Alert archive / Oklahoma / Mesoscale Discussions in 2012

Mesoscale Discussion 847

May 20, 201220 counties in Oklahoma

The Storm Prediction Center issued this mesoscale discussion at May 20, 2012, 1:30 AM CDT for 20 counties in Oklahoma. It was in force for 90 min.

The area

The outline as issued.

The facts

Issued: May 20, 2012, 1:30 AM CDT (06:30 UTC)
Expired: May 20, 2012, 3:00 AM CDT
In force: 90 min
Issued by: the Storm Prediction Center

Counties Caddo County, OK, Canadian County, OK, Cleveland County, OK, Comanche County, OK, Creek County, OK, Garvin County, OK, Grady County, OK, Kingfisher County, OK, Kiowa County, OK, Lincoln County, OK, Logan County, OK, McClain County, OK, Murray County, OK, Okfuskee County, OK, Oklahoma County, OK, Pontotoc County, OK, Pottawatomie County, OK, Seminole County, OK, Stephens County, OK, Washita County, OK

The radar

The Norman radar (KTLX), 63 km from the middle of the area, began a volume at 06:32 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

Norman, OK (KOUN), launched 00:00Z, 6.5 hours before the alert went out and 47 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: 539 J/kg
Mixed-layer CIN: -464 J/kg
Mixed-layer LCL: 1944 m above ground
0-6 km bulk shear: 40 kt
0-1 km storm-relative helicity: 211 m²/s²
0-3 km storm-relative helicity: 337 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.

610 
ACUS11 KWNS 200631
SWOMCD
SPC MCD 200630
OKZ000-200800-

MESOSCALE DISCUSSION 0847
NWS STORM PREDICTION CENTER NORMAN OK
0130 AM CDT SUN MAY 20 2012

AREAS AFFECTED...SRN AND CNTRL OK

CONCERNING...SEVERE THUNDERSTORM WATCH 284...

VALID 200630Z - 200800Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 284
CONTINUES.

SUMMARY...AN ISOLATED SEVERE THREAT WILL LIKELY CONTINUE ACROSS WW
284 AND EWD ACROSS CNTRL OK FOR A FEW MORE HOURS. HAIL AND A FEW
DAMAGING WIND GUSTS WILL BE POSSIBLE BUT THE THREAT IS EXPECTED TO
BECOME INCREASINGLY MARGINAL WITH TIME.

DISCUSSION...A CLUSTER OF STRONG TO SEVERE THUNDERSTORMS IS ONGOING
ACROSS WRN AND CNTRL OK ALONG A CORRIDOR OF MODERATE INSTABILITY
WHERE SBCAPE VALUES ARE ESTIMATED IN THE 1000 TO 1500 J/KG RANGE.
THE ACTIVITY IS LOCATED NEAR THE NOSE OF THE LOW-LEVEL JET SHOW BY
MESOANALYSIS WITH 20 TO 30 KT OF LOW-LEVEL FLOW. THIS ALONG WITH 40
KT OF FLOW NEAR 500 MB IS CREATING MODERATE DEEP LAYER SHEAR
PROFILES FAVORABLE FOR SEVERE STORMS. THE INSTABILITY COMBINED WITH
STEEP MID-LEVEL LAPSE RATES APPROACHING 8.0 C/KM AT 500 MB EVIDENT
ON FORECAST SOUNDINGS SHOULD BE SUPPORTIVE OF HAIL WITH THE STRONGER
CORES. ALTHOUGH THE NEAR SFC LAYER IS SOMEWHAT STABLE ESPECIALLY TO
THE EAST OF THE WATCH...MATURE SHORT LINE SEGMENTS COULD ALSO POSE
AN ISOLATED WIND DAMAGE THREAT. AS THE STORMS MOVE EWD INTO
INCREASINGLY STABLE AIR...THE SEVERE THREAT SHOULD GRADUALLY BECOME
MARGINAL EARLY THIS MORNING.

..BROYLES.. 05/20/2012

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

ATTN...WFO...TSA...OUN...

LAT...LON   35439931 34699918 34369835 34229757 34359681 34869624
            36009632 36069776 35439931

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 19, 7:03 PM CDT	Mesoscale Discussion	SPC	Alfalfa, Grant	57 min
May 19, 9:03 PM CDT	Severe Thunderstorm Watch	SPC	Alfalfa, Beckham, Blaine, Caddo, Canadian, Comanche and 21 more	7 hr
May 19, 11:09 PM CDT	Mesoscale Discussion	SPC	Blaine, Caddo, Canadian, Comanche, Garfield, Grady and 16 more	66 min
May 20, 3:00 AM CDT	Mesoscale Discussion	SPC	Caddo, Cleveland, Grady, Kiowa, McClain, Okfuskee and 2 more	90 min

Nearby

Mesoscale Discussions in Oklahoma, 2012 Every 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.