Severe Thunderstorm Watch Until 9pm Elsa Moving Northeastward
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Severe Thunderstorm Watch Until 9pm Elsa Moving Northeastward
Tropical Storm Elsa is still in North Carolina but making progress moving northeastward. Ahead of the tropical storm it is obvious we are in a steam bath of temperatures in the 80s and dew points in the 70s. The atmosphere is very unstable and severe thunderstorms are developing.
The Storm Prediction Center has posted a Severe Thunderstorm Watch effective until 11pm. Don’t be surprised if another one follows for overnight as Elsa comes into play. The watch extends from Southeastern Pennsylvania northeast across Northern and Central New Jersey, the Lower Hudson Valley, most of Connecticut and Long Island. This includes NYC and Philadelphia. Here are a list of counties.
CONNECTICUT COUNTIES INCLUDED ARE
FAIRFIELD HARTFORD LITCHFIELD
MIDDLESEX NEW HAVEN NEW LONDON
. NEW JERSEY COUNTIES INCLUDED ARE
BERGEN ESSEX HUDSON
HUNTERDON MERCER MIDDLESEX
MONMOUTH MORRIS PASSAIC
SOMERSET SUSSEX UNION
. NEW YORK COUNTIES INCLUDED ARE
BRONX DUTCHESS KINGS
NASSAU NEW YORK ORANGE
PUTNAM QUEENS RICHMOND
ROCKLAND SUFFOLK ULSTER
. PENNSYLVANIA COUNTIES INCLUDED ARE
BERKS BUCKS CARBON
CHESTER DELAWARE LEHIGH
MONROE MONTGOMERY NORTHAMPTON
Take a look at the local radars from Upton and Fort Dix as thunderstorms are developing quickly with some very strong cells. We have already had reposts of hail in parts of Northern New Jersey and warnings are coming rather quickly.
Meanwhile on the regional radar we can see the rain shield from Tropical Storm Elsa in Southeastern Virginia down to North Carolina. The leading edge of that rain is approaching Southern Delaware. The rain shield is larger than what weather models have been showing so we will bear that in mind regarding adjusting any rainfall forecasts.
…ELSA CONTINUES MOVING NORTHEASTWARD OVER NORTH CAROLINA…
…HEAVY RAINS SPREADING INTO VIRGINIA…
SUMMARY OF 200 PM EDT…1800 UTC…INFORMATION
ABOUT 25 MI…40 KM SW OF RALEIGH NORTH CAROLINA
ABOUT 190 MI…305 KM WSW OF NORFOLK VIRGINIA
MAXIMUM SUSTAINED WINDS…45 MPH…75 KM/H
PRESENT MOVEMENT…NE OR 40 DEGREES AT 20 MPH…31 KM/H
MINIMUM CENTRAL PRESSURE…1007 MB…29.74 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Tropical Storm Warning is in effect for…
* South Santee River, South Carolina, to Sandy Hook, New Jersey
* Pamlico and Albemarle Sounds
* Chesapeake Bay south of North Beach and the tidal Potomac south
of Cobb Island
* Delaware Bay south of Slaughter Beach
* Long Island from East Rockaway Inlet to the eastern tip along the
south shore and from Port Jefferson Harbor eastward on the north
* New Haven, Connecticut to Merrimack River, Massachusetts including
Cape Cod, Block Island, Martha’s Vineyard, and Nantucket
There are no changes in the early forecasts regarding what to expect. Everything seems to be on course regarding timing and forecast weather conditions.
WHAT TO EXPECT HUDSON VALLEY FLASH FLOOD WATCH IN EFFECT
Assuming a coastal slightly offshore track, the main impact will be rain from 1am to 11am Friday (give or take an hour or two) with some heavy downpours. Rainfall amounts here could also be in the 1 to 3 inch range with some locally higher amounts possible. Wind should not be a big issue though along the shores of Long Island Sound it could get gusty at times. After the rain ends, weather conditions should improve in the afternoon though another shower or thunderstorm going into the evening Friday can’t be ruled out.
WHAT TO EXPECT EASTERN SOUTHEASTERN, SOUTHCENTRAL PENNSYLVANIA
These areas will be on the western edge of the precipitation shield. Notice on the rainfall forecast map above that the one inch rainfall line cuts off sharply once you go west of the New Jersey Pennsylvania border. Rain arrives here around 8pm but there will be some thunderstorms that develop this afternoon and evening from the nearby frontal boundary. The rain shield clips this area overnight and it is done by morning. Note that if the track is a little further west then we will have to shift the heavier rain numbers westward but for now we are comfortable with what we have. Weather conditions improve Friday but there could be another round of showers and thunderstorms late in the day as a cold front and upper trough pass through.
WHAT TO EXPECT LONG ISLAND & SOUTH COASTAL CONNECTICUT
The forecast track will bring the center of Elsa very close to Long Island Friday morning. The big overhanging question is an upper trough over the Great Lakes and whether Elsa responds to that by strengthening a bit as it approaches. That is a tough call at this point. This will be a 6 to 8 hour event. Rain will be on the order of up to 2 inches or so and there could be some localized flooding where amounts are locally higher.
The period of time to watch will be from midnight Friday to noon Friday with the worst of it in the hours approaching daybreak until about 8 or 9am. Winds are a tougher call because that will depend on the track. If the low center passes to say NYC, we would be on the east side with likely less rain and more wind. If the center cuts Long Island in half then conditions will be different west of the low verses east. Also we don’t know how strong the low will be and if it doesn’t react to the upper trough over the Great Lakes, then we could see a weaker system that is more of a nuisance then anything else. Once Elsa goes by to our north weather conditions should improve Friday though another shower or thunderstorm is possible in the evening. Then we move a head to a warm and humid weekend with only a slight chance for a pop up downpour or thunderstorm each afternoon.
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MANY THANKS TO TROPICAL TIDBITS & F5 WEATHER FOR THE USE OF MAPS
Please note that with regards to any severe weather, tropical storms, or hurricanes, should a storm be threatening, please consult your local National Weather Service office or your local government officials about what action you should be taking to protect life and property.