Questions continue on East Coast Threat

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We have an extremely variable situation going on right now for the weekend forecast. Obviously most of, if not all of you have heard of the potential for a major winter storm this weekend for the area. The question is…how major does this system become for us, north of NYC, what is the systems track, what is the exact timing, what is the possibility of having significant snow (over 6″), and finally, what is the possibility of getting a glancing blow from the system. THESE are all questions that are out there, and questions that have not been answered, and likely will not be answered until Wednesday evening or Thursday at the very least. 

WeatherInTheHud will be releasing our first call snow map on Thursday afternoon/evening for the potential Friday Night-Sunday morning event, if needed. 

So, lets dive right into what is going on.

The first, and biggest ingredient to the storm is the parent energy (I will use NRG to abbreviate energy) that is currently about 75-80% if not more finally on shore North American soil. The track that this energy takes, where it phases, and where it deepens and forms an upper low is crucial to setting up who gets the snow, and who gets the most snow, in addition where this storm goes. You can see the NRG on the Water Vapor Satellite Image


Notice I have drawn some arrows showing the possible tracks. This represents the possible ways this storm can go. Let us get into the details of this. We had amazing consistency between the models and their ensembles for the large part of the last 4-5 days on the track of the storm, and snowfall amounts. The problem was, and still is (until tomorrow afternoon) is that all these model runs have been initializing with poor data on the most important piece of the puzzle, this NRG. There are not many sampling stations in the middle of the Pacific to get data on these systems, and so the models assume things about it – and sometimes this can lead to misleading runs. THAT BEING SAID, The consistency was incredible, which led to a high confidence of something big occurring.

Now the wrinkle – the latest model runs today, namely the European model, which many consider to be superior and more accurate drove the storm way way south of the track that it has been taking. The 18z GFS model run followed suit, although instead of moving 300 miles south it moved the low 40-60 miles south – So, still south, but enough to still give us snow. See the GFS 12z run below, and then the 18z model run.


                                             12z GFS run with 10-20″ well into Southern New England


                 18z GFS with the snow a good 50 miles further south, and 4-8″ across Southern New England.

And here is the Euro 12z run, notice the 3″ going through Westchester and the immediate CT southern Coastline, No snow for New England, but 20-30″ across Virginia and northern NC.


So why in the world are the models showing this shift? Let me make it clear that neither of these model runs had sampling data from the NRG as it was still offshore when they got the data for the runs..So here is the thing, will the Euro be right? Why is the Euro saying this? A key to this system lies in the Northern Stream, or Northern Jet. The jet needs to be strong enough to deliver cold air into the region to give us precipitation in the form of snow, yet it also needs to be weak enough so that the southern stream can lift the system up to the north. The Euro is saying, Nope, no room, and so it drives the system on the path of least resistance – straight out and east. You can see on the model runs they are colder as well, another hint that the Jet up north is **going** to be stronger than originally thought.

I personally do not buy this solution, that is the Euro Solution. That being said, I do not necessarily buy that this will be a “New England” special, delivering feet of snow. I believe the answer lies in the middle. One thing the models have been consistent on is that this is, for the most part, a Mid Atlantic Threat. Meaning, DC, Philly, Baltimore, to Virginia, West Virginia, mountains of NC, and into SE Pennsylvania, Central NJ get the most of the snow, no matter what. This has always been the case. Question is, how far north do we get? The key is where the upper low forms, or that is the center of low pressure at 500mb. See it here on the GFS, with the track outlined in Blue, and then Euro, outlined in purple, and the optimal solution for us to get a big snowfall outlined in red.


So here is another question, why do I believe the Euro is wrong right now? There are a number of reasons:

  1. Climatologically  it does not fit in with the upper air configuration currently in place. To me looking at the overall upper air setup in NA right now, the suppressed track does not make much sense once it gets into the Mississippi valley. I am not saying it is impossible, however I find it hard to believe that the Low will move SE that much as seen by the 12z Euro. The Northern jet is not that strong to accomplish this, and with heights building from the west, and south, I find it improbable that the low pushes its way through that when it has a clear opening to come north, again, at first. If the low does indeed get that far south, than the HP pressing in from above will have a chance to move further south, inhibiting any low from moving north.
  2. Even though the latest GFS moved a good bit south, it makes much more sense given the overall configuration. In addition to this, the European is right now, the outlier – no matter how you look at it, even though the GFS moved south. There is a huge plethora of guidance telling us that the upper low tracks through VA/NC and then deepens coming ENE out of the Chesapeake Bay. Jumping out 100 miles, than deepening into a strong storm seems very unlikely, especially given the huge amount of warm water close to the coast.
  3. Although not a scientifically proven rule, Norm McDonald, an amazing forecaster created a rule of thumb saying that where the energy enters the west coast, it will exit the east coast at a similar Latitude. This NRG moving into the West coast is roughly at the same latitude as Southern New England, which, by the rule of thumb says it exits around SNE.
  4. It is ONE RUN of the Euro Model. The Euro may be thought of to be a King, but it does make mistakes, and it does have bad runs. IF the trend continues through multiple runs, than we have to talk about changing our ideas…but one run of a model is not a trend.
  5. Storms going through rapid deepening, or Bombogenesis, which this storm will be doing, often slow down and move NW on their track, not push further East, unless something really strong is pushing it out of the way. IN this case – we do not have that something pushing it out with extreme force.

Bottom line is that a big storm will be developing, and someone will be getting a heck of a lot of snow with that. Will it be us? Probably not. But I would not, whatsoever take the storm threat down for us, as there are 3 days to refine details, and 3 days in which everything and anything could go right or wrong. The models have biases, and this all contributes to their model runs as well. In the end, we will not know exactly who is getting the most snow until the low forms and things start ramping up.

Tomorrow afternoon’s runs should have full sampling data from the NRG, and this will help fortify confidence in a track of the storm, and whether or not we will get snow. Regardless, I think Virginia, Southern Jersey, West Virginia, Northern NC, and SE Pennsylvania needs to prepare for some sort of major winter storm. Long Island, Westchester, Southern NE, lets keep a very keen eye on this and not give up anything just yet.

Have a great evening, IF you have twitter, come follow us @weatherinthehud we will be tweeting live during the day when we can as new model runs come out. 

Forecaster: Remy Mermelstein

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