Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 1569

July 24, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Jul 24, 2012, 1:42 PM EDT for 4 states. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Jul 24, 2012, 1:42 PM EDT (17:42 UTC)
Expired
Jul 24, 2012, 3:45 PM EDT
In force
2 hr
Issued by
the Storm Prediction Center
All 75 counties

Sussex County, DE, Calvert County, MD, Dorchester County, MD, Saint Mary's County, MD, Somerset County, MD, Wicomico County, MD, Worcester County, MD, Bertie County, NC, Camden County, NC, Chowan County, NC, Currituck County, NC, Gates County, NC, Halifax County, NC, Hertford County, NC, Northampton County, NC, Pasquotank County, NC, Perquimans County, NC, Tyrrell County, NC, Vance County, NC, Warren County, NC, Washington County, NC, Accomack County, VA, Amelia County, VA, Brunswick County, VA, Caroline County, VA, Charles City County, VA, Charlotte 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, 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 George County, VA, King William County, VA, Lancaster County, VA, Louisa 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, 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), 62 km from the middle of the area, began a volume at 17:45 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

Wallops Is Stn, VA (KWAL), launched 12:00Z, 5.7 hours before the alert went out and 115 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-pSkew-T log-p diagram, Wallops Is Stn, VA at 12:00Z on 2012-07-24Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 1253 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Wallops Is Stn, VA at 12:00Z on 2012-07-24The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 179 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
1253 J/kg
Mixed-layer CIN
-123 J/kg
Mixed-layer LCL
1256 m above ground
0-6 km bulk shear
25 kt
0-1 km storm-relative helicity
179 m²/s²
0-3 km storm-relative helicity
214 m²/s²
Significant tornado parameter
0.0
Supercell composite
4.0

Open this sounding in Storm Lab

The text

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

881 
ACUS11 KWNS 241742
SWOMCD
SPC MCD 241742 
DEZ000-MDZ000-VAZ000-NCZ000-241945-

MESOSCALE DISCUSSION 1569
NWS STORM PREDICTION CENTER NORMAN OK
1242 PM CDT TUE JUL 24 2012

AREAS AFFECTED...SRN MD INTO SERN VA AND NERN NC

CONCERNING...SEVERE THUNDERSTORM WATCH 510...

VALID 241742Z - 241945Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 510
CONTINUES.

SUMMARY...ADDITIONAL STORMS MAY FORM WITHIN THE LOW PRESSURE
TROUGH...WITH DAMAGING WINDS AND HAIL LIKELY.

DISCUSSION...TEMPERATURES HAVE RISEN INTO THE MID 90S F OVER VA AND
SRN MD...WHILE DEWPOINTS REMAIN IN THE LOWER 70S F. VISIBLE IMAGERY
RECENTLY INDICATES THAT STABLE WAVE CLOUDS WERE MIXING
OUT...SUGGESTING THAT CAPPING IS BEING REMOVED. FURTHER HEATING IS
LIKELY...WITH WILL ENHANCE SFC CONVERGENCE ALONG THE TROUGH AXIS. 

MOST MODEL SUGGEST A SEPARATE AREA OF DEVELOPMENT WILL TAKE PLACE IN
THIS AREA BETWEEN 18-20Z. GIVEN VERY LARGE INSTABILITY AND AMPLE W
TO NWLY FLOW ALOFT...EXPLOSIVE DEVELOPMENT WOULD OCCUR WITH STORMS
QUICKLY BECOMING SEVERE WITH LARGE HAIL...THEN MERGING INTO SEWD
MOVING CLUSTERS PRODUCING DAMAGING WIND...WITH SOME SIGNIFICANT
GUSTS POSSIBLE.

IF TCU BEGIN TO FORM IN THESE AREAS AS PREDICTED BY SEVERAL HIGH
RESOLUTION MODELS...THE WATCH MAY NEED TO BE EXTENDED TO INCLUDE THE
REST OF SERN VA AND FAR NERN NC.

..JEWELL.. 07/24/2012

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

ATTN...WFO...PHI...AKQ...MHX...LWX...RAH...RNK...

LAT...LON   35967551 35747627 35907735 36337849 36957874 37377871
            37947815 38217759 38737619 38827570 38787529 38577487
            38157500 37587546 37257565 36967583 36517581 35967551

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 24, 1:08 PM EDTSevere Thunderstorm WatchSPCKent, New Castle, Sussex6 hr
Jul 24, 11:48 AM EDTMesoscale DiscussionSPCAllegany, Anne Arundel, Baltimore, Calvert, Caroline, Carroll and 15 more87 min
Jul 24, 1:12 PM EDTMesoscale DiscussionSPCAlamance, Alexander, Anson, Avery, Buncombe, Burke and 37 more93 min
Jul 24, 2:36 PM EDTSevere Thunderstorm WatchSPCAlamance, Alexander, Anson, Avery, Buncombe, Burke and 53 more5 hr
Jul 24, 3:46 PM EDTMesoscale DiscussionSPCBeaufort, Bertie, Bladen, Brunswick, Camden, Carteret and 40 more89 min
Jul 24, 4:24 PM EDTSevere Thunderstorm WatchSPCBeaufort, Bertie, Bladen, Brunswick, Camden, Carteret and 24 more4 hr
Jul 24, 11:43 AM EDTMesoscale DiscussionSPCBuchanan, Dickenson, Wise, City of Norton62 min
Jul 24, 12:33 PM EDTSevere Thunderstorm WatchSPCBuchanan, Dickenson, Lee, Russell, Scott, Washington and 3 more6 hr
Jul 24, 1:52 PM EDTMesoscale DiscussionSPCBuchanan, Dickenson, Wise, City of Norton53 min
Jul 24, 3:25 PM EDTMesoscale DiscussionSPCBuchanan, Dickenson, Lee, Russell, Scott, Smyth and 5 more95 min

Nearby

Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in North Carolina, 2012Mesoscale Discussions in Maryland, 2012Every mesoscale discussion in 2012

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.