Tuesday, November 06, 2012

Updating The Coastal Storm

A couple of "encouraging" signs for those who don't want a battering of wind at the Shore are coming out of last night's (the stuff that comes out between 10 PM and 1 AM) guidance. First, signs are pointing towards a somewhat weaker coastal storm developing than what was formerly modeled. Second, there's a slight nudge east in the Euro on its track and a more significant nudge east in the GFS model in last night's runs. The general consensus is for the storm to track a bit more east than previously modeled...and part of that is due to the weaker scenario the models are starting to suggest may develop. The exception to that is the NAM model, which moved a bit to the west with last night's run and is pretty close in track/location to the Euro at this point.

(Note -- the early AM (6z) GFS did come back west with the low, showing a more potent storm solution...but it is an outlier compared to the trend of the model overall).

You can see the weaker shift in the Euro graphics below.  The midday (12z) run from yesterday shows a low pressure center below 988 mb east of Cape May, with heavier precipitation breaking out across Southeast PA and Delaware.  Last night's run shows a weaker (sub 992) low that's a little farther east, a little weaker, and a bit less precipitation on the board.


From a wind standpoint, the Euro's weaker output is an encouraging sign. This is the top winds for Wednesday night, at the storm's peak intensity. While there are some pretty gusty breezes that could reach 40-45 mph, there is not the same impact of intense wind that prior runs were suggesting would occur.  There could be some minor coastal flooding along the Shore but again, not as bad as some of the suggestions in past modeling.  It's still a bit of slap from Mother Nature but not a pummeling...could slow recovery but not a full blown beat down.


Regarding snow, there is some potential for it still on the table.  However, the lighter precipitation and the weaker low don't necessarily support the snow that the precip output maps are showing.  Winds would track off of the ocean, which is still pretty mild, and given the precip rates aren't the heaviest it may be pretty tough to get snow to fall to the surface without it melting on the way down.   The good news is that the bulk of precipitation would fall late in the afternoon through evening so without any sun action at work there could be a bit of a shot for snow to stick to grassy surfaces IF precip is heavy enough.

The main areas, if you were to believe the Euro, would be across New Jersey and Delaware.


The NAM also showed this potential in New Jersey as well in the 0z (last night) run -- showing a moderate to heavier swath of precipitation (deformation banding?) that lines up east of Philadelphia and along the spine of the Garden State, northeast through the NYC Metro and up into Connecticut.


So, where does this leave us?   The slower intensification that the models are leaning towards allows the storm to scoot a little bit further east.  If we do get a band of precipitation to fire up on the western flank, some snow is definitely possible to mix if not fall to the surface.  However, the odds of this suggest (as of now) that Jersey may get this instead of Philly and points west as modeling nudges east with the storm.  This is a very fine line as some model runs still show the potential for a bomb and more explosive development which would throw precipitation back west and bring snow farther west.  However, the overall trend from the models is to go slightly weaker and keep the snow axis (should it develop) to the city's east.

If snow were to fall, we'd probably be looking at the prospect of an inch or two on grassy surfaces on average wherever that band of precipitation sets up.  A stronger scenario as past modeling indicated may suggest more but odds, like I said, are trending weaker with the storm...so, for now, an inch to three inches seems a reasonable play for interior sections of New Jersey...generally in a swath from along I-95 eastward to about ten miles in from the coast.   This includes the city, includes Lower Bucks, Delaware County, Lower Montco, Trenton, and down to about Wilmington.  The coast might see some wet snowflakes mix in but odds for snow to stick here is lower than farther west.  Our thoughts on the snow being wet, heavier, denser are still very much on the table.  If this storm does end up closer to the coast and a bit stronger, those totals are low...as of now, that's the first guess we're going with.

We'll update on Facebook and Twitter later on today -- and provide another round of blog on this later this evening which will include a forecast accumulation map.