Wed, Feb 15, 2012 06:08 PM
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
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
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
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
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
Starting around Feb. 8, he said, temperatures are forecast to begin
sliding a few degrees below normal throughout the east coast and
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
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
Meteorologists with the Climate Prediction Center are working with
Cohen to see if his research can help improve official forecasts,
"It's not always easy to take a research finding and translate that
to information that contributes to the skill of a forecast,"
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
Copyright 2012, Sarasota Herald-Tribune. Reprinted by express
permission of the Sarasota Herald-Tribune
Publication Date: 02/02/2012