Tornadoes and Flash Flooding in Texas, October 28 to 29, 2002

SOUTHEAST TEXAS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
920 AM CST MON OCT 28 2002

ALL INGREDIENTS IN PLACE FOR HEAVY RAINFALL/POSSIBLE SEVERE EVENT
OVER AT LEAST SE HALF OF CWA THROUGH THIS EVENING. STRONG SHORTWAVE
NEAR EL PASO WILL PUSH EASTWARD INTO WEST TX BY THIS EVENING
ENHANCING LIFT OVER AREA. CWA ALSO LIES IN RRQ OF 300 MB JET MAX
EXITING NORTH TX. AMPLE MOISTURE IN PLACE WITH PWS AROUND 2 INCHES
AND 850 MB DEWPOINTS AROUND +16C. SFC ANALYSIS SHOWS WARM FRONT
LYING ABOUT 40 MILES OFFSHORE. EXPECT FRONT TO PUSH NORTHWARD INTO
COASTAL ZONES BY EARLY AFTN...PROBABLY LIFTING INTO CENTRAL CWA
LATE...PLACING LARGE PORTION OF CWA IN WARM SECTOR. EXPECT THREAT
FOR DOWNBURSTS/ISOLATED TORNADOES AND INCREASE IN RAINFALL RATES AS
WARM FRONT PUSHES INLAND. BASED ON RAINFALL RATES WITH CONVECTION
MOVING OVER OFFICE NOW...APPEARS TROPICAL Z-R MAY HAVE BETTER HANDLE
ON SITUATION. WILL KEEP FFA IN CURRENT CONFIGURATION...AND UP POPS
IN CENTRAL ZONES TO 80 PCT. NO OTHER CHANGES ANTICIPATED.

35/42

.HGX...FFA SE OF A COLUMBUS TO CONROE TO LIVINGSTON LINE.

PRELIMS...
CLL TB 072/062 081/061 076 552
IAH TB 075/067 081/063 077 872
GLS TB 079/072 080/070 076 873

PREVIOUS DISCUSSION...
SFC PLOT TONIGHT SHOWS A WEAK LOW ACROSS CEN LA/W MISS. WARM FRONT
STILL OFFSHORE OF THE UPPER SE TX COAST. LIGHT NORTHERLY FLOW EXISTS
ACROSS MOST OF THE INLAND ZONES WITH SFC HIGH WELL TO THE NORTH. LOW
CLOUDS AND PATCHY DRIZZLE AND LIGHT FOG WILL CONTINUE INTO THE EARLY
MORNING HOURS.

ACTIVE WEATHER DAY EXPECTED BEGINNING THIS AFTERNOON AND INTO THE
OVERNIGHT HOURS AS SW U.S. TROUGH MOVES NORTHEAST ACROSS TEXAS. 120
KT UPPER LEVEL JET CORE WILL MOVE ACROSS NORTH-CEN TX WITH FA IN RR
QUAD OF THIS FEATURE LATER TODAY AND TONIGHT. WF IS EXPECTED TO
BEGIN LIFTING NORTHWARD THIS MORNING AND IS LIKELY TO PROVIDE A
FOCUS FOR SHWR AND TSTM DEVELOPMENT. PW WATER VALUES WILL CLIMB
ACROSS COASTAL AND PORTIONS OF CENTRAL ZONES TO NEAR 2 INCHES BY
EARLY THIS AFT. ETA/AVN ARE IN GOOD AGREEMENT WITH THE PRECIP
PATTERN OVER THE REGION TODAY BUT DIFFER ON AMOUNTS. WITH THE AVN
HAVING A MUCH HIGHER QPF. REALLY DOES NOT MATTER MUCH FOR THE FLOOD
WATCH DECISION BECAUSE THE GROUND IS SATURATED...BUT LEADS TO LOW
CONFIDENCE ON QPF. WILL ISSUE A FLOOD WATCH ALONG AND SE OF A
COLUMBUS TO CONROE TO LIVINGSTON LINE AND WORD THE WATCH THROUGH
TONIGHT.

SVR WX POTENTIAL IS VERY TRICKY. LOW-LEVEL JET AND INSTABILITY ARE
MARGINAL OVER THE REGION. MODELS SHOW S/SW 850 FLOW OF AROUND 25 TO
30 KNOTS. HOWEVER...THINK WITH GOOD UPPER LEVEL DIVERGENCE AND
STRONG MID-LEVEL WINDS COUPLED WITH POSSIBLE ENHANCEMENT TO
LOW-LEVEL SHEAR ALONG THE BOUNDARY THIS AFTERNOON...THE POSSIBILITY
OF SVR TSTMS WILL EXIST OVER THE REGION THIS AFT AND EVENING. WILL
HAVE TO GET THROUGH A CAP THAT IS EVIDENT IN THE CRP 00Z SOUNDING.
BELIEVE SYNOPTIC SCALE LIFT WITH THE APPROACH OF THE MID-LEVEL TROF
AND CONVERGENCE ALONG THE WF WILL HELP WITH THAT THIS AFT. WILL
MENTION THE THREAT IN THE ZONES ALONG WITH LOCALLY HEAVY RAINFALL.

DISAGREEMENT EXISTS ON THE DEGREE OF DRYING THAT OCCURS ON TUESDAY
BETWEEN AVN AND ETA. WILL KEEP SLIGHT CHC WORDING ALL DAY...AS AVN
MAY BE TOO AGGRESSIVE WITH DRYING. WILL ALSO TREND LOW TEMPS HIGHER
THAN AVN NUMBERS.

NO BIG CHANGES PLANNED FOR THE EXTENDED...STILL LOOKING COLD FOR
THIS TIME OF YEAR THIS COMING WEEKEND.

33/41

GMZ300-330-335-350-355-370-375-TXZ163-164-176>179-195>200-210>214-226-
227-235>238-291300-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE HOUSTON/GALVESTON TX
630 AM CST MON OCT 28 2002

...FLOOD WATCH IS IN EFFECT TODAY AND TONIGHT ACROSS CENTRAL AND
COASTAL PORTIONS OF SOUTHEAST TEXAS...
...SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY AND TONIGHT AREAWIDE...

.DAY ONE...
TODAY...
AN UPPER LEVEL DISTURBANCE APPROACHING FROM THE WEST AND A WARM FRONT
MOVING NORTH FROM THE GULF OF MEXICO ARE EXPECTED TO TRIGGER
NUMEROUS SHOWERS AND THUNDERSTORMS ACROSS SOUTHEAST THIS
MORNING...WITH HIGH RAIN CHANCES CONTINUING INTO THE EVENING HOURS.
A VERY MOIST ATMOSPHERE WILL CREATE THE POSSIBILITY OF HEAVY RAINFALL.
RAINFALL ACCUMULATIONS TODAY AND TONIGHT ARE EXPECTED TO AVERAGE 1 TO
2 INCHES WITH ISOLATED TOTALS OF 3 TO 4 INCHES POSSIBLE.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS ALL OF SOUTHEAST
TEXAS TODAY AND TONIGHT. DAMAGING WINDS...LARGE HAIL...AND ISOLATED
TORNADOES ARE ALL THREATS TODAY.

.SPOTTER CALL TO ACTION STATEMENT...SPOTTER ACTIVATION IS POSSIBLE
TODAY AND TONIGHT.

.DAYS TWO THROUGH SEVEN...
TUESDAY THROUGH SUNDAY...HAZARDOUS WEATHER IS NOT EXPECTED.