Alert archive / Maine / Mesoscale Discussions in 2020

Mesoscale Discussion 1399

August 4, 20208 counties in Maine; Essex County, Middlesex County, Suffolk County, Massachusetts; 6 counties in New Hampshire

The Storm Prediction Center issued this mesoscale discussion at Aug 4, 2020, 5:44 PM EDT for 8 counties in Maine; Essex County, Middlesex County, Suffolk County, Massachusetts; 6 counties in New Hampshire. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 4, 2020, 5:44 PM EDT (21:44 UTC)
Expired: Aug 4, 2020, 7:45 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center
Concerning: Tornado watch 417

Counties Essex County, MA, Middlesex County, MA, Suffolk County, MA, Androscoggin County, ME, Cumberland County, ME, Kennebec County, ME, Knox County, ME, Lincoln County, ME, Sagadahoc County, ME, Waldo County, ME, York County, ME, Belknap County, NH, Carroll County, NH, Hillsborough County, NH, Merrimack County, NH, Rockingham County, NH, Strafford County, NH

The radar

The Portland,ME radar (KGYX), 28 km from the middle of the area, began a volume at 21:47 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

Albany, NY (KALY), launched 12:00Z, 9.7 hours before the alert went out and 313 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: 71 J/kg
Mixed-layer CIN: -67 J/kg
Mixed-layer LCL: 818 m above ground
0-6 km bulk shear: 41 kt
0-1 km storm-relative helicity: 135 m²/s²
0-3 km storm-relative helicity: 223 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.6

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
Aug 4, 6:45 AM EDT	Mesoscale Discussion	SPC	Hampden	3 hr
Aug 4, 11:34 AM EDT	Mesoscale Discussion	SPC	Bristol, Dukes, Essex, Franklin, Hampden, Hampshire and 5 more	86 min
Aug 4, 12:43 PM EDT	Tornado Watch	SPC	Barnstable, Berkshire, Bristol, Dukes, Essex, Franklin and 8 more	6 hr
Aug 4, 3:05 PM EDT	Mesoscale Discussion	SPC	Berkshire, Bristol, Essex, Franklin, Hampden, Hampshire and 5 more	85 min

Nearby

Mesoscale Discussions in Maine, 2020 Mesoscale Discussions in New Hampshire, 2020 Mesoscale Discussions in Massachusetts, 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.