Alert archive / Maryland / Mesoscale Discussions in 2011

Mesoscale Discussion 2009

August 18, 20115 states

The Storm Prediction Center issued this mesoscale discussion at Aug 18, 2011, 6:39 PM EDT for 5 states. It was in force for 96 min.

The area

The outline as issued.

The facts

Issued: Aug 18, 2011, 6:39 PM EDT (22:39 UTC)
Expired: Aug 18, 2011, 8:15 PM EDT
In force: 96 min
Issued by: the Storm Prediction Center

All 29 counties

New Castle County, DE, Anne Arundel County, MD, Baltimore County, MD, Cecil County, MD, City of Baltimore, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Burlington County, NJ, Camden County, NJ, Gloucester County, NJ, Hunterdon County, NJ, Mercer County, NJ, Middlesex County, NJ, Salem County, NJ, Somerset County, NJ, Bucks County, PA, Chester County, PA, Delaware County, PA, Montgomery County, PA, Philadelphia County, PA, Arlington County, VA, City of Alexandria, VA, City of Fairfax, VA, City of Falls Church, VA, Fairfax County, VA

The radar

The Dover AFB radar (KDOX), 91 km from the middle of the area, began a volume at 22:40 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

Phillips Aaf/Abe, MD (KAPG), launched 12:00Z, 10.7 hours before the alert went out and 2 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: 780 J/kg
Mixed-layer CIN: -64 J/kg
Mixed-layer LCL: 1022 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 83 m²/s²
0-3 km storm-relative helicity: 143 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

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SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 18, 2:59 PM EDT	Mesoscale Discussion	SPC	Albemarle, Amherst, Appomattox, Bedford, Botetourt, Buckingham and 27 more	2 hr

Nearby

Mesoscale Discussions in Maryland, 2011 Mesoscale Discussions in New Jersey, 2011 Mesoscale Discussions in Pennsylvania, 2011 Every mesoscale discussion in 2011

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.