Expect A Mild Winter, But Not Like Last Year

//
NOAA CPC's three month climate outlook map for Dec. 2012 through Feb. 2013. CREDIT: NOAA National Weather Service Climate Prediction Center

Much of the United States enjoyed a warm start to December, but

meteorologists agree there is little probability of another winter as

balmy as last year's.

“Last year was an extreme,” Mike Halpert,

deputy director of the National Oceanic and Atmospheric Administration’s

Climate Prediction Center (CPC), told Discovery News. “This year,

although the U.S. is favored to see above average temperatures in some

areas, Florida and parts of the Upper Midwest have probabilities leaning

towards cooler than average weather.”

PHOTOS: Top 10 Worst Weather Disasters

The CPC produced a set of three month outlook maps

that show a probability of warm winter temperatures centered at first

in the Four Corners region of the Southwest and gradually spreading

east. By April much of the U.S. east of the Rocky Mountains is forecast

to have above average temperatures. The north coast of Alaska may also be milder than average.

However, Halpert noted that

long-term forecasts are based on probabilities, not certainties, and that averages can represent the middle ground between two extremes, not actual temperatures.

“While

the consensus of many computer forecasts point to a milder than average

winter, centered over the southern Plains, it is unlikely that it will

be as mild as 2011-12 winter since the factors that govern seasonal

weather are arranged differently as we approach winter,” Paul Knight,

meteorologist at Penn State and Pennsylvania State Climatologist, told

Discovery News.

VIDEO: Monitoring Climate Change

ANALYSIS: Mild Winter = Hot Summer? Not Exactly

One factor that changed this year were the atmospheric circulation patterns in the Arctic, noted Knight.

“The

center of chilliest air, which last winter oscillated between northeast

Siberia and Alaska, seemed to be split this year with one cold core in

central Siberia and another in northwest Canada,” said Knight.

That

cold air core in Canada makes it easier for Arctic air to sweep into

the northern section of the U.S., which wasn’t the case last year.

Another

difference this year is the state of the El Nino Southern Oscillation

(ENSO). The La Nina conditions that affected last years’ winter faded

away, but was not replaced by an El Nino. When the ENSO is in a neutral

state as it is now, forecasting can become more difficult. Instead of an

800 pound gorilla in the room, there are numerous 300-pounders, and

there is no easy way to know which atmospheric ape will be the top

banana as the season progresses.

“The El Niño cycle will likely

play little role in this year’s winter,” Halpert said. “That adds

another layer of uncertainty, because it removes the influence of a

major force in global climate patterns.  On a global scale we can

generally forecast what El Niño or La Niña will do, but without their

overpowering influence there are many other phenomena which can affect

winter weather in ways that are harder to predict.”

Precipitation is forecast by the CPC maps as "equal chances"

for most of the U.S. this winter. Equal chances means that anything is possible, above, near, or below average

precipitation, explained Halpert. In parts of the South, centered around Tennessee and Kentucky, precipitation may be above average.

NOAA CPC's three month climate outlook map for Feb. 2012 through April 2013. CREDIT: NOAA National Weather Service Climate Prediction Center

A forecast by Accuweather predicted heavy precipitation in the Northeast and Mid-Atlantic. Will yet another intense storm scourge the area lashed by Sandy?

“Accuweather

has a proprietary technique for seasonal forecasts, which we are not

privy to,” said Knight. “Our approach would be a blend of the most

reliable computer seasonal forecasts merged with an analog/statistical

approach. We do not see any useable information in predicting

precipitation a season in advance.”

No matter what happens in the

Northeast, if the center of the nation doesn’t get much rain or snow,

American farmers may have a tough 2013. Farmers depend on winter rains

to moisten the soils for spring planting. Melting ice and snow  also

swell waterways used for irrigation.

BRIEF: What Happens If the Mississippi Runs Dry?

November

brought no relief to a parched country. Besides the aftermath of

Superstorm Sandy, the month was very dry. The U.S. faces the possibility

of a multi-year drought that could seriously reduce agricultural

productivity and halt barge traffic on the Mississippi River.