1900 EST FEB 8
I am getting a lot of questions as to why the this system which is coming in from the lower Plains and Mississippi delta is not going to become a significant east coast storm like so many Southern Systems have so far this winter. So this is a good time to explain some of the points I have made over on the facebook page in greater detail.
In my last post here on the web site I stated in no uncertain terms that I believe the threat for February 10 was a phantom threat and it was NOT a serious East coast snowstorm. I made that judgment based upon what I viewed as serious problems with the upper air pattern which is not conducive for an East coast snowstorm with this next system for February 10.
I have said this many times before in many different ways but this is a very good opportunity to show you exactly what I am referring to when I say that east coast snowstorms are not going to occur simply because a weather model has a big L somewhere along the Georgia or Carolina Coast. It doesn’t work that way. ( hereafter called SECS… Significant East Coast Snowstorm).
This first image is from the NAM Model and it shows you the actual upper air map from late this Tuesday morning at 500 MB or jet stream level. I have highlighted some important features that you need to beware of as you go through these maps.
Then I will compare this current map and situation with the two fairly recent major SECS events: the blizzard of 26 DEC 2010 and 6 FEB 2010 DC to PHL Blizzard.
In this first image you can see that the ridge is along the West coast of North America which is a very good position for those who like SECS. You can also see the powerful upper air system over Arizona and Southern Nevada. This system is pretty vigorous and it is going to bring a major snowstorm to portions of Oklahoma Kansas and Northern Texas and Arkansas. Also what you need to notice it is the large powerful polar vortex which is situated over Eastern Canada.
It is a strong and powerful rule or guideline that the appearance of a large deep of vortex over Eastern Canada during the winter months is a NEGATIVE factor for seeing large SECS events. If you remember your basic weather science the more lines you have around the low pressure area the more winds you have. This is true with surface Low pressure areas whether you are looking at a coastal storm or hurricane and it is also true in the upper levels of the atmosphere. In this case with this current setup for February 10 the large powerful polar vortex has many lines or 500 mb height contours around it. And that means a lot of wind in a tightly compacted area.
To get a big storm on the East coast and especially to get a major snowstorm you need to have the northern or polar jet stream MERGE or PHASE with the southern jet stream. It is this merging or phasing of the jet streams which is why the Low pressure area over the southeast states comes up the coast.
If the two Jet streams do not merge then most of the time the Low pressure area will slide off the coast and head out to sea.
In this next image at 36 HRS…. We can see the system that was over Arizona and Nevada is still looking fairly strong. This is one of the reasons why those areas of the lower Plains are going to see a significant snowstorm. However the polar vortex is still very large and very deep and it is the large size of the polar vortex which is forcing the polar jet stream to come way to the south. I have highlighted the southern jet stream in green and the northern jet stream in blue. As you can see from the map the two jet streams are not merging at all. If anything the blue Jet stream is beginning to crusher or overpower the green Jet stream.
In this 3rd image at 72 hrs the NAM model– along with all the other model data– shows that what was a powerful shortwave or piece of energy in the jet stream is now being crushed as it moves off the SE Coast. No phasing is taking place at all and the large polar vortex has force the polar or northern jet to plunge way to the south.
Now at this point some of you are asking… Why do the jet streams phase some of the time over the eastern US and bring about a significant east coast winter storm and yet at other times they do not Phase ?
This is where the blocking patterns come into play over the central and eastern Canada and Greenland. Something has to force the jet stream to change their flow so they can interact and begin to Phase or merge. When there are large blocking features over Greenland or Eastern Canada or near Newfoundland for example… the jet streams are forced to plunge southward or take unusual patterns and that greatly increases the chances of the two jet streams Phasing and thus allowing for significant east coast winter storm to occur!.
Let’s take a look at the great East Coast blizzard December 25-26. I have presented 3 maps from DEC 24 25 and 26 all of them 500 MB maps.
As you look at these maps it becomes readily apparent that the patterns are vastly different for the east coast them what we are seeing with this non event for February 10.
DEC 24 we can see that we have no large intense deep vortex over the Eastern Canada of any kind. There is no deep LOW with a large number of contours around it. That is a major difference. In addition we have a large ocean low centered over or near Newfoundland Canada which is often for to as the 50/50 Low. And we had a massive block in the jet stream over Greenland which is a subtype of the -NAO ( item #3) . The 2 Blue lines are two pieces of energy in the the northern and southern jet streams which are going to merge or phase and develop the huge East coast storm.
So the setup going into the 26 DEC BLIZZARD was totally different in every possible way when compared to the current setup for February 9 and 10.
On December 25 and 26… The blocking features which I just talked about… the 50 / 50 Low and the Greenland Block (-NAO) …. is what forces the two pieces of energy to phase into the Monster East coast storm.
In this next image we can look at the 500 MB for the DC BWI FEB 6 2010 Blizzard from almost one year ago…. And again that we quickly notice massive differences in the overall pattern.
There is no large deep polar vortex centered over central and Eastern Canada with numerous concourse around it. There are a few areas Low pressure which have a few lines around them but that is not the same thing as what we see over Canada on with this next event FEB 10.
We can see a very clear and very distinct large ocean Low located near Newfoundland Canada ( the 50/50 Low) and we can see a massive about all blocking over Greenland once again…. and the LOW over eastern KY is the beginning of the massive snowstorm which hit Washington, DC Baltimore and Philadelphia.
Lastly we have the following event on February 10, 2010…. Which if you recall was another major east coast winter storm which bought another round of blizzard conditions to the areas from Washington, DC to Philadelphia.
First off we can see a huge block in the jet stream over Eastern Canada. This is the exact opposite of seeing a large deep vortex over Eastern Canada which is what we have right now on February 10 , 2011. !!!!! Once again we have a larger area of Low pressure located near Newfoundland Canada…. And we had a rapidly developing system exploding over West Virginia moving into Virginia and Maryland which is going to cause the massive east coast snowstorm to develop.
You have got to see that it is the pattern that determines the East coast snowstorm chances . It is not a model that produces the LOW on the weather map. If you don’t see this you are never going to be able to assess the overall pattern and snow storm potential with anything based on reality.
One other point before close out this evening. many of you have been asking or wondering is the winter over the eastern half of the CONUS over?
There are several ways to answer the question. First let me point this out. If you think winter continues until March 20/ the spring equinox then you are a moron. That is when astronomical winter end and spring begins but that has nothing to do with WEATHER and winter weather and spring weather patterns inter ending and spring beginning. Weather patterns. The weather is NOT affected by when the sun crosses the tropic of cancer or Capricorn. It has nothing to do with astronomy.
Undoubtedly the worst of the winter pattern is clearly over because even if the the pattern re-builds and we turn colder late February or March over the eastern half of the country …it still going to be very late in the season.
Here is the European ensemble mean for day 9 and it’s a pretty darn warm looking map. There is fairly deep trough over the Pacific Northwest which extends down into California and a fairly strong ridge over the southeastern U.S. At the surface there is a strong area of High pressure off the SE coast mild air dominates the country the east of the Rockies.
This next image gives us an eight better interpretation of what the pattern and temperatures going to look like on February 18. The bright greens and yellows are pretty warm temperatures. In VA 850 temps are … according to the European ensemble.. at +6 or +7c…. And were bright sunshine and westerly winds that gives us +10c. Add 11C for Mid FEB= 21c which is around 70°.
This last image shows you the overall hemispheric map and we can point out some important features here as well. Item #1 represents blocking which has developed over Scandinavia and the area north of Great Britain. This may or may not be a east based NAO…. But it can also be counted as a Scandinavian block which is a totally different feature.
Item 2 represents the polar vortex which has according to the European ensemble at day 10 become aligned in a west east direction . That is very bad news for those like cold conditions and very good news for those who like mild conditions over the central and eastern US. Item #3 is the west coast trough… And all these features together support item #4 which is the southeast ridge.
Finally the only did mechanism which I can see which might change the pattern as we go into the end February or early March …is the the deep Polar Vortex over Japan. If this feature moves east and stays south of Aleutian islands it would if cause a strong ridge to form the jet stream over Western Canada and fundamentally change the entire pattern. Of course there is no guarantee or certainty that this feature is going to move and it could stay for several weeks.