Alert archive / Virginia / Mesoscale Discussions in 2012
Mesoscale Discussion 1973
The Storm Prediction Center issued this mesoscale discussion at Sep 18, 2012, 6:15 PM EDT for 5 states. It was in force for 30 min.
The area
The outline as issued.
The facts
- Issued
- Sep 18, 2012, 6:15 PM EDT (22:15 UTC)
- Expired
- Sep 18, 2012, 6:45 PM EDT
- In force
- 30 min
- Issued by
- the Storm Prediction Center
All 33 counties
Kent County, DE, Sussex County, DE, Somerset County, MD, Wicomico County, MD, Worcester County, MD, Camden County, NC, Carteret County, NC, Chowan County, NC, Currituck County, NC, Dare County, NC, Gates County, NC, Hertford County, NC, Hyde County, NC, Pasquotank County, NC, Perquimans County, NC, Tyrrell County, NC, Atlantic County, NJ, Cape May County, NJ, Cumberland County, NJ, Salem County, NJ, Accomack County, VA, 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, Isle of Wight County, VA, Mathews County, VA, Northampton County, VA, York County, VA
The radar
The Norfolk radar (KAKQ), 110 km from the middle of the area, began a volume at 22:15 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, 10.3 hours before the alert went out and 153 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
- 205 J/kg
- Mixed-layer CIN
- -9 J/kg
- Mixed-layer LCL
- 778 m above ground
- 0-6 km bulk shear
- 33 kt
- 0-1 km storm-relative helicity
- 134 m²/s²
- 0-3 km storm-relative helicity
- 150 m²/s²
- Significant tornado parameter
- 0.1
- Supercell composite
- 0.9
The text
As transmitted, in the capitals the NWS used until 2016.
261
ACUS11 KWNS 182215
SWOMCD
SPC MCD 182215
NJZ000-DEZ000-MDZ000-VAZ000-NCZ000-182245-
MESOSCALE DISCUSSION 1973
NWS STORM PREDICTION CENTER NORMAN OK
0515 PM CDT TUE SEP 18 2012
AREAS AFFECTED...DELMARVA SWD INTO NC OUTER BANKS
CONCERNING...TORNADO WATCH 642...644...
VALID 182215Z - 182245Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 642...644...CONTINUES.
SUMMARY...AN ISOLD WEAK TORNADO RISK WILL CONTINUE IN AREAS ALONG
AND AHEAD OF THE EWD MOVING QLCS. CONVECTIVE OVERTURNING VIA THE
QLCS WILL NEGATE THE TORNADO THREAT AND COUNTIES CAN BE CLEARED FROM
THE WEST WITH THE EXISTING TORNADO WATCHES AS THIS OCCURS.
DISCUSSION...LATEST SURFACE MESOANALYSIS AND RADAR MOSAIC
INTERROGATION SHOW A LOW LEVEL THETA-E PLUME INCREASINGLY BECOMING
PINCHED TO THE IMMEDIATE COASTAL AREAS FROM DELMARVA SWD TO THE NC
OUTER BANKS. THIS IS OCCURRING IN CONCERT WITH THE EWD PROGRESSION
OF AN EXTENSIVE N-S ORIENTED QLCS. STRONG LOW LEVEL SHEAR /35-40 KT
0-1 KM SHEAR/ WITHIN A MOISTURE RICH AIRMASS WILL MAINTAIN A RISK
FOR AN ISOLD WEAK TORNADO...DESPITE MARGINAL INSTABILITY /MLCAPE
250-750 J/KG/. AS SUCH...ANY STRONGER UPDRAFTS WITHIN INCREASINGLY
COMPLEX CONVECTIVE STRUCTURES /I.E. SUPERCELL-QLCS MODES/ MAY POSE
ISOLD DMGG WINDS...IN ADDITION TO A WEAK TORNADO.
LINEAR EXTRAPOLATION INDICATES A LOCAL EXTENSION-IN-TIME MAY BE
NEEDED FOR AREAS NEAR THE COAST IN TORNADO WATCH 642. COUNTIES CAN
BE CLEARED FROM THE EXISTING WATCHES BEHIND THE MAIN CONVECTIVE
LINE.
..SMITH.. 09/18/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...PHI...AKQ...MHX...
LAT...LON 34787667 35847636 36307717 37437636 39697538 39507394
37797511 36857552 35197522 34527617 34787667SPC that day
Everything else SPC issued on the same UTC day.
| Issued | Product | Office | Counties | Lasted |
|---|---|---|---|---|
| Sep 18, 11:14 AM EDT | Mesoscale Discussion | SPC | New Castle | 91 min |
| Sep 18, 11:19 AM EDT | Mesoscale Discussion | SPC | Kent, New Castle | 86 min |
| Sep 18, 12:10 PM EDT | Tornado Watch | SPC | Kent, New Castle, Sussex | 9 hr |
| Sep 18, 1:56 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 64 min |
| Sep 18, 4:21 PM EDT | Mesoscale Discussion | SPC | Kent, New Castle, Sussex | 114 min |
| Sep 18, 6:08 PM EDT | Mesoscale Discussion | SPC | Kent, Sussex | 67 min |
| Sep 18, 8:49 AM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Charles, Frederick and 8 more | 116 min |
| Sep 18, 10:54 AM EDT | Tornado Watch | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Charles, Dorchester and 11 more | 9 hr |
| Sep 18, 1:27 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Carroll, Charles, Dorchester and 10 more | 63 min |
| Sep 18, 3:52 PM EDT | Mesoscale Discussion | SPC | Anne Arundel, Baltimore, Calvert, Charles, Dorchester, Howard and 7 more | 113 min |
| Sep 17, 8:14 PM EDT | Mesoscale Discussion | SPC | Cherokee, Clay, Graham, Haywood, Henderson, Jackson and 4 more | 2 hr |
| Sep 18, 12:23 AM EDT | Mesoscale Discussion | SPC | Alexander, Buncombe, Burke, Cabarrus, Caldwell, Catawba and 14 more | 97 min |
| Sep 18, 9:45 AM EDT | Tornado Watch | SPC | Alamance, Anson, Chatham, Cumberland, Davidson, Durham and 25 more | 8 hr |
| Sep 18, 11:35 AM EDT | Mesoscale Discussion | SPC | Union | 85 min |
| Sep 18, 1:00 PM EDT | Tornado Watch | SPC | Beaufort, Carteret, Craven, Dare, Duplin, Greene and 9 more | 5 hr |
| Sep 18, 1:21 PM EDT | Mesoscale Discussion | SPC | Alamance, Anson, Chatham, Cumberland, Davidson, Durham and 25 more | 84 min |
| Sep 18, 4:11 PM EDT | Mesoscale Discussion | SPC | Alamance, Anson, Beaufort, Carteret, Chatham, Craven and 40 more | 94 min |
Nearby
Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in North Carolina, 2012Mesoscale Discussions in New Jersey, 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.