Alert archive / Massachusetts / Mesoscale Discussions in 2020

Mesoscale Discussion 1806

November 15, 202013 counties in Massachusetts; Nassau County, Suffolk County, New York; 5 counties in Rhode Island

The Storm Prediction Center issued this mesoscale discussion at Nov 15, 2020, 9:37 PM EST for 13 counties in Massachusetts; Nassau County, Suffolk County, New York; 5 counties in Rhode Island. It was in force for 113 min.

The area

The outline as issued.

The facts

Issued: Nov 15, 2020, 9:37 PM EST (02:37 UTC)
Expired: Nov 15, 2020, 11:30 PM EST
In force: 113 min
Issued by: the Storm Prediction Center
Concerning: Severe thunderstorm watch 512

Counties Barnstable County, MA, Berkshire County, MA, Bristol County, MA, Dukes County, MA, Essex County, MA, Franklin County, MA, Hampden County, MA, Hampshire County, MA, Middlesex County, MA, Norfolk County, MA, Plymouth County, MA, Suffolk County, MA, Worcester County, MA, Nassau County, NY, Suffolk County, NY, Bristol County, RI, Kent County, RI, Newport County, RI, Providence County, RI, Washington County, RI

The radar

The Boston radar (KBOX), 62 km from the middle of the area, began a volume at 02:35 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 00:00Z, 2.6 hours before the alert went out and 137 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: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 633 m above ground
0-6 km bulk shear: 66 kt
0-1 km storm-relative helicity: 741 m²/s²
0-3 km storm-relative helicity: 834 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Nov 15, 7:01 PM EST	Mesoscale Discussion	SPC		59 min
Nov 15, 7:32 PM EST	Severe Thunderstorm Watch	SPC	Greater Bridgeport Planning Region, Capitol Planning Region, Northwest Hills Planning Region, Lower Connecticut River Valley Planning Region, Naugatuck Valley Planning Region, Southeastern Connecticut Planning Region and 1 more	5 hr

Nearby

Mesoscale Discussions in Massachusetts, 2020 Mesoscale Discussions in Connecticut, 2020 Mesoscale Discussions in Rhode Island, 2020 Every mesoscale discussion in 2020

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.