Wednesday, August 24, 2011

Irene Guidance Shifting and Nudging Eastward

Hurricane Irene has intensified a bit overnight and is now sporting maximum winds of 110 mph and an eye that is visible on satellite imagery. Computer modeling with the storm has nudged eastward a bit, resuming a trend that started locally on Monday in the GFS and is now picking up steam in the European guidance as well.   Both model camps are now showing an offshore track for the storm, which is a huge break for us unless you are a fan of floods and 60-70 mph winds at the Shore.    This doesn't mean we dodge the bullet, entirely, of course, as we could still see at least some significant rainfall; however, the trend is going away from widespread several inch rainfall totals for everyone.

The two models (Euro up, GFS down below) show the storm tracking east of our region, with the Euro the closer of the two.  The GFS track suggests minimal impacts to the region as a whole since it is farther east -- generally some wind within 20-30 miles of South Jersey and Delaware coastlines, rain generally confined to east of I-95 (rainfall more modest).  The Euro, by virtue of being a bit closer to the coast and taking a Gloria style track in this morning's run, brings rain to most of the region (although heaviest just east of 95) and gustier winds to the coastline that could reach 50 mph if the Euro's outcome were right.

While we're not "locked" in to an outcome yet it seems the odds for a nasty storm impacting all of us may be trending downward.   The storm's shift right in the models is the result of the slightly weaker Bermuda High allowing for a greater path of lower resistance for the storm to travel a bit more northerly.   Also, the stronger storm is more prone to feel the upper level troughs that travel along the border and across Canada (one of those same disturbances will bring us thunderstorms tomorrow and also help pull Irene north to get captured by a second one that travels through Canada).   This goes back to the point I made that a 100-150 mile shift east or west means a huge change in final outcome for us -- but that such a shift is not uncommon this far out in computer modeling.  We're to the point where the average error in modeling for tropical cyclones can still be on the order of 150 miles so nothing is "locked" in.   However, signs are encouraging that the worst of the storm's impact (east side of the eye) will not impact our region.

Matt Lanza will have a writeup later on today that explains more on Irene.