What Can we Expect from Hermine Across southern New England?

The biggest weather story we have been dealing with the past few days is that of what is now Tropical Storm Hermine.  Hermine made landfall as a category one hurricane early Friday morning near St. Marks, FL and is expected to move northeastward along the eastern seaboard.  It is from here we have to watch closely as several computer forecast models have hinted that the system could move far enough northward to provide some impacts across portions of extreme southern New England.

As of 11:00 AM EDT Friday morning we see the 500mb energy associated with Hermine already well inland across southeastern GA.  From here the system is expected to track right up along the eastern seaboard, however, there are some questions with this.  There is still a possibility that the system (or at least the eye...or what's left of it) could move right back over the warm ocean waters off the coast of the Carolina's.  If this does occur there would be a strong possibility that Hermine could actually one again strengthen and keep it's tropical characteristics (remain a warm-core system).  If, however, the system stays centered over land, Hermine will continue to weaken and eventually become extratropical in nature (it will evolve from a warm-core to a cold-core system) and end up becoming baroclonic in nature (meaning it develops warm and cold fronts.  If this happens the system will occlude and that would promote further weakening all well south of southern New England.

As Hermine works up the coast something rather interesting will happen.  There is an area of high pressure that is sliding off to the east across northern New England.  As this area of high pressure pushes off the coast of ME it will act as a "block".  This "block" will do one of two things; 1) it will prevent Hermine from pushing out to sea and 2) It will actually allow for Hermine to stall off the east coast...the big question is where exactly does Hermine stall and this will ultimately determine how significant of an impact we see.

Over the past day or so computer forecast models have become in better agreement that Hermine will stall somewhere either off the Carolina coast or NJ coast.  This scenario would mean for insignificant impacts for extreme portions of southern New England.  We would be looking at periods of heavy downpours and gusty winds.  While not a major issue by any means we could see some minor coastal flooding across the CT shoreline and RI coastline.  This scenario, however, would spell major trouble for the Carolina and especially NJ coastline up to the NYC coast.  With the system potentially stalling and sitting out there for several days we would be looking at significant coastal flooding across these locations and this would be a very bad situation for anyone along the immediate coasts from the Carolina's up to the NYC coast.

What should we expect across CT/RI/SE MA?  In all likelihood, Hermine will occlude too far south to provide much in the way of significant impacts across much of southern New England outside of some gusty winds, periods of heavy downpours, and minor coastal flooding.  Taking a look at some GFS bufkit profiles for New Haven, CT, North Kingstown, RI, and Falmouth, MA during the day on Sunday the GFS is only advertising wind gust potential as much as 35-45 mph and that is more likely along the immediate coast then further inland where gusts could be as high as 30-35 mph.  Much of winds may be do more to the pressure gradient between Hermine and the area of high pressure to our northeast than with Hermine alone.  This is actually something to watch as well because if Hermine is stronger to our south and the high pressure is a bit stronger as well, this would increase the gradient and could allow for some stronger wind gusts...if this occurs we would have to watch for some isolated power outages.

All in all beginning late Saturday we should see an increase in both clouds and humidity levels with a few isolated showers possible.  Overnight Saturday into Sunday the winds should slowly begin to increase as well with the running risk for a heavy downpour.  These conditions will persist through all of Sunday and perhaps lasting into Monday or even Tuesday depending on how long Hermine sits off the coast and where Hermine stalls.  While major to significant impacts across extreme southern New England aren't looking very likely (remember this will be the case from coastal Carolina's up to NYC coast where significant coastal flooding is looking more likely), we will still receive some minor impacts with the periods of heavy downpours, gusty winds, and minor coastal flooding.  If any significant changes to the track, strength, and forecast occur they will be highlighted in any later blog posts.