Alert archive / Virginia / Tornado Watches in 2004

Tornado Watch 836

September 17, 20045 states

The Storm Prediction Center issued this tornado watch at Sep 17, 2004, 6:50 PM EDT for 5 states. It was in force for 5 hr.

The area

The outline as issued.

The facts

Issued: Sep 17, 2004, 6:50 PM EDT (22:50 UTC)
Expired: Sep 18, 2004, 12:00 AM EDT
In force: 5 hr
Issued by: the Storm Prediction Center

All 93 counties

Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Caroline County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Dorchester County, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Kent County, MD, Montgomery County, MD, Prince George's County, MD, Queen Anne's County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Washington County, MD, Bertie County, NC, Camden County, NC, Chowan County, NC, Currituck County, NC, Gates County, NC, Hertford County, NC, Northampton County, NC, Pasquotank County, NC, Perquimans County, NC, Adams County, PA, Franklin County, PA, Fulton County, PA, Lancaster County, PA, York County, PA, Accomack County, VA, Arlington County, VA, Caroline County, VA, Charles City County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Chesapeake, VA, City of Colonial Heights, VA, City of Emporia, VA, City of Fairfax, VA, City of Falls Church, VA, City of Franklin, VA, City of Fredericksburg, VA, City of Hampton, VA, City of Hopewell, VA, City of Manassas, VA, City of Manassas Park, 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, Clarke County, VA, Dinwiddie County, VA, Essex County, VA, Fairfax County, VA, Fauquier County, VA, Gloucester 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, Loudoun County, VA, Mathews County, VA, Middlesex County, VA, New Kent County, VA, Northampton County, VA, Northumberland County, VA, Prince George County, VA, Prince William County, VA, Richmond County, VA, Southampton County, VA, Spotsylvania County, VA, Stafford County, VA, Surry County, VA, Sussex County, VA, Westmoreland County, VA, York County, VA, Berkeley County, WV, Jefferson County, WV

The radar

The Sterling radar (KLWX), 96 km from the middle of the area, began a volume at 22:52 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.

Warnings issued inside it

25 tornado, severe thunderstorm and flash flood warnings for its counties while it was in force.

Issued	Product	Office	Counties	Lasted
Sep 17, 6:59 PM EDT	Tornado Warning	AKQ	Middlesex	16 min
Sep 17, 7:00 PM EDT	Tornado Warning	LWX	Clarke	60 min
Sep 17, 7:03 PM EDT	Flash Flood Warning	LWX	Allegany, Washington	3 hr
Sep 17, 7:06 PM EDT	Tornado Warning	AKQ	City of Norfolk	24 min
Sep 17, 7:11 PM EDT	Tornado Warning	LWX	Fairfax, Prince William, City of Fairfax, City of Falls Church	64 min
Sep 17, 7:14 PM EDT	Tornado Warning	AKQ	Lancaster	16 min
Sep 17, 7:17 PM EDT	Flash Flood Warning	AKQ	Amelia, Caroline, Chesterfield, Dinwiddie, Essex, Goochland and 7 more	118 min
Sep 17, 7:19 PM EDT	Tornado Warning	AKQ	Chesterfield	26 min
Sep 17, 7:20 PM EDT	Tornado Warning	CTP	Franklin	40 min
Sep 17, 7:21 PM EDT	Flash Flood Warning	LWX	Clarke, Culpeper, Fauquier, Orange, Rappahannock, Warren	3 hr
Sep 17, 7:27 PM EDT	Tornado Warning	LWX	Charles	63 min
Sep 17, 7:29 PM EDT	Tornado Warning	CTP	Fulton	46 min
Sep 17, 7:42 PM EDT	Tornado Warning	LWX	Frederick, Washington	33 min
Sep 17, 7:43 PM EDT	Tornado Warning	CTP	Adams, Franklin	47 min
Sep 17, 7:47 PM EDT	Tornado Warning	LWX	Berkeley	43 min
Sep 17, 7:51 PM EDT	Tornado Warning	LWX	Prince George's	54 min
Sep 17, 7:54 PM EDT	Severe Thunderstorm Warning	LWX	Stafford	51 min
Sep 17, 8:07 PM EDT	Tornado Warning	AKQ	Hertford	23 min
Sep 17, 8:16 PM EDT	Tornado Warning	LWX	Washington	44 min
Sep 17, 8:46 PM EDT	Severe Thunderstorm Warning	LWX	Berkeley	44 min
Sep 17, 9:44 PM EDT	Tornado Warning	AKQ	Gates	16 min
Sep 17, 9:56 PM EDT	Tornado Warning	AKQ	City of Suffolk	34 min
Sep 17, 10:10 PM EDT	Flash Flood Warning	LWX	Washington	2 hr
Sep 17, 10:14 PM EDT	Tornado Warning	AKQ	Isle of Wight	16 min
Sep 17, 11:19 PM EDT	Flash Flood Warning	LWX	Berkeley, Morgan	3 hr

Discussions around it

SPC mesoscale discussions over the same counties from four hours before the watch to its end.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 10.8 hours before the alert went out and 88 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: 105 J/kg
Mixed-layer CIN: -89 J/kg
Mixed-layer LCL: 687 m above ground
0-6 km bulk shear: 49 kt
0-1 km storm-relative helicity: 74 m²/s²
0-3 km storm-relative helicity: 150 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

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

000 
WWUS20 KWNS 172255
SEL6  
SPC WW 172250
DCZ000-MDZ000-NCZ000-PAZ000-VAZ000-WVZ000-CWZ000-180400-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 836
NWS STORM PREDICTION CENTER NORMAN OK
650 PM EDT FRI SEP 17 2004

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF 

       DISTRICT OF COLUMBIA
       MARYLAND
       NORTHEAST NORTH CAROLINA
       A SMALL PART OF SOUTH CENTRAL PENNSYLVANIA
       EASTERN VIRGINIA
       THE EASTERN WEST VIRGINIA PANHANDLE
       COASTAL WATERS

EFFECTIVE THIS FRIDAY NIGHT FROM 650 PM UNTIL MIDNIGHT EDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS
TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE TORNADO WATCH AREA IS ALONG AND 60 STATUTE MILES EAST AND WEST
OF A LINE FROM 45 MILES NORTHEAST OF HAGERSTOWN MARYLAND TO 25
MILES SOUTH SOUTHWEST OF ELIZABETH CITY NORTH CAROLINA.

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA.
PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING
WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 833...TORNADO WATCH NUMBER 834. WATCH NUMBER 833 834
WILL NOT BE IN EFFECT AFTER 650 PM EDT. CONTINUE...WW 835...

DISCUSSION...THREAT FOR SUPERCELLS AND TORNADOES WILL PERSIST FOR
THE NEXT FEW HOURS AS THE REMNANTS OF IVAN CONTINUE TO MOVE NEWD
ACROSS VA.  STRONG L0W-LEVEL SHEAR /0-1 KM SRH OF 150-250 M2/S2/ AND
BOUNDARY LAYER DEWPOINTS IN THE MID-UPPER 70S WILL SUPPORT THE
CONTINUED DEVELOPMENT AND MAINTENANCE OF SUPERCELLS...WITH THE
THREAT EXPECTED TO EXTEND NWD TO NEAR A SURFACE BOUNDARY ACROSS SRN
PA.  THE TORNADO THREAT WILL GRADUALLY DIMINISH LATER TONIGHT AS THE
BOUNDARY LAYER STABILIZES.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE WIND
GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.
MEAN STORM MOTION VECTOR 19025.


...THOMPSON

400,0755 355,0751 355,0772 400,0781

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Sep 17, 12:33 PM EDT	Mesoscale Discussion	SPC	Charles, Saint Mary's	117 min
Sep 17, 1:15 PM EDT	Tornado Watch	SPC	Anne Arundel, Calvert, Charles, Prince George's, Saint Mary's	7 hr
Sep 17, 3:33 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Carroll, Frederick, Harford, Howard and 1 more	117 min
Sep 17, 3:50 PM EDT	Tornado Watch	SPC	Anne Arundel, Baltimore, Carroll, Frederick, Harford, Howard and 3 more	4 hr
Sep 17, 3:53 PM EDT	Mesoscale Discussion	SPC	Calvert, Charles, Prince George's, Saint Mary's	2 hr
Sep 17, 6:19 PM EDT	Mesoscale Discussion	SPC	Anne Arundel, Baltimore, Calvert, Carroll, Charles, Frederick and 6 more	116 min
Sep 16, 8:45 PM EDT	Tornado Watch	SPC	Cabarrus, Cleveland, Gaston, Lincoln, Mecklenburg, Polk and 1 more	6 hr
Sep 16, 11:42 PM EDT	Mesoscale Discussion	SPC	Gaston, Mecklenburg	2 hr
Sep 17, 1:51 AM EDT	Mesoscale Discussion	SPC	Alexander, Burke, Caldwell, Catawba, Cleveland, Gaston and 6 more	84 min
Sep 17, 9:26 AM EDT	Mesoscale Discussion	SPC	Alamance, Anson, Bladen, Caswell, Chatham, Cumberland and 24 more	2 hr
Sep 17, 10:10 AM EDT	Tornado Watch	SPC	Alamance, Anson, Bladen, Brunswick, Caswell, Chatham and 37 more	7 hr
Sep 17, 11:03 AM EDT	Mesoscale Discussion	SPC	Alamance, Bertie, Caswell, Chatham, Cumberland, Durham and 26 more	87 min
Sep 17, 1:37 PM EDT	Mesoscale Discussion	SPC	Alamance, Bladen, Brunswick, Caswell, Chatham, Columbus and 29 more	113 min
Sep 17, 4:01 PM EDT	Mesoscale Discussion	SPC	Bladen, Brunswick, Columbus, Cumberland, Duplin, Franklin and 6 more	59 min
Sep 17, 4:35 PM EDT	Tornado Watch	SPC	Bladen, Brunswick, Columbus, Duplin, Edgecombe, Franklin and 14 more	3 hr
Sep 17, 7:23 PM EDT	Mesoscale Discussion	SPC	Duplin, Edgecombe, Greene, Halifax, Lenoir, Nash and 4 more	37 min

Nearby

Tornado Watches in Virginia, 2004 Tornado Watches in Maryland, 2004 Tornado Watches in North Carolina, 2004 Every tornado watch in 2004

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.