Severe Thunderstorm Warning 203, NWS New Orleans, LA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE NEW ORLEANS/BATON ROUGE LA
1015 PM CST TUE NOV 23 2004

.UPDATE...HAVE UPDATED THE ZONES AND SOME OF THE SHORT TERM GRIDS TO
REFLECT CURRENT TREND AND TO ADD TORNADO WATCH HEADLINE.

SPLIT JET FLOW ALOFT AT 00Z HAS LARGE SYNOPTIC SCALE UPWARD OMEGA
ACROSS THE REGION BUT CURRENTLY LACKING A FOCUS FOR CONVECTION. THE
BULK OF ACTIVITY HAS BEEN MOVING TO THE NORTH OF THE CWA AND WILL
REMAIN THE CASE AT LEAST THROUGH 08Z. THE MAIN CONCERN WILL BE WITH
THE ACCELERATING FRONTAL BOUNDARY RACING ACROSS EAST TEXAS THAT
SHOULD ARRIVE IN THE ATCHAFALAYA RIVER BASIN AROUND 09Z /03 AM CST/
AND CONTINUE ACROSS LAKE PONTCHARTRAIN/METRO NEW ORLEANS AREA AROUND
4-5 AM CST. DAMAGING WIND GUSTS GENERATED BY JUST THE STORM MOTION
ALONE SHOULD BE AROUND 50 MPH BUT COULD BE AS HIGH AS 70 MPH IN THE
PRE-DAWN HOURS.

.PREV DISCUSSION...OUR NORMAL SECONDARY PEAK OF SEVERE WEATHER WILL
AFFECT THE CENTRAL GULF COAST TONIGHT. IR SATELLITE IMAGERY SHOWED
THE NEUTRAL TILTED LOW/TROUGH OVER EASTERN NEW MEXICO AND CONVECTION
OVER THE ARKLATEX REGION UNDERNEATH THE 3H LEVEL DIVERGENCE. THE
TROUGH/LOW WILL LIKELY BECOME NEGATIVELY TILTED AS IT APPROACHES THE
ARKLATEX REGION. GFS AND ETA FORECASTED THE JET MAX AT THE BASE OF
THE TROUGH TO INCREASE TO 130 KNOTS OVER CENTRAL TEXAS COAST AND THE
BEST DIVERGENCE FROM EAST TEXAS ACROSS CENTRAL AND NORTH LOUISIANA
TO MISSISSIPPI BY TONIGHT. LOW LEVEL JET AT 850MB WAS ANALYZED OVER
CENTRAL TEXAS. GFS IS MORE AGGRESSIVE IN DEVELOPING 40 TO 50 KNOTS
OVER WEST LOUISIANA BY 00Z WEDNESDAY. THIS MATCHES WITH VELOCITY
DATA OFF OF SHV RADAR. SHV VWP SHOWED SOUTHWEST WINDS OF 40 KNOTS
FROM 1KFT TO 13KFT. ISOLATED TO SCATTERED COVERAGE THIS AFTERNOON IN
THE WARM SECTOR HAS PROMPTED THE OFFICE TO LEAN TOWARD HIGHER POPS
LATER TONIGHT AND WEDNESDAY. WILL CONFINE CATEGORICAL CONVECTION TIL
AFTER MIDNIGHT AND WEDNESDAY MORNING. ETA MODEL SOUNDING AT BTR
REVEALED 0-3KM STM REL HELICITY JUMPS UP FROM AROUND 100 M2/S2 00Z
WEDNESDAY TO 390 M2/S2 BY 06Z WEDNESDAY. WITH CAPE VALUES AROUND
2000 J/KG...H2O VALUES NEAR 1.5 INCHES AND GOOD DIRECTIONAL
SHEAR...LIFTING OF THIS AIR MASS WILL SUSTAIN STORMS ALONG THE
ASSOCIATED ALONG THE FRONTAL BOUNDARY A LITTLE AFTER 12Z WEDNESDAY.
AS A RESULT...THE RISK FOR SEVERE THUNDERSTORMS PRODUCING DAMAGING
WINDS...POSSIBLY LARGE HAIL...AND ISOLATED TORNADOES WILL EXIST
AFTER 9 PM THIS EVENING INTO WEDNESDAY MORNING AND PRECIPITATION
ENDING WEDNESDAY AFTERNOON. BEHIND THIS SYSTEM DRY AND COOLER
WEATHER WILL PREVAIL FOR THANKSGIVING AND FRIDAY WITH A CHANCE OF
RAIN EARLY SATURDAY WITH ANOTHER SYSTEM AND DRY SATURDAY THROUGH
SUNDAY EVENING. THE ASSOCIATED BOUNDARY WILL PASS THROUGH THE AREA
EARLY SATURDAY AND RETREAT NORTH EARLY MONDAY. ANOTHER LOW WILL
DEVELOP OVER SOUTHWEST CONUS MONDAY AND STRENGTHEN WEST TO SOUTHWEST
FLOW OVER GULF. EMBEDDED DISTURBANCES IN THE SOUTHWESTERLY FLOW
ALOFT WILL BRING A CHANCE OF RAIN FOR NEXT WEEK.

&&

PRELIM POINT TEMP/POPS...
MCB 64 71 40 57 / 90 60 00 00
BTR 65 72 45 58 / 90 50 00 00
MSY 68 75 49 59 / 80 80 00 00
GPT 68 74 44 59 / 80 80 00 00

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
MS...NONE.
SE LA AND MS COASTAL WATERS...SMALL CRAFT ADVISORY TONIGHT PQL TO
ATCHAFALAYA RIVER OUT 60 NM INCLUDING TIDAL LAKES.
&&

24

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE NEW ORLEANS LA
345 PM CST TUE NOV 23 2004

LAZ034>040-046>050-056>070-MSZ068>071-077-080>082-241300-
AMITE-ASCENSION-ASSUMPTION-EAST BATON ROUGE-EAST FELICIANA-HANCOCK-
HARRISON-IBERVILLE-JACKSON-LIVINGSTON-LOWER JEFFERSON-
LOWER LAFOURCHE-LOWER PLAQUEMINES-LOWER ST BERNARD-LOWER TERREBONNE-
ORLEANS-PEARL RIVER-PIKE-POINTE COUPEE-ST CHARLES-ST HELENA-ST JAMES-
ST JOHN THE BAPTIST-ST TAMMANY-TANGIPAHOA-UPPER JEFFERSON-
UPPER LAFOURCHE-UPPER PLAQUEMINES-UPPER ST BERNARD-UPPER TERREBONNE-
WALTHALL-WASHINGTON-WEST BATON ROUGE-WEST FELICIANA-WILKINSON-
345 PM CST TUE NOV 23 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL AND SOUTHEAST
LOUISIANA AND EXTREME SOUTHWEST...SOUTH CENTRAL AND COASTAL
MISSISSIPPI.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THUNDERSTORMS...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE
THIS AFTERNOON AND PRIMARILY WEST OF A TYLERTOWN MISSISSIPPI
TO LAKE MAUREPAS TO MORGAN CITY LOUISIANA LINE. THERE IS A SLIGHT
RISK OF SEVERE THUNDERSTORMS THIS EVENING AND TONIGHT ACROSS THE
REMAINDER OF SOUTHEAST LOUISIANA AND SOUTH MISSISSIPPI.

THUNDERSTORMS WILL INCREASE IN COVERAGE AND INTENSITY THIS EVENING
AS AN UPPER LEVEL TROUGH APPROACHES FROM THE SOUTHERN PLAINS TONIGHT.
THE MAIN THREATS FROM THE SEVERE THUNDERSTORMS DURING THE PERIOD WILL
BE DAMAGING WIND GUSTS OF UP TO 70 MPH. A FEW TORNADOES ARE POSSIBLE
OVER NIGHT...WITH THE POSSIBILITY OF LONGER LIVED AND SIGNIFICANT
TORNADOES. THE HIGHEST THREAT OF DAMAGING WINDS AND TORNADOES WILL BE
OVER SOUTHWEST MISSISSIPPI AND EAST CENTRAL LOUISIANA INCLUDING BATON
ROUGE METRO AREA. LOCALLY HEAVY RAINFALL MAY ALSO OCCUR TONIGHT WITH
UP TO TWO INCHES OF RAIN POSSIBLE.

MARINE...ONSHORE FLOW IS EXPECTED TO INCREASE TO AROUND 20 KNOTS
TONIGHT. A SMALL CRAFT ADVISORY IS IN EFFECT TONIGHT FROM PASCAGOULA
MISSISSIPPI TO THE ATCHAFALAYA RIVER OUT 60 NM INCLUDING LAKES
PONTCHARTRAIN AND MAUREPAS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH TUESDAY

THUNDERSTORMS...WIDESPREAD THUNDERSTORM ACTIVITY IS EXPECTED
WEDNESDAY MORNING...ESPECIALLY OVER EXTREME SOUTHEAST LOUISIANA
AND THE MISSISSIPPI COAST. THERE IS A SLIGHT RISK OF SEVERE
THUNDERSTORMS WITH DAMAGING WIND GUSTS AND ISOLATED TORNADOES.
THUNDERSTORM ACTIVITY WILL DECREASE RAPIDLY WEDNESDAY AFTERNOON AS A
HIGH PRESSURE BUILDS INTO THE AREA BRINGING COOLER AND DRIER
AIRMASS.

ADDITIONAL SCATTERED THUNDERSTORMS ARE FORECAST TO DEVELOP SATURDAY
AND AGAIN SUNDAY NIGHT THROUGH TUESDAY.

MARINE...SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED WEDNESDAY AND
THURSDAY AS WINDS OF 20 TO 25 KNOTS PREVAIL IN THE WAKE OF A STRONG
COLD FRONT.

.SPOTTER INFORMATION STATEMENT...

THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS AND EMERGENCY
MANAGEMENT PERSONNEL...IN SUPPORT OF SEVERE WEATHER OPERATIONS...IS
REQUESTED THIS EVENING AND OVERNIGHT.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE NEW ORLEANS LA
200 AM CST WED NOV 24 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

1225 AM     TORNADO         LACOMBE                  30.31N 89.93W
11/24/2004                  ST. TAMMANY         LA   PUBLIC

            TORNADO SPOTTED.

1240 AM     TORNADO         SLIDELL                  30.28N 89.78W
11/24/2004                  ST. TAMMANY         LA   LAW ENFORCEMENT

            *** 4 INJ *** SLIDELL PD REPORTING 80-90 HOMES DAMAGED
            WITH A FEW HOMES LIFTED FROM THEIR FOUNDATION IN BEL AIR
            SUBDIVISION WITH INJURIES.

1240 AM     TORNADO         SLIDELL                  30.28N 89.78W
11/24/2004                  ST. TAMMANY         LA   LAW ENFORCEMENT

            NUMEROUS PROPERTY DAMAGE REPORTS ALONG AIRPORT RD.

1240 AM     TORNADO         SLIDELL                  30.28N 89.78W
11/24/2004                  ST. TAMMANY         LA   LAW ENFORCEMENT

            DAMAGE REPORTED AT CENTENNIAL PARK.

1240 AM     TSTM WND GST    SLIDELL                  30.28N 89.78W
11/24/2004                  ST. TAMMANY         LA   LAW ENFORCEMENT

            70 MPH WIND GUST AT NWS SLIDELL.

&&

17