Weather

Just how unusual is the lack of cold and snow this month?

After more wet—not white—weather Thursday, it’s still mild. While we needed the rain (estimated amounts below), you may be asking why it is still so darn warm in the middle of December. Has something gone terribly wrong with the jet stream? Is this a sign of a new normal? Is this what climate change looks like?

rainfall estimates.png

We have pretty short memories, but last winter brought one of the snowiest, coldest periods in the record books, yet December 2014 was also mild without much snow. Snowfall and temperatures in New England are highly variable, and there have been wild swings in each for centuries.

Around Boston, Decembers 2003, 2007, 2008 and 2010 all had more than 20 inches of snow, which is at least double the average. Two years ago, there was nearly a foot of snow in December, so the lack of snow the past two years is completely within the highly variable nature of snowfall here.

A warm and snowless December isn’t good for many businesses, but it’s great to be able to drive around on bare pavement, save money on heating costs and not have a need to spend time or physical labor clearing the snow.


Cold Won’t Stick
It’s going to become temporarily colder this weekend before another blast of warm air arrives next week. Christmas Eve might see readings in the 60s and there is a chance some records could be set. The warmest Christmas Eve recorded was back in 1996 when Logan Airport recorded a balmy 61 degrees. There’s a very good chance we will break that record. The warmest Christmas on the record books is way back in 1889 when reached 65 degrees, but I’m not sure we’ll break that one.

Advertisement:

More Than El Nino
El Nino is certainly a major player in this month’s warmth, but it’s also other factors such as the polar vortex spinning around so fast, it’s not letting the cold air slip south. The map below shows snow cover as of this morning. The jet stream, which carries storms and moves air masses, has been positioned in such a manner as to keep the snow and cold out west and leave the eastern part of the United States warm. This means that any storms that do approach are in the form of rain and not snow.
 

trough ridge pattern.png

 

Post-Christmas Remains Mild
Take a look at the map below which is valid just after Christmas. This map, courtesy of Tropical Tidbits, shows how much temperatures are forecast to be above average.

ecmwf-ens_T850a_us_11.png

Notice the pattern of cold and warmth is similar to how the jet stream has been flowing all month. In other words, no changes yet. As we enter January there will be more pressure on the pattern to flip to a colder one, however it may take much of that month for winter to set in and by then we might be into the second half of the season. I’ll have more this unusual pattern and how climate change may or may not be playing a role next week.