both speed ...
5
votes
2answers
298 views

Is there a standardized way to define weather icons based on quantifiable data?

Weather APIs often provide weather icons which symbolize the state of the sky at a given point, or as an average. Is there a standardized way to define what the icon should be, based on quantifiable ...
5
votes
1answer
298 views

How do spectral methods work in the context of numerical weather prediction models?

I am broadly familiar with the concept of numerical weather prediction models using various finite methods to solve the primitive equations used in these models, but how do spectral methods work, ...
5
votes
1answer
73 views

Can the forecast N+1 days ahead be more certain than the forecast N days ahead?

The Swedish meteorological agency SMHI on its website (NB: freezes Firefox on Linux for me, likely due to plugins, works in Chrome) indicates how certain the forecast for a particular day is. Looking ...
5
votes
1answer
440 views

How do I interpret the specs of a weather balloon?

I'm planning a high-altitude weather balloon project (to around 100000 feet, or 30 km) some time down the line to take video and pictures of near space altitudes and I have some questions I need to ...
5
votes
1answer
191 views

How do I interpret this “sky cover” chart?

The image below is a screenshot of forecasted sky cover in percentage for various parts of Arizona. Is the sky cover percentage the percentage of each pixel that has cloud, or is it the percentage of ...
5
votes
1answer
241 views

What is the difference between the freezing level and 0C isotherm in NOAA's GFS?

I'm playing around with NOAA's GFS forecast data and I see that it contains both a "0C isotherm level" and a "Highest tropospheric freezing level". Could someone tell me the difference between these ...
5
votes
0answers
82 views

Using salinity to predict rainfall

Recently, a new method has been proposed by Ray Schmitt (WHOI) and collaborators to use salinity patterns in the ocean to predict weather events (more specifically, rainfall) at scales from weeks to ...
5
votes
0answers
573 views

Why did the GFS switch to hourly forecasts through hour 120?

About a month ago, the GFS was upgraded. Among other things (like making parallel GFS data available), the upgrade notice said: Include hourly forecasts out to 120 hr Now, this seemed ...
5
votes
0answers
102 views

Initial indexes for calculating the Fire Weather Index (in the Canadian Forest Fire Weather Index System)

I am applying the Canadian Fire Weather Index (FWI) on the Forest Fire Warning System of my laboratory. My problem is in calculating the Fine Fuel Moisture Code (FFMC), the Duff Moisture Code (DMC) ...
4
votes
2answers
3k views

Interpolate Gaussian grids to regular fixed grids using bilinear interpolation?

I want to regrid GCM data available on Gaussian grids to regular grids, say at 1 deg X 1 deg. How to do this using CDO or Python ...
4
votes
2answers
178 views

Are we changing Earth's weather with global warming?

I think that when the air heats up in the day, the radiation from the ground contributes way more to its heating at altitudes more than 300 meters above the ground than convection currents of air heat ...
4
votes
1answer
65 views

Freely available and re-distributable weather observations over the US?

I am looking for a (small) data set of weather observations for a few (say 5-20) weather stations in the US, with observations of precipitation, temperature and wind speed for the year 2016. The data ...
4
votes
2answers
1k views

Historical NWS GFS forecast data

The National Weather Service (NWS) makes the results from its Global Forecast System model (GFS) available for download as GRIB2 files. While accessing current (or recent) forecasts is straight-...
4
votes
1answer
245 views

Why is it always rainy in Addis Ababa?

I watch the news and in the weather forecast it's always rainy in central Africa, especially in Addis Ababa. Why is that?
4
votes
1answer
110 views

ISA Model and GFS data

I have a newbie question... I always used the International Standard Atmosphere model whenever I needed to calculate the temperature in a given altitude. It always looked accurate to me... However,...
4
votes
1answer
192 views

Global Gridded Daily Temperature (at 2m): difference between GEFS Reforcast and NCEP Reanalysis

I am looking for gridded/raster estimates of daily mean temperature (ideally ambient/at 2 meter) for a public health analysis. Specifically, I want to correlate daily mortality counts with daily mean ...
4
votes
1answer
130 views

Best sources / methods to find additional cloud information for current weather conditions?

I posted this question on Aviation Stack Exchange here. One of the responses suggested that I post my question on Earth Science Stack Exchange. I need a source that reports necessary current cloud ...
4
votes
2answers
127 views

Need help understanding variables that relate to meterology terminology

I am working on a project in predicting the weather and I had a few brief questions. I understand that radar works by bouncing waves off of precipitation and measuring reflectivity. I have a variable ...
4
votes
0answers
47 views

What software for cloud motion forecasting

I have a large sequence of images in .png (10 second resolution) from sky image system. Is there any inexpensive software for processing images and forecasting cloud motion? I have found out that ...