Forecasters face challenges

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PITTSFIELD -- Asked to name her biggest professional challenge, National Weather Service meteorologist Kimberly McMahon is quick to answer.

She's also specific.

"Definitely, mixed-precipitation weather events involving snow, freezing rain, or a transition to rain, and how long it will last," said McMahon, a Pittsfield resident.

Predicting snow amounts is high on the list of priorities, complicated by the vast territory her Albany, N.Y., office covers -- 19 counties in four states, from the Adirondacks south through Saratoga, the Capital District, the Hudson Valley, the Catskills, southern Vermont, the Berkshires, and northwest Connecticut.

The big concern as this snowy winter begins to wind down is the threat of severe flooding -- McMahon said National Weather Service (NWS) hydrologists are carefully monitoring ice and snow buildups on frozen rivers and streams. The most worrisome concern is a heavy rainstorm combined with snowpack melt accelerated by temperatures above freezing.

"I tried to measure the snow depth the other day," McMahon said, "and it was so hard because there are so many layers of ice."

Pinpointing intense summer thunderstorms and potential tornadoes is another major challenge, but the effort involves the entire staff in the Albany office, in conjunction with nearby NWS centers in Boston, Hartford, Binghamton, N.Y., and Burlington, Vt.

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The national Storm Prediction Center in Norman, Okla., issues regional severe-weather watches, and local offices then issue specific warnings once storms develop and are tracked on radar and ultra-high-tech software developed specifically for the government meteorologists.

But McMahon acknowledged that high tech can be a mixed blessing. There are so many weather-prediction computer models that forecasters have to make informed judgments on which ones are most likely to be accurate, since they often disagree days ahead on the track of major storms.

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"The system is highly variable; the models have so many solutions," she said.

"There's so much to look at. It's good and bad in its own way, and it's great to have a lot of variety, but when they're all diverging, we know not to get excited right away. We don't jump the gun, and we need to be more cautious to try to figure out what's going on. Yes, it's sometimes frustrating."

She noted that early this winter, the computers tended to be more in sync, but by mid-January they started conflicting, creating a headache for meteorologists.

"You have to go through as much data as you possibly can to get a firm understanding of what each model is trying to say," McMahon emphasized. "You do your best with what you've learned in school and from experience."

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Forecasters know that some computer models are more trustworthy at certain times of the year, while others do well for weeks and suddenly lose their mojo.

In the end, accurate prediction requires a combination of art and science, as meteorologists refine forecasts by interpreting the vast array of the constantly updated flood of information.

"Interpreting all the data is an art form in itself," McMahon said.

And she acknowledged there have been no easy answers for the severity of this season.

Forecasters cite the jet stream dipping into the Deep South, funneling cold air into areas that normally have only moderate winter chill, and then curving northward along the Atlantic seaboard, serving as a conveyor belt for storms caused by the clash between Arctic air and sub-tropical warmth.

Researchers will long be studying the causes of what people are calling the Wicked Winter of 2010-11.


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