FXUS64 KLIX 292051
AFDLIX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS LA
251 PM CST SUN NOV 29 2009
.SHORT TERM...
SOME SLIGHT CONFUSION IN PLACEMENT AND TIMING OF DIFFERENT
SOLUTIONS TODAY. BUT WE WILL TRY TO CLEAR IT ALL UP. THE 12Z GFS
IS ABOUT 15KTS STRONGER WITH WIND SPEEDS AT 30H ROUNDING THE BASE
OF THE EXITING WEAK EAST COAST UPPER TROUGH. THIS WILL DIG THE
UPPER TROUGH A LITTLE MORE WHILE MOVING IT OUT TO SEA QUICKER.
THIS ALSO TRANSLATES UPSTREAM IN TIME. THE GFS COLD FRONT MOVES
IN SLIGHTLY FASTER THAN THE EUROPEAN SOLUTION BUT IS ALMOST
NEGLIGABLE AT ABOUT 1 TO 2 HOURS EARLY. AS WE MOVE FURTHER IN TIME
ABOUT WHEN THE SFC LOW FORMS AND MOVES THROUGH...WE FIND THIS
GFS ERROR HAS MULTIPLIED AND BRINGS THE SFC LOW THROUGH HERE
ALMOST 6 HOURS TOO FAST. THE EUROPEAN SOLUTION DOES A SLIGHTLY
BETTER JOB BUT IS NOT WITHOUT ITS PROBLEMS. WIND SPEEDS AROUND THE
UPPER LOW IN THE SW ARE AROUND 5 TO 10 KNOTS TOO WEAK SETTING THE
STAGE FOR A SLIGHTLY SLOWER SOLUTION. AS FAR AS STRENGTH OF THE
SYSTEM...THE MODELS ARE RELATIVELY SIMILAR AND ARE DOING A GOOD
JOB WITH MASS FIELD PROPORTIONALITY. WILL BE LEANING A LITTLE
CLOSER TO THE ECMWF WHILE USING THE GFS AS A QUANTITY GUIDE.
LONG STORY SHORT...COLD FRONT GETS INTO BTR AROUND 730AM MON...MSY
RIGHT AT NOON...AND GPT ABOUT NOON30. THE FRONT STALLS OVER THE
NORTHERN GULF LATER IN THE DAY. SFC LOW BEGINS TO FORM ON THE TAIL
END OF THE STALLED FRONT MON NIGHT. FEELS THE TUG OF THE NEXT
STRONG UPPER TROUGH DIGGING INTO THE CENTRAL PLAINS AND BEGINS
MOVING ENE TUE. THE LOW BEGINS TO ACCELERATE TUE EVENING LANDING
IT ONSHORE SE LA AROUND MIDNIGHT TUE INTO WED. THE LOW MOVES
INLAND AND STARTS TO OCCLUDE CAUSING WRAP AROUND CLOUDS AND LIGHT
PRECIP TO CONTINUE AFTER THE FRONT HAS MOVED THROUGH WED. SKIES
BEGIN TO CLEAR LATE WED NIGHT INTO THU MORNING.
WITH CONCERNS TO SEVERITY. THE CURRENT SCENARIO WOULD BRING A
SLIGHT CHANCE TO THOSE GULF COASTAL PARISHES INCLUDING AND
ADJACENT TO PLAQUEMINES PARISH NE INTO JACKSON CO. BY FAR...MOST OF
THE STRONGEST AND HEAVIEST ACTIVITY WILL REMAIN OFFSHORE AND NEAR
THE COAST.
THE NEXT THING TO START THINKING ABOUT IS THE AMOUNT OF COASTAL
FLOODING THAT MAY TAKE PLACE IN HANCOCK CO LATE TUE NIGHT INTO
EARLY WED MORNING. WITH THE GFS TOO STRONG AND TOO FAST...WE HAVE
OPTED TO TEMPER ITS COASTAL SURGE SOLUTION. SOME LOCAL GUIDANCE
TOOLS ARE SHOWING A FEW ROADS IN THE SW COASTAL SECTIONS OF THE
COUNTY GETTING 4 TO 6 INCHES OF WATER OVER THEM AND NOT THE 1.5
FEET AS INDICATED BY THE GFS. THIS WILL CONTINUE TO HINGE ON THE
EXACT PATH OF THE SFC LOW BUT THNIGS ARE BEGINNING TO SHOW A TREND
TOWARD WHAT THE LAST SEVERAL DAYS OF FCASTS HAVE BEEN ILLUDING
TO...A LOW OF MODERATE STRENGTH PROVIDING 25 TO 35 KNOT WINDS OVER
A 300 MILE FETCH FROM THE SOUTHEAST WITH PROBLEM NUMBER ONE BEING
THE DURATION. THESE WINDS ARE NOT OVER THIS FETCH FOR AN EXTENDED
PERIOD AND WILL NOT BE ABLE TO PROVIDE THE AMOUNT OF WATER BULK TO
CAUSE THE DEGREE OF INUNDATION BEING SHOWN BY THE GFS. BUT THERE
WILL BE A GOOD AMOUNT OF WIND SPEEDS TO KICK UP TIDE LEVELS ENOUGH
TO CAUSE CONCERN ALONG THE IMMEDIATE LOWEST LYING COASTAL AREAS.
NEXT PROBLEM...RAINFALL AMOUNTS. 2 TO 4 INCHES NEAR THE COAST
TAPPERING TO 1 TO 2 INCHES AWAY FROM THE COAST TO THE NW LOOKS
LIKE A GOOD BET AT THIS POINT. AGAIN...THIS IS ALL BETTER THAN 50
HOURS AWAY AND IS QUITE HARD TO PIN DOWN EXACTLY WHO WILL SEE THE
MOST RAINFALL SO THESE CONSERVATIVE ESTIMATES MAY BE INCREASED OR
DECREASED WITH TIME.
WATCHES WARNINGS AND ADVISORIES MAY BEGIN TO BE POSTED WITHIN THE
NEXT 24 HOURS.
.LONG TERM...
NEXT SYSTEM LOOKS TO START AFFECTING THE AREA BY NEXT WEEKEND.
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL AT EACH OF THE TAF SITES DURING THE
REMAINDER OF THE AFTERNOON AND THROUGH THE EVENING HOURS.
VISIBILITIES AND CEILINGS ARE EXPECTED TO LOWER INTO THE MVFR
CATEGORY AFTER 08Z OR 09Z MONDAY...AND POSSIBLY LOWER INTO THE IFR
CATEGORY AT TIMES DUE LOW CEILINGS AFTER SUNRISE MONDAY AT KBTR AND
KMCB. RAIN CHANCES WILL BE ON THE INCREASE AFTER 10Z AT KBTR AND
KMCB AND WILL INCREASE AT KMSY AND KGPT AFTER 12Z. A COLD FRONT WILL
APPROACH AND LIKELY PUSH THROUGH KBTR AND KMCB TOWARD 18Z MONDAY AND
THEN PUSH SOUTHEAST ACROSS KMSY AND KGPT DURING THE AFTERNOON HOURS
MONDAY. MAINLY MVFR CEILING ARE EXPECTED MONDAY AFTERNOON. RAIN
CHANCES WILL CONTINUE THROUGH THE DAY MONDAY AT KMSY AND KGPT...BUT
WILL BEGIN TO TAPER OFF DURING THE AFTERNOON AT KBTR AND KMCB. 11
&&
.MARINE...
A LIGHT SOUTHERLY FLOW WILL GENERALLY PREVAIL ACROSS THE COASTAL
WATERS THROUGH TONIGHT BEFORE BEGINNING TO VEER AND INCREASE
SOMEWHAT IN MAGNITUDE DURING THE DAY MONDAY AS A COLD FRONT
APPROACHES FROM THE NORTHWEST. THIS COLD FRONT WILL PUSH INTO THE
COASTAL WATERS MONDAY AFTERNOON AND EVENING. OFFSHORE FLOW WILL
INCREASE BEHIND THIS FRONT MONDAY NIGHT AND MAY APPROACH SMALL CRAFT
ADVISORY CRITERIA BY TUESDAY MORNING. LOW PRESSURE DEVELOPING IN THE
WESTERN GULF OF MEXICO MONDAY IS FORECAST TO MOVE TOWARD THE
NORTHERN GULF COAST TUESDAY. THE GFS SOLUTION WITH THE MOVEMENT OF
THIS LOW IS CONSIDERABLY FASTER THAN THAT OF THE ECMWF AND NAM. A
SLOWER ECMWF SOLUTION WAS PREFERRED FOR THIS FORECAST WHICH BRINGS
THE LOW INTO THE FORECAST AREA TUESDAY NIGHT AND WEDNESDAY. WINDS
ARE EXPECTED TO INCREASE SIGNIFICANTLY AS THIS FEATURE APPROACHES
AND WILL EASILY MEET SMALL CRAFT ADVISORY CRITERIA TUESDAY AND MAY
APPROACH GALE FORCE TUESDAY NIGHT AND WEDNESDAY. AS THE LOW PULLS
OFF TO THE NORTHEAST BY THURSDAY...STRONG OFFSHORE FLOW WILL PREVAIL
WHICH WILL GRADUALLY DIMINISH FOR THE END OF THE WEEK. 11
&&
.PRELIMINARY POINT TEMPS/POPS...
MCB 54 58 43 55 / 30 70 20 60
BTR 57 63 46 57 / 30 70 30 70
MSY 60 71 50 58 / 10 50 30 80
GPT 57 71 48 58 / 10 50 20 70
&&
.LIX WATCHES/WARNINGS/ADVISORIES...
LA...NONE.
GM...NONE.
MS...NONE.
GM...NONE.
&&
$$
