Mesoscale Discussion 1681

Issued

Sep 2, 2021, 3:38 AM EDT (07:38 UTC)

Expired

Sep 2, 2021, 5:15 AM EDT

In force

97 min

Issued by

the Storm Prediction Center

Concerning

Tornado watch 486

Counties Barnstable County, MA, Dukes County, MA, Nantucket County, MA, Newport County, RI

The Boston radar (KBOX), 84 km from the middle of the area, began a volume at 07:42 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

014 
ACUS11 KWNS 020739
SWOMCD
SPC MCD 020738 
MAZ000-RIZ000-020915-

Mesoscale Discussion 1681
NWS Storm Prediction Center Norman OK
0238 AM CDT Thu Sep 02 2021

Areas affected...Southeast New England coast

Concerning...Tornado Watch 486...

Valid 020738Z - 020915Z

The severe weather threat for Tornado Watch 486 continues.

SUMMARY...The threat for a tornado and isolated damaging gusts will
persist along the southeast New England coast until the remnants of
Ida move offshore by about 11z.

DISCUSSION...Earlier supercells moved into southeast MA and became
elevated north of the surface warm front.  This boundary has moved a
little northward in the past hour, with Martha's Vineyard and
Nantucket both in the surface warm sector as of 07z.  Some slight
additional northward movement of the warm front is possible into
extreme southeast MA as the increasingly baroclinic remnants of Ida
move east-northeastward along the baroclinic zone aligned along the
southern New England coast.  Vertical shear remains favorable for
supercells with large hodographs and effective SRH at or above 300
m2/s2.  Where surface temperatures can warm into the low-mid 70s
with low 70s dewpoints, there will be sufficient surface-based
buoyancy to maintain the threat for a tornado or two and damaging
gusts.  These threats will persist within the the primary convective
band until it moves across the southeast MA coast by about 11z.

..Thompson.. 09/02/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BOX...

LAT...LON   41256965 41037064 41157149 41507143 41727078 41827015
            41866978 41726962 41256965

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The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.