Thursday, October 25, 2012

A Blast of Sandy

Sandy underwent a rapid phase of intensification last night while traversing between Jamaica and Cuba, aided in part by enhanced outflow in the northern quadrant of the storm due to the upper jet to the storm's north.  This allowed Sandy to intensify from a Category 1 to near major hurricane status in a few hours' time before the center came ashore earlier this morning over Eastern Cuba.   It helps that those waters between Cuba and Jamaica are also among the warmest in the Caribbean Sea as well...but the interaction of the upper jet over the Bahamas and Florida did a great job in intensifying the storm.

The model spread on Sandy is still pretty wide -- in timing and in track.  The Euro continues its consistent trend in bringing the storm's center ashore back inland over our region -- most of the modeling from the Euro has had a landfall point between the Delmarva and Long Island with the storm, with the timing varying somewhat.  The GFS is still suggesting a landfall much farther northeast, with the storm feeding energy back into the cold trough that digs in but not fully phasing or capturing the storm.  While we would be breezy, chilly, and showery...the worst impacts would be over New England and Atlantic Canada in the GFS scenario.

From a modeling standpoint, the Euro track from last night is probably presents the worst case scenario for the Shore and Delaware as far as a coastal flooding, beach erosion, and wind standpoint.  The model shows a pretty sustained swath of 60 mile per hour winds along the coast, gusting perhaps to hurricane intensity.  The northeast and east wind along the coast and down Delaware Bay means a high coastal flooding threat for the beach towns and the Delaware side of the bay.  More importantly, because the storm's track would be close to the region those wind impacts will be felt over a wider swath of real estate inland.   Unlike a typical tropical system where the wind impacts are highest closest to the center, gusty winds will be felt over a wider swath of real estate...and wind impacts from a Bethany Beach "hit" would be felt up the coast to Long Island...not just near Bethany itself.

So...if a close to coast track occurs...besides the additional wind, coastal flooding, beach erosion factor...rains will be an issue as well.  Rainfall totals could reach a few to several inches across the region, which means some inland flooding will be an issue as well.

The saving grace track would be something similar to the GFS or something close to that -- a track near Atlantic Canada or eastern Maine.  Such a scenario would still produce wind, some coastal flooding, and some beach erosion...but the magnitude of impact will be much lower than the Euro...300 miles of difference in track will do that.

Regarding Sandy today, it will work north into the Atlantic and through the Bahamas.  As the storm interacts with the upper jet that we mentioned at the beginning of the post, the storm will probably begin a slow transition away from purely tropical characteristics tonight and towards a hybrid status over the weekend.  This transition will not be rapid but the transition will increase the size of the storm, enlarge its wind field, and set the stage for its East Coast impacts next week.  Odds right now lean towards the greatest impacts being from Maryland to Long Island but a shift east with the storm will shift those greatest impacts farther up the coast.  Nothing is stone with the storm yet.