More wet, not white, weather is on the way for this evening and overnight and this means you should prepare for a slower homeward commute. While we need the rain, (image 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?

Total Expected Rainfall Through Friday

Total Expected Rainfall Through Friday

We have pretty short memories, but last winter brought one of the snowiest and coldest periods in the record books. December 2014 was also mild without much snow. I’ve written numerous times that snowfall and temperatures in New England are highly variable.

Wild Swings In Snowfall
Around southern Maine, Decembers in the past 15 years have actually been quite snowy. Since 2000, there have been 10 years with average or above average snowfall. December 2012 and December 2013 brought over 2 feet of snow to Portland. The lack of snow the past two Decembers is completely within the typically highly variable nature of snowfall here.

Having 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 1957 when the Jetport in Portland reach 53 degrees. There’s a very good chance we will break that record. The warmest Christmas in the record books is way back in 1888 when Portland recorded a 57 degree reading. In more modern times, last year’s 53 degrees tops the chart. I’m not a sure about that record, because cooler air will arrive Christmas Day and it might get here early enough to prevent a new record from being established.

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 has meant any storms which do approach are in the form of rain and not snow.

trough ridge pattern

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

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.


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