Alert archive / Texas / Mesoscale Discussions in 2009

Mesoscale Discussion 511

April 18, 200928 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Apr 18, 2009, 9:47 AM CDT for 28 counties in Texas. It was in force for 28 min.

The area

The outline as issued.

The facts

Issued
Apr 18, 2009, 9:47 AM CDT (14:47 UTC)
Expired
Apr 18, 2009, 10:15 AM CDT
In force
28 min
Issued by
the Storm Prediction Center
All 28 counties

Anderson County, TX, Angelina County, TX, Austin County, TX, Brazoria County, TX, Brazos County, TX, Chambers County, TX, Cherokee County, TX, Fort Bend County, TX, Galveston County, TX, Grimes County, TX, Hardin County, TX, Harris County, TX, Houston County, TX, Leon County, TX, Liberty County, TX, Madison County, TX, Matagorda County, TX, Montgomery County, TX, Nacogdoches County, TX, Polk County, TX, Rusk County, TX, San Jacinto County, TX, Trinity County, TX, Tyler County, TX, Walker County, TX, Waller County, TX, Washington County, TX, Wharton County, TX

The radar

The Houston radar (KHGX), 128 km from the middle of the area, began a volume at 14:49 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.

The nearest sounding before it

Lake Charles Mun, LA (KLCH), launched 12:00Z, 2.8 hours before the alert went out and 208 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-pSkew-T log-p diagram, Lake Charles Mun, LA at 12:00Z on 2009-04-18Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 778 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Lake Charles Mun, LA at 12:00Z on 2009-04-18The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 160 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
778 J/kg
Mixed-layer CIN
-108 J/kg
Mixed-layer LCL
573 m above ground
0-6 km bulk shear
37 kt
0-1 km storm-relative helicity
160 m²/s²
0-3 km storm-relative helicity
499 m²/s²
Significant tornado parameter
0.0
Supercell composite
8.3

Open this sounding in Storm Lab

The text

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

000 
ACUS11 KWNS 181448
SWOMCD
SPC MCD 181447 
TXZ000-181515-

MESOSCALE DISCUSSION 0511
NWS STORM PREDICTION CENTER NORMAN OK
0947 AM CDT SAT APR 18 2009

AREAS AFFECTED...PORTIONS E-CENTRAL/SE TX.

CONCERNING...SEVERE POTENTIAL...WATCH NEEDED SOON 

VALID 181447Z - 181515Z

TORNADO WW WILL BE ISSUED WITHIN MOMENTS FOR EMBEDDED/SMALL
SUPERCELLS DEVELOPING AND TIGHTENING CIRCULATIONS RAPIDLY WITHIN
BROAD AREA OF RAIN AND TSTMS OVER DISCUSSION AREA.  WW WILL PARTLY
OVERLAP/REPLACE ERN PORTIONS WW 164.

..EDWARDS.. 04/18/2009

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

ATTN...WFO...LCH...SHV...HGX...FWD...

LAT...LON   29539440 28749564 28639626 29599645 30879645 31979587
            32269536 32269489 31999435 31279416 29539440

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Apr 17, 9:33 PM CDTMesoscale DiscussionSPCChildress, Collingsworth, Cottle, Foard, Gray, Hansford and 13 more27 min
Apr 17, 11:44 PM CDTMesoscale DiscussionSPCAtascosa, La Salle, McMullen61 min
Apr 18, 3:22 AM CDTMesoscale DiscussionSPCAtascosa, Bandera, Bastrop, Bee, Bexar, Blanco and 34 more113 min
Apr 18, 4:21 AM CDTSevere Thunderstorm WatchSPCAransas, Atascosa, Austin, Bandera, Bastrop, Bee and 43 more7 hr
Apr 18, 6:32 AM CDTMesoscale DiscussionSPCAtascosa, Bandera, Bastrop, Bexar, Caldwell, Comal and 17 more118 min
Apr 18, 9:53 AM CDTTornado WatchSPCAnderson, Angelina, Austin, Brazoria, Brazos, Burleson and 23 more6 hr
Apr 18, 10:52 AM CDTMesoscale DiscussionSPCAransas, Atascosa, Bee, Calhoun, DeWitt, Duval and 15 more53 min
Apr 18, 11:26 AM CDTMesoscale DiscussionSPCAnderson, Angelina, Austin, Brazoria, Brazos, Burleson and 29 more2 hr
Apr 18, 1:01 PM CDTTornado WatchSPCHardin, Jasper, Jefferson, Newton, Orange, Sabine and 3 more7 hr
Apr 18, 1:14 PM CDTMesoscale DiscussionSPCArcher, Clay, Wichita61 min
Apr 18, 1:43 PM CDTMesoscale DiscussionSPCAngelina, Austin, Brazoria, Chambers, Fort Bend, Galveston and 10 more92 min
Apr 18, 3:11 PM CDTSevere Thunderstorm WatchSPCArcher, Clay, Collin, Cooke, Dallas, Denton and 14 more9 hr
Apr 18, 3:38 PM CDTMesoscale DiscussionSPCHardin, Jasper, Jefferson, Newton, Orange, Sabine and 3 more97 min
Apr 18, 5:14 PM CDTMesoscale DiscussionSPCCooke, Denton, Grayson91 min
Apr 18, 5:46 PM CDTMesoscale DiscussionSPCHardin, Jasper, Jefferson, Newton, Orange, Sabine and 3 more59 min

Nearby

Mesoscale Discussions in Texas, 2009Every mesoscale discussion 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.