Alert archive / North Carolina / Mesoscale Discussions in 2006

Mesoscale Discussion 1921

September 1, 200618 counties in North Carolina; City of Chesapeake, City of Virginia Beach, Virginia

The Storm Prediction Center issued this mesoscale discussion at Sep 1, 2006, 2:55 AM EDT for 18 counties in North Carolina; City of Chesapeake, City of Virginia Beach, Virginia. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Sep 1, 2006, 2:55 AM EDT (06:55 UTC)
Expired: Sep 1, 2006, 5:00 AM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

Counties Beaufort County, NC, Bertie County, NC, Camden County, NC, Carteret County, NC, Chowan County, NC, Craven County, NC, Currituck County, NC, Dare County, NC, Gates County, NC, Greene County, NC, Hyde County, NC, Martin County, NC, Pamlico County, NC, Pasquotank County, NC, Perquimans County, NC, Pitt County, NC, Tyrrell County, NC, Washington County, NC, City of Chesapeake, VA, City of Virginia Beach, VA

The radar

The Morehead City radar (KMHX), 92 km from the middle of the area, began a volume at 06:54 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.

Tornado Watch 762Sep 1, 4:30 AM EDT

The nearest sounding before it

Newport, NC (KMHX), launched 00:00Z, 6.9 hours before the alert went out and 91 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: 66 J/kg
Mixed-layer CIN: -26 J/kg
Mixed-layer LCL: 636 m above ground
0-6 km bulk shear: 27 kt
0-1 km storm-relative helicity: 194 m²/s²
0-3 km storm-relative helicity: 321 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

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

000 
ACUS11 KWNS 010656
SWOMCD
SPC MCD 010655 
NCZ000-VAZ000-010900-

MESOSCALE DISCUSSION 1921
NWS STORM PREDICTION CENTER NORMAN OK
0155 AM CDT FRI SEP 01 2006

AREAS AFFECTED...PORTIONS ERN NC...EXTREME SERN VA.

CONCERNING...TORNADO WATCH 761...

VALID 010655Z - 010900Z

REPLACEMENT WW IS EXPECTED BEFORE SCHEDULED 9Z EXPIRATION OF WW 761.
 TS ERNESTO HAS MOVED INLAND AND WILL CONTINUE TO MOVE NNEWD ACROSS
ERN NC COASTAL PLAIN THROUGH REMAINDER MORNING...PER NHC FCST. AS
THIS OCCURS...FAVORABLE STRENGTHENING OF GRADIENT WINDS ARE EXPECTED
ABOVE SFC ACROSS SERN VA AND NERN NC...NE OF TS CENTER.  PRIMARY
SUPERCELL-PRODUCING SPIRAL BAND SHOULD SHIFT NNEWD ACROSS ALBEMARLE
AND NERN PAMLICO SOUND REGION DURING NEXT 3-4 HOURS...THOUGH MORE
ISOLATED SUPERCELLS MAY MOVE ONSHORE FROM OUTER BANKS TO NEAR VA
BORDER.

6Z SFC MESOANALYSIS SHOWS FRONT AND COLLOCATED WIND SHIFT LINE FROM
OAJ NEWD ACROSS WRN PORTIONS JONES...CRAVEN...BEAUFORT...THEN ENEWD
ACROSS WASHINGTON/TYRRELL COUNTIES NC AND ERN ALBEMARLE
SOUND...CROSSING COAST NEAR CURRITUCK/DARE COUNTY LINE.  PRIND FRONT
WILL LIFT NWD ACROSS NERN NC AND PERHAPS EXTREME SERN VA...BENEATH
STRENGTHENING WINDS ALOFT.  HODOGRAPHS WILL BE MAXIMIZED INVOF FRONT
WHERE SFC WINDS ARE RELATIVELY BACKED...BUT WILL REMAIN FAVORABLE TO
ITS E IN RELATIVELY UNSTABLE MARITIME/TROPICAL AIR AS WELL.  0-1 KM
SRH ACROSS NERN NC SHOULD INCREASE TO AOA 500 J/KG AS LOW LEVEL
SHEAR VECTOR LENGTHENS.  FRONT IS A BUOYANCY-LIMITING TYPE...WITH
TORNADO PROBABILITIES DROPPING GREATLY FROM E-W INTO THE COOLER AIR.
ALTHOUGH THE E-W THETAE DROP THROUGH FRONT IS SUBTLE...THIS IS
SUFFICIENT TO REMOVE SBCAPE AND GREATLY INCREASE CINH BENEATH
WEAK/MOIST-ADIABATIC DEEP-LAYER LAPSE RATES.  THEREFORE TORNADO RISK
WILL BE STRONGLY TIED TO LOCATION OF MARINE AIR -- ALONG AND E OF
FRONT.

..EDWARDS.. 09/01/2006

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

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

34317709 35137736 35547781 36747659 37047584 36837551
36247542 35827517 35177522 34897538 34827583 34447623
34267646

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Aug 31, 11:59 PM EDT	Mesoscale Discussion	SPC	Beaufort, Camden, Carteret, Chowan, Craven, Currituck and 9 more	91 min
Sep 1, 4:35 AM EDT	Tornado Watch	SPC	Beaufort, Bertie, Camden, Chowan, Currituck, Dare and 8 more	9 hr
Sep 1, 7:45 AM EDT	Mesoscale Discussion	SPC	Camden, Currituck, Dare, Gates, Pasquotank, Tyrrell	2 hr
Sep 1, 12:30 PM EDT	Mesoscale Discussion	SPC	Gloucester, Isle of Wight, James City, Lancaster, Mathews, Middlesex and 11 more	90 min

Nearby

Mesoscale Discussions in North Carolina, 2006 Mesoscale Discussions in Virginia, 2006 Every mesoscale discussion in 2006

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.