Alert archive / Virginia / Mesoscale Discussions in 2009

Mesoscale Discussion 847

May 16, 20097 counties in Maryland; 26 counties in Virginia; Jefferson County, West Virginia

The Storm Prediction Center issued this mesoscale discussion at May 16, 2009, 2:36 PM EDT for 7 counties in Maryland; 26 counties in Virginia; Jefferson County, West Virginia. It was in force for 24 min.

The area

The outline as issued.

The facts

Issued: May 16, 2009, 2:36 PM EDT (18:36 UTC)
Expired: May 16, 2009, 3:00 PM EDT
In force: 24 min
Issued by: the Storm Prediction Center

All 34 counties

Baltimore County, MD, Carroll County, MD, City of Baltimore, MD, Frederick County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Albemarle County, VA, Arlington County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Staunton, VA, City of Waynesboro, VA, Clarke County, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Greene County, VA, Loudoun County, VA, Louisa County, VA, Madison County, VA, Orange County, VA, Page County, VA, Prince William County, VA, Rappahannock County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Jefferson County, WV

The radar

The Sterling radar (KLWX), 39 km from the middle of the area, began a volume at 18:37 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

Washington/Dulle, VA (KIAD), launched 12:00Z, 6.6 hours before the alert went out and 42 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: 216 J/kg
Mixed-layer CIN: -64 J/kg
Mixed-layer LCL: 608 m above ground
0-6 km bulk shear: 17 kt
0-1 km storm-relative helicity: 54 m²/s²
0-3 km storm-relative helicity: 60 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.5

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
May 16, 12:05 PM EDT	Mesoscale Discussion	SPC	Allegany, Garrett	55 min
May 16, 1:00 PM EDT	Severe Thunderstorm Watch	SPC	Brooke, Hancock, Marion, Marshall, Monongalia, Ohio and 1 more	7 hr
May 16, 2:46 PM EDT	Mesoscale Discussion	SPC	Barbour, Boone, Braxton, Cabell, Calhoun, Clay and 20 more	59 min
May 16, 3:55 PM EDT	Mesoscale Discussion	SPC	Monongalia	65 min

Nearby

Mesoscale Discussions in Virginia, 2009 Mesoscale Discussions in Maryland, 2009 Mesoscale Discussions in West Virginia, 2009 Every mesoscale discussion in 2009

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.