op 6z GFS shows severe Arctic Outbreak; makes my post about Stunning Pattern reveral ( last SAT) Look good!

Sorry about the fact that yesterday there was no midday update but that's because there really was not a lot to change. As I stated yesterday the key to any sort of wave Low pressure development after the 15th of January along the southeast Coast is what happens to the energy hanging back over the Southwest states.

Since the midday runs ysterday-- the euro CMC ukmet and GFS -- all ended up crushing the shortwave as it tried to pull east from the southwestern states there was no reason to go into a detailed analysis. Part of what's happening is that the models are ripping apart the shortwave in the Southwest with some of the models taking a piece of it and shoving it west or another in other words and retrograding it into California and off the Southern California coast. I am not really confident that this solution is correct but that's one reasons why the system gets crush because these models are ripping apart to pieces.

Of course we are going to have to watch this very carefully as there is a window of opportunity for some sort of wave to develop warm front over the southeast JAN 16-18. But notice what most of the models ate doing here. Without any High latitude blocking the trough becomes very deep and the strong High pressure area drops or falls into the trough... tracking from western Canada along the east side of the Rockies all the way into Texas and Oklahoma. This is a very bad sign for significant snowstorm activity for the East Coast and especially the Northeast.
This is WHY the blocking pattern over Eastern Canada is SO importnat becasue it forces the arctic High pressure systems to stay to the North and track along the US Canada border.... instead of falling into the central and Lower Plains. The High to the north keeps temperatures cold over the East coast but also provides access to ocean moisture as well as being BIG player in the set up all of ageostrophic flow when East coast Low pressure development is underway.

On the other hand when you do NOT have any high latitude blocking then you have got real problems in terms of getting a good winter pattern cooking. There is a tendency among weather hobbyists to really downplay the significance of high latitude blocking ....such as a sustained negative phase of the NAO. I know that there are some out there who say while you can still get big snow oin the Northeast without a Greenland block as long as you have lots of cold air. Often times the February 1995 noreaster is cited as a classic case of a good snow for the I-95 cities that and as rain and there was no high latitude blocking.

Well that may be true but also proves the rule. You see the issue is not whether you can get a good snow in the Northeast without any high latitude blocking or negative phase of the NA O. You most certainly can BUT it won't stay all snow and that in my opinion is always the big issue. The February 95 system was such a rapid moving system that by the time the warm air got into the big cities of the Northeast most of precipitation had already fallen so we ended up with 85- 90% of the precip fell as snow and then the rest as drizzle or freezing drizzle. If the 2/1995 had noreaster move at a more typical speed OR if the Noreaster had closed off in the upper levels the High latitiude blocking would of been far more important. Tthe warm air would have had more time to drive inland into the I-95 cities.... meaning less snow and more rain.

It's imperative that when folks discuss snow storm patterns on a synoptic scale we have to make a clear distinction. If you want the event to stay all snow... then you do NEED a confluent flow over the Great Lakes and southern Canada / Northern New England... and this comes about because of the High latitude blocking over Eastern Canada and Greenland . Moreover the high latitude blocking keeps the cold high in place during the actual period of time when the precipitation is falling. Without these features in place you can get a good snow over the Big cities of the East coast but it wont stay all snow.

In this sort of pattern our you can not have a - NAO ... and in fact it when the NAO is strongly positive.. the overall best pattern you can probably get for snow events on East Coast is to have the trough access developing neutral tilt after costs as the Mississippi River or both time and reaches Appalachian Mountains. You do not want to see the trough access development negative tilt in this pattern in a matter how cold the air mass is over the Eastern have to the US. Without any high latitude blocking and negatively tilt the trough axis will force the system to track in .... and as it develops rapidly...warm air will surge into the coastal plain.

Instead what you want to see is either POSITIVELY tilted trough axis when the short wave or longwave trough reaches the Mississippi River OR one that reaches a neutral tilt by the time and reaches the Appalachians. And on top of that you want surface and 850 Low pressure areas to develop fairly far to the south latitude so that there is good overrunning and the Low pressure wave does not become too strong until it was off the coast.

I suppose the other big story has to be the operational 6z GFS this Wednesday morning showing a severe arctic outbreak developing by 324 hours ... or about Jan 22. As I stated in the last couple of blog entries the only way this sort of severe arctic outbreak happens is if we get some sort of high latitude blocking over Eastern cat or Greenland. In other words the +NAO has to switch phase and turned Nagtive. This is what the 6z GFS is doing and its reasons why the model shows the severe arctic outbreak.

Now that being the case let's talk about couple things here. The operational 6z GFS has no support from any other model nor does it even have any suport from the 0z or 6z GFS ensembles. It's possible that the 6z operational GFS might be correct BUT I would NOT bet any money on it. Of course I am sure that those who were talking about the severe cold in the January 15 -- February 15 time frame as being one of the top 10 coldest thirty day periods in many years are going to jump up-and-down about how the 6z op- GFS is likely to verify.
It may but until I see some of the model support on not going down that road and you should not either.

One last point is the 0z operational European which develops 2 hortwaves into one large system over the western US by D10 and then begins to break down the cold pattern. Of the 51 members in the European ensembles only 7 of them show any sort of similar pattern. The vast majority of the 51 member ensembles do not show a large merging of the 2 shortwaves over the western US into a close 500 low or 500 trough. Therefore I consider the operational 0z European models to be bogus.