Alert archive / Oklahoma / Mesoscale Discussions in 2012

Mesoscale Discussion 507

April 13, 201215 counties in Oklahoma; 9 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 13, 2012, 12:10 PM CDT for 15 counties in Oklahoma; 9 counties in Texas. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Apr 13, 2012, 12:10 PM CDT (17:10 UTC)
Expired: Apr 13, 2012, 2:15 PM CDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 24 counties

Caddo County, OK, Canadian County, OK, Carter County, OK, Comanche County, OK, Cotton County, OK, Garvin County, OK, Grady County, OK, Jackson County, OK, Jefferson County, OK, Kiowa County, OK, Love County, OK, McClain County, OK, Murray County, OK, Stephens County, OK, Tillman County, OK, Archer County, TX, Baylor County, TX, Clay County, TX, Foard County, TX, Hardeman County, TX, King County, TX, Knox County, TX, Wichita County, TX, Wilbarger County, TX

The radar

The Altus AFB radar (KFDR), 20 km from the middle of the area, began a volume at 17:11 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 160Apr 13, 1:30 PM CDT

The nearest sounding before it

Norman, OK (KOUN), launched 12:00Z, 5.2 hours before the alert went out and 172 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: 1194 J/kg
Mixed-layer CIN: -77 J/kg
Mixed-layer LCL: 554 m above ground
0-6 km bulk shear: 36 kt
0-1 km storm-relative helicity: 477 m²/s²
0-3 km storm-relative helicity: 512 m²/s²
Significant tornado parameter: 2.0
Supercell composite: 23.9

Open this sounding in Storm Lab

The text

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

808 
ACUS11 KWNS 131711
SWOMCD
SPC MCD 131710
OKZ000-TXZ000-131915-

MESOSCALE DISCUSSION 0507
NWS STORM PREDICTION CENTER NORMAN OK
1210 PM CDT FRI APR 13 2012

AREAS AFFECTED...NWRN TX THROUGH SWRN OK

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 131710Z - 131915Z

STORMS ARE EXPECTED TO DEVELOP SOON FROM NWRN TX INTO SWRN OK.
INITIAL PRIMARY THREAT WILL BE SUPERCELLS WITH LARGE HAIL DURING THE
AFTERNOON WITH THREAT FOR ISOLATED TORNADOES INCREASING DURING THE
EARLY EVENING. AREA IS BEING MONITORED FOR A WW.

A PRE-FRONTAL BOUNDARY EXTENDS FROM ERN KS SWWD THROUGH WRN OK AND
NWRN TX. MOIST AXIS WITH MID-UPPER 60S DEWPOINTS ARE IN PLACE IN
WARM SECTOR BENEATH 7-7.5 C/KM MID LEVEL LAPSE RATES PROMOTING AN
AXIS OF 2000-2500 J/KG MLCAPE. THE ATMOSPHERE SHOULD DESTABILIZE
FURTHER AS LOW CLOUDS MIX OUT AND THE BOUNDARY LAYER WARMS. VISIBLE
IMAGERY CONTINUES TO SHOW AN INCREASE IN CUMULUS DEVELOPMENT IN
VICINITY OF THE CONVERGENCE BOUNDARY OVER NWRN TX INTO SWRN OK AS
WELL AS A LITTLE FARTHER EAST INTO S-CNTRL OK WITHIN ZONE OF WEAK
WARM ADVECTION. MORNING RAOB DATA FROM FWD AND OKC INDICATED A
MODEST INVERSION AROUND 750 MB...AND LATEST OBJECTIVE ANALYSIS SHOW
ONLY A WEAK CAP REMAINING. INDICATIONS ARE THAT THUNDERSTORMS MAY
SOON DEVELOP IN THIS REGION. EFFECTIVE DEEP LAYER SHEAR AROUND 40 KT
SUPPORTS SUPERCELLS. LOW LEVEL WINDS HAVE BEEN VEERING AND WEAKENING
AS PRIMARY LLJ SHIFTS THROUGH THE MS VALLEY IN ASSOCIATION WITH
SHORTWAVE TROUGH EJECTING NEWD THROUGH ERN SD. THIS MAY DELAY A MORE
ROBUST TORNADO THREAT UNTIL EARLY EVENING WHEN THE LLJ WILL
STRENGTHEN OVER THE SRN PLAINS.

..DIAL.. 04/13/2012

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

ATTN...WFO...FWD...OUN...SJT...LUB...

LAT...LON   34379987 35809815 34399681 33789731 33359926 33500056
            34379987

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 13, 1:28 PM CDT	Tornado Watch	SPC	Alfalfa, Beckham, Blaine, Caddo, Canadian, Cherokee and 42 more	8 hr
Apr 13, 3:39 PM CDT	Mesoscale Discussion	SPC	Alfalfa, Beckham, Blaine, Caddo, Canadian, Cleveland and 27 more	96 min
Apr 13, 5:47 PM CDT	Mesoscale Discussion	SPC	Blaine, Caddo, Canadian, Cleveland, Comanche, Creek and 25 more	88 min
Apr 13, 6:06 PM CDT	Severe Thunderstorm Watch	SPC	Armstrong, Briscoe, Carson, Childress, Collingsworth, Cottle and 8 more	7 hr

Nearby

Mesoscale Discussions in Oklahoma, 2012 Mesoscale Discussions in Texas, 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.