Alert archive / Massachusetts / Mesoscale Discussions in 2021
Mesoscale Discussion 1559
The Storm Prediction Center issued this mesoscale discussion at Aug 19, 2021, 10:49 AM EDT for 5 counties in Massachusetts; Bristol County, Kent County, Providence County, Rhode Island. It was in force for 86 min.
The area
The outline as issued.
The facts
- Issued
- Aug 19, 2021, 10:49 AM EDT (14:49 UTC)
- Expired
- Aug 19, 2021, 12:15 PM EDT
- In force
- 86 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Bristol County, MA, Middlesex County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Bristol County, RI, Kent County, RI, Providence County, RI
The radar
The Boston radar (KBOX), 29 km from the middle of the area, began a volume at 14:54 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
Brookhaven, NY (KOKX), launched 12:00Z, 2.8 hours before the alert went out and 191 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.
- Mixed-layer CAPE
- 1927 J/kg
- Mixed-layer CIN
- 0 J/kg
- Mixed-layer LCL
- 459 m above ground
- 0-6 km bulk shear
- 31 kt
- 0-1 km storm-relative helicity
- 113 m²/s²
- 0-3 km storm-relative helicity
- 137 m²/s²
- Significant tornado parameter
- 1.0
- Supercell composite
- 5.5
The text
As transmitted.
908
ACUS11 KWNS 191450
SWOMCD
SPC MCD 191449
MAZ000-RIZ000-CTZ000-191615-
Mesoscale Discussion 1559
NWS Storm Prediction Center Norman OK
0949 AM CDT Thu Aug 19 2021
Areas affected...Eastern MA...RI...far northeastern CT
Concerning...Severe potential...Watch unlikely
Valid 191449Z - 191615Z
Probability of Watch Issuance...20 percent
SUMMARY...Weakly rotating storms capable of locally damaging wind
and/or a brief tornado remain possible this morning.
DISCUSSION...At 1445Z, a cluster of convection (associated with the
midlevel remnant of T.C. Fred) is approaching eastern MA and
northern RI. Occasional rotation has noted with convection on the
western edge of the cluster, and that will likely continue through
the morning, given the favorable wind profile noted in the KBOX VWP.
Widespread cloudiness and precipitation should tend to limit the
severe threat, but the stronger cells will be capable of locally
damaging wind and a brief tornado, especially as they interact with
a weak baroclinic zone noted across eastern MA.
The threat is expected to begin diminishing this afternoon as
midlevel drying overspreads the region. Due to the relatively
limited duration and magnitude of the threat, watch issuance is
unlikely.
..Dean/Dial.. 08/19/2021
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BOX...
LAT...LON 42457183 42627127 42637074 42387070 42127070 41587087
41637152 41707170 41957183 42247184 42457183Nearby
Mesoscale Discussions in Massachusetts, 2021Mesoscale Discussions in Rhode Island, 2021Every 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.