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Staff photo by Don Himsel


A lonesome looking snowball occupies a spot in a grassy field at the Lange home on South Merrimack Road in Hollis Friday, February 3 2012. The snowball was once about 4 feet in diameter, said Jeff Lange, and was destined to be part of a snowman built by two of his daughters, Hunter and Raven. It was rolled during the last snowstorm, one of only a few cases of snowfall this season.
Saturday, February 4, 2012

January: Mild, dry, with snow below normal

Doug Webster

Winter continued to vacation in Alaska during January, likely pleasing most people, since heating and snow-removal bills were lower than expected.

Few daily commutes have been snow- and ice-filled, and schools have had few days worthy of cancellation since October.

As is always the case while one part of the globe is mild and dry, another is cold and wet. Alaska is suffering through one of the most severe winters on record. Record snows have fallen through southern Alaska, totaling 105 inches at Valdez, and temperatures through the interior have averaged as much as 25 degrees below normal, setting all-time records for January. Valdez has seen 257 inches of snow since Dec. 1.

After Europe and parts of the U.S. suffered through severe winters during the last two years, it’s our turn for a respite. That’s the way weather and climate works around our planet, and it has always been that way.

Extremes averaged together make up the normal values that you see on TV or in the paper each day. Nearly unheard of is a month that’s right at normal values for rain, snow or temperature. Much more normal is to be above or below normal by some moderate value.

La Nina, the cold episode in the tropical Pacific, continues to make its mark on the nation. The winter is actually going much like it should given a moderate La Nina without the high-latitude high-pressure blocks of the last two winters. Helping out is the Madden Julian Oscillation (MJO) position through the Maritime Continent.

The details of what La Nina, the NAO, MJO and many other large-scale climate indices are and how they affect our weather are too great to explain here, but a wealth of information can be found from the Climate Prediction Center at www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/climwx.shtml.

The last two winters would probably have taken on more of the characteristics of this winter if the blocking across Greenland hadn’t developed. Again, a block is a high-pressure area stuck for a time in a region where the jet stream would normally flow, much like a large stone in a stream.

The jet stream is then deflected around the high to more southerly latitudes much like the water being deflected around the stone. In the case of the jet stream, it can bring cold air farther south than normal and bring a series of storms. Nearly absent this winter are the classic nor’easters, or coastal storms.

So far this year, the big storms have been across the North Pacific, affecting southern and western Alaska. The jet stream has been for the most part staying across the northern U.S. and Canada and moving in a west-to-east fashion, not in a big ridge and trough pattern that can bring cold south and help ignite storms.

The reason it has been so mild everywhere is that Pacific air has been moving from west to east across the U.S., with any shots of polar air brief and with less punch than normal. Air coming from the North Pacific during the winter is generally quite mild for the U.S.

The lack of storms has a lot to do with why we’ve seen below-normal snow during the last couple of months. We have seen some snow at times – in fact, on 13 days during January – but most storms were weak and moisture-starved. The one larger storm during late January was mainly rain across southern New Hampshire but deposited a moderate snowfall for ski country.

Nature works in extreme ways, and we’re enjoying the pendulum swing onto the mild, dry side so far, but it can and will go the other way at some point down the road, whether it’s later this winter, next winter or two years from now.

During the snow season of 1994-95, a mere 22 inches fell on Nashua. The next winter, the all-time record of 112 inches was recorded.

I can find plenty of similar examples of large changes from year to year with snow, rain, and temperature throughout Nashua’s weather history dating to 1884.

While it seems like we’re having a record mild and low snow winter, we aren’t near record levels. The average January temperature of 28.4 degrees is more than 6 degrees below the record set in 1913. We’ve had several very snowy and fairly cold winters recently, and when you go from huge snow piles to nearly none, the contrast is great.

Temperatures in the Gate City averaged 5.7 degrees above normal during January, and that brought us the 14th-mildest January since 1885. That means we have a milder January than we saw this year about every 10 years.

We only have to go back five years to find a January when only 1.8 inches of snow fell and temperature were more than 2 degrees milder than this year. The snowfall total of 5.9 inches was 10.6 inches below normal and was the 14th least snowy January since 1884. Last year, we had a surplus of 20.6 inches during January.

For the season, we’re just shy of 20 inches thanks to the October storms. While that’s light, we’re already above any record low total for a season, with a few more months of potential to see snowfall.

Precipitation totaled 2.89 inches last month, a deficit of 0.53 inches, making January the 56th driest on record.

While winter weather remains scarce around these parts, severe cold has arrived across parts of Europe during the last days of January. Alaska is also undergoing a strong warming trend and there are other signals that point to a possible temporary break in our mild winter pattern by the middle of February. Stay tuned.

Weather & Climate appears the first or second Saturday of each month, depending on when final weather data are available. Doug Webster of Hudson is senior meteorologist at Telvent DTN in Woburn, Mass.