Alert archive / Virginia / Mesoscale Discussions in 2004

Mesoscale Discussion 2152

August 30, 20044 counties in Maryland; 52 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Aug 30, 2004, 6:40 PM EDT for 4 counties in Maryland; 52 counties in Virginia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Aug 30, 2004, 6:40 PM EDT (22:40 UTC)
Expired: Aug 30, 2004, 8:45 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 56 counties

Saint Mary's County, MD, Somerset County, MD, Wicomico County, MD, Worcester County, MD, Accomack County, VA, Amelia County, VA, Brunswick County, VA, Caroline 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, Cumberland County, VA, Dinwiddie County, VA, Essex County, VA, Fluvanna County, VA, Gloucester County, VA, Goochland 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, Louisa County, VA, Lunenburg County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Nottoway County, VA, Powhatan County, VA, Prince Edward 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), 110 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 10.7 hours before the alert went out and 71 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: 2008 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 468 m above ground
0-6 km bulk shear: 25 kt
0-1 km storm-relative helicity: 45 m²/s²
0-3 km storm-relative helicity: 61 m²/s²
Significant tornado parameter: 0.4
Supercell composite: 2.5

Open this sounding in Storm Lab

The text

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

553 
ACUS11 KWNS 302242
SWOMCD
SPC MCD 302240 
VAZ000-NCZ000-DEZ000-MDZ000-310045-

MESOSCALE DISCUSSION 2152
NWS STORM PREDICTION CENTER NORMAN OK
0540 PM CDT MON AUG 30 2004

AREAS AFFECTED...MUCH OF SERN VA...PORTIONS SERN MD

CONCERNING...TORNADO WATCH 797...

VALID 302240Z - 310045Z

REMNANTS OF TC GASTON -- CENTERED OVER SURREY COUNTY VA AS OF 22Z --
WILL CONTINUE TO MOVE NEWD ACROSS TIDEWATER REGION THROUGH REMAINDER
TONIGHT.  REMAINDER OF WW NNW THROUGH ESE OF CIRCULATION CENTER --
COMPRISING SECTOR WITH MOST FAVORABLE VERTICAL SHEAR -- SHOULD BE
MAINTAINED UNTIL SCHEDULED EXPIRATION. MARGINAL TORNADO POTENTIAL
WILL REMAIN THROUGH REMAINDER OF TONIGHT AND SPREAD NEWD ACROSS
PORTIONS SERN MD.  HOWEVER...THREAT SHOULD CONTINUE TO DIMINISH SUCH
THAT WW CAN BE ALLOWED TO EXPIRE WITHOUT ADDITIONAL ISSUANCE.

SFC MESOANALYSIS SHOWS TROUGH EXTENDING GENERALLY EWD FROM LOW
ACROSS SRN TIP DELMARVA PENINSULA.  AS IT MOVES SLOWLY NWD ACROSS
ERN CHESAPEAKE BAY REGION...AHEAD OF LOW CENTER...THIS FEATURE WILL
CONTINUE LOSING BAROCLINICITY BECAUSE OF
1. ABUNDANT PRECIP ON BOTH SIDES AND
2. LOSS OF SFC DIABATIC/DIFFERENTIAL HEATING.
PRESSURE FALL AXIS IS ANALYZED FROM LOW NEWD ACROSS ACCOMACK COUNTY
VA AND AS SUCH DENOTES MOST PROBABLE TRACK OF LOW DURING NEXT
SEVERAL HOURS.

VERTICAL SHEAR REMAINS FAVORABLE OVER A SMALL SECTOR OF NERN
QUADRANT OF CIRCULATION OF GASTON.  0-1 KM SRH 100-200 J/KG IS
ESTIMATED N OF SFC TROUGH...BASED ON MODIFIED MODEL SOUNDINGS AND
NEWD SHIFT OF VWP TRENDS FROM AKQ.  MAIN AREA OF INTEREST REMAINS
ALONG AND N OF SFC TROUGH/WIND SHIFT LINE AND INVOF PRESSURE FALL
AXIS...PARTICULARLY IF ANY DISCRETE STORMS/MINI-SUPERCELLS
MOVE THROUGH THAT CORRIDOR.  AREA BETWEEN TROUGH AND ISALLOBARIC
AXIS SHOULD SERVE AS MAX OF ANY REMAINING TORNADO PROBABILITIES. 
MAIN NEGATIVE FACTOR IS WEAKENING SFC-BASED INSTABILITY AND
RESULTANT DECREASE COVERAGE/INTENSITY OF DISCRETE CONVECTION ACROSS
FAVORABLY SHEARED SECTOR OF CYCLONE.

..EDWARDS.. 08/30/2004

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...AKQ...LWX...RNK...PHI...

36367558 36757846 38237848 37807562 

38057721 38277676 38457569 38477506 38187507 37877537
37687558 37807564

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 30, 12:07 PM EDT	Mesoscale Discussion	SPC	Saint Mary's	113 min
Aug 30, 12:50 PM EDT	Tornado Watch	SPC	Amelia, Brunswick, Caroline, Charles City, Chesterfield, Cumberland and 44 more	7 hr
Aug 30, 3:06 PM EDT	Mesoscale Discussion	SPC	Accomack, Amelia, Brunswick, Caroline, Charles City, Chesterfield and 45 more	114 min

Nearby

Mesoscale Discussions in Virginia, 2004 Mesoscale Discussions in Maryland, 2004 Every mesoscale discussion in 2004

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.