Alert archive / Oklahoma / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 124, NWS Norman, OK

April 18, 20094 counties in Oklahoma

NWS Norman, OK issued this severe thunderstorm warning at Apr 18, 2009, 4:27 PM CDT for 4 counties in Oklahoma. It was in force for 48 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued: Apr 18, 2009, 4:27 PM CDT (21:27 UTC)
Expired: Apr 18, 2009, 5:15 PM CDT
In force: 48 min
Issued by: NWS Norman, OK
Area: Storm-based polygon

Counties Dewey County, OK, Major County, OK, Woods County, OK, Woodward County, OK

The radar

The Vance AFB radar (KVNX), 82 km from the middle of the area, began a volume at 21:27 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 watch it was issued in

The SPC watch in force over the same counties when this warning went out.

Issued	Product	Office	Lasted
Apr 18, 1:28 PM CDT	Tornado Watch	SPC	6 hr

The nearest sounding before it

Lamont, OK (KLMN), launched 12:00Z, 9.5 hours before the alert went out and 131 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: 452 J/kg
Mixed-layer CIN: -33 J/kg
Mixed-layer LCL: 456 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 51 m²/s²
0-3 km storm-relative helicity: 60 m²/s²
Significant tornado parameter: 0.1
Supercell composite: 0.7

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Norman, OK wrote its last area forecast discussion before this severe thunderstorm warning went out at Apr 18, 1:27 PM CDT, 3 hours earlier.

Area forecast discussion, Apr 18, 1:27 PM CDT, 3 hours before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
127 PM CDT SAT APR 18 2009

.DISCUSSION...
A LARGE ARE OF RAIN AND THUNDERSTORMS IS EXPECTED IN NORTHERN
OKLAHOMA THIS EVENING AND OVERNIGHT NEAR THE INFLUENCE OF THE
UPPER LOW PRESSURE CENTER WHICH IS MOVING SLOWLY EAST. THE COLD
FRONT WILL MOVE ACROSS THIS AREA THIS EVENING PROVIDING ADDITIONAL
LIFT FOR A LARGER AREA OF RAIN AND THUNDERSTORMS. A FEW
THUNDERSTORMS MAY CONTINUE IN SOUTHWEST OKLAHOMA HAVING BEEN
INITIATED ALONG THE DRY LINE EARLIER. THE EFFECTS OF THE UPPER LOW
WILL LEAVE OKLAHOMA SUNDAY MORNING. NORTHWEST MID-LEVEL FLOW WILL
REMAIN IN PLACE THROUGH MID-WEEK WHEN TWO COLD FRONTS ARE EXPECTED
BEFORE WEDNESDAY. LITTLE MORE THAN A WIND SHIFT IS EXPECTED WITH
THESE DRY FRONTS. DURING THE SECOND HALF OF THE WEEK, THE LARGE-
SCALE PATTERN IS EXPECTED TO CHANGE WHEN THE PLAINS WILL BE UNDER
THE INFLUENCE OF SOUTHWEST FLOW AND A MORE HUMID AIRMASS. THE NEXT
CHANCE FOR RAIN COMES SATURDAY WITH THE APPROACH OF AN UPPER WAVE
FROM THE WEST.

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK  51  67  45  73 /  50  10  10   0
HOBART OK         47  64  42  73 /  30  10   0   0
WICHITA FALLS TX  50  69  46  74 /  20  10   0   0
GAGE OK           43  63  40  73 /  40  10   0   0
PONCA CITY OK     49  65  42  71 /  70  30  10   0
DURANT OK         53  69  48  72 /  40  10  10  10

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...NONE.
TX...NONE.
&&

06/09

Hazardous weather outlook, Apr 18, 11:55 AM CDT, 4 hours 32 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
1155 AM CDT SAT APR 18 2009

OKZ004>048-050>052-TXZ083>090-191000-
HARPER-WOODS-ALFALFA-GRANT-KAY-ELLIS-WOODWARD-MAJOR-GARFIELD-NOBLE-
ROGER MILLS-DEWEY-CUSTER-BLAINE-KINGFISHER-LOGAN-PAYNE-BECKHAM-
WASHITA-CADDO-CANADIAN-OKLAHOMA-LINCOLN-GRADY-MCCLAIN-CLEVELAND-
POTTAWATOMIE-SEMINOLE-HUGHES-HARMON-GREER-KIOWA-JACKSON-TILLMAN-
COMANCHE-STEPHENS-GARVIN-MURRAY-PONTOTOC-COAL-COTTON-JEFFERSON-
CARTER-JOHNSTON-ATOKA-LOVE-MARSHALL-BRYAN-HARDEMAN-FOARD-WILBARGER-
WICHITA-KNOX-BAYLOR-ARCHER-CLAY-
1155 AM CDT SAT APR 18 2009

THIS HAZARDOUS WEATHER OUTLOOK COVERS NORTHERN...WESTERN...
CENTRAL...AND SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS.

.DAY ONE...THIS AFTERNOON AND TONIGHT...

THUNDERSTORM OUTLOOK...
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING OVER MUCH OF OKLAHOMA...AND PART OF WESTERN NORTH TEXAS.

LOCATION...
THE SLIGHT RISK INCLUDES THE AREA LOCATED EAST OF A LINE FROM
LAVERNE IN NORTHWEST OKLAHOMA...TO ELK CITY...WICHITA FALLS...AND
ARCHER CITY.

TIMING...
THE MOST LIKELY TIME FOR SEVERE THUNDERSTORMS WILL BE FROM 2 PM
THROUGH 11 PM.

IMPACTS...
MINOR HAIL DAMAGE TO AUTOMOBILES...TENDER VEGETATION...AND POSSIBLY
TO ROOFTOPS. HAIL SIZES WILL RANGE UP TO GOLF BALL.

WIND DAMAGE TO TREES...MOBILE HOMES...AND POSSIBLY TO ROOFTOPS.

RECOMMENDED ACTIONS...
STORM SPOTTER GROUPS AND EMERGENCY MANAGEMENT PERSONNEL ACROSS THE
RISK AREA SHOULD PLAN FOR SEVERE WEATHER OPERATIONS FROM 2 PM UNTIL
11 PM.

DISCUSSION...
AN UPPER LEVEL STORM SYSTEM LOCATED OVER THE HIGH PLAINS WILL MOVE
EAST AND SOUTH ACROSS NORTHERN AND CENTRAL OKLAHOMA THROUGH TONIGHT.
AN ASSOCIATED UPPER LEVEL DISTURBANCE WILL MOVE ACROSS WEST TEXAS
AND INTO OKLAHOMA THIS AFTERNOON AND EVENING.  A DRYLINE AND PACIFIC
COLD FRONT WILL PUSH ACROSS PARTS OF SOUTHWEST OKLAHOMA AND WESTERN
NORTH TEXAS THIS AFTERNOON...WHILE ANOTHER SURFACE BOUNDARY ENTERS
NORTHWEST OKLAHOMA.  MODERATE INSTABILITY WILL DEVELOP AHEAD OF
THESE SURFACE FEATURES AS TEMPERATURES WARM INTO THE UPPER 60S
AND MID 70S.  ALTHOUGH LOW LEVEL WINDS WILL NOT BE PARTICULARLY
STRONG...SHEAR IN THE MID AND UPPER LEVELS WILL SUPPORT SEVERE
STORMS.

STORMS MAY FORM INITIALLY ACROSS PARTS OF SOUTHWEST OKLAHOMA AND
WESTERN NORTH TEXAS NEAR THE DRYLINE...WITH OTHER STORMS FORMING
NEAR THE OTHER BOUNDARY ACROSS FAR NORTHWEST OKLAHOMA.   THE
STRONGEST LIFT BY THIS EVENING WILL BE ACROSS NORTHERN OKLAHOMA
WITHIN A REGION OF STRONG UPPER LEVEL DIVERGENCE.  STORMS THAT FORM
THIS AFTERNOON WILL MOVE INTO CENTRAL PARTS OF THE STATE THIS
EVENING AND INTO EASTERN PARTS OF THE STATE LATE THIS EVENING AND
OVERNIGHT.

PROBABILITY TABLE...
VALID THROUGH 700 AM CDT SUNDAY APR 19.
PROBABILITY OF THUNDERSTORMS OCCURRING IN THE
              NWS NORMAN COUNTY WARNING AREA...100 PERCENT.
PROBABILITY OF SEVERE STORMS IF STORMS OCCUR...80 PERCENT.

OTHER HAZARDOUS WEATHER...
NONE.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY...

THUNDERSTORM OUTLOOK...
A FEW WEAK THUNDERSTORMS MAY CONTINUE EARLY SUNDAY MORNING EAST OF
INTERSTATE 35. THE CHANCE FOR THUNDERSTORMS WILL QUICKLY DIMINISH AS
HIGH PRESSURE MOVES INTO THE SOUTHERN PLAINS IN THE AFTERNOON. DRY
WEATHER IS  EXPECTED FOR THE REST OF THE WEEK.

.OTHER HAZARDOUS WEATHER...
NONE.

THE NEXT SCHEDULED HAZARDOUS WEATHER OUTLOOK WILL BE ISSUED AT
5 AM SUNDAY.

In the hours before

Special weather statement, Apr 18, 2:04 PM CDT, 2 hours 23 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
204 PM CDT SAT APR 18 2009

OKZ005-010-181915-
WOODWARD OK-WOODS OK-
204 PM CDT SAT APR 18 2009

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR WOODS AND WOODWARD COUNTIES.

A STRONG THUNDERSTORM WAS LOCATED 3 MILES SOUTHWEST OF ALABASTER
CAVERNS STATE PARK AT 205 PM CDT...MOVING NORTHEAST AT 25 MPH.

SMALL HAIL AND WINDS AROUND 50 MPH ARE POSSIBLE.

WR

Special weather statement, Apr 18, 2:23 PM CDT, 2 hours 4 minutes before

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE NORMAN OK
223 PM CDT SAT APR 18 2009

OKZ004-005-010-181945-
WOODWARD OK-HARPER OK-WOODS OK-
223 PM CDT SAT APR 18 2009

...SIGNIFICANT WEATHER ADVISORY...

THIS SIGNIFICANT WEATHER ADVISORY IS FOR HARPER...WOODS AND WOODWARD
COUNTIES.

A LINE OF STRONG THUNDERSTORMS WAS LOCATED FROM 18 MILES NORTHWEST OF
CAMP HOUSTON TO 4 MILES SOUTHWEST OF ALABASTER CAVERNS STATE PARK AT
224 PM CDT...MOVING EAST AT 15 MPH.

SMALL HAIL AND WINDS AROUND 50 MPH ARE POSSIBLE.

WR

Local storm report, Apr 18, 3:59 PM CDT, 28 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
359 PM CDT SAT APR 18 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0356 PM     HAIL             2 E CORA                36.80N 98.88W
04/18/2009  E1.50 INCH       WOODS              OK   TRAINED SPOTTER

            RELAYED VIA SPOTTER NETWORK

&&

SMITH

Local storm report, Apr 18, 4:01 PM CDT, 26 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
401 PM CDT SAT APR 18 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0400 PM     HAIL             CORA                    36.80N 98.92W
04/18/2009  E1.75 INCH       WOODS              OK   STORM CHASER

&&

SMITH

Local storm report, Apr 18, 4:14 PM CDT, 13 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NORMAN OK
414 PM CDT SAT APR 18 2009

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0413 PM     HAIL             10 W ALVA               36.80N 98.85W
04/18/2009  E2.75 INCH       WOODS              OK   STORM CHASER

&&

SMITH

The office that day

Everything else NWS Norman, OK issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 17, 7:39 PM CDT	Severe Thunderstorm Warning	OUN	Greer, Harmon	51 min
Apr 17, 8:39 PM CDT	Severe Thunderstorm Warning	OUN	Beckham, Custer, Roger Mills	36 min
Apr 18, 8:31 AM CDT	Dense Fog Advisory	OUN	Carter, Comanche, Cotton, Garvin, Greer, Harmon and 7 more	2 hr
Apr 18, 2:28 PM CDT	Severe Thunderstorm Warning	OUN	Woods, Woodward	47 min
Apr 18, 3:08 PM CDT	Severe Thunderstorm Warning	OUN	Woods	52 min
Apr 18, 3:20 PM CDT	Tornado Warning	OUN	Woods	40 min
Apr 18, 3:39 PM CDT	Severe Thunderstorm Warning	OUN	Harper, Woods, Woodward	66 min
Apr 18, 3:59 PM CDT	Severe Thunderstorm Warning	OUN	Woods	61 min
Apr 18, 4:45 PM CDT	Tornado Warning	OUN	Alfalfa, Woods	45 min
Apr 18, 4:59 PM CDT	Severe Thunderstorm Warning	OUN	Woods	31 min
Apr 18, 5:10 PM CDT	Severe Thunderstorm Warning	OUN	Alfalfa, Blaine, Dewey, Major, Woods	65 min
Apr 18, 5:18 PM CDT	Severe Thunderstorm Warning	OUN	Alfalfa, Grant, Woods	57 min
Apr 18, 6:11 PM CDT	Severe Thunderstorm Warning	OUN	Alfalfa, Blaine, Garfield, Grant, Kingfisher, Major	34 min
Apr 17, 7:13 PM CDT	Severe Thunderstorm Warning	OUN	Foard, Hardeman	47 min

Nearby

Severe Thunderstorm Warnings in Oklahoma, 2009 Every severe thunderstorm warning 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.