December 2018: Sunny, mild and dry; little snow
December broke ranks with fall as temperatures turned mild, plenty of sun returned, and rain and snow diminished. El Nino continued to be the reason behind the noted change from fall to our first month of winter. One could almost make the argument that December and November traded places this year.
After seeing the wettest fall on record Nashua residents saw below normal amounts of precipitation during December. El Nino continued its’ active pattern across the South but as the polar jet grew stronger these storms began to be deflected to our south, something expected during a moderate El Nino.
Every so often we do see the subtropical and polar jet streams link up and that’s when we see stormy weather. For December that happened just three times with most of the other weather systems weak and moisture starved due to their association with the polar jet stream.
After a record wet fall and November Nashua saw below normal precipitation for the final month of 2018. The gauge at Pennichuck Water Works measured 2.60 inches for December, 1.31 inches below normal. December was the 32nd driest out of 135 years of record.
The persistent cold of the late fall came to close by mid-December as the cold air making machine across Canada became disrupted by El Nino. Pacific air began to flow into interior North America boosting temperatures and taking away the bitterness of the source for cold air heading into the U.S.
Cold air has been lingering through eastern-most Canada during the past weeks and months and was why we did see some pretty cold weather during the first half of December. Temperatures averaged 12 degrees below normal on December 12 before we saw a temperature rebound.
Cold was more persistent across far northern New England and Maine where Caribou saw December readings average 2 degrees colder than normal.
We will have to occasionally watch for quick bursts of cold out of eastern Canada during the remainder of the winter despite an expected milder than average pattern overall.
Across southern and central New England temperatures rebounded smartly during the second half of December. Temperatures averaged above normal on all but one day after the 15th, peaking at 23 degrees above normal on the 22nd.
Temperatures for Nashua during December averaged at 30.9 degrees, 1.8 degrees above normal, ranking as the 23rd mildest December out of 124 years of record. One record high was recorded on the 22nd when the mercury reached 64 degrees bettering the mark of 61 from 1990.
Nearly no snow fell around the Nashua area during December. A trace was all that was noted at the Pennichuck Water Works location with other local sites seeing just a few tenths of an inch. For Nashua the trace ties for the 2nd least snow for December with 3 other years, 2011, 1941, and 1899. No snow was recorded during December 1999.
After a snowy start to the season we seem to have gotten into a rut with respect to snowfall but anyone who has lived in these parts knows that things can change radically during a given winter and like last year even during spring. Nashua’s season snow tally of 7.9 inches is only 5.8 inches below normal, something a moderate snowfall can wipe out in a few hours.
Very little snow fell all the way through the middle of January 4 seasons ago and we ended up with the 5th snowiest winter season on record. That is merely an observation, not a forecast. Snowfall does not fall in a linear fashion during most years but rather in fits and starts.
I also have in the back of my mind the fact that we are much overdue for a few, maybe several winters with little snow. The past 25 years have seen a major upswing in snowfall amounts across the Northeast, nearly 7 inches per season for Nashua. During the past decade Boston has seen snow average 14.6 inches above the long term average.
Long stretches of bare ground and only a couple of moderate snowfalls were pretty much the norm during many winters during the late 1970s and 1980s, 1940s and early 1950s as well as during the 1900s into the early 1910s.
Christmas was a brown one this year at Nashua, not at all an unusual occurrence. Data dating back more than a century shows little change in the 58 percent average occurrence of a white Christmas for Nashua.
The sun made a return during December. While the final tally is not yet in from the Blue Hill Observatory it appears December will see possible sunshine average around 10 percent above normal.
The climate summary for 2018 tells us that we saw a mild, wet, and snowy year.
Bitter cold began the year followed by record warmth in February and record snow in March. Dry weather took hold during the late spring and early summer followed by record wetness along with cool temperatures during the fall. Summer was very warm and very humid.
The annual average temperature for 2018 was 49.3 degrees, 1.8 degrees above normal and the 12th warmest out of 123 years of record. The Gate City saw its’ 5th wettest year of record with 57.54 inches, 9.57 inches above normal. Snowfall for the annual period totaled 74.2 inches, 19.3 inches above normal.
January can bring many extremes from severe cold to the classic January Thaw. Big storms of rain and snow are always possible during the core of winter as cold and warm clash.
El Nino should continue to tame winter some but that doesn’t mean a couple of sizable snowfalls can’t still happen. Cold weather should be brief in nature for the remainder of the winter, but not absent. We will still see some of the roller coaster weather that is completely normal for our region.
Like the changeable weather in the short term our long-term climate going back millions of years tells us that climate change is normal, not something that can be politicized.