Alert archive / Virginia / Mesoscale Discussions in 2009
Mesoscale Discussion 1221
The Storm Prediction Center issued this mesoscale discussion at Jun 18, 2009, 8:21 PM EDT for Camden County, Currituck County, Pasquotank County, North Carolina; 17 counties in Virginia. It was in force for 24 min.
The area
The outline as issued.
The facts
- Issued
- Jun 18, 2009, 8:21 PM EDT (00:21 UTC)
- Expired
- Jun 18, 2009, 8:45 PM EDT
- In force
- 24 min
- Issued by
- the Storm Prediction Center
Counties Camden County, NC, Currituck County, NC, Pasquotank County, NC, City of Chesapeake, VA, City of Hampton, VA, City of Newport News, VA, City of Norfolk, VA, City of Poquoson, VA, City of Portsmouth, VA, City of Suffolk, VA, City of Virginia Beach, VA, City of Williamsburg, VA, Gloucester County, VA, Isle of Wight County, VA, James City County, VA, King and Queen County, VA, Lancaster County, VA, Mathews County, VA, Middlesex County, VA, York County, VA
The radar
The Norfolk radar (KAKQ), 51 km from the middle of the area, began a volume at 00:21 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 00:00Z, 0.4 hours before the alert went out and 138 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
- 1538 J/kg
- Mixed-layer CIN
- -24 J/kg
- Mixed-layer LCL
- 553 m above ground
- 0-6 km bulk shear
- 52 kt
- 0-1 km storm-relative helicity
- 76 m²/s²
- 0-3 km storm-relative helicity
- 128 m²/s²
- Significant tornado parameter
- 1.0
- Supercell composite
- 4.5
The text
As transmitted, in the capitals the NWS used until 2016.
000
ACUS11 KWNS 190021
SWOMCD
SPC MCD 190021
NCZ000-VAZ000-190045-
MESOSCALE DISCUSSION 1221
NWS STORM PREDICTION CENTER NORMAN OK
0721 PM CDT THU JUN 18 2009
AREAS AFFECTED...SERN VA
CONCERNING...SEVERE THUNDERSTORM WATCH 464...
VALID 190021Z - 190045Z
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 464
CONTINUES.
ISOLD LARGE HAIL/DMGG WIND POTENTIAL WILL LIKELY CONTINUE THROUGH
THE HOUR ACROSS PARTS OF SERN VA. WW WILL BE ALLOWED TO EXPIRE BUT
AN ISOLD SEVERE THREAT MAY CONTINUE BEYOND 01Z.
LATEST RADAR/SURFACE COMPOSITE SHOWS STRONG/SEVERE STORMS ARE NOW
CONFINED TO SERN VA NEAR DIFFUSE WARM FRONTAL SEGMENT ATTENDANT TO A
WEAK SURFACE LOW OVER SERN PA. THE ONLY 2 STORMS OF SIGNIFICANCE
/SUPERCELLS LOCATED OVER ISLE OF WIGHT/KING AND QUEEN COUNTIES AS OF
0015Z/ WILL LIKELY CONTINUE TO MOVE SEWD ALONG AFOREMENTIONED
BOUNDARY.
STRONGLY VEERING LOW LEVEL CLOCKWISE CURVED HODOGRAPHS WITH OBSERVED
STORM MOTIONS ROUGHLY AT 335 DEG/17 KTS SHOWS 0-1 KM SRH 150-200
MS/S2 ACCORDING TO AKQ VWP DATA...BENEATH 45 KTS 0-6 KM SHEAR. THIS
WILL CONTINUE TO SUPPORT UPDRAFT ROTATION WITHIN THETA-E AXIS
EXTENDING NEWD INTO THE TIDEWATER AREA. COMBINED WITH A VERY MOIST
BOUNDARY LAYER FAVORING A LOW LCL ENVIRONMENT BELOW 1000 M...A
NON-ZERO THREAT FOR AN ISOLD TORNADO MAY EXIST IN THE NEAR TERM.
WITH THAT SAID...THESE STORMS WILL PROBABLY POSE A LARGE HAIL AND
ISOLD DMGG WIND THREAT BEFORE GRADUAL DIURNAL STABILIZATION AND A
GENERAL OVERALL WEAKENING TREND IS EXPECTED.
..SMITH.. 06/19/2009
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...AKQ...
LAT...LON 36437661 37237691 37827694 37957671 37777636 37247605
36597587 36247586 36217637 36437661Nearby
Mesoscale Discussions in Virginia, 2009Mesoscale Discussions in North Carolina, 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.