Moving To A European Solution
Models at this point should begin to be moving to some sort of solution but the process can be very slow. The European model has been probably the most consistent of all the models the last few days which really isn’t saying much but we will go with it until proven otherwise.
Polar Vortex Remains Key
The biggest key to all this going forward is the polar vortex. The polar vortex or PV for short is moving to the geographic position that is favorable for a winter storm along the east coast. That position is roughly at 50 degrees north or 50 degrees west or what we call the 50-50 low. The reason why that low is so important is that it creates upper air conditions that cause storms to track south of Southern New England. The strength of the PV and how it interacts with the storm system in question determines whether it moves close enough to bring big snows to the Northeast or is it so strong that it forces the track further south and offshore. If its too weak, then we have a surface low that hugs the coast and brings snow to rain for the coastal plain. It also determines the strength and extent of cold air in the east. These are the reasons why snowstorms are so difficult to forecast for the Northeast. Anyone who has this all figured out right now; all i can say is congratualtions! You are a better forecaster than most. Put your forecast to bed and wake up next Tuesday.
There are three systems in the subtropical jet that are in question here. The map above is for Friday morning January 15th. You can clearly see how complicated this set up is. You have the polar vortex at 50N 50 W with an arm that is rotating on the west side of this back to Lake Winnepeg. You have three very strong short waves in the southern stream and the European has become increasingly stronger with the lead system. That arm rotating back westward is extremely important because if the polar vortex splits and partially reforms to the west, it will cause an more westerly and northerly track of any surface low. Remember this is the same system that the European had well offshore a few days ago and has now come around to the idea that this is not going to be the case.
Now we move along to the next time frame which is Saturday morning. The European model is lifting up system 1 as system 2 comes around. The polar vortex remains in place. The second vortex is forming but remains weaker than the P.V. The result of this is heavy precip is lifted northward into the northeast. How strong those 2 vortexes are and which one dominates will be the key to what happens along the coast. This European model run suggests that inland areas from Pennsylvania, Northwest New Jersey, the Hudson Valley and interior Connecticut and points north and west would be in a mainly snow event. For the coast the outcome will depend in the end on the Polar Vortex at 50N 50W. If that vortex is more dominant it will force colder air further south into the coastal plain. It would produce a slightly flatter look with a weaker surface low. Literally the European would also introduce an icing situation for areas just inland of the coastal plain on this particular run. I WANT TO EMPHASIZE THIS IS NOT MY FORECAST.
Differences With GFS
Above is the GFS model and the differences between it and the European are huge. The most important difference is that the GFS has moved the polar vortex out much faster than the European. This actually creates a ridge between the PV and the midwest system as it becomes a separate feature. Without the stronger polar vortex, the Midwest system does not dive southward like the European has. This creates a warmer solution all the way around. The ideas of both models are similar but it becomes a matter of speed and timing. IF the European is right you will have a colder solution because the polar vortex is stronger and takes longer to pull out. Past situations like this have usually seen the polar vortex be stronger and further left as reality comes into play. The strength of the block will determine this with regards to whether we will be moving to a colder solution as we get closer to the event time frame.
Subtropical System In The Atlantic
This is one variable I want to bring up. The intense low that has been moving to the Central Atlantic will in my view be an interesting player here. Should this strengthen even further as either a non tropical or subtropical system, it could strengthen the ridge to the north of it more than forecast which would mean a stronger block that lasts longer than forecast by all models. This could change the profile of everything across the board.
We still have many runs to go before moving to a final resolution of all this but at least the overall picture of how this is going to play out is becoming a little clearer. If model trends continue you will know my view when I begin to take a more serious stand on the outcome. Meanwhile you can check the European model Video from this morning to use as a comparison and explain things further.
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