At issue this evening is the creature that's been retrograding westward toward the Mid-Atlantic coast. I'd hoped to post here about this storm earlier today, but was limited on time and ended up tweeting instead. First, to set my frame of reference, I'll include the list of my tweets from 11 AM this morning (I'm @mattnoyes on Twitter for those who'd like to follow). Then, I'll deliver my thoughts on where we stand as of now (Thursday night):
List of Tweets From 11 AM:
- Initiating a full analysis of the storm developing off NJ coast. Need to determine what, if any, potential exists of this going tropical.
- Visible and IR satellite imagery indicates dual convective clusters rotating around mid-level center, *displaced* from low level center
- Though mid-level circulation is displaced, t'storm clusters are both N/NE and S/SW of surface low at long/lat 72W, 36N
- Atlantic City, NJ, marina gusting 38 mph. Largely pressure gradient driven. 36 mph gusts buoys 44025, 44017, 44008, all far from storm.
- Water temp under storm circulation is abt 80 degrees. MIT potential storm strength puts this area as Cat 3 or 4, 960-965 mb potential.
- Mid-level wind shear is strong, 4cast to weaken, then pick back up again. 35-40 mph gusts will continue, but stronger wind core to develop.
- Summary: Storm at 36N/72W to move W and "landfall" Southern Delaware Bay approx 2AM. Tropical features, but not tropical.
- Wind too removed S side of storm, shear too great to allow full organization, symmetry is lost by day's end.
- Mixing to 950mb with wind 55-60 kt means gust 60+ mph Cntrl/Srn NJ coast likely, iso 70 mph possible but unlikely to b recorded.
- In NewEng, gust to 40mph Long Island Sound early Fri AM, coastal flooding W end of sound. Otherwise, breezy leftover rain all that's left!
8:30 PM EDT THURSDAY ANALYSIS - HYBRID CREATURE RAMPING UP:
So, now the question is, how is this coming together this evening and where do we stand on the potential for damaging wind associated with the circulation. I have to say I was quite surprised...
this morning when conducting the above analysis to see the only advisories in effect were wind advisories for the Mid-Atlantic coastline that were set to expire at 7 PM, associated only with pressure gradient induced wind gusts, and not with the storm that seemed quite evident to make "landfall" overnight Thursday night. This was concerning because of what seemed like strong potential for damaging wind gusts overnight on the north side of the cyclone, that would apparently strike with little official warning. By mid-afternoon, the wind advisory was extended until 9 PM for gusts to 45 mph.
I'm writing this at 8:30 PM and the wind has only been increasing, gusting to 45 mph at the Delaware Bay buoy, 40 mph at the Atlantic City Marina (sustained at 31 mph) and Brandywine Shoal Light (sustained at 37 mph), and we still have a long way to go. As indicated in my tweets, I was expecting a "landfall" into Southern Delaware Bay around 06Z by this surface circulation, with the strongest wind on the north side of the circulation. The GFS and NMM both indicated mixing to 950 mb, with a low level, pressure-gradient induced jet of 60+ kts ready to be tapped, which supports 60+ mph gusts right at the coast on the north side of the circulation. Though the deep convection presents some tropical characteristics, and the storm is warm core according to the cyclone phase analysis conducted by Florida State University, the storm is asymmetric and also has featured lopsided wind, remaining slightly removed from the center.
That storm circulation appears to have redeveloped farther south this evening, off the Virginia coast at 75W/37N, and this is supported by the highest gust on the east coast of 47 mph (44 mph sustained) at Chesapeake Light as of 8 PM EDT. This could be deceiving, however - while this appears to be one circulation, another still appears present farther northeast, closer to 72.5W/32.5N, and convection is evident wrapping around this center on IR imagery, where the coldest tops to -60 C are present.
The guidance is varied, and generally favors carrying the surface low into the Delaware Coast overnight, farther south that earlier runs that took the storm into Delaware Bay. What's interesting is the CMC solution to stall the low off the coast the first half of Friday, then move in northwest into Delaware Bay. This essentially is the southern circulation pausing and then being wrapped into the northern circulation and associated mid-level circulation. The RUC has now picked up on this, as well, and given the satellite presentation, this seems not only plausible but increasingly likely. The result will be lashing wind and waves from Virginia Beach through the Central Jersey coast, continuing through the night and even the first half of Friday, with moderate coastal flooding to vulnerable east and northeast facing shorelines, and isolated gusts to 60+ mph with more widespread immediate coastal gusts of 50+ mph possible all the way through early Friday. Lashing rainbands will be another feature - the heaviest evident just offshore on radar - and this rainband is likely to stall on the west side of the circulation, enhanced by Atlantic inflow, and some rain amounts of .50" per hour that are observed as of this writing should increase to .75"-1" per hour in heaviest banding due to increasing frontogenesis in the lowest levels, and some amounts may exceed 4" and near 5" along the immediate coast of Delware through Southern New Jersey!
Of course, the combination of heavy rain and continued, lashing wind will result in some tree damage/uproots, not to mention toppling of lightweight objects like patio furniture. The coastal flood problem will be greater than has been advertised if the storm stalls as I'm expecting, with a widespread moderate event for many vulnerable coasts.
We'll see how this verifies, but an already nasty looking system, a hybrid, asymmetric warm core system, looks to be even nastier with the potential for a stall.
I hope some of you in the Mid-Atlantic will offer observations/analysis. Feel free to comment on my post, or even better, become a correspondent and submit your own analysis or reports of what's happening. Flickr photos do the trick, too!
Matt (aka "Supercell")