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Saturday, March 10, 2012

February 2012: Record low snowfall, very mild and very dry

Doug Webster

February was a memorable month from a weather standpoint by having nearly no snow, rain or significant cold.

Normally a month noted for snow and cold, winters’ wrath all but disappeared from central New England.

Those who dislike winter were happy, while winter sports fans were disappointed.

The lack of snow set a record for February, as well as for meteorological winter, but no record will be set for the season snowfall. While temperatures didn’t set a record for last month, we did set a standard for the winter.

The reasons for our nearly lack of winter weather continue to be a combination of several large-scale global weather systems, including La Nina, working together to block cold weather and the main storm track from our region.

Completely absent all winter have been the high-latitude jet stream roadblocks across Greenland that gave us roof-crushing snow and blasts of cold during the last two winters. This year, these upper-air roadblocks have given Europe and Alaska more than their share of snow and cold.

La Nina has been present for three straight years but has produced two cold, snowy seasons followed by a mild winter with little snow. The key to why this winter was so different from the previous two was the lack of a Greenland block, better known by some as a negative NAO.

In case you’re wondering whether we’ve ever had winters similar to this year, the answer is yes. During the early 1930s, early 1950s and late 1980s, there were groups of two or three years with persistently mild temperatures and diminished snow.

The threat that La Nina will return next winter is low, and more likely, we’ll see either a neutral ENSO situation or a weak El Nino. The likely result for us will be a different sort of winter than what we’ve just experienced.

After having above-normal snow for the majority of the past 20 years, could we be seeing a return of the 1980s-type winters during the next few years? Only time will tell.

Not only do La Nina winters tend to produce mild weather across the central and eastern United States, but there is also strong correlation for above-average amounts of severe weather during the spring. We’ve already seen a couple of major episodes of tornado activity through the South and Midwest and there is likely to be more during the next few months.

Locally, snowfall for the season now stands at 32 inches, making the 2011-12 snow season the eighth-least snowy, with still several weeks to go when it can snow.

For the winter, defined as December, January and February, a record for low snowfall was set with only 8.2 inches.

For February, only a trace of snow fell, a record low total, breaking the 0.6-inch value from 1987.

For the record, weather data for National Weather Service Cooperative observing stations, like the one located in Nashua, is kept from 7 a.m.-7 a.m. For that reason, February ended at 7 a.m. on the 29th, leaving the snow that fell later in the day for the March 1 total.

At the state capital, Concord, weather data is kept on a calendar-day basis.

February’s snow total was 13 inches below normal this year, but we saw a surplus of 13 inches last year. That’s why one year of different weather doesn’t make for a trend. For all we know, we may be cold and snowy again next winter.

Temperatures for February were persistently mild, with only one brief shot of Arctic air on Feb. 13. The average temperature for the month of 32.3 was 6.1 degrees above normal, making last month the third-warmest February on record.

No record high temperatures were noted, but we did see 21 days with high temperatures at 40 degrees or higher. Only one day failed to reach 32 last month. The lowest temperature for the month was just 12 degrees during a month when a few nights typically fall below zero.

The average winter temperature of 31.9 degrees was 6.0 degrees above normal, making it the mildest on record for Nashua. The old record of 31.7 degrees was set during the winter of 2001-02.

For New Hampshire, February was the fourth-warmest and the fourth-driest on record since 1895.

Snow wasn’t the only weather phenomenon lacking during February. The rain total of 0.68 inches was 2.68 inches below normal, making last month the second-driest February since 1884. There have only been 22 months that have been drier during the last 128 years.

The winter precipitation total of 7.83 inches was 2.89 inches below normal, making 2011-12 the 16th-driest winter on record.

Astronomical spring, which is March 20 this year, has nothing to do with weather. Temperatures being their upward swing in late January and have already recovered to mid-November levels by March 20.

March is home to some of the most fickle weather of the year. Being abnormal is normal during March. No other month brings more potential extremes.

Midwinter-type blizzards, summer heat, strong winds, bitter cold, spring temperatures, flooding, ice storms, rain storms and, of course, mud season are all possibilities during March.

While meteorological winter may be over, the snow season isn’t, and it can extend into April and in rare cases into May. Current upper-air patterns point to a very mild, if not unusually mild, stretch of weather continuing well into, if not through, March.

It’s hoped we won’t see one of those late-season snows during the middle or end of April after the grass has turned green.

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.