2000  EST  26  NOV  2011….    STARDATE  201111.26

 
While thanksgiving is over  and MOST  the turkey  has been  eaten  so it’s time to get back to the weather biz.      (although I am a anticipating one more delicious Turkey left over lunch on Sunday afternoon)        First I’m extremely happy with the way this weekend forecast turned out.  Up and down the entire East Coast and in to the Ohio and Tennessee Valley this has been an extremely nice long thanksgiving weekend.     I do believe  one could make the case   that this   has  been  nicest thanksgiving weekend in the last 50 years or more!    Given a that I made this forecast  here on the  WEB  page and over on  FACEBOOK  for the  1st time back   on NOV   15-16…  I am  darn happy.

 However when I made that forecasts and in the subsequent updates to that I talked about how of as we came out of the holiday weekend  — NOV 27  –  it could be a difficult travel day for many areas over the eastern U.S.     The ixssue  is  a  slow moving   but important cold front which can be seen crossing the Midwest and the Delta  regions on the Saturday early evening radar.     Over the past several days the weather models have slowed the system down a  bit so that by the time and reaches this maximum intensity it will actually be Monday the 28th.
That being said … the  overall scenario really has not changed …its just a timing issue.     All the model data shows that energy coming into the base of the trough over the Delta region will cause an upper Low to form and separate itself from the main  trough over the Midwest.      When this happens is called a  CUTOFF  LOW.    But in this case… the   cutoff  Low develops a    negative tilt. …which is a sign of a very strong and rapidly developing system   over the TN  and Ohio valleys.

To show you what this looks like  here is the  12z    SATURDAY   GFS  Model  at  60  72  and 84  hrs   at the 500 MB  level.  I have  drawn in the trough axis or the tilt of the upper low and you can see it’s running from the northwest towards the southeast….  which is by definition a negative tilt. 

As you can see here the European models strongly agrees with the scenario as those the British model and the Canadian. 

 
At the surface a second area of   Low pressure is going to form over the Gulf coast states and be pulled northward then northwest under this deep   closed   cutoff  Low .  In addition the strong area of High pressure off the East Coast  — the feature giving  the eastern US   this  great weekend..  will still be a factor.   The  High off the coast will be  feeding  a  significant inflow of very moist air from the southwest Atlantic into the    the entire East Coast  region.    Over the Appalachian mountains    and into   the  elevated terrain  of  TN   and KY rainfall amounts will be quite impressive over the next three days.   Possibly as much as 6 inches a rain and some locations.

BUT then  things  get  tricky.  Note in those  GFS 500 MB  maps how many of those Black Lines develop around the upper Low.     At   72 hrs  the GFS  shows 4  closed contours around this very impressive   “monster”  upper Low.       That represents a great deal of very cold air in the middle and upper levels of the atmosphere  and as result the  GFS   Model shows that the low levels  COULD become cold enough over the high terrain for the rain to go over snow Monday night into Tuesday over Northern Alabama   portions of  Tennessee  into  Indiana   and much of Michigan.

 
For this reason I  have issued a  FIRST    GUESS map with regard to this potential for snow.  This is a very risky forecast and it is quite possible that the cold air never gets down to the surface in time to cause force the rain to change over snow.

Further to the east it  is pretty clear that there is  going to be a large band of heavy showers and thunderstorms developing over the coastal areas of GA  and SC     then  move into all of  North Carolina southern and   western   Virginia…  central Virginia   and all of  WV   and into MD and    western PA.    However as this band pushes to the north and northeast   it  will  weaken and fall apart once  it  reaches central and northeastern Pennsylvania and New Jersey.

Longer term we can see some major changes occurring in the overall pattern.  Of course it may not mean much for your particular location BUT….   if you want to take a look of the big picture there are some things to point out which are significant.

In this image  we can see the  Upper air    pattern  (500 mb)    from November 21 and compare it to the forecast to  the  day 10 European model valid for December 8.     We can see some major differences.    Note that the huge vortex and deep troug in the gulf Alaska and the Eastern Pacific Ocean on November 21 has been replaced by a very strong Ridge  that pushes up to the coast of Alaska!    Also the ridge over the central  CONUS is now being replaced by a fairly deep trough.  The strong Ridge  over Europe gets replaced by a deep trough.      So things are changing.

If we look at some other Teleconnection indices however we see some discrepancies.     If we look of the two week forecast in Trends from the GFS  ensemble   from  the ESRL    web site…  the    regular  GFS  and   the  PSD  version of the GFS both showed the NAO staying strongly positive for most of the time frame   ( perahps  beginning to move towards a Neutral  by day 13-14).   However they do NOT agree on the PNA.       The regular GFS model shows  moderately strong positive PNA  through  day  10-11….  whereas the  PSD version of the GFS shows an extremely strong negative PNA.

Clearly these two things are not the same.  The reason is that the PSD  definition of what constitutes a  -PNA  vs a   +PNA  is not the  same as   CPC/ NCEP definition.

We see the same sort of problem looking at the  Western Pacific   and EPO Teleconnection trends.  Both versions of the GFS are in pretty good agreement over the next 11 to 12 days with regard to the Western Pacific Teleconnection.    But they do not agree   over the  EPO  trends.  As you can see the PSD   version of the GFS shows wild swings back and forth  fromn positive to negative   then  negative back the positive  with regard to the EPO.

One of the ways and getting around this sort of discrepancy is to look of the European model and the European  ensembles.  I have placed the operational European run  at day 10 next to the  day 10 European ensemble.    The European  ensemble has a weaker ridge over the southeastern CONUS      so  temperatures are somewhat colder   east  of the Mississippi River.     But the important thing here is that both  the Operational   Europeran and  the European ensemble  show a very strong Ridge over the eastern Pacific pushing up towards the coast of Alaska .  To be sure this   is NOT   massive  or highly amplified  Ridge…  but it clearly shows  that   the PNA   is going to be in the positive phase   at  day 10.    

Clearly the   PSD   run of the GFS is    wrong. 

If we look at the   GFS   ENSEMBLE  temperatures at Day 7 we can see a lot of dark blue and some purple actually showing up over portions of the eastern U.S.–  mainly over the southern portions of the U.S.  while over the Northeast and the Great Lakes sees seasonal  early  DEC temperatures.   At Day 13…  we  see more of the same…

      Finally I suppose it’s  fair to say that there are TWO ways to look at the first 10 or 12 days of December 2011.  It is clearly not going to be as cold as what some of the private energy forecasters have been calling for.  On the other hand given the fact   that  +PNA is only of average intensity…    the AO  this still clearly positive  as is the NAO…  it is   almost a   miracle  that   Deep South looks  cold   while the   Great Lakes and the Northeast  looks  seasonal for   early    December.

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1900  EST  NOV  23  2011… STARDATE  20111.23

I am hearing report some various meteorologists both within the private commercial sector and in the energy sector which are either killing off the winter  of 2011-12   over the eastern half of the CONUS ….  Or they are significantly downplaying it.

I suppose to a lot of folks this sort of decision doesn’t make a lot of sense especially given that we’re just now entering the thanksgiving holiday.  From my point of view of I agree.  I think part of   the problem…  may be that the last two winters were so significant over so much of the country east of the Rockies and especially east the Mississippi River…  that many have become spoiled.    And because  there have been  2 significant winters in a row ..the anticipation and build up… the  excitement about the potential for this winter…  especially given some of the early forecast calls…  have all  contributed significantly to ” expectations” .      As a result …IF  it turns out that this winter is not going to be as impressive as the last two winters…  and you have been telling folks  and your clients that  thid winter  WILL be…     well then  you may have a problem.
We now KNOW   that November  2011  will end up  been pretty mild and there  has  been a real lack of cold air over any portion of North America.  Of course as I pointed out in a previous posting November 2010 was pretty mild as well…  So    this current  Mild NOV does necessarily mean anything.  But you have to understand if you are weather hobbyists WHY some of these other forecast services and private forecasters are already  downplaying  and/or backpedaling on the winter of 2011-12.

Essentially they  have been  following the overall pattern and they see the number of things wrong with it and they figure that by the time things change so that we are seeing  even   “seasonal cold”  temperatures  it may be  DEC 10  or 15.   Of course past the past December we still have January February and for most of     the CONUS   a good portion of March as well.  There is just too much data and indication out there   — the above and much above normal snowfall over the northern hemisphere and especially over Eurasia… the  super  warm  North Atlantic  ( the +AMO) … the weak    negative QBO and the   fact that the La Nina  has NOT strengthened steadily or dramatically over the past few weeks    (recall last Sept and OCT   the La Nina   dropped  like a  Rock)   to bail out on the Winter.

So at this point I have not given up in the winter and I certainly have not given up on December still being at least seasonally cold   or fairly close to being seasonally cold for a good portion of the central and eastern CONUS.     That being said some of us are just going to have to get used to the fact the last couple winters have been really good    with respect to  EARLY  season cold and snow for large portions of the central and eastern U.S.     The last 2 winters   really got cranking in December…  but there have been a lot of winters in the weather history of the country  in which December  was   either Mild  or   just OK  ( DEC 93 of the winter of 1993-94  comes to mind)   that did not get cracking until January and February.

If we take a look of the latest MJO plots 

    you will see that most of the Plots   show the  current MJO  swings around   into   Phase   3 and 4  and 5  over the next  2 weeks.    As you can see  here      in DEC    Phase 4 and 5    are    very Mild  temps  patterns  for  the  central and eastern  US.    This would lead one to believe that the mild pattern  over the central and   eastern US  is going to continue into the first 10 days of December.  

However that most of the medium range models do not agree with that scenario.  Keep in mind  tha the  current MJO  impulse   is pretty weak and it  is very possible   that it might  collapse  into the   ” circle of  Death”.

For example here is the first image which shows the DAY 10 European model hemispheric projection  from 0z   FRIDAY  NOV  23.  As you can see it does not show a very promising looking pattern at all.  All the cold air is bottled up across the arctic region and the overall pattern across the CONUS looks pretty darn benign.

 However the   12z NOV 23  European model both at the operational and the  ensemble level    looks  much more significant and promising.  At the operational level we can see  ( the Hemispheric  projection)  a major Ridge  developing in the eastern Pacific pushing  North  into  the Yukon and Eastern Alaska…  and a  rapidly in deepening major trough over Western Canada pushing into the Pacific Northwest and northern Rockies.  That certainly is a major change from the  0z   Operational  European  run!  The day 10  operational  European model    at day 10   shows a  3  WAVE  pattern –  3  distinct troughs over the hemisphere.  

Focusing more on the CONUS  at day 10 you can see the very impressive amount of cold air pouring south at a Western Canada driving across the continental divide  trying  to reach location such as Seattle  and Boise.

     At the   Ensemble Level  Day 10 day    the 12z  European shows a more improved pattern both at the hemispheric level and at the regional level.  At the hemispheric perspective we can see two distinct polar vortexes :  One is over northeastern Canada and the other  is over eastern Siberia.  This is a significant change from earlier in the month when we have the  PV  in Alaska and the Yukon.  In addition we no longer have a deep trough in the gulf Alaska slamming into Western Canada but now we have a “flat” or  Broad  Ridge.  Again NOT  good for  serious serious cold  air   getting into the CONUS   but  its not nearly  as awful when you compare it to what the pattern is look like over the past 10-14  days.

    This can be seen with better clarity on the regional shot  of   the day 10 European  ensemble   map.

It is quite possible that the deep trough over Western Canada will swing through an across the Rockies the Plains  the Midwest and into the East Coast during early in the middle portions of December.  It is also quite possible that the trough may stay over the western U.S.  and perhaps just reach portions of the Plains.    Certainly that is what the  MJO   amd its forecast   of  Phase  4-5  is indicating.