Alert archive / Texas / Mesoscale Discussions in 2003

Mesoscale Discussion 1850

July 15, 200310 counties in Texas

The Storm Prediction Center issued this mesoscale discussion at Jul 15, 2003, 1:41 AM CDT for 10 counties in Texas. It was in force for 3 hr.

The area

The outline as issued.

The facts

Issued: Jul 15, 2003, 1:41 AM CDT (06:41 UTC)
Expired: Jul 15, 2003, 4:45 AM CDT
In force: 3 hr
Issued by: the Storm Prediction Center

Counties Austin County, TX, Brazoria County, TX, Chambers County, TX, Colorado County, TX, Fort Bend County, TX, Galveston County, TX, Harris County, TX, Jefferson County, TX, Waller County, TX, Wharton County, TX

The radar

The Houston radar (KHGX), 37 km from the middle of the area, began a volume at 06:42 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

Lake Charles Mun, LA (KLCH), launched 00:00Z, 6.7 hours before the alert went out and 228 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: 3 J/kg
Mixed-layer CIN: -124 J/kg
Mixed-layer LCL: 1628 m above ground
0-6 km bulk shear: 16 kt
0-1 km storm-relative helicity: 25 m²/s²
0-3 km storm-relative helicity: 34 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.

280 
ACUS11 KWNS 150641
SWOMCD
SPC MCD 150641 
LAZ000-TXZ000-150945-

MESOSCALE DISCUSSION 1850
NWS STORM PREDICTION CENTER NORMAN OK
0141 AM CDT TUE JUL 15 2003

AREAS AFFECTED...PORTIONS SE TX

CONCERNING...TC TORNADO POTENTIAL 

VALID 150641Z - 150945Z

MID-UPPER TX COAST TORNADO RISK COULD INCREASE NEXT 4-6 HOURS AS
MORE OF N-CENTRAL/NERN PORTION OF HURCN CLAUDETTE CIRCULATION MOVES
OVER AREA.  WW MAY BE REQUIRED.

MAIN CONCERN FOR DISCRETE SUPERCELL FORMATION IS WITH BANDS OF
CONVECTION NOW BETWEEN 28N-28.5N -- SE GLS TO SE BPT...AND MORE
PERIPHERAL BAND NOW OVER COAST BETWEEN BPT AND ERN GLS BAY.  THESE
SHOULD SHIFT WWD TOWARD AREA FROM MATAGORDA/BRAZORIA/WHARTON
COUNTIES THROUGH HOU METRO.  STRONGER KINEMATIC FIELDS ASSOCIATED
WITH CLAUDETTE SHOULD GRADUALLY SPREAD ACROSS PORTIONS TX COAST AS
CLAUDETTE MOVES W AND STRENGTHENS PER NHC FCSTS...REF LATEST NHC
BULLETINS FOR MORE DETAILED GUIDANCE.  THIS WILL INCREASE BOUNDARY
LAYER SHEAR OVER MORE OF AREA. S-R HODOGRAPH SIZE INCREASES
SUBSTANTIALLY WITH WWD AND NWD COMPONENTS OF CELL MOTIONS...WHICH
WOULD BE OPTIMALLY RIGHTWARD-DEVIANT BASED ON MODIFIED HGX VWP. 
THIS YIELDS 100-200 J/KG SRH IN 0-1 KM LAYER.  

EXPECT LOW-MIDLEVEL THERMODYNAMICS TO BECOME SOMEWHAT MORE FAVORABLE
WITH 500-1000 J/KG SBCAPE INSIDE MAIN PRECIP ENVELOPE AS

1. MIDLEVEL MOISTURE GRADIENT -- ERN EDGE OF DRYING ALOFT THAT WAS
EVIDENT IN 00Z RAOBS OVER SRN LA -- SHIFTS WWD.  06Z LCH RAOB
INDICATES THIS PROCESS PASSING W OF LCH.
2. SFC MOIST ADVECTION FROM GULF REPLACES RELATIVE DRY POCKET
ANALYZED PAST SEVERAL HOURS OVER PORTIONS SE TX.  THIS SFC DRYING
APPEARS TO HAVE ORIGINATED FROM COMBINATION OF DIURNAL VERTICAL
MIXING AND SUBSIDENT LOW-MIDLEVEL PARCELS...AND SHOULD SHIFT AWAY
FROM AREA.

..EDWARDS.. 07/15/2003

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

ATTN...WFO...LCH...HGX...EWX...

28769561 28979632 29239665 29679685 29969660 30199578
30159470 29959402 29699379 29309414

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 15, 6:40 AM CDT	Tornado Watch	SPC	Brazoria, Chambers, Fort Bend, Galveston, Hardin, Harris and 4 more	6 hr
Jul 15, 7:57 AM CDT	Mesoscale Discussion	SPC	Brazoria, Chambers, Fort Bend, Galveston, Hardin, Jackson and 3 more	4 hr
Jul 15, 9:48 AM CDT	Mesoscale Discussion	SPC	Brazoria, Calhoun, Colorado, DeWitt, Fort Bend, Goliad and 8 more	117 min
Jul 15, 12:05 PM CDT	Tornado Watch	SPC	Aransas, Brazoria, Calhoun, Chambers, Fort Bend, Galveston and 8 more	7 hr
Jul 15, 3:00 PM CDT	Tornado Watch	SPC	Atascosa, Bee, DeWitt, Frio, Goliad, Jackson and 7 more	7 hr

Nearby

Mesoscale Discussions in Texas, 2003 Every mesoscale discussion in 2003

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.