Alert archive / Virginia / Mesoscale Discussions in 2009
Mesoscale Discussion 784
The Storm Prediction Center issued this mesoscale discussion at May 9, 2009, 5:58 PM EDT for 7 counties in Maryland; 26 counties in North Carolina; 46 counties in Virginia. It was in force for 62 min.
The area
The outline as issued.
The facts
- Issued
- May 9, 2009, 5:58 PM EDT (21:58 UTC)
- Expired
- May 9, 2009, 7:00 PM EDT
- In force
- 62 min
- Issued by
- the Storm Prediction Center
All 79 counties
Caroline County, MD, Dorchester County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Worcester County, MD, Bertie County, NC, Camden County, NC, Chatham County, NC, Chowan County, NC, Durham County, NC, Edgecombe County, NC, Franklin County, NC, Gates County, NC, Granville County, NC, Greene County, NC, Halifax County, NC, Hertford County, NC, Johnston County, NC, Lee County, NC, Martin County, NC, Nash County, NC, Northampton County, NC, Pasquotank County, NC, Perquimans County, NC, Pitt County, NC, Vance County, NC, Wake County, NC, Warren County, NC, Washington County, NC, Wayne County, NC, Wilson County, NC, Accomack County, VA, Amelia County, VA, Brunswick County, VA, Charles City County, VA, Chesterfield County, VA, City of Chesapeake, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Franklin, VA, City of Hampton, VA, City of Hopewell, VA, City of Newport News, VA, City of Norfolk, VA, City of Petersburg, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Richmond, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Williamsburg, VA, Dinwiddie County, VA, Essex County, VA, Gloucester County, VA, Greensville County, VA, Hanover County, VA, Henrico County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, King William County, VA, Lancaster County, VA, Lunenburg County, VA, Mathews County, VA, Mecklenburg County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Nottoway County, VA, Prince George County, VA, Richmond County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA
The radar
The Norfolk radar (KAKQ), 78 km from the middle of the area, began a volume at 21:59 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 watches that followed
Watches SPC issued over any of the same counties within four hours of this discussion.
The nearest sounding before it
Roanoke, VA (KRNK), launched 12:00Z, 10.0 hours before the alert went out and 173 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.
- Mixed-layer CAPE
- 589 J/kg
- Mixed-layer CIN
- -21 J/kg
- Mixed-layer LCL
- 666 m above ground
- 0-6 km bulk shear
- 39 kt
- 0-1 km storm-relative helicity
- 22 m²/s²
- 0-3 km storm-relative helicity
- 33 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.6
The text
As transmitted, in the capitals the NWS used until 2016.
000
ACUS11 KWNS 092159
SWOMCD
SPC MCD 092158
DEZ000-MDZ000-VAZ000-NCZ000-092300-
MESOSCALE DISCUSSION 0784
NWS STORM PREDICTION CENTER NORMAN OK
0458 PM CDT SAT MAY 09 2009
AREAS AFFECTED...PARTS OF ERN NC AND VA...THRU THE DELMARVA
CONCERNING...SEVERE POTENTIAL...WATCH LIKELY
VALID 092158Z - 092300Z
AN ADDITIONAL WW WILL BE ISSUED EAST OF WW 281 SHORTLY.
SMALL STORM CLUSTER CONTINUES TO EVOLVE OVER THE NORTH CAROLINA
PIEDMONT...AIDED BY FORCING/ENHANCED SHEAR ASSOCIATED WITH A 50 KT
WEST SOUTHWESTERLY 500 MB SPEED MAXIMUM NOSING TO THE LEE OF THE
SOUTHERN APPALACHIANS. STRONGER DIVERGENT UPPER FLOW FIELD IS
EXPECTED TO SPREAD TOWARD SOUTHERN VIRGINIA AND EASTERN NORTH
CAROLINA COASTAL AREAS BETWEEN NOW AND 01-02Z. ALTHOUGH THE
WESTERLY COMPONENT TO SURFACE FLOW AHEAD OF THE CONVECTIVE SYSTEM
INTO COASTAL AREAS IS NOT IDEAL...30 KT SOUTHWESTERLY 850 FLOW IS
CONTRIBUTING TO AN EASTERLY STORM RELATIVE INFLOW COMPONENT
SUPPORTIVE OF AT LEAST MODEST CONVERGENCE ALONG THE LEAD EDGE OF THE
STRENGTHENING SURFACE COLD POOL. WITH WEAK FRONT TO REAR HIGH LEVEL
SYSTEM RELATIVE FLOW ALLOWING ANVIL CLOUD COVER/ PRECIPITATION TO
SPREAD TO THE REAR OF THE CONVECTIVE SATEM...AND AND A HEATED
BOUNDARY LAYER WITH SIZABLE TEMPERATURE/DEW POINT SPREADS AHEAD OF
IT...THE ENVIRONMENT APPEARS FAVORABLE TO SUSTAIN OR INCREASE THE
STRENGTH OF THE CONVECTIVE SYSTEM THROUGH EARLY EVENING.
POTENTIALLY DAMAGING PEAK GUSTS WILL PROBABLY AT LEAST APPROACH 50
KT ALONG A SWATH TOWARD NORFOLK VA/ELIZABETH CITY NC AREA.
..KERR.. 05/09/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PHI...AKQ...MHX...LWX...RAH...RNK...
LAT...LON 36707891 37747755 39187561 38107519 35837637 35717682
35247818 35427898 35547950 36177888 36707891SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| May 9, 1:17 PM EDT | Severe Thunderstorm Watch | SPC | Saint Mary's | 8 hr |
| May 9, 6:25 PM EDT | Severe Thunderstorm Watch | SPC | Calvert, Caroline, Dorchester, Somerset, Talbot, Wicomico and 1 more | 4 hr |
| May 8, 8:30 PM EDT | Mesoscale Discussion | SPC | Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 19 more | 90 min |
| May 8, 10:01 PM EDT | Tornado Watch | SPC | Caswell, Rockingham, Stokes | 4 hr |
| May 8, 11:37 PM EDT | Mesoscale Discussion | SPC | Alleghany, Ashe, Forsyth, Rockingham, Stokes, Surry and 3 more | 53 min |
| May 9, 12:51 AM EDT | Mesoscale Discussion | SPC | Caswell, Edgecombe, Franklin, Gates, Granville, Halifax and 7 more | 84 min |
| May 9, 12:47 PM EDT | Mesoscale Discussion | SPC | Alamance, Alexander, Burke, Cabarrus, Caldwell, Caswell and 32 more | 118 min |
| May 9, 4:30 PM EDT | Mesoscale Discussion | SPC | Alamance, Cabarrus, Caswell, Catawba, Chatham, Davidson and 19 more | 90 min |
| May 9, 1:07 AM EDT | Tornado Watch | SPC | Amelia, Brunswick, Charles City, Chesterfield, Cumberland, Dinwiddie and 39 more | 4 hr |
Nearby
Mesoscale Discussions in Virginia, 2009Mesoscale Discussions in North Carolina, 2009Mesoscale Discussions in Maryland, 2009Every 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.