Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 2148

September 7, 20118 counties in North Carolina; 17 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Sep 7, 2011, 4:10 PM EDT for 8 counties in North Carolina; 17 counties in Virginia. It was in force for 65 min.

The area

The outline as issued.

The facts

Issued: Sep 7, 2011, 4:10 PM EDT (20:10 UTC)
Expired: Sep 7, 2011, 5:15 PM EDT
In force: 65 min
Issued by: the Storm Prediction Center

All 25 counties

Bertie County, NC, Edgecombe County, NC, Greene County, NC, Halifax County, NC, Hertford County, NC, Martin County, NC, Northampton County, NC, Pitt County, NC, Charles City County, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Franklin, VA, City of Hopewell, VA, City of Petersburg, VA, City of Williamsburg, VA, Greensville County, VA, Henrico County, VA, James City County, VA, King and Queen County, VA, King William County, VA, New Kent County, VA, Prince George County, VA, Southampton County, VA, Surry County, VA, Sussex County, VA

The radar

The Norfolk radar (KAKQ), 56 km from the middle of the area, began a volume at 20:12 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

Newport, NC (KMHX), launched 12:00Z, 8.2 hours before the alert went out and 194 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: 2965 J/kg
Mixed-layer CIN: 0 J/kg
Mixed-layer LCL: 462 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 68 m²/s²
0-3 km storm-relative helicity: 68 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 2.9

Open this sounding in Storm Lab

The text

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

223 
ACUS11 KWNS 072010
SWOMCD
SPC MCD 072010 
VAZ000-NCZ000-072115-

MESOSCALE DISCUSSION 2148
NWS STORM PREDICTION CENTER NORMAN OK
0310 PM CDT WED SEP 07 2011

AREAS AFFECTED...PARTS OF NERN NC INTO SERN VA

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 072010Z - 072115Z

TSTMS ARE EXPECTED TO CONTINUE THROUGH THE LATE AFTERNOON INTO EARLY
EVENING ACROSS PARTS OF NERN NC INTO SERN VA /JUST N OF OAJ TO ABOUT
30 N RIC/.  STRONGER STORMS IN THIS CORRIDOR WILL HAVE THE POTENTIAL
TO PRODUCE STRONG WIND GUSTS AND A POTENTIAL TORNADO CANNOT BE RULED
OUT.  HOWEVER...WEAK LOW LEVEL SHEAR SUGGESTS THE TORNADO THREAT IS
FAIRLY LIMITED.

MID AFTERNOON SURFACE STREAMLINE ANALYSES INDICATED A PERSISTENT
ZONE OF LOW LEVEL CONVERGENCE FROM ERN NC TO SERN VA...WITH REGIONAL
RADAR IMAGERY SHOWING NEW TSTM DEVELOPMENT /SINCE 1845-19Z/
EXTENDING FROM EAST CENTRAL NC /20 N OAJ/ TO 30 ENE RIC.  THIS AREA
WHICH WAS PLAGUED BY CLOUDS/PRECIPITATION EARLIER TODAY CLEARED OUT
PER VISIBLE SATELLITE IMAGERY ALLOWING FOR STRONGER SURFACE HEATING.
THUS...LOW LEVEL LAPSE RATES HAVE STEEPENED SOME AND THE MOIST AIR
MASS HAS BECOME MODERATELY UNSTABLE.

WATER VAPOR IMAGERY INDICATED A SHORTWAVE TROUGH TRACKING NWD
THROUGH WRN/CENTRAL NC AND SWRN VA...WITH AN ATTENDANT 50 KT SLY
MIDLEVEL JET.  FORCING FOR ASCENT WITH THESE FEATURES MAY BE
GLANCING NERN NC/SERN VA JUST ENOUGH TO ENCOURAGE MORE PERSISTENT
UPDRAFTS.  WSR-88D VAD AT WAKEFIELD VA INDICATED DEEP LAYER SHEAR
AROUND 30 KT SUPPORTIVE FOR MULTICELLS...WHILE LOW LEVEL SHEAR WAS
RELATIVELY WEAK.  THUS...A FEW STRONGER STORMS WILL BE POSSIBLE INTO
EARLY EVENING WITH STRONGER WIND GUSTS BEING THE PRIMARY THREAT.

..PETERS.. 09/07/2011

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

ATTN...WFO...AKQ...MHX...RAH...

LAT...LON   35587703 35237756 35837789 36507772 37477740 37817718
            37797671 37117670 36187688 35587703

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in North Carolina, 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.