Severe Thunderstorm Warning 161, NWS Lake Charles, LA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
1010 AM CDT FRI AUG 21 2009

.UPDATE...
SURFACE COLD FRONT THIS MORNING NORTH OF THE AREA ACROSS THE
ARKLATEX. THEREFORE...FORECAST AREA STILL IN A VERY MOIST AND
UNSTABLE ATMOSPHERE. PWAT FROM THIS MORNINGS KLCH SOUNDING WAS
OVER 2.4 INCHES...AND LATEST LAPS ANALYSIS HAS LIS AROUND (-8)
WITH CAPES OVER 3000 J/KG. TRIGGER TEMPS ARE PROJECTED IN THE
UPPER 80S...SO WOULD EXPECT CONVECTION TO BEGIN TO DEVELOP BY 11
AM. WITH HIGH PWAT VALUES...LOCALLY HEAVY RAINFALL MAY OCCUR WITH
THE STORMS. ALSO...WITH HIGH CAPES...HIGH PWAT AND LIGHT AND
VARIABLE VERTICAL WIND PROFILE...TROPICAL FUNNEL CLOUDS WILL AGAIN
BE POSSIBLE.

NO CHANGES TO CURRENT FORECAST AT THIS TIME.

RUA

&&

.PREV DISCUSSION... /ISSUED 558 AM CDT FRI AUG 21 2009/

DISCUSSION...
EVENING UPPER AIR ANALYSIS AND OVERNIGHT WATER VAPOR SATELLITE
IMAGERY SHOWED UPPER LOW CENTERED OVER THE WESTERN GREAT LAKES
AMID A MEAN TROF THAT DOMINATES THE NORTH CENTRAL CONUS. ONE LOBE
OF ENERGY WAS TRANSLATING THROUGH THE BASE OF THE TROF AND HEADING
EAST TWD THE OHIO RIVER VALLEY. THIS INITIAL PUSH HAS SENT THE SFC
FRONT TO NEAR A TYLER TEXAS TO EL DORADO ARKANSAS LINE AS OF 09Z.
UPSTREAM...ANOTHER SURGE OF ENERGY WAS HEADED SOUTH THROUGH THE
NORTHERN PLAINS. THIS IS WHAT WILL SUBSEQUENTLY DRIVE THE FRONT
THROUGH THE REGION AND INTO THE GULF WATERS.

IN THE MEANTIME...FLOW OVER THE AREA FROM H85 AND ABOVE...WHICH
WAS ALREADY WESTERLY ON THE KLCH 00Z RAOB SAVE FOR SOUTHWESTERLY
WINDS AT H25 AROUND AN UPPER TROF OVER THE WESTERN GULF...ARE
BECOMING MORE NORTHWESTERLY WITH TIME PER OVERNIGHT PROFILER OBS
AND KLCH 88D VAD...AS THE DIGGING MEAN TROF SQUASHES WHAT REMAINS
OF THE MID/UPPER RIDGE THAT HAD BEEN IN PLACE ACROSS THE SOUTHEAST
CONUS. AT THE SFC...FLOW CONTINUES TO BE FROM THE SOUTHWEST AROUND
THE WESTERN EDGE OF THE BERMUDA HIGH. HOWEVER...THIS FEATURE TOO...IS
STARTING TO BREAK DOWN.

ALREADY SEEING SCATTERED SHOWER AND THUNDERSTORM ACTIVITY OVER THE
GULF WATERS AND IMMEDIATE COASTAL LOCATIONS...AND THIS CONVECTION
IS EXPECTED TO BECOME MORE NUMEROUS OVER INLAND AREAS AS THE DAY
PROGRESSES. GREATEST COVERAGE IS AGAIN ANTICIPATED OVER THE
EASTERN HALF OR SO OF THE AREA...PARTICULARLY SOUTH CENTRAL
LOUISIANA...WHERE LAPS ANALYSIS SHOWS H85 THETA-E RIDGE. NOT
ANTICIPATING WIDESPREAD SEVERE WEATHER TODAY...THOUGH STORMS WILL
BE CAPABLE OF LOCALLY HEAVY RAINFALL...AND STRONG OR ISOLATED
SEVERE STORMS WILL BE CAPABLE OF PRODUCING DAMAGING WINDS. FOR
TONIGHT...I HAVE LEFT POPS INTO THE EVENING HOURS TO ACCOUNT FOR
LINGERING AFTERNOON ACTIVITY PRIOR TO MIDNIGHT...AND NOCTURNAL
ACTIVITY THAT DEVELOPS OVER THE COASTAL WATERS AND ADJACENT INLAND
LOCATIONS AFTER MIDNIGHT. THE SFC FRONT...MEANWHILE...IS NOT
EXPECTED TO MAKE MUCH ADDITIONAL PROGRESS TO THE SOUTH TODAY OR
TONIGHT...AS THE INITIAL VORT LOBE LIFTS OUT TO THE EAST.

THAT WILL CHANGE SATURDAY...HOWEVER...AS THE SECONDARY VORT
DIVING SOUTH THROUGH THE PLAINS REACHES THE LOWER MISSISSIPPI
RIVER VALLEY. DRIER AIR WILL BEGIN TO SPILL INTO THE AREA AHEAD OF
THE FRONT TONIGHT AS OUR SFC WINDS VEER TO THE WEST AND THEN
NORTHWEST ON SATURDAY...WITH THE FRONT ITSELF PROGGED TO REACH
NEAR A VILLAGE MILLS TO OPELOUSAS LINE BY SATURDAY EVENING.

BY SUNDAY MORNING...AS THIS VORT REACHES THE SOUTHEAST CONUS...THE
FRONT IS EXPECTED TO REACH THE 20-60NM GULF ZONES...WHERE IT WILL
THEN SUBSEQUENTLY STALL. FOR THE TIME BEING...I HAVE KEPT THE
FORECAST BEYOND SATURDAY PRECIP FREE...THOUGH I SHOULD NOTE THAT
THE NAM/GFS/ECMWF SHOW A NORTHWEST TO SOUTHEAST ORIENTED RIBBON OF
MOISTURE FROM EAST TEXAS INTO THE COASTAL WATERS...AND GENERATE
LIGHT QPF IN THIS ZONE THROUGH SUNDAY. THIS IS NOT ALTOGETHER
UNREASONABLE GIVEN THE PRIMARY PUSH OF DRIER AIR WILL BE FROM
NORTHWEST TO SOUTHEAST LOUISIANA...AND PERTURBATIONS WILL LIKELY
BE TRANSLATING THROUGH THE REGION AMID THE NORTHERLY FLOW ALOFT.

OTHERWISE...THE AIRMASS USHERED IN BY THIS ANOMALOUS TROF WILL BE
CHARACTERIZED BY SFC DEWPOINTS IN THE 60S...AND PERHAPS UPPER 50S
OVER EAST CENTRAL LOUISIANA. THE CONSEQUENCE OF THIS WILL BE
OVERNIGHT LOWS RUNNING 5 TO 10 DEGREES BELOW NORMAL...AND A MOSTLY
CLEAR SKY.

THIS DRY WEATHER...ASIDE FROM THE SUNDAY POTENTIAL MENTIONED
ABOVE...IS EXPECTED TO LAST INTO AT LEAST TUESDAY...AND PERHAPS
EVEN BEYOND THAT. THE GLOBAL MODELS HAVE STARTED TO WAFFLE AROUND
A BIT ON WHAT EXACTLY HAPPENS WITH THE TROF THAT CUTS OFF OVER THE
SE CONUS ON MONDAY...WHERE THEY HAD BRIEFLY AGREED ON RETROGRADING
IT WEST OF THE AREA. THIS SOLUTION IS STILL SHOWN BY THE 21/00Z
ECMWF...THOUGH A LITTLE BIT LATER THAN PREVIOUS RUNS...AND ITS
PREVIOUS RUN WAS COMPLETELY DIFFERENT. THE GFS HAS SIMILARLY BEEN
DIFFERENT FROM RUN TO RUN. UNTIL THE MODELS SETTLE DOWN A
BIT...OPTED TO LEAVE THE POP FORECAST ALONE...WHICH SHOWS RAIN
CHANCES STARTING TO INCREASE FROM EAST TO WEST TUESDAY NIGHT.

MARINE...
LIGHT TO MODERATE SOUTHWEST FLOW WILL CONTINUE TODAY...BECOMING
MORE WESTERLY TONIGHT AND AROUND TO THE NORTHWEST ON SATURDAY AS A
COOL FRONT ADVANCES INTO THE GULF WATERS. RAIN CHANCES WILL REMAIN
IN PLACE UNTIL THE FRONTAL PASSAGE.

AVIATION...
S FLOW OFF THE GULF CONTINUES TO BRING A TROPICAL MOISTURE RICH
ATMOSPHERE TO THE REGION AHEAD OF A COOL FRONT. NOCTURNAL
SHRA/TSRA MOVING INLAND OFF THE GULF WILL INTERMITTENTLY AFFECT
KBPT/KLCH/KLFT/ KARA TERMINALS THE NEXT FEW HOURS...WITH COVERAGE OF
SHRA/TSRA EXPECTED TO INCREASE BY LATE MORNING INTO THE AFTERNOON
HOURS. EXPECTING A BETTER THAN AVERAGE CHANCE OF KBPT/KLCH/KLFT/KARA
TERMINALS RECEIVING A TSRA/MVFR CEILING & VSBY BETWEEN
16-20Z...AND KAEX BETWEEN 18-22Z. NW WINDS WILL BEGIN TO USHER
DRIER AIR INTO THE REGION OVERNIGHT AND INTO EARLY SATURDAY...BRINGING
AN END TO RAINFALL CHANCES.

&&

.PRELIMINARY POINT TEMPS/POPS...
KLCH  91  73  93  70  89 /  60  40  20  10  10
KBPT  93  73  95  72  90 /  60  40  20  10  10
KAEX  93  69  93  64  91 /  70  30  10  10  10
KLFT  91  73  93  68  89 /  70  30  20  10  10

&&

.LCH WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
TX...NONE.
GM...NONE.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LAKE CHARLES LA
606 AM CDT FRI AUG 21 2009

GMZ430-432-435-450-452-455-470-472-475-LAZ027>033-041>045-051>055-
TXZ180>182-201-215-216-221115-
SABINE LAKE-CALCASIEU LAKE-VERMILION BAY-
COASTAL WATERS FROM CAMERON, LA TO HIGH ISLAND, TX OUT 20 NM-
COASTAL WATERS FROM INTRACOASTAL CITY TO CAMERON, LA OUT 20 NM-
COASTAL WATERS FROM LOWER ATCHAFALAYA RIVER TO INTRACOASTAL CITY,
LA OUT 20 NM-
WATERS FROM CAMERON, LA TO HIGH ISLAND, TX EXTENDING FROM 20 NM
TO 60 NM-
WATERS FROM INTRACOASTAL CITY, LA TO CAMERON, LA EXTENDING FROM
20 NM TO 60 NM-
WATERS FROM LOWER ATCHAFALAYA RIVER TO INTRACOASTAL CITY, LA
EXTENDING FROM 20 NM TO 60 NM-VERNON-RAPIDES-AVOYELLES-BEAUREGARD-
ALLEN-EVANGELINE-ST. LANDRY-CALCASIEU-JEFFERSON DAVIS-ACADIA-
LAFAYETTE-UPPER ST. MARTIN-CAMERON-VERMILION-IBERIA-ST. MARY-
LOWER ST. MARTIN-TYLER-JASPER-NEWTON-HARDIN-JEFFERSON-ORANGE-
606 AM CDT FRI AUG 21 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE NORTHWEST
GULF OF MEXICO...CENTRAL LOUISIANA...SOUTH CENTRAL LOUISIANA...
SOUTHWEST LOUISIANA...WEST CENTRAL LOUISIANA AND SOUTHEAST TEXAS.

.DAY ONE...TODAY AND TONIGHT

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL IMPACT THE
ENTIRE AREA TODAY...PARTICULARLY IN THE AFTERNOON HOURS. LOCALLY
HEAVY RAINFALL WILL BE POSSIBLE WITH THE STRONGER SHOWERS AND
STORMS. ALTHOUGH THE OVERALL SEVERE WEATHER THREAT IS VERY
LOW...ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE...WITH THE MAIN
HAZARD BEING DAMAGING WIND GUSTS. IN ADDITION...THUNDERSTORMS
THAT DEVELOP ON OR INTERACT WITH OUTFLOW BOUNDARIES WILL BE
CAPABLE PRODUCING BRIEF TORNADOES. THUNDERSTORM ACTIVITY WILL
DIMINISH AROUND SUNSET WITH ONLY ISOLATED TO WIDELY SCATTERED
ACTIVITY EXPECTED TONIGHT.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY
SCATTERED SHOWERS AND THUNDERSTORMS WILL AGAIN BE POSSIBLE ON
SATURDAY BEFORE A COLD FRONT BRINGS DRY WEATHER SUNDAY INTO EARLY NEXT
WEEK.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT EXPECTED TODAY OR TONIGHT.

13

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LAKE CHARLES LA
130 PM CDT FRI AUG 21 2009

LAZ043-211915-
ACADIA LA-
130 PM CDT FRI AUG 21 2009

...SIGNIFICANT WEATHER ALERT FOR ACADIA PARISH UNTIL 215 PM CDT...

AT 129 PM CDT...A LINE OF STRONG THUNDERSTORMS WAS INDICATED BY
NATIONAL WEATHER SERVICE DOPPLER RADAR ALONG A LINE EXTENDING FROM 2
MILES EAST OF CHURCH POINT TO 5 MILES NORTH OF IOTA...MOVING
SOUTHEAST AT 15 MPH.

* THESE STRONG THUNDERSTORMS WILL BE NEAR...
  IOTA BY 140 PM CDT...
  BRANCH BY 205 PM CDT...
  MIRE AND RAYNE BY 215 PM CDT...

FREQUENT CLOUD TO GROUND LIGHTNING...PEA SIZE HAIL...AND WIND GUSTS
TO 50 MPH ARE LIKELY WITH THIS STORM. HEAVY RAINFALL WILL CAUSE
PONDING OF WATER ON AREA ROADWAYS...ESPECIALLY THOSE IN POOR DRAINAGE
AREAS. RESIDENTS ARE ENCOURAGED TO MONITOR THE SITUATION CLOSELY AND
BE PREPARED TO TAKE THE PROPER ACTIONS SHOULD A WARNING BE ISSUED.

SHAMBURGER

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LAKE CHARLES LA
139 PM CDT FRI AUG 21 2009

LAZ041-211915-
CALCASIEU LA-
139 PM CDT FRI AUG 21 2009

...SIGNIFICANT WEATHER ALERT FOR WESTERN CALCASIEU PARISH UNTIL 215
PM CDT...

AT 138 PM CDT...A STRONG THUNDERSTORM WAS INDICATED BY NATIONAL
WEATHER SERVICE DOPPLER RADAR 6 MILES NORTHEAST OF VINTON...MOVING
EAST AT 15 MPH.

* THE STRONG THUNDERSTORM WILL BE NEAR...
  SULPHUR BY 205 PM CDT...
  CARLYSS AND WESTLAKE BY 215 PM CDT...

FREQUENT CLOUD TO GROUND LIGHTNING...PEA SIZE HAIL...AND WIND GUSTS
TO 50 MPH ARE LIKELY WITH THIS STORM. HEAVY RAINFALL WILL CAUSE
PONDING OF WATER ON AREA ROADWAYS...ESPECIALLY THOSE IN POOR DRAINAGE
AREAS. RESIDENTS ARE ENCOURAGED TO MONITOR THE SITUATION CLOSELY AND
BE PREPARED TO TAKE THE PROPER ACTIONS SHOULD A WARNING BE ISSUED.

SHAMBURGER

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LAKE CHARLES LA
153 PM CDT FRI AUG 21 2009

LAZ054-055-212000-
LOWER ST. MARTIN LA-ST. MARY LA-
153 PM CDT FRI AUG 21 2009

...SIGNIFICANT WEATHER ALERT FOR EASTERN ST. MARY AND LOWER ST.
MARTIN PARISHES UNTIL 300 PM CDT...

AT 151 PM CDT...A LINE OF STRONG THUNDERSTORMS WAS INDICATED BY
NATIONAL WEATHER SERVICE DOPPLER RADAR ALONG A LINE EXTENDING FROM 3
MILES EAST OF MORGAN CITY TO 6 MILES WEST OF BURNS POINT...MOVING
EAST AT 10 MPH.

* STRONG THUNDERSTORMS WILL BE NEAR...
  BURNS POINT BY 200 PM CDT...
  AMELIA BY 215 PM CDT...

FREQUENT CLOUD TO GROUND LIGHTNING...PEA SIZE HAIL...AND WIND GUSTS
TO 50 MPH ARE LIKELY WITH THIS STORM. HEAVY RAINFALL WILL CAUSE
PONDING OF WATER ON AREA ROADWAYS...ESPECIALLY THOSE IN POOR DRAINAGE
AREAS. RESIDENTS ARE ENCOURAGED TO MONITOR THE SITUATION CLOSELY AND
BE PREPARED TO TAKE THE PROPER ACTIONS SHOULD A WARNING BE ISSUED.

SHAMBURGER

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