Are computers used in weather forecasting?

Posted on August 21, 2023 by WeatherGuys Editor
Twin supercomputers Dogwood (pictured here) and Cactus are the newest additions to NOAA’s weather and climate operational supercomputing system. Located in Manassas, Virginia, and Phoenix, Arizona, respectively, each supercomputer operates at a speed of 12.1 petaflops — three times faster than NOAA’s former system. (Image credit: General Dynamics Information Technology (GDIT))

Weather forecasting is a challenging and fascinating aspect of meteorology. An accurate forecast requires a thorough knowledge of all the variables of the atmosphere. There are also conservation principles of momentum, mass, energy and moisture, combined with the ideal gas law from chemistry that forecasters must consider.

The physical principles are represented as equations, and with current weather conditions, are used to solve for variables meteorologists care about — wind, temperature and precipitation. Computers are used in numerical weather prediction to solve these mathematical models to predict the weather based on current weather conditions.

A numerical forecast is only as accurate as the observations that go into the forecast at the beginning of its model run, referred to as “initial conditions.” Weather moves from one place to another rapidly; tomorrow’s weather is influenced by today’s weather far upstream. For this reason, forecasters must have lots of data worldwide. Large data storage enables better model initiation.

The National Weather Service uses supercomputers to produce weather forecasts, watches, warnings and a whole host of data for the public. These computers run sophisticated computer programs, called numerical models, to create forecasts used by the private sector and the public.

The U.S. Department of Commerce and the National Oceanic and Atmospheric Administration, or NOAA, have recently expanded the capacity of their Weather and Climate Operational Supercomputing System by 20%. The increased computing power and data storage helps improve weather prediction.

The supercomputing capacity supporting NOAA’s new operational prediction and research enables about 42 quadrillion operations per second. This faster computing allows NOAA to run more complex forecast models, while increased storage space enables more data to be used and assimilated into the system. The increased computing power and storage will help to improve weather forecasts for years to come and enable weather prediction advances.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu

Category: Climate, Meteorology

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Do birds get struck by lightning?

Posted on August 14, 2023 by WeatherGuys Editor

Lightning over Madison Wisconsin in July 2016. Photographer: Chris Niendorf

Yes, birds do get struck by lightning, although it’s not very common. When birds are flying during a storm, they are exposed to lightning strikes and thus can get hit directly.

Birds will typically avoid flying in a thunderstorm. They prefer to find hiding spots, such as in bushes, trees and tall grasses. If a bird is waiting out a storm in a tree and the tree gets struck by lightning, the bird likely will die. If struck, an electric charge will be carried along the tree and electrocute any birds sitting in it.

Recently, there were photographs on social media showing several dead birds around the base of a tree after a recent thunderstorm in the Madison area. It is likely the birds were in the tree when it got struck by lightning.

Lightning poses an ongoing threat to all living beings, including humans. Lightning tends to strike the tallest object in an area, and in many cases that is a tree. The physical flash you see strikes a point, but the lightning is radiating out from that point as a current and can be deadly.

Standing under a tree in a lightning storm is extremely dangerous, especially under an isolated tree. When lightning strikes a tree, the charge doesn’t penetrate deep into the ground but spreads out along the ground surface in a ground current that can lead to injuries and death for those beneath the tree.

While standing under a tree in a lightning storm is extremely dangerous, according to National Oceanic and Atmospheric Administration records, most people who died from lightning strikes were hit while out in the open.

There is no completely safe place outside in a thunderstorm. The best thing to do is to get inside a safe building or vehicle.

“When thunder roars, go indoors!”

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Meteorology, Severe Weather

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What are the trade winds?

Posted on August 7, 2023 by WeatherGuys Editor

On the morning of August 3, 1492, Christopher Columbus set sail on his first voyage to the Americas. He sailed south along the west coast of Africa, searching for the easterly “trade winds,” discovered earlier by the Portuguese, that would propel his fleet westward toward what he thought was India.

The trade winds are created by a cycle of warm, moist air rising near the equator. The air eventually cools and sinks a bit further north in the tropics. This phenomenon is called the Hadley cell. (Image credit: NASA/JPL-Caltech)

The trade winds are a component of a global-scale tropical circulation feature known as the Hadley cell. This cell is driven by the fact that the equator is heated more intensely than latitudes to its north and south, resulting in the production of collections of thunderstorms girdling the globe roughly along the equator.

The rising air that fuels these thunderstorms spreads out at the tropopause (about nine miles high) and heads both north and south. Cooling at the cloud tops of this poleward-directed air forces it to sink at about 25 degrees latitude on either side of the equator. The sinking air that reaches the surface in the Northern Hemisphere heads southward toward the equator in a huge vertical circulation cell. The rotation of the Earth, and the resulting Coriolis force, turns this southward moving air to its right, creating the near surface trade winds.

Though known by mariners for centuries, it was not until 1735 that George Hadley proposed this explanation for the trade winds. It was not until the 1950s, amazingly, that observational evidence provided by balloon soundings of the atmosphere finally confirmed the veracity of Hadley’s conjecture.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Meteorology, Phenomena, Tropical

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Why are cities hotter than the surrounding rural areas?

Posted on July 31, 2023 by WeatherGuys Editor

On average, the city is warmer than the countryside. This difference in temperature is referred to as the urban heat island effect. A number of factors contribute to the relative warmth of cities, such as heat from industrial activity, the thermal properties of buildings and the evaporation of water.

The architecture of cities intensifies Urban Heat Island effect and the absence of vegetation reduces evaporative cooling. (Image credit: CIMSS, UW-Madison)

For example, the heat produced by heating and cooling city buildings, and running planes, trains, buses and automobiles contributes to the warmer city temperatures. Heat generated by these objects eventually makes its way into the atmosphere, adding as much as one-third of the heat received from solar energy.

The thermal properties of buildings and roads are also important in defining the urban heat island. Asphalt, brick and concrete retain heat better than do natural surfaces. Buildings, roads and other structures add heat to the air throughout the night and, thus, reduce the nighttime cooling of the air so that the maximum temperature difference between the city and surroundings occurs during the night. The canyon shape of the tall buildings and the narrow space between them magnifies the longwave energy gains. During the day, solar energy is trapped by multiple reflections off the many closely spaced, tall buildings, reducing heat losses by longwave radiation.

The urban heat effect of Chicago and other smaller cities is readily apparent in this enhanced IR satellite image. (Credit: CIMSS)

Evaporation of water may also play a role in defining the magnitude of the urban heat island. During the day, the solar energy absorbed near the ground in rural areas evaporates water from the vegetation and soil. Thus, although there is a net energy gain from the sun, heating is reduced to some degree by evaporative cooling during evapotranspiration. In cities, where there is less vegetation, the buildings, streets and sidewalks absorb the majority of solar energy input and warm up rapidly.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, Meteorology, Seasons

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Can ChatGPT forecast the weather?

Posted on July 24, 2023 by WeatherGuys Editor

Yes, ChatGPT can create weather forecasts, but the real question will be their accuracy.

Hurricane specialists at NOAA study satellite imagery and computer models to make their forecasts. (Photo credit: Mike Mascaro, NOAA)

People have started exploring how to use ChatGPT and other artificial intelligence methods to experiment with forecasts. This is not surprising as we have always needed weather forecasts and humans have used many techniques over the decades. Some of the earliest forms of forecasts were short rhymes, and, although memorable, were often of uneven quality.

Forecasts improved as weather observations became more available and consistent. A statistical forecast uses historical data to project what future weather could be based on what happened in the past with similar conditions. A trend forecast assumes that weather will change based on the movement and approach of current weather features. A trend forecast assumes that although the weather features are moving, they are not otherwise changing. Numerical weather prediction is a basis for today’s modern forecasts, which use mathematical models to predict the weather based on current weather conditions.

ChatGPT, or any AI approach, can forecast weather patterns that are statistically plausible given previous events. AI methods are being developed and applied to radar observations for short-term forecasting of precipitation. Observations of high-quality weather radar are freely available across the U.S. An AI adoption of a trend forecast to radar observations has the potential to account for changing speed, size, intensity, and direction of movement of the storm.

Given the capability of AI to handle large data volumes, upcoming AI weather forecasts are likely to combine numerical weather predictions with current and recent weather observations to make a forecast.

There are risks in relying on AI forecasts. All AI models require data training sets. Those data records might not include extreme events. AI systems can be unpredictable when the existing conditions have never, or rarely, been encountered.

AI weather forecasting requires the same constraints as all forecasts — accurate and consistent observations.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at 11:45 a.m. the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: History, Meteorology

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