WINTER GETTING TIRED OF BEING A DOORMAT OVER THE EASTERN US?

I got a email yesterday asking me about the possible pattern change and that everyone else was talking about it and how come I wasnt? I can only conclude that the person sending me that eamil is one stupid bastard b/c I have been arguing for a colder 2nd half of the winter for several weeks never mind my winter forecast. That is what the talk about the weakening El Nino has been all about.

Some of you may have come across a News wire story (especially in the energy markets ) that one of my competitors in New England continue to forecast a mild winter for the second half right into March of 2007. That forecast came from WSI yesterday and was carried in the News wire services. In reading this story and trying to assess the forecast reasoning it appeared at the Lead forecaster asserted the El Nino was STILL moderate and was going to continue without any weakening right to March 2007. Well I can only assert my counterclaim that that's reasoning is bogus and this strongly indicates to me that they simply don't know how to read the data from the current El Niño. Nobody with any sort of forecast sjkill could possibly assert that the current event is as strong as was just the 3 weeks ago and that it's not going to continue to weaken.

However as I've been pointing out now for three or four weeks the evidence is pretty strong that the El Niño is weakening. And this would argue for a significantly colder pattern developing in the second half the winter.


I've also seen some talk that the weakening El Niño is going to have a significant lag effect and that there is little chance of the weakening El Niño will have an impact on the weather patterns over l North America before March. Again the meteorologists that will have been making that argument really don't know what the talking about. While there is a lag time when they El Niño or La Nina is ramping up because the El Nino / La Nina has to reach a certain threshold before they can significantly impact the overall northern hemisphere patterns.... once in the event is underway the atmosphere is a lot more sensitive and reacts a lot faster to changes in the El Niño/ La Nina so the idea that there is still large lag time of several weeks even though the El Niño or La Nina is already underway.... is simply not correct.


All of the weather models continue to show that pattern change is going to get underway around January 6 or 7. The pattern begins to shift because the Bering Sea vortex -- that's between eastern Siberia and Western Alaska --is going to shift or breakdown. The position of this feature over the Bering Sea is a common position when you have a moderate or strong El Niño. This results in the strong Pacific jet slamming into the western Canada and prevents any sort of Ridging over western Canada. Thus mild Pacific air overruns the much of North America... which has been the case over the last six weeks... and all cold air is bottled up in central and northern Canada. In addition the other feature that we've been lacking has been the position of the Polar Vortex (PV) which has been located over the Asian side of the world in the last six weeks. The position of the PV is critical in determining where the coldest air masses are likely to go and has a major impact upon storm tracks and development.

The European Canadian and American models this morning especially after Day10 shows a increasingly strong Ridge developing over western Canada and colder air finally moving into much of the central and eastern US. The data does not show severe or extreme cold by any stretch imagination but certainly seasonal cold which is pretty impressive considering how warm it's been. If you recall we had pattern amplification which occurred in the first week of December but that cold shot did not last because the fundamentals of the pattern did not shifted /change. The vortex was STILL located over the Bering Sea and the PV was still located over the Asian side of the world. This told forecasters that the cold shot in the first week of December was not going to last.


WHAT CAN GO WRONG

The THREE dominating features the pattern over the last six weeks has been the appearance of a strong vortex or large upper low situated over the Bering Sea which is between Alaskan and Siberia. This Vortex results in a positive phase of EPO. When the EPO is in that position it results in the Pacific Jet crashing into western Canada and the Western CONUS which results in mild Pacific air overrunning the country and the arctic air getting bottled up in central and northern Canada. This is well we saw in January 2006 when the nation saw record warmth.

I have seen some talk of the flat ridge over the central North Pacific being a key feature as well.. This is really just spliting hairs... the Teleconnection of the Bering Sea Vortex IS the flat ridge in the cntral North Pacific.

SECOND...the lack of any sort of high latitude blocking over eastern Canada Greenland.. known as the +NAO effect. This has allowed the Polar Jet to continue to North of the Great Lakes so again the very cold air stays well north of the Canada border. In addition a + NAO means that the "mean trough position" ( or storm track) is for more likely to be located over the Plains & Midwest and indeed that has been the case over the last six weeks. The THIRD feature to talk about is the main Polar vortex which is a huge area of very low pressure in the Jet stream ( called the AO or arctic oscillation). The position and location of the AO is responsible for bringing about the coldest air masses and when it is not a located in the Western Hemisphere Aiken often bring about a very mild winter. The AO over the past six weeks has been located over in Eurasia or on the other side of the world ( called a +AO) and hence that's where the coldest air masses have been. Over the last several winters the AO for the most part has been either neutral and / or Negative and the winters over the Eastern US have been active and stormy.

Overnight almost ALL of the extended range weather models -- OP Ecwmf to D16... The Ecwmf ensembles to D16... the 0z CMC to D16 the CMC ensembles to D16 all show significant changes. Interestingly some of the GFS ensembles are not as aggressive with the change to a colder pattern and the ridging development of the West Coast as what they were yesterday. On the other hand the European ensembles are very aggressive with the cold pattern and after 300 hours really begin to go to town in the amplification of a significant Ridge developing over western portions of North America.

Even so we're still a long way off and while the model consistency is beginning to become significant and impressive nothing stone happen until January 6-7 and it may not reach the Eastern US until the 10th or 12th.

There's a lot of data that shows significant warming occurring at the very high latitudes. It has argued (because the research has shown) that such warming is indictative of the Arctic Oscillation beginning to switch back towards North America. But I am NOT a big fan of th AO-- I think its the most over rated thing since T.O. or Hillary Clintion. It must be kept in mind that last year the AO was negative -- or over North America --but all the cold air stayed over Asia and Europe. Still it IS good to see the AO dhift back to the this side of the wordl ..IF indeed that is the case but it is not by any means a sure thing.

Next... the models are very strong in showing that the vortex located over the Bering Sea is going to shift position. It really does not make a difference which direction the vortex moves... if the feature shifts back into eastern Siberia will that's very good news for the development of cold air and a colder pattern over the eastern half the US. On the other hand if the vortex slides to the east into the Gulf of Alaska... that too is also very good news for the development of a significantly colder pattern. The point is as long as the vortex stays over the Bering Sea which is a classic position for a moderate or strong El Niño the pattern over N the orth America remains very warm as the jet stream will be coming into western Canada too strong to buckle or develop any sort of Ridging... and too strong to allow anything except for a +NAO .

The data does not show severe or extreme cold by any stretch imagination by Mid January but certainly seasonal cold which is pretty impressive considering how warm it's been. If you recall we had a pattern amplification which occurred in the first week of December but that cold shot did not last because the fundamentals of the pattern did not shifted /change. The vortex was STILL located over the Bering Sea and the PV was still located over the Asian side of the world. This told forecasters that the cold shot in the first week of December was not going to last.

If the overnight weather models are correct what we looking at is a fundamental shift in the overall pattern since the vortex over the Bering Sea appears to breakdown or slide back into central Siberia and the PV that has been over Eurasia makes an appearance over the Western Hemisphere. While I expect a lot of model variance and flip flopping the KEY point will be Jan 3-7... by then we should know IF and when the vortex over the Bering Sea is going to slide or die. If the Bering Sea Vortex does not the winter may be over .

The bottom line is that there are increasing indications that Winter is coming back but for how long and how in strong of course is still the big question.