Sept. 16 (Bloomberg) -- The winter of 2011-2012 will probably be colder than normal for much of the northern U.S., although a repeat of the worst of last year’s East Coast snowstorms is unlikely, forecasters said.
A cooling in the Pacific Ocean known as La Nina is predicted to return this year, joined by another season of frigid Arctic blasts caused by pressure differentials over the North Pole and northern Atlantic Ocean.
“We’re looking at a cold start to the winter with maybe a mild finish,” said Matt Rogers, president of Commodity Weather Group LLC in Bethesda, Maryland.
Forecasters are predicting the coldest weather from the Great Plains to the Great Lakes, along with heavy snows across the northern tier. Cold weather is likely to increase demand for heating and power-plant fuels.
The coming winter may be colder than both the 30- and 10-year averages, increasing heating demand, said Travis Hartman, a meteorologist at MDA EarthSat Weather in Gaithersburg, Maryland. Nov. 1 to March 31 will probably be 7 percent colder than the 10-year norm and 1.3 percent colder than last year, Rogers said.
New York City may be hit by several snowstorms, according to Hartman. He doesn’t expect a repeat of the past two years, when snow records fell in Central Park and some city streets were unplowed for days.
“As far as calling for another blockbuster year, we’re not there,” Hartman said.
The upper Great Plains, Great Lakes and Midwest may see another year of heavy snow, he said. When the snow pack from the winter of 2010-2011 melted, it caused record flooding along the Ohio, Mississippi and Missouri rivers as far south as Louisiana.
Hartman said that depending on how fast and when the snow melts, more flooding may be in store in the first half of 2012.
The coldest area may be the northern Great Plains, Midwest and Great Lakes region, said Paul Pastelok, a meteorologist at AccuWeather Inc. in State College, Pennsylvania. The Northeast probably won’t be as cold or snowy as last year, he said.
The U.S. Climate Prediction Center’s latest forecast for January to March 2012 calls for most of the U.S. to have seasonal temperatures, with about a 50 percent chance the upper Plains and Great Lakes will be below normal.
“It’s not too much outside the normal winter outlook,” said Eric Bickel, a commodity analyst at Summit Energy Services Inc. in Louisville, Kentucky. He said his company relies on the CPC and other government forecasts.
Bickel said natural gas production remains strong along with inventories. When the heating season starts, there should be “a good cushion” built up, he said. Power plants use about 30 percent of the nation’s gas supplies, according to the Energy Department.
MDA has developed an index of heating degree days to measure the severity of winter made up of information from 200 weather stations across the U.S. The data is weighted according to historical natural gas usage from December to February.
The value projected for this year is 2,725, Hartman said. The 30-year average value is 2,619.3 and the 10-year average is 2,617.57.
This season’s MDA number has an extra day because 2012 is a leap year, Hartman said.
Heating degree days value is derived by subtracting the average daily temperature from a base of 65 degrees Fahrenheit (18.3 Celsius) and is designed to show energy demand. The higher the value, the cooler the weather, and thus the more energy probably being used to heat homes and business.
Rogers said he’s confident the start of winter will be colder because when there are back-to-back La Ninas, as in 2010 and 2011, the second one tends to bring lower temperatures to the U.S.
On average, La Ninas occur every three to five years and last from nine to 12 months. Last year’s La Nina was a contributor to record flooding in Australia, the persistent Texas drought and an above-average Atlantic hurricane season.
Forecasters are also watching to see if low pressure develops over the North Pole, a pattern called the negative phase of the Arctic Oscillation. When this happens, cold air is pushed down into the temperate regions of North America, Europe and Asia and the pole is warmer than normal.
It can also cause blocks that disrupt the normal flow of the atmosphere. If the blocking occurs off the East Coast, then New York, New England and the mid-Atlantic may see a lot of snow, Pastelok said. If it is further west, the Midwest, Great Lakes and upper Great Plains will bear winter’s brunt, he said.
Hartman and Pastelok believe this will happen because the Arctic ice cap is shrinking. The sea ice has fallen to its second-lowest amount since 1979, when satellites started tracking it, the U.S. National Snow and Ice Data Center said yesterday.
Rogers said that while he doesn’t subscribe to the sea ice theory, he forecasts the blocking will occur because of cyclical variation.
Since the mid-1970s, the Arctic Oscillation has been positive, meaning warmer winters for the temperate regions in the Northern Hemisphere. In the past two winters, however, there have been major negative episodes which have resulted in record snowfalls. Last winter, 49 of the 50 U.S. states, all except Florida, had some snow cover.
If major snows develop this year, they may bring colder temperatures as well, said Pastelok. A large snowpack chills the air and creates a “feedback” in which cold brings snow that brings more cold, he said.
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