Alert archive / Massachusetts / Mesoscale Discussions in 2021

Mesoscale Discussion 1333

July 23, 20214 states

The Storm Prediction Center issued this mesoscale discussion at Jul 23, 2021, 5:47 PM EDT for 4 states. It was in force for 58 min.

The area

The outline as issued.

The facts

Issued: Jul 23, 2021, 5:47 PM EDT (21:47 UTC)
Expired: Jul 23, 2021, 6:45 PM EDT
In force: 58 min
Issued by: the Storm Prediction Center
Concerning: Severe potential...watch unlikely
Chance of a watch: 20%

All 22 counties

Bristol County, MA, Essex County, MA, Middlesex County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Worcester County, MA, Androscoggin County, ME, Cumberland County, ME, Sagadahoc County, ME, York County, ME, Belknap County, NH, Carroll County, NH, Grafton County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI

The radar

The Portland,ME radar (KGYX), 96 km from the middle of the area, began a volume at 21:48 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.

The nearest sounding before it

Gray, ME (KGYX), launched 12:00Z, 9.8 hours before the alert went out and 96 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 16 J/kg
Mixed-layer CIN: -94 J/kg
Mixed-layer LCL: 1504 m above ground
0-6 km bulk shear: 10 kt
0-1 km storm-relative helicity: -19 m²/s²
0-3 km storm-relative helicity: -5 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

374 
ACUS11 KWNS 232148
SWOMCD
SPC MCD 232147 
MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-232245-

Mesoscale Discussion 1333
NWS Storm Prediction Center Norman OK
0447 PM CDT Fri Jul 23 2021

Areas affected...portions of New England.

Concerning...Severe potential...Watch unlikely 

Valid 232147Z - 232245Z

Probability of Watch Issuance...20 percent

SUMMARY...Scattered strong to isolated severe storms are forecast to
persist for a few hours.

DISCUSSION...Despite weak shear, several severe storms have occurred
across the Northeast over the past few hours with reports of
damaging wind and severe hail. The instability fueling this activity
is entirely diurnally driven and thus the threat should start to
wane pretty quickly this evening. However, in the meantime, MLCAPE
around 500 J/kg and cool air aloft will continue to support a threat
for a few strong to isolated severe storms. This is supported by the
20Z HRRR which shows storms mostly weakened by 00Z.

..Bentley/Edwards.. 07/23/2021

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

ATTN...WFO...GYX...BOX...BTV...

LAT...LON   44627151 44216988 43876953 43716959 43587001 43337033
            42997058 42727069 42167057 41637048 41367092 41467130
            41807206 42987210 43997220 44697197 44627151

Nearby

Mesoscale Discussions in Massachusetts, 2021 Mesoscale Discussions in New Hampshire, 2021 Mesoscale Discussions in Maine, 2021 Every mesoscale discussion in 2021

Sources

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.