Alert archive / Massachusetts / Mesoscale Discussions in 2021
Mesoscale Discussion 1944
The Storm Prediction Center issued this mesoscale discussion at Nov 12, 2021, 3:01 PM EST for Barnstable County, Dukes County, Massachusetts. It was in force for 89 min.
The area
The outline as issued.
The facts
- Issued
- Nov 12, 2021, 3:01 PM EST (20:01 UTC)
- Expired
- Nov 12, 2021, 4:30 PM EST
- In force
- 89 min
- Issued by
- the Storm Prediction Center
- Concerning
- Severe potential...watch unlikely
- Chance of a watch
- 20%
Counties Barnstable County, MA, Dukes County, MA
The radar
The Boston radar (KBOX), 85 km from the middle of the area, began a volume at 20:05 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, 8.0 hours before the alert went out and 187 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
- 191 J/kg
- Mixed-layer CIN
- -19 J/kg
- Mixed-layer LCL
- 601 m above ground
- 0-6 km bulk shear
- 50 kt
- 0-1 km storm-relative helicity
- 262 m²/s²
- 0-3 km storm-relative helicity
- 370 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 1.9
The text
As transmitted.
673 ACUS11 KWNS 122001 SWOMCD SPC MCD 122001 MAZ000-122130- Mesoscale Discussion 1944 NWS Storm Prediction Center Norman OK 0201 PM CST Fri Nov 12 2021 Areas affected...southeast MA Concerning...Severe potential...Watch unlikely Valid 122001Z - 122130Z Probability of Watch Issuance...20 percent SUMMARY...Mini supercells embedded within a rain shield will continue north towards southeast MA over the next 1-2 hours. A brief tornado and/or wind damage are possible. DISCUSSION...KBOX radar imagery shows a few weak mesocyclones to the southwest of Martha's Vineyard moving to the north and approaching the MA coast over the next hour. The airmass continues to slowly destabilize near the coast with temperatures in the lower 60s with dewpoints ranging from 58-60 deg F. The KBOX VAD shows intense low-level wind shear with 70 kt flow sampled at 1 km MSL. The observed storm motion is resulting in around 250 m2/s2 0-1 km SRH per the KBOX VAD (less than the 500 m2/s2 implied using the Bunker's storm motion estimate). Given the weak buoyancy and slow-to-destabilize marine layer near the coast, it seems the severe risk will remain isolated. However, a brief tornado and/or wind damage could accompany any supercell moving ashore in southeast MA during the next couple of hours. ..Smith/Hart.. 11/12/2021 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...BOX... LAT...LON 40827120 41777074 41947032 41516994 40767078 40827120
Nearby
Mesoscale Discussions in Massachusetts, 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.