Alert archive / Oklahoma / Severe Thunderstorm Warnings in 2009

Severe Thunderstorm Warning 718, NWS Norman, OK

September 21, 2009McClain County, Pontotoc County, Pottawatomie County, Oklahoma

NWS Norman, OK issued this severe thunderstorm warning at Sep 21, 2009, 3:41 PM CDT for McClain County, Pontotoc County, Pottawatomie County, Oklahoma. It was in force for 64 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: Sep 21, 2009, 3:41 PM CDT (20:41 UTC)
Expired: Sep 21, 2009, 4:45 PM CDT
In force: 64 min
Issued by: NWS Norman, OK
Area: Storm-based polygon

Counties McClain County, OK, Pontotoc County, OK, Pottawatomie County, OK

The radar

The Norman radar (KTLX), 45 km from the middle of the area, began a volume at 20:44 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
Sep 21, 2:00 PM CDT	Severe Thunderstorm Watch	SPC	8 hr

The nearest sounding before it

Norman, OK (KOUN), launched 12:00Z, 8.7 hours before the alert went out and 43 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: 2002 J/kg
Mixed-layer CIN: -95 J/kg
Mixed-layer LCL: 920 m above ground
0-6 km bulk shear: 20 kt
0-1 km storm-relative helicity: 104 m²/s²
0-3 km storm-relative helicity: 26 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

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 Sep 21, 3:06 PM CDT, 35 minutes earlier.

Area forecast discussion, Sep 21, 3:06 PM CDT, 35 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
306 PM CDT MON SEP 21 2009

.DISCUSSION...A SEASONABLY STRONG COLD FRONT WILL SIGNAL THE ARRIVAL
OF FALL...WITH COOL NORTHERLY WINDS KICKING IN TONIGHT AND TOMORROW.
THE WIND SHIFT WAS ALREADY THROUGH MUCH OF WESTERN AND NORTHERN
OKLAHOMA THIS AFTERNOON. THE FRONT WILL DRIVE MORE QUICKLY TO THE
SOUTH RATHER THAN EAST...AS ITS ASSOCIATED UPPER LEVEL LOW DIGS
STRONGLY SOUTHWARD THROUGH THE ROCKIES.

THIS SYSTEM WILL MEET A WARM AND MOIST AIR MASS OVER CENTRAL AND
SOUTHERN OKLAHOMA...AND WESTERN NORTH TEXAS. SEVERE STORMS WERE
ONGOING MONDAY AFTERNOON JUST TO OUR NORTHEAST...AND ADDITIONAL
STRONG STORMS WILL BUILD DOWN THE FRONT DURING THE EVENING. UPPER
LEVEL FORCING IS MINIMAL...BUT SUSTAINED LIFT IN THE LOW LEVEL
FRONTAL ZONE SHOULD COMBINE WITH THE WEAKLY CAPPED AND MODERATELY
UNSTABLE AIR MASS TO YIELD WIDESPREAD STORMS TONIGHT. STORM MOTIONS
TO THE EAST AND NORTHEAST SHOULD KEEP INDIVIDUAL CELLS NEARLY
SURFACE BASED...INCREASING THE COVERAGE OF SEVERE WEATHER. WIND
SHEAR AND THERMODYNAMIC PROFILES...HOWEVER...FAVOR MARGINALLY SEVERE
HAIL AND WIND...WITH MORE INTENSE AND ORGANIZED STORMS BEING FEWER
IN NUMBER. ONE CONCERN COULD BE INTENSE RAINFALL...AS BOTH THE NAM
AND GFS HAVE A STRONG QPF SIGNAL IN SOUTHEAST OKLAHOMA. GIVEN THE
SPEED OF MOVEMENT OF THE INDIVIDUAL STORMS AND THE FRONT...THOUGH...
IT WOULD TAKE QUITE A BIT OF TRAINING TO PRODUCE EXCESSIVE RAINFALL.

BACK BEHIND THE FRONT...MODELS INDICATE AN ORGANIZED ZONE OF MID
LEVEL FRONTOGENESIS ROTATING THROUGH OUR REGION FROM WEST TO EAST
BEGINNING THE SECOND HALF OF TONIGHT. THE ACTIVITY WILL BE
LIGHTER...WITH ONLY EMBEDDED THUNDER EXPECTED. GIVEN THE COVERAGE OF
BOTH FORCING AND QPF IN THE MODELS...THOUGH...WE INCREASED POPS
ABOVE MAV GUIDANCE FOR TONIGHT AND TOMORROW...AND LOWERED MAX
TEMPERATURES WHERE CLOUD COVER IS EXPECTED TO PERSIST. IN FACT...THE
COOLER NAM 2-METER TEMPERATURES LOOKED PREFERABLE TO THE MAV MOS FOR
HIGH TEMPS BOTH TUE AND WED.

IN THE EXTENDED...THE GFS AND ITS ENSEMBLE HAVE BEEN CONSISTENT IN
KICKING THE UPPER LOW OUT OF THE ROCKIES FROM THURSDAY INTO FRIDAY.
WE REMAIN SOMEWHAT IN THE MID LEVEL DRY SLOT...BUT WITH THE RECENT
WET WEATHER AND WET GROUND...SOME INSTABILITY IS LIKELY TO
DEVELOP...WITH SCATTERED DIURNAL THUNDERSTORMS. NO CHANGES TO THE
GRIDS BEYOND DAY 3.

&&

.PRELIMINARY POINT TEMPS/POPS...
OKLAHOMA CITY OK  58  69  52  73 /  60  40  10   0
HOBART OK         56  67  52  74 /  60  40  10   0
WICHITA FALLS TX  61  69  54  77 /  60  40  10   0
GAGE OK           48  72  42  72 /  50  10  10  10
PONCA CITY OK     54  69  51  73 /  60  30  20   0
DURANT OK         66  73  59  74 /  90  50  20  10

&&

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

32/22
BURKE

Hazardous weather outlook, Sep 21, 11:55 AM CDT, 3 hours 46 minutes before

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In the hours before

Special weather statement, Sep 21, 2:57 PM CDT, 44 minutes before

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Special weather statement, Sep 21, 3:15 PM CDT, 26 minutes before

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Special weather statement, Sep 21, 3:37 PM CDT, 4 minutes before

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The office that day

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

Issued	Product	Office	Counties	Lasted
Sep 21, 3:25 PM CDT	Severe Thunderstorm Warning	OUN	Lincoln, Pottawatomie	35 min
Sep 21, 3:52 PM CDT	Severe Thunderstorm Warning	OUN	Hughes, Seminole	53 min
Sep 21, 4:09 PM CDT	Severe Thunderstorm Warning	OUN	Seminole	66 min
Sep 21, 5:00 PM CDT	Severe Thunderstorm Warning	OUN	Cleveland, Pottawatomie	60 min
Sep 21, 5:18 PM CDT	Severe Thunderstorm Warning	OUN	Carter, Garvin, Stephens	57 min
Sep 21, 5:48 PM CDT	Severe Thunderstorm Warning	OUN	Lincoln, Pottawatomie	57 min
Sep 21, 6:09 PM CDT	Severe Thunderstorm Warning	OUN	Seminole	66 min
Sep 21, 6:19 PM CDT	Areal Flood Advisory	OUN	Hughes, Seminole	3 hr
Sep 21, 6:38 PM CDT	Severe Thunderstorm Warning	OUN	Love	67 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.