RAPID PATTERN CHANGE DEVELOPING

[DTWXRISK]

FIRST  let me start by saying that back in the third week of October  I made  the call  that November 2014 will could end up being pretty mild .  That forecast is going to be wrong.  Badly wrong.  But more importantly I hope that call I made   for NOV 2014 did not influenced anybody into thinking that they have time for the winter preparations.  And that is why I am making this post now. 

 

 

This first image is a large scale hemispheric  view of the Jetstream or  500 MB pattern over North America   as of NOV 1.  I  have highlighted some important features here.    We can see a 5   Wave pattern which is a unstable weather pattern  but one which is typical during the autumn months. 

 

 

Wave #2 is the Alaskan Low which is also known as  +EPO.  This feature continues to bring in strong weather systems across the  Northeast Pacific Ocean and that in turn is weakening the warm water off the coast of Canada.  Some have speculated that the +PDO (warm  waters  off the west coast of Canada/ US )  will continue to weaken throughout the winter months the cause the Aleutian low was not going to move.   This is nonsense but I've seen a couple people talk about it.  

 

2.   Because of the Alaska Low and the enhanced northern Pacific jet stream ...we see a TROUGH  in the jet stream over the West Coast which is bringing that area much needed rain fall specially over Northern California and the Pacific Northwest into British Columbia.

 

3  the PV  - Polar Vortex .   We   can see the PV is  still partially within the Arctic circle. 

 

4. The -NAO .. we also see  Above Normal  500mb heights or  " ridging " over North Central Canada into Greenland .  

 

5  Therefore with a  -NAO combined with the PV still located over a portion of the Arctic circle  the  Arctic Oscillation  (AO)  itself is neutral.

 

Our second image is the European hemispheric map at DAY 10 from the Sunday afternoon or  12z  run of the European ensemble mean.  The changes are huge and has serious implications for the second half of  November.

 

 

 

The biggest and most important change has to do with the development of above Normal Heights or RIDGING north of Alaska into the southwest   portion of the Arctic circle.   This is called the  - EPO.    This does SEVERAL important things to the overall pattern

 

1. It  forces  the  Alaska Low to retrograde or move back to the west towards the Aleutian islands.
   
2. This movement shuts down the pipeline of large  Low pressure  area  moving through the northeastern Pacific and slamming into the West Coast of British Columbia or the Pacific Northwest.   And this in turn means that the upwelling and the weakening of the warm water in the northeastern Pacific ( The +PDO)  is going to come to an end. 
   
3. The Movement of the  Low/ trough  from   Alaska to the   western Aleutian islandA/ Bering Sea allows or  " teleconencts" to  Ridge in the Jet stream over  West coast of North America  ...called +PNA).  
   
4. The PV  on that was located on the  western  side of the  ARCTIC circle  is forced  South INTO  central Siberia   where the snow cover  is  very deep  and massive.  That Asian PV will stay  there for along time.    
   
5. This allows  for the   Arctic Oscillation  to move from Neutral to   NEGATIVE  ... and allows for the  Scandinavia Ridge  to   expand  North  towards northeast Greenland.   ** IF  the  Scandinavia Ridge  were to move  North ...into Greenland/  east  Arctic Circle  it would have major implications over   the central/ eastern  CONUS 2nd half of November and  beyond
   

 FINALLY ...  the euro  ensembles  day 10   to day 15   shwo a   strong Western North American ridge  and  a good supply of  cold air  into  central/ eastern  CONUS. NOT  record shattering   but clearly colder than Normal.

 

 

 

[wildweatherman179]

Looks like a solid cold DJF is coming for everyone east of the Rockies. Good post and good corrections.

[Amped]

That -EPO ridge is what brought all the cold and snow last year with a +NAO.   -NAO and -EPO are both good for cold and snow, however the two of them together during midwinter could over suppress the storm track and produce a cold dry pattern.  This pattern maybe best for snow in early December and March. I'm not saying it will persist that long though.

[SnowGoose69]

That -EPO ridge is what brought all the cold and snow last year with a +NAO.   -NAO and -EPO are both good for cold and snow, however the two of them together during midwinter could over suppress the storm track and produce a cold dry pattern.  This pattern maybe best for snow in early December and March. I'm not saying it will persist that long though.

 

The problem last winter though was we could not get a really big storm, much like 93-94...I guess 93-94 did have "big storms" but they were not deep low pressure systems with bowling balls at 500mb, they were long duration or well timed overrunning events, the +NAO generally kills any chance of seeing a winter like 09-10 or 10-11.

[Amped]

The problem last winter though was we could not get a really big storm, much like 93-94...I guess 93-94 did have "big storms" but they were not deep low pressure systems with bowling balls at 500mb, they were long duration or well timed overrunning events, the +NAO generally kills any chance of seeing a winter like 09-10 or 10-11.

 

I am pretty sure we beat 10-11 last year here and in most places south of Philly.    Was a unique occurrence for us to get that much snow out of a +NAO winter though.

[DTWXRISK]

CORRECT..  

The Winters 1976-77   1993-94   2013-14   were all +TNH  patterns... which all featured  a HUGE PV .  When   the  PV was up by the Arctic  the  AO  was positive.  But   in  +TNH  patterns the  PV always   ..  ALWAYS --  drops  south.... often to the Great Lakes.  When the PV  does  so the AO  goes negative 

 
This movement of the PV  dropping from North to south  then swinging back  up  into far eastern Canada ...only  to  " reload"   meant  that  by   DEFINITION the  NAO    could only be  positive.   Ergo  Big   east coast snowstorms   were  hard to get. Instead you get   " nickeled and dimed to  death "   This was also  the case in   winter of 1993-94  and 1976-77


 

The problem last winter though was we could not get a really big storm, much like 93-94...I guess 93-94 did have "big storms" but they were not deep low pressure systems with bowling balls at 500mb, they were long duration or well timed overrunning events, the +NAO generally kills any chance of seeing a winter like 09-10 or 10-11.

[Absolute Humidity]

I am pretty sure we beat 10-11 last year here and in most places south of Philly.    Was a unique occurrence for us to get that much snow out of a +NAO winter though.

Yes PV suppression depression north of 40 served the MA well last March. We'll see how things unfold this winter.

[Quakertown needs snow]

Thanks for all the latest and greatest info.

[DTWXRISK]

  FROM hpc  this   monday morning    always good to see  HPC  match my  analysis  from Sunday

 

 

..DETERMINISTIC MODEL DETAILS CONTINUE TO FAVOR USING A BLEND OF THE
3/00Z GFS/ECMWF...WHICH DEPICT A DEEPENING SURFACE WAVE OVER NEW
ENGLAND AND THE NORTHEAST---BENEATH A SHARP BUT ENERGETIC
UPPER-LEVEL TROUGH AND JET AXIS. BY DAY 5...

 

THE TRAJECTORY OF THE FLOW ALOFT BETWEEN THE NEW ENGLAND COAST AND ATLANTIC CANADA  REPRESENTS A FUNDAMENTAL SHIFT IN THE GUIDANCE AND DOWNSTREAM
PATTERN---IE THE POSSIBILITY OF SETTING UP A 'BLOCKY'   DOWNSTREAM RIDGE INVOF THE DAVIS STRAIT-GREENLAND. .....IN OTHER WORDS.. .A POTENTIAL EARLY-SIGNAL SHIFT IN THE NAO CONFIGURATION. AND  ON/AFTER DAY 5...

WE SEE THE FIRST VESTIGES OF THE POTENTIAL CHANGE OVER HUDSON BAY...WITH THE ECMWF/GFS ARRIVING AT VASTLY DIFFERENT  SOLUTIONS ALOFT AND THE LOCATION OF A CLOSED UPPER-LEVEL FEATURE ALONG THE WESTERN SHORES OF HUDSON BAY. HERE...THE MEANS WILL SUFFICE TO HANDLE THE FLOW FOR DAY 6-7...AND WILL ALLOW SOME
PACIFIC INFLUENCE TO TRANSITION ACROSS THE LOWER 48.

[AlaskaETC]

:snowing:

[negative-nao]

Is the Monster storm in the Bering Sea the one that will pull down all of this arctic air after day 6 ?

[Hambone]

"Taken together they signal greater chances for frigid air to spill out of the Arctic into more temperate regions of North America, Europe and Asia, said Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research in Lexington, Massachusetts, who developed the theory linking Siberian snow with winter weather.

“A rapid advance of Eurasian snow cover during the month of October favors that the upcoming winter will be cold across the Northern Hemisphere,” Cohen said in an interview yesterday. “This past October the signal was quite robust.”

There are a few steps to get from the snows of Siberia to the chills in New York City.

Cold air builds over the expanse of snow, strengthening the pressure system known as a Siberian high. The high weakens the winds that circle the North Pole, allowing the cold air to leak into the lower latitudes. The term Polar Vortex actually refers to those winds, not the frigid weather."