Talk about a model spread. The op GFS is completely flat, sending the storm right through the southeast and into the Atlantic even south of Bermuda. The Euro has wavered a little, but still shows the potential for a high impact nor'easter for the entire east coast. The UKMET, and GGEM are in between the two extremes and probably the best compromise at this time. Also in the mix, the latest Euro ensemble mean is in fact west of the op Euro which is impressive considering it is the mean of 51 ensemble forecasts. The GFS ensembles are a little west of the op GFS but still suppressed very far to the south and east. However, the spread on the GFS ensembles is over 12mb for a large portion of the NW Atlantic.
The main disagreements between the models that are affecting the storm intensity and resulting track are:
1) The intensity of the shortwave moving south of the region tomorrow
2) The timing of the next Pacific system entering the NW.
3) The intensity of the polar vortex in Canada.
Here is what would would be more favorable for east coast cyclogenesis:
1) Shortwave is weaker.
2) The Pacific system is slower.
3) The polar vortex is weaker.
In the short term, we can track the shortwave as it cuts through the Ohio Valley and Mid Atlantic tomorrow. A stronger shortwave would flatten the flow east of the Mississippi River, and allow for the potential storm next week to scoot to the south. A weaker shortwave allows for more "buckle" potential in the flow and a more amplified pattern.
The Pacific pattern has been giving us problems all winter long as the La Nina drives an active jet stream. As for this situation the Pacific needs to be watched around 84 hours. The PNA is currently negative and will remain so through the period, but a transient east based high pressure ridge will develop downstream of the next Pacific system to come on board the west coast. The 00z Euro showed strong ridging over the Rockies, while the GFS is flatter and also has the ridge axis further east. Today's 12z Euro has shifted more towards the GFS forecast.
Last is the polar vortex positioning in northern Quebec. The Euro 00z today and back to the 00z yesterday were consistent in a weaker vortex, again allowing more "buckle" potential and amplification. The latest run is a little closer to the GFS solution which shows a stronger vortex driving strong mid level winds in the southeast. This limits the wind that the shortwave on Monday can differentiate on and therefore resulting in a weaker, less amplified system.
The latest model guidence has taken a step toward a flatter track. However, the model forecasts that lie on the south/east side of the guidence is still in disagreement as the reasoning is different. While the Euro has trended east in the past two days, it still is hanging onto a storm not too far east of the benchmark, which offers some hope. Personally, I also think the GFS run is off the mark, and I doubt the storm will end up that suppressed. On the other hand, the trend has been towards the east, and even the furthest west model is a close call for us. There is also a consensus on a fairly sharp cutoff in precipitation to west with the storm.
My current outlook on the storm: It is becoming more unlikely that anyone gets plowable snowfall west of I95 in New England. Inside the I95 Corridor, there is still potential for a high impact storm. Based on the factors I've mentioned and the features that will be sampled tomorrow, I think by tomorrow afternoon we'll have a clear idea of what this storm is going to do.
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