![]() This reminds me of a storm about 10 years ago that was dubbed a ‘Flurricane’ due to the winds and light snow. The latest model guidance supports that sharp cutoff line near or just east of Baltimore and I-95. If you have read my prior reports, I have been hedging my bets on a sharp cutoff line, with a big bump higher on the Eastern Shore and less farther west. "But a forecast error of 50 miles in the populated Northeast corridor is noticed by a lot of people.This is a brief update since I am behind schedule to post My First Call For Snowfall. "The thing is we were really close," he says. And the edge of this slow-moving Nor'Easter shifted farther north and east than predicted. An intrusion of warm air, about 1,000 feet up, changed expected snowfall into rain or freezing rain. Jon Neese, chief meteorologist with the Franklin Institute of Science in Philadelphia says that's because at least two wild cards entered the weather maps late in the scene early today. Still, Hoke points out that forecasters were mostly accurate in forecasting the storms now pummeling the Northeast and West since they predicted the amount of precipitation, even if they may not have always guessed right how much of each kind would fall. "There are many areas over the oceans where we don't get frequent observations," says McCarthy. An incorrect temperature reading, for example, would not only skew a short-term forecast, it could also significantly alter long-term forecasts.Īnd even though weather services are gleaning more data from sources like airplane instruments, weather balloons, radar and satellites, there are still locations where data are spare. By simplifying equations, they're made less accurate.īad data can also throw off predictions. One reason is some weather equations must be simplified before computers may easily work with them. These instruments record information like wind and air pressure and temperature as they take off and land and relay the readings to national weather stations.ĭespite the improvements, forecasts are never flawless. Nearly all large passenger airplanes, for example, are equipped with automated weather instruments. "The 5-day temperature forecasts we make now have the same accuracy our 3-day forecasts did 20 years ago," says Hoke.ĭata has also gotten better. Today, thanks to more powerful computers that can make up to 140 billion calculations per second, the weather service can calculate weather data using grids only 7-8 miles apart, according to Kevin McCarthy, deputy director of the Hydrometeorological Prediction Center. The smaller the grid size, the more detailed a forecast will be. Once weather is calculated within each piece of the grid, the computers determine how one region will affect weather in neighboring grids. "It's like a giant math problem that's constantly changing," says Ralph Roskies, scientific director for the Pittsburgh Supercomputing Center. These equations, or models, have been devised by generations of meteorologists who have watched the effects of factors like wind direction and strength, barometric pressure, evaporation rates, Earth temperature and temperatures above the Earth. Meteorologists then use powerful computers to crunch numbers within each grid by applying what Hoke calls "the most complicated equations in science." Weather forecasts are made by dividing the atmosphere into a three-dimensional grid and then inserting weather data into each square of the vast grid. And, more commonly, unexpected factors can arise and effectively throw off predictions. Using the wrong weather models can skew predictions. ![]() Weather data, for example, can be inaccurate or patchy. There are a number of possibly misleading factors.
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