Could Arizona tragedy been prevented?

PositionWildfires

Meteorologists are using a sophisticated forecasting model to better understand the weather conditions that played into the tragic events that claimed the lives of 19 firefighters battling the Yarnell Hill Fire southwest of Prescott, Ariz., in June. University of Arizona. Tucson. is home to one of only a handful of atmospheric science departments in the country that runs a forecasting model in real time, just like the National Weather Service. This Weather Research and Forecast Model, or WRF, offers about five to 10 times more detail than what is commonly available to the National Weather Service, and it is the only one of its kind in the Southwest.

The data showed 19 mph winds from the southwest, with gusts up to 22 mph--nothing too unusual but, at some point between 4 p.m. and 5 p.m., around the time the firefighters went into the area that would become a death trap, winds shifted rapidly to the opposite direction and doubled in speed.

"Thunderstorms had built UP that day north of the area. and they were moving south and toward the fire," recounts Michael Leuthold. a meteorologist and computer specialist in the Department of Atmospheric Sciences. "Typically when they start moving down into the low deserts, they die off but, while they do, they send out strong outflows, and those are columns of rain-cooled. denser air that flows out of a decaying thunderstorm. Those flows hit the ground and spread horizontally. In general, those downdrafts are relatively benign, but they can also come in violent microbursts, and that may have been what happened in this case."

After piecing together the meteorological conditions surrounding the event Leuthold wanted to see whether the model was able to forecast the dramatic weather events that were observed and contributed to the danger of the situation.

"We took the model run from Sunday morning and checked if it would have forecast the wind speed, sudden shift in direction, the location and the timing over a 12-hour forecast period. To generate a forecast, the model relies on a flurry of data fed into it from weather stations, oceanic sensors and weather balloons, among other sources.

"Our model generates a three-dimensional grid of the atmosphere with parameters like temperature, relative humidity, wind speed, air pressure, and...

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