The Mountain Times

After a balmy January, is cool air on the way?

Editors note: This article was first published in the Sarasota Herald-Tribune on Feb. 2. Since then the scientists predictions have proven true. It was brought to our attention by avid reader of The Mountain Times, who thought our audience might also enjoy the read as Vermont's economy is so closely tied with weather patterns. It is being rerun here with full permissions.

If February turns chilly in Southwest Florida as some forecasters predict, the catalyst may be in Siberia.

A new scientific study links the rapid expansion of October snow in Eurasia to later cold weather outbreaks in the eastern U.S. and western Europe.

If the scientists are right, forecasters will be able to use that October snow rate to predict important weather patterns that influence winter temperatures here and across the globe.

Knowing how the winter is likely to unfold months in advance is important for farmers, energy companies, the tourism industry and other businesses that need to plan for changes in the weather.

In Florida, for example, farmers need a heavy supply of water and equipment to protect crops, such as strawberries and oranges, from unusual blasts of freezing weather.

With new forecasts for cooler weather next week, the link appears to be holding up this winter.

Snow spread slowly in Eurasia during most of October, but rapidly expanded late in the month, producing an average snow rate overall. If the next few weeks are colder, the temperature average for the winter also would hit the normal mark.

"I would say things are going pretty well over this winter. It's not over yet," Judah Cohen, lead author of the study and director of seasonal forecasting for Atmospheric and Environmental Research, a Verisk Analytics company, said of the research.

The study was presented last week at the American Meteorological Society meeting in New Orleans.

The weather pattern that has the biggest influence on winter temperatures for the eastern U.S. coast is called the Arctic Oscillation. In one phase, Arctic air escapes south, sending blasts of frigid weather to unlikely places, such as Florida.

Some scientists, including Cohen, think those cold blasts are connected to the pace of Euasian snowfall, though most of their colleagues currently believe the pattern is random.

If the relationship is even half as good as his research suggests, it would bring tremendous improvements to winter forecasting.

One Arctic Oscillation pattern is called "negative" and another "positive." It was negative at the beginning of last winter and in mid-winter two years ago, making for record-breaking cold across the state.

This year the opposite trend held through December and most of January, helping to make this winter warmer than normal.

But 10 days ago, the pattern reversed, from positive to negative -- and it's expected to stay that way for the next couple of weeks, said Dan Collins, a research meteorologist with the National Oceanic and Atmospheric Administration's Climate Prediction Center.

Starting around Feb. 8, he said, temperatures are forecast to begin sliding a few degrees below normal throughout the east coast and Florida.

For the Sarasota area, that would mean daytime highs in the upper 60s and nights in the high 40s. It is too early for a precise short-term forecast and the official National Weather Service forecast does not reflect the climate center's prediction.

Collins noted that other weather patterns could potentially override the shift in the Arctic Oscillation, keeping temperatures from significantly dropping.

The scientists think the link between the Arctic Oscillation and snow in Eurasia is due to the way snow affects temperature and other weather conditions there.

"We're looking at how the snow influences the surface and how the surface influences the overlying atmosphere," said Justin Jones, a scientist who worked on the research with Cohen.

How fast snow accumulates over Eurasia in October has a greater influence on the Arctic winter weather pattern than just the expanse of snow, the study showed. Jones and Cohen said they are still trying to figure out the reason for that stronger tie.

In general, they said greater snowfall cools the surface and creates high pressure in the atmosphere. The high pressure interferes with the normal circulation of air over the North Pole, a situation Cohen likened to a boulder in a river affecting streamflow.

The change over the pole forces currents in the atmosphere to send Arctic air southward instead of eastward.

Other studies have linked the Arctic Oscillation's negative phase to low Arctic sea ice in the fall, which might be related to expanding snow cover over Eurasia, Cohen said. Less Arctic ice creates warming, which allows the atmosphere to absorb more moisture. That additional moisture falls from the sky as snow.

Meteorologists with the Climate Prediction Center are working with Cohen to see if his research can help improve official forecasts, Collins said.

"It's not always easy to take a research finding and translate that to information that contributes to the skill of a forecast," Collins said.

Cohen said that coming up with a measurement that appears to make an accurate forecast on paper does not always work when the measurement is used to make a forecast in reality.

"I'm not going to declare victory after one winter," Cohen said.

Copyright 2012, Sarasota Herald-Tribune. Reprinted by express permission of the Sarasota Herald-Tribune

Publication Date: 02/02/2012

Tagged: winter, weather