1200 NOV 12 2011
While it may be popular for some to argue that reality is based upon perception— and that certainly is true in politics and public opinion polls— is not true in the world of science. At least not in this sense.
The last two winters have been pretty impressive over much of the central and eastern U.S. And given the number of winter forecasts which believe that this winter will be the same kind of winter as what we experience in 2009-10 and 2010-11… there is strong tendency for some to forget HOW we got to those winters and what the Novembers were like.
Now with regard to November of 2009… wll that was just a nasty cold Autumn and there arw no two ways to get around. However most of the time most people make this specious connection about d October and November weather patterns and Winter. This is especially true for cold and stormy Octobers and Novembers . Often times even though the pattern appears to be promising for winter weather lovers based upon those two months… there are many many cases where the pattern breaks down as we move into winter or the middle of the winter .
In other words it becomes very difficult– and it is NOT typical –for a cold & stormy pattern to last from say November to March. This applies to whether you are dealing with the West Coast the Plains the Midwest or the East Coast. When you do get a prolonged cold stormy pattern that lasts for that ALL of the Winter …or most of it… well THAT is what defines a “Historic Winter”.
For example last winter the cold and stormy pattern broke down in February of 2011 … so I would NOT call the winter of 2010-11 “a historic winter”. However I would call the winter of 2009-10 a historic winter. The same definition also applies and defines WHY we remember the great winter’s of 1976-77 1977-78 and 1978-79 as well as the winter of say 1960-61 1962-63 and 1993-94. Ya follow?
That is why events such as strong La Nina and or El NIno events are so important. These event can and do provide enough energy into the atmosphere to keep the pattern locked into place.
But before LAST winter kicked in ….November 2010 was exceptionally mild for much of the central and eastern U.S. without a whole lot of significant cold air outbreaks or storminess on the East Coast. The pattern flipped after Thanksgiving 2010 so that by the time you reach the first week of December there was a massive trough over the eastern U.S. (recall tht last winter saw a high end Moderate La Nina event).
Since some of you have forgotten what November of 2010 was like REALLY like… I think it is time for a little bit of hard reality and actual maps. What is striking in that when we look at November 2010 is how identical it is to the the CURRENT NOV 2011 pattern over North America.
This first image shows us the 500 MB pattern from NOV 9 through the NOV 28 2010. Again the apparent similarity between those maps on what we are seeing right now is striking and it should be somewhat reassuring for those individuals who for what ever stupid reason they can come up … are already modifying or cancelling their expectations regarding the winter of 2011-12.
This first image has 5 maps in it. The first map is from 9 NOV 2010… And you can clearly see the deep trough over the West Coast and a fairly strong ridge over the Midwest. The NAO is strongly positive. The SECOND map is NOV 15…. The trough has moved into the Plains but there still are Ridge over the East Coast … and it looks like some sort of ridge is trying to form on the West Coast. The 3rd map is 18 NOV 2010…. And we see a new deep trough developing over Western Canada and the Pacific Northwest and a very +NAO!! (Look familar?) The 4th Map is 22 NOV 2010… Which again the shows a new massive trough over the western conus (really the entire west coast of North America ) and a very strong Ridge over the southeast U.S. and a slightly negative NAO. The fifth map is from 28 NOV 2010… Again shows a another deep persistent trough over the West Coast… a strong Ridge over the Midwest and a very +NAO.
Now lets compare those maps to the second image…. which is the current 500 MB map from the last 10 days.
The first one is dated 6 NOV 2011… And of course we can see a massive trough over the West Coast and very strong ridge over the eastern CONUS… and +NAO . The next map is from 10 NOV 2011 and we can see a moderate sized trough moving into the Midwest… with are near neutral NAO. The 3rd map is from 12 NOV 2001… TODAY. And what do we see ? A new persistent wrath over the West Coast…. and a trough leaving the Northeast US and -NAO . The 4th Map is the 0z European model from NOV 12 VALID for NOV 19… Which shows a another deep persistent wrath over the West Coast a -NAO and shallow trough over Eastern Canada and a ridge over the Lower Plain and Deep South.
As you can see the pattern is strikingly similar to what we saw last year in NOVEMBER 2010. It’s very rare in the weather basis to see 2 different Novembers that similar in overall pattern back to back like this.
The final map is from 6 DEC 2010…. which shows a massive trough over the East Coast a steady and large -NAO and the ridge over the west coast of Canada !!! This should convince you that the pattern can evolve quite quickly … and that the mild November we are currently experiencing for most the country has no direct connection to all as to what is or is NOT was going to happen in the heart of the winter of 2011-12.
That being said… it is also true that just because NOV 2010 evolved into of decent winter pattern for the heart of the winter od 2010-11 … that it does not necessarily mean that THIS November of 2011 will also evolve the same way.
The point here is not the panic at all and that give the pattern some time. The big thing about this current pattern for the next 20 days is that it’s going to allow for significant snow cover and colder buildup throughout all of Canada.