Alert archive / New Jersey / Mesoscale Discussions in 2020

Mesoscale Discussion 1394

August 4, 202011 counties in New Jersey; Philadelphia County, Pennsylvania

The Storm Prediction Center issued this mesoscale discussion at Aug 4, 2020, 8:59 AM EDT for 11 counties in New Jersey; Philadelphia County, Pennsylvania. It was in force for 91 min.

The area

The outline as issued.

The facts

Issued: Aug 4, 2020, 8:59 AM EDT (12:59 UTC)
Expired: Aug 4, 2020, 10:30 AM EDT
In force: 91 min
Issued by: the Storm Prediction Center
Concerning: Tornado watch 416

Counties Atlantic County, NJ, Burlington County, NJ, Camden County, NJ, Cape May County, NJ, Cumberland County, NJ, Gloucester County, NJ, Mercer County, NJ, Middlesex County, NJ, Monmouth County, NJ, Ocean County, NJ, Salem County, NJ, Philadelphia County, PA

The radar

The Philadelphia radar (KDIX), 42 km from the middle of the area, began a volume at 13:02 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 1.0 hours before the alert went out and 201 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: 472 J/kg
Mixed-layer CIN: -6 J/kg
Mixed-layer LCL: 648 m above ground
0-6 km bulk shear: 52 kt
0-1 km storm-relative helicity: 254 m²/s²
0-3 km storm-relative helicity: 273 m²/s²
Significant tornado parameter: 0.8
Supercell composite: 2.9

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, 2:26 AM EDT	Tornado Watch	SPC	Cape May, Cumberland, Salem	9 hr
Aug 4, 5:15 AM EDT	Mesoscale Discussion	SPC	Atlantic, Burlington, Camden, Cape May, Cumberland, Gloucester and 1 more	3 hr
Aug 4, 6:45 AM EDT	Mesoscale Discussion	SPC	Atlantic, Bergen, Burlington, Camden, Cumberland, Essex and 14 more	3 hr
Aug 4, 7:23 AM EDT	Tornado Watch	SPC	Atlantic, Bergen, Burlington, Camden, Essex, Gloucester and 12 more	9 hr
Aug 4, 11:13 AM EDT	Mesoscale Discussion	SPC	Bergen, Burlington, Camden, Essex, Hudson, Hunterdon and 8 more	92 min

Nearby

Mesoscale Discussions in New Jersey, 2020 Mesoscale Discussions in Pennsylvania, 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.