DEC 2014 AND THE MJO

[DTWXRISK]

Now that the NOV 27 East Coast winter storm  and Thanksgiving 2014   has come to end and I have  had a chance  to catch my breath ...we can start taking a look at December.  I will do the new   THIS WEEK  IN WEATHER  video on Saturday...  with a special focus  regarding WHY   the NOV 27 East Coast winter storm was not a big snowstorm for interstate 95  cities   (despite the insistence by some that  was  going to be).  

In my winter forecasts I  have been  calling  for the first half of December to be fairly mild with a mean trough position over the West Coast.  In fact I am not sure if even the second half of December is going be all  THAT  cold.   I do not know IF  other  forecasters / forecast services  were calling for a mild first half of December....  but the data is quite strong  that is  going to be the case.   ( Therefore  if by  DEC 15  the snow is not yet up to the 2nd floor  of your house  ... dont kill your self )

 

 

Let me explain  how i see   DEC 2014  and my  assertion that December would be the mildest of the four months   -  DEC JAN FEB MAR.

 

This first image shows you what the December Jetstream  / 500mb pattern looks like when you have a positive PDO -- like we do know .  The red ...orange ... and yellow areas represent positive height anomalies.  The dark blues and purples represent negative height anomaly    What I  have  highlighted here with a big black circle is the strong RED area of positive height anomaly over  Iceland just north of the U.K.  nto Scandinavia.  

 

Now some may   refer to this as a " EAST BASED   -NAO"  pattern but I think that is really stretching.  That   dark RED   blob is over Scandinavia and it extends towards Iceland....  so one could make the case that this is actually a Scandinavian positive height anomaly.  This position is NOT ideal for a colder than normal pattern over the eastern half of the CONUS and it is a pretty bad pattern  for East Coast snowstorms. 

 

 

But in addition if we take a look what ' is happening in Pacific we can see two extremely important and very large anomalies.  The dark green with blobs of yellow    represent the central Pacific  RIDGE that covers  the Hawaiian islands and extends out towards the dateline.  The dark  PURPLE area represents a very strong negative anomaly which is quite  large  and elongated .  This is significant because it tells us   that at times ... in DECEMBER ... when there is a strong Aleutian Low in in the upper levels the atmosphere  it will   cause  a Ridge  to form over Alaska   ( the -EPO pattern)  and that in turn will set up a cold pattern.  But at  other times ...the Aleutian Low will migrate eastward into Alaska  into  Alaska  OR the gulf Alaska in which case the EPO turns positive and the pattern favors milder than normal temperatures over the central and eastern CONUS.  

 

 

In addition this sort of overall pattern in the central and east the Pacific will always produce a strong or enhanced Pacific jet stream-- THE BROWN ARROW -- which streak  across the central /northern Pacific and slam into the West Coast of North America.  When the Pacific jet is enhance the  EPO will go POSITIVE ... there  be significant  widespread rains along the West Coast  and a mild pattern for the central and eastern CONUS .

 

 

As the look of the short  range  and a medium range models we see this sort of thing exactly taken place.  There is  a fairly strong cold front which will move into the Midwest and the East Coast  DEC 1...  but it is just a glancing blow and it does not last. 

 

This map from the European  ensemble  DAY 6 clearly shows why.  I have  highlighted the strong Pacific jet streak the across central and eastern north Pacific.  The Aleutian Island Low has moved into Alaska so the the  EPO  turns positive as has the NAO.  On the right hand side of this image we can see the temperature anomalies at the surface. Notice the pool of cold air over Eastern Canada .  Sure  it looks pretty impressive but it's also not entering the U.S. ....  and we can see increasing warm temperatures over the Rockies .

 

 

At day 10 we can see more the same sort of thing.  There is some indication that the EPO may be moving back to neutral position  but the NAO is still clearly positive and the PV   (polar  vortex)  is a way to the north over Baffin island in far northeastern Canada.  The models are trying to show a little bit of RIDGE over Western Canada   but  we can clearly see the very warm temperature anomalies over South Central Canada and the upper Plains as well as the Great Lakes.

 

ENTER THE   MJO ......

 

Of course there IS  another way of determining what the overall pattern is going to be completely independent of what any weather models  is showing.   This method is  useful  especially for those for uncertain as to whether not to believe   weather models are showing in the medium and extended range forecasts.... ( 6-10 DAY...  11-15  day 16-20 day  )   This method is known as the Madden  Julian Oscillation or MJO  for short.

 

 

For example...  This image shows the current MJO  " impulse".  As you can see the MJO just recently left phase 2   and it has now moved into  phase 3 .

 

In the month of November the phase 2  of the MJO results in this type of weather pattern ...    and this pattern was  very close match to the east coast winter storm pattern of NOV  25-26-27.  

 

The match is  very similar  and shows how when the MJO is very strong.... it the  can dominate a pattern and give you a really good heads up about what's coming.

 

Phase 3 of the MJO in late November corresponds to a seasonally mild pattern developing across  the Plains the  and Midwest with near normal temperatures on the East Coast and that is exactly what we are seeing right now .

 

These two weather models   -- the European and the GFS --show that the current very strong MJO impulse is going to swing around to the various phases over the next several days into the first week of December.  As I stated above each one of these phases represents a different type the weather pattern.  In this way we can see whether not a weather model is making  SENSE or if perhaps the weather model solution is full of crap.

 

Got it   ?  For example both of these model show the current MJO will move into phase  4...5....6...7..  and phase  8 by the time we reach DEC 12.   

 

WHAT DOES PHASE 4  OF THE MJO IN DECEMBER LOOK LIKE??

 

This image shows the  UPPER AIR  PATTERN ON THE  LEFT  hand side and the surface temperature anomalies on the RIGHT hand side.  As you can see there is a strong indication of  HUGE   ridge the in the Jet stream developing over the eastern half of North America  and specifically over the eastern U.S. when the MJO reaches phase 4.

 

 

Notice that the  NAO is strongly positive  and the  EPO is strongly positive and the pattern implies a strong Pacific jet stream.   With respect to temperatures the image on the right hand side  shows above and much above normal temperatures for the central and eastern portions of the country.  This strongly supports the European model solution at  day 6 and the especially at day 10 of much above normal temperatures over the central and eastern portions of the country as well as  south central and  southeast  Canada.

 

Finally we can see that the models are in strong agreement that the MJO impulse will reach phase  8  by   DEC 12 or so.   As a general Rule Phase 8 is always a  COLD pattern for the eastern US.... but this is what  it look like  in  DEC.

 

 

The image on the LEFT  SIDE  shows the overall Jet stream pattern  and as you can  see things are VASTLY different. There is +PNA  / west coast Ridge  ...and a -EPO  and     STRONG   negative NAO .... ALL of which combined to produce a   deep  trough over the  Eastern Conus...  and a   FAVORABLE  mid  DECEMBER    East coast snowstorm  set up.

 

 

 

[TeleConnectSnow]

Before I even read this, I would like to publicly apologize for what I said the other day about you not being wrong. Plain stupid of me to even bring that up. Great work always DT.

[DTWXRISK]

its cool... believe  me  ..if I see a BIG snow  for NYC  I  will not   hesitate to bang that drum like a cheap hooker ...

 

 

Before I even read this, I would like to publicly apologize for what I said the other day about you not being wrong. Plain stupid of me to even bring that up. Great work always DT.

[cny rider]

I come to this website to learn and really appreciate posts like this one.

Thank you.

[uncle W]

good post Dave...the ao/nao forecast is all over the place again...The PNA looks good though...I hope things fall into place by Christmas...

[CoastalWx]

Good post Dave. The dynamical MJO forecasts are at odds a bit with each other (GFS vs EC) but the general idea is that the forcing should eventually move into the western Hemi near or after mid month or so. You can see it on the VP anomalies at 200mb. Also, I wonder how or if whatever TC develops in the WPAC will effect the pattern. That can alter those dynamical MJO forecasts and if it moves poleward, potentially have a downstream response.

[wkd]

Great information Dave.  Nice to see you posting in here again.

[nzucker]

Awesome post, DT.

 

Really depends on if the GFS is correct with its more robust Phase 8 MJO or the Euro which brings it into the circle of death...