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First about the pattern after the x-mas events have passed.
KC mentioned in another post, the longwave trough backing all the way up into the western US. I don’t agree. The North pacific SSTA configuration no longer favors that.
The SSTA warm pool is now located between 120 and 150W and 30-60N in the Northeast pacific – that favors a –EPO and weakening pacific jet. Recall in the winter outlook I said that the SSTA warm pool would eventually re-develop in that region and force the changes in the upper level pattern which would allow the PAC jet to slow and the PNA to turn predominantly positive. The ideas were correct; however I forecasted the onset of it two weeks too early.
In a related WxBlog segment I mentioned that in every other years (I went all the way back to the 1850s to look for similar years using Kaplan’s SSTA reconstructions) where the warm pool was located in the NE PAC during the MAY-JUL period that it would eventually redevelop there again the following winter IF El Nino conditions remained intact. They did and the correlation has now verified once again.
The new D 8-10 ECMWF is developing an omega like ridge over the being Sea, which is indicative of a –WPO (western PAC oscillation). But notice the other two predominant longwaves are located in places which signal a EUS trough – over Japan and Scandinavia. The ridge up near 70E (Caspian connection) means that the PV is over on our side of the pole, which it is -- over North central Canada, and another center may try to form over SCANDINAVIA and near Japan.
If we can get the possible secondary PV center over Scandinavia to Slide a little more southeastward, and the primary center over N central Canada to slip over the Hudson bay, the ridge over the central Atlantic would be allowed to amplify northward toward Greenland and set-up a –NAO for the first week of JAN.
Furthermore I see no signals of a SE ridge on the D10 ECMWF. The point is the North pacific signal no longer favors a persistent SE ridge.
http://www.allwx.125mb.com/image002.jpg
WRT the Xmas storm (or the post Xmas event for the East coast at least) it may come in two segments, w/ one event for the OV and lakes and another (BIGGER?) event for the EUS. That’s right folks a MILLER A.
The idea here is that the follow up s/w or the one that will act as a kicker to push the DEC 19-20 event off the east coast will drag a cold front across the Midwest on day 3 and 4 (TUE-WED) which will temporarily stall out as the initial low associated w/ our clipper (the DEC 19-20 kicker s/w) will weaken and pull northeastward as another s/w sliding down the ridge ejects out of the 4-courners region and develops a new SFC low along the quasi-stationary front that moves up along it through the OV and into the Eastern low lakes on D5. Since the trough has retrograded somewhat and the DEC 19-20 event is NOT going to become the new 50-50 low this first wave is likely going be an inland runner. The front will eventually end up along the east coast by 6 as the energy heads up into Canada and a follow-up s/w dropping out of Alberta Canada into the longwave trough on D 5 and 6 and progresses eastward into the Lower MS valley D 7 developing a new SFC low along the front over FL.
Keep in mind this s/w will be stronger than the previous one which develops the first low along the front, and will eventually tilt negative w/ time as it lifts out so the potential will exist for rapid SLP intensification as the low moves northward up the coast. Eventhough there is no 50-50 low or –NAO in place the trough axis appears to be located at a longitude which would allow the s/w to take a track which is favorable for the SFC low moving northward up the coast NOT inland from it.
Also Note the high over Quebec on D 7 that is VERY important sine it would funnel the cold air well southward setting up and ice threat for the SE (that’s right KC AN ICE STORM THREAT!!!) and potential MAJOR east coast snowstorm Miller A style for the east coast from the Carolinas to Maine DEC 25-28.
The 0z 12-18 GGEM looks similar to the ECMWF 12z.
The implication of the 0z GGEM would be HUGE for the I-95 cities since the big high is up there to keep the cold air in place and the SLP area deepen to < 1000mb off the VA/NC coast. There would be plenty of wraparound and a huge deformation zone. If the Canadian is to be correct, this would be a Major east coast snowstorm for everyone in the I-95 cities.
Note to you southerners about the snow chances:
Several of you have been hanging on the GFS for the past few days which has showed the potential for a MAJOR southern snowstorm w/ this event as the SLP emerges from the Gulf of Mexico BUT there are MAJOR problems w/ that.
First of all the GFS is notorious for overrunning the pattern w/ cold air in the long range –especially east of the Rockies. This is due in part to the model resolution at that range which truncates to T170-77km at the range in we are looking at for the event in the southeast. I think there is the potential for A SIGNIFICANT ICE and snow event from Northern AL/MS through perhaps eastern TN, GA, and SC w/ as previously stated a good chance for a MAJOR or even dare I say severe east coast snowstorm NC and Northward.
CLIMO is against what the GFS is saying and most of the other data would support the aforesaid ideas. The GFS truncation error combined w/ its inability to handle the STJ (Subtropical jet) make it essentially useless after 144 hrs.
For situations where STJ energy is involved the ECMWF is best, UKMET is better in phasing situations when you have the STJ, PJ or all three branches involved.
my Cowboys 
