Heatmiser's Revenge

Meteorological winter began on December 1st but thus far mother nature has not gotten the memo in the Eastern US.
NCEP North America 2 m temperature anomaly December to date (image credit Weatherbell)

Temperatures fell to average this weekend but they will rebound to near record warmth for Christmas Eve.  So in the words of Vince Lombardi...what the hell is going on out there?

It could be Heatmiser's revenge for this past January and February.  Rumor has it he is very mad at his brother Snowmiser for the stunt he pulled on Southern New England last winter.
Snowmiser, Heatmiser from The Year Without a Santa Claus
Just as she did in "The Year Without A Santa Claus" Mother Nature may have stepped in to mediate the fight.  She is allowing for some nice spring weather in December for the northeast.

Another theory is that this is simply a boring weather pattern for winter weather lovers.  As you must have heard by now the Pacific Ocean is experiencing an El Nino.   This is among the strongest on record in certain regions of the Pacific.
NOAA OSPO Sea Surface Temperature Anomaly 12.14.15
The Pacific Ocean is really the key player in all global weather patterns.  The Pacific is larger than all of the world's landmasses combined and it has about 46% of the hydrosphere.  So far we have seen a consistent ridge of high pressure in the Northeast Pacific.  That in turn has led to a trough in the Western United States.  That is where the snow is.  That has left a constant ridge in the east.
06z GFS 500 mb vort 1 AM Wednesday (image NCEP)
Using paint I have highlighted the ridges in red, the trough in blue.  This type of configuration means the source of our air mass is from the tropical Pacific Ocean.  There is no snow cover in the Midwest so this air mass is not being moderated either.  As a result we are seeing a potentially record warm December.  Some of these western troughs will try to move east and they will for a few days.  There is nothing to keep them in place however.

The polar jet stream is staying tucked away to the north.  This happened in 2011-12 as well and it never came south.  The Pacific in 2011-12 could not have been more different however.
NOAA/OSPO December 15, 2011 SSTA
Now remember- even though this was a La Nina and Pacific water was cooler than average it is still mild tropical air.  Last year our source region was the Arctic and Siberia.  Water just doesn't heat and cool like the land does.
NOAA/OSPO January 29, 2015 SSTA
A permanent ridge over the NE Pac and Western North America allowed for a deep trough to stay in the Eastern US.  This blocked the Pacific warmth so our source region was from the Arctic and Siberia.  The tropical jet was able to stay active and met up with the polar jet off the East Coast.  The Gulf Stream was able to blow up storm after storm.  This isn't a pattern we are likely to see again.  For snow this winter we need to see several things.
NOAA/OSPO December 15, 2015 SSTA
1.  Need a negative Sea Surface Temperature Anomlay to develop north of Hawaii.  This will prevent the Pacific ridge from being too far west.  A trough further west means the Western US gets a trough and cold and snow.  The East stays warm.

2. The El Nino needs to weaken and back further west.  This will really energize the subtropical jet stream.  If the trough is indeed in the east this sets the stages for Nor'Easters.

3.  Keep the cold pool in the North Atlantic.  This tends to help with blocking which allows for the polar and subtropical jet to phase off the east coast.

Of these 3 factors the first one is least likely to happen.  The big storm in the Bering Sea this past weekend will help but it may not be enough.  El Nino's generally peak in December so that is good for snow lovers.  It may not be far enough west however.  I am not convinced the pattern will flip until the middle of January.  However there have been encouraging signs for those who depend on winter weather for income.   I'll keep an eye on it.  In the meantime I will be posting my top 5 Southern New England weather events of 2015 over the next 2 weeks.  Enjoy the warm Christmas.

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