* Tropical Cyclone Evan can be seen right along the dateline (177E -20S) This is very characteristic of a phase 1 MJO with the strongest upper level diffluence located over this region and favorable sfc and low level convergence.  

*Although plots show a phase 1 MJO we obviously did not see this work to our advantage with the composites favoring a trough in the East which I thought would shift the December 19th storm to the east.  But the strong subtropical jet (not characteristic of the phase 1) was blasting and likely contributed to the warmer solution with the last few storms.  If the loop works above you can see this feature weaken from earlier state which is a good thing.  

*If loop works you can also see convection being enhanced just to the west of Tahiti as convection decreases across Darwin.  Based off eye balling the lifting I would expect a fairly dramatic drop in the SOI and that is currently happening:

*Above IR image shows a phase 1 MJO but we need to increase convection across the Indian Ocean for a phase 2 which models are predicting:

MJO Composite of a phase 2 in December:

So from the above:

*The tropical forcing and rapid decline in SOI strongly supports an East Coast Trough on the 26th

Now to the models!

GFS:

The GFS does something unusual (shocker!) but the problem is the operational European agrees with it to an extent.  We will have a block in place and through most of the GFS it sets us up for a big time snow event for the Northern Middle Atlantic and Northeast:

Instead we get this at 192hrs...

Deepening system entering the Southern Plains with very strong downstream height rises as block is pushed out.  The trough from the arctic comes down and due to the the upstream height rises are rex block is destroyed and the ULL is pushed east given way to the height rises.  Ridge over the West Trough over Plains Ridge over the East this looks like March instead of December.

Instead of running underneath the block and becoming a big wintry event for the Middle Atlantic into the Northeast it stops in the Plains and deepens until the block is weakened then it shoots the low inland.

This is not supported by the pattern with the active pacific and it is not supported by the MJO and it is not supported by the recent decrease in SOI.

The GFS ENSEMBLES:

Compared to the image from the operational GFS the ensembles are COMPLETELY different and show the system moving beneath the block and becoming a winter storm for the Middle Atlantic and Northeast. Notice the active Pacific jet kicking the system east and not allowing it to sit in the Plains and deepen along with the block preventing the inland track.  

So the GFS ensembles show a winter storm and makes sense!

Now onto the European...

The Rex blocking signature is impressive and at the sfc a very strong high pressure system is just as impressive.  That is why I put a question mark over the height rises over the Northern Plains.  The GFS does this also but look at the SFC which strongly suggest this will not happen.  

But somehow the Operational European shows this:

A very warm inland solution.

Euro Ensembles:

The Euro ensembles show a much less amplified system compared to the Operational run but not by far as it is still an impressive system.  The block breaks down pretty quick on the ensembles and just like the GFS it is probably having trouble handling the rex blocking signature.  Even if this is not a true rex blocking signature models break down the blocking pretty quickly.  This would support a colder system than suggested by the euro ensembles but the end result is still a winter storm for the Northeast and Middle Atlantic.

Summary:

*Tropical forcing/Rapid drop in SOI/Blocking developing all suggest the East Coast trough during the time frame of this storm

*The Operational Models show a warm inland solution.  They do this by going against physic by driving warm air ahead of a high pressure system pushing down very cold air into the Plains.  Does not make much sense.  The models avoid going underneath the block by deepening in the Plains until block weakens.  Very suspicious!

*Ensembles show the system going beneath the block which allows the East Coast Winter Storm threat to exist.  

*Kicker s/w the system coming in off the Pacific will push things east avoiding an inland solution. As it is pushed east the blocking will prevent any inland solution.  

*Models are weakening the block fairly quickly which is also suspicious.  The GFS cold bias might be in full effect across the arctic regions leading to upstream height falls losing the rex blocking signature.  The rex block does not go away that easily usually!

Winter Storm Threat increasing for the Northeast and Middle Atlantic right after Christmas!