Mesoscale Discussion 2012
NWS Storm Prediction Center Norman OK
0823 AM CDT Fri Aug 18 2023
Areas affected…Eastern Massachusetts
Concerning…Severe potential…Watch unlikely
Valid 181323Z – 181430Z
Probability of Watch Issuance…5 percent
SUMMARY…Brief tornadoes will remain possible over the next hour as
a line of thunderstorms approaches the eastern Massachusetts coast.
DISCUSSION…Over the past 30-45 minutes, at least two tight,
low-level velocity couplets associated with possible tornadoes have
been observed from the KBOX radar as a line of thunderstorms
approaches the Boston area. VPW observations are sampling 0-1 km SRH
on the order of 500 m2/s2, which is very favorable for a continued
tornado threat assuming low-level thermodynamics remain favorable.
Based on observed and forecast soundings, temperatures in the low
70s are required to achieve adequate low-level buoyancy for
near-surface based convection capable of pose a tornado threat.
Latest surface observations show these conditions exist immediately
ahead of the line along a warm frontal zone draped from the Boston
area southward into Plymouth county. Consequently, additional brief
tornadoes will be possible before this line of storms reaches the
coast – especially on the northern end where a supercell-line hybrid
storm mode is noted. Given the very small spatial and temporal scale
of this threat, a watch is not expected.
…Please see www.spc.noaa.gov for graphic product…
LAT…LON 42397107 42467092 42457065 42367026 42157002 41957008
41787036 41717069 41647122 41717132 42067114 42277118