Mesoscale Discussion 1393
NWS Storm Prediction Center Norman OK
0545 AM CDT Tue Aug 04 2020
Areas affected...Much of New Jersey...southern New York...southern
Concerning...Severe potential...Tornado Watch likely
Valid 041045Z - 041315Z
Probability of Watch Issuance...95 percent
SUMMARY...Conditions will become more favorable for tornadoes this
morning from New Jersey into parts of southern New England.
DISCUSSION...A prominent arc of storms which have a history of
tornadoes continues to move northward across the Delmarva.
Supporting the threat of tornadoes is strong pressure falls, a very
moist air mass, and 0-1 SRH in excess of 300 m2/s2.
Extending north from the tropical storm Isaias, a quasi-stationary
zone of rain and storms persists from the PA/NJ border into southern
NY and western CT. East of this area, dewpoints are well into the
70s F, resulting in MLCAPE in excess of 500 J/kg as of 11Z.
As the cyclone continues north, strengthening easterly surface winds
will allow the instability gradient to shift a bit further inland,
while shear increases. Further destabilization is possible,
especially if there can be pockets of heating.
While isolated cells, including mini-supercells, will be possible,
the greatest threat for supercells and a few tornadoes is expected
to remain with the primary, long-lived arcing band of storms, just
ahead of the cyclone and where pressure falls are strongest.
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 40277387 39787399 39467419 39297439 39187486 39387551
39687569 40517544 41427473 41897412 42137344 42177261
42027210 41887177 41337168 41017184 40727264 40567321