AFDLIX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NEW ORLEANS LA 401 AM CDT THU SEP 1 2011 .SHORT TERM... PLUME OF VERY RICH MOISTURE IS HEADED TOWARDS THE AREA FROM THE SOUTHEAST PER WATER VAPOR IMAGERY AS WELL AS GOES TOTAL PRECIP WATER IMAGERY WHICH INDICATES 2.3 INCHES OR SO AROUND 100NM OFFSHORE. 00Z SOUNDING LAST NIGHT HAD 1.7. MODEL SOUNDINGS INDICATE SHOULD BE ABOUT 2.2 THIS MORNING AND HOLD THROUGH THE DAY. RADAR ALREADY SHOWING INCREASING COVERAGE OF SMALL/WEAK SHOWERS MOVING IN TO THE AREA FROM THE GULF BUT WITH STRONGER CELLS FURTHER OFFSHORE. THIS SHOULD CONTINUE THROUGH THE DAY AND HAVE INCREASED POPS TO THE 60-70PCT RANGE TODAY FROM HUM TO GPT AND SOUTHEASTWARD. .LONG TERM... FOR THE LAST FEW DAYS OR MORE...MODELS HAVE INDICATED THE DEVELOPMENT OF AN UPPER AND SURFACE LOW IN THE WESTERN GULF JUST OFF THE LOUISIANA COAST. AT THIS TIME IT APPEARS THE SYSTEM WILL BE A SUBTROPICAL OR HYBRID STORM OF SORTS. THE MAIN CONCERN ISNT SO MUCH WHETHER ITS COMPLETELY TROPICAL OR NOT AND ITS INTENSITY BUT RATHER THE RAINFALL POTENTIAL WITH THIS EVENT. THOUGH THERE HAS BEEN A GENERAL LACK OF RUN TO RUN AND MODEL TO MODEL CONTINUITY...THE BASIC AGREEMENT IS THERE WILL BE PLENTY OF RAIN...ESPECIALLY ALONG THE COAST. SO...BIGGEST CHANGE FROM PREVIOUS FCST IS THE RATHER LARGE INCREASE IN AREAL RAIN CHANCES THROUGH THIS WEEKEND. DIVULGING INTO A FEW OF THE MODELS: CANADIAN...DEVELOPS LOW SOUTH OF SABINE PASS FRIDAY AND BRINGS IT INTO SOUTHERN TEXAS COAST SUNDAY NIGHT. NAM12...DEVELOPS LOW SOUTH OF LCH TONIGHT AND BRINGS IT INTO VERMILLION BAY SATURDAY NIGHT. DGEX CONTINUES THE LOW ON A WOBBLY NEWD TRACK THROUGH EARLY NEXT WEEK. SREF...IS SAME AS NAM12 BUT SLIGHTLY SLOWER ON INLAND MOVEMENT WITH THE LOW STILL IN VERMILLION BAY MID DAY SUNDAY. ECMWF...DEVELOPS THE LOW TONIGHT SOUTH OF SABINE PASS...BRINGS IT NORTHEAST TOWARDS THE SOUTH CENTRAL LA COAST THROUGH MIDDAY SUNDAY...TRACKS SWWD AWAY FROM THE COAST TILL THE MIDDLE TO LATE NEXT WEEK AND THEN BACK NORTHEAST ACROSS THE AREA TOWARDS THE APPALACHIAN MTNS. GFS...DEVELOPS THE LOW FARTHER SOUTH OF LCH THAN THE OTHERS TONIGHT...BRINGS IT INLAND OVER SOUTH CENTRAL LA SATURDAY NIGHT... THEN BACK OFF SHORE AND CONTINUED SOUTHWEST TO BROWNSVILLE TX MIDWEEK. SLEW OF MULTIPLE TROPICAL MODELS...IT WOULD TAKE A BOOK TO DESCRIBE THEM AS THE SOLUTIONS ARE VERY WIDELY SPREAD IN TRACKS AND TIMING. THEY SEEM TO ZIG ZAG OFF THE LA COAST AND THE LOW COULD BE ANYWHERES FROM NORTHERN MEXICO TO EASTERN GULF IN 5 DAYS ACCORDING TO THESE MODELS. SO...LOOKING AT ALL THIS MODEL DATA...DIFFERENT ONES HAVE SIMILARITIES IN PARTS OF ITS SOLUTIONS WITH OTHERS. WITH THE FORECAST...HAVE TRIED TO INCORPORATE AN ENSEMBLE OF ALL OF THESE RESULTS INTO A SOMEWHAT CONSISTENT SOLUTION. THE RESULT IS THAT THERE SHOULD BE A SUBSTANTIAL AMOUNT OF RAINFALL ACROSS SOUTHEAST LA/MS MAINLY FROM FRIDAY THROUGH AT LEAST THE WEEKEND. THINKING IS THAT THROUGH THE NEXT 5 DAYS...AMOUNTS WILL RANGE FROM AROUND 3 INCHES OVER FARTHER INLAND AREAS SUCH AS BATON ROUGE AND THEN UPWARDS TO POSSIBLY NEAR 1 FOOT ALONG COASTAL LOUISIANA PARISHES. ALL IS PLAUSIBLE WITH SUCH A TROPICAL AIRMASS TO BE IN PLACE. MODEL SOUNDINGS INDICATE 2.65+ INCHES OF PRECIP WATER AT MSY FRIDAY AND SATURDAY. SO...WILL BE A VERY EFFICIENT RAIN PRODUCING ENVIRONMENT WITH HEAVY RAIN EXPECTED. GOING WITH THIS THEME...WILL BE ISSUING FLASH FLOOD WITH FCST PACKAGE THIS MORNING. DECIDED ON ASSUMPTION PARISH TO LAKE PONTCHARTRAIN AND SOUTHWARD AS WELL AS COASTAL MS COUNTIES. FOR TIMING...THE BULK OF THE HEAVY RAIN LOOKS LIKE IT WILL BE FROM FRIDAY THROUGH SUNDAY SO FRI-12Z TO MON-00Z IS THE TIME FRAME. AREAL COVERAGE OF THE WATCH COULD EXPANDED NORTH AND TIME MAY BE LENGTHENED WITH LATER FCSTS BUT FOR NOW IS THE BEST FIRST GUESS. JUST LOOKS TO BE LIKE TOO WET OF A SCENARIO ABOUT TO PLAY OUT TO NOT HAVE THE WATCH OUT. STILL A BIT OF UNCERTAINTY BEYOND THE WEEKEND. COULD BE A FAIRLY WET OR DRIER START TO THE WEEK DEPENDING ON WHERE THE LOW TRACKS. MEFFER && .AVIATION... AREA TAFS WILL HAVE CONVECTION AT LEAST AS TEMPOS IF NOT PREVAILING FOR ADVANCING TROPICAL MOISTURE INTO THE AREA. EASTERLY WINDS WILL ALSO BE DEEPENING FROM THE SURFACE UPWARD TO ABOUT 10KFT. SMOKE MAY STILL BE A FACTOR AT KMSY...KNEW...KHDC...KBTR AS INCREASING WINDS MAY FAN THE FIRE A BIT BEFORE RAINS START IMPACTING THE AREA LATER TODAY. 24/RR && .MARINE... ELEVATED COASTAL PLATFORMS ARE ALREADY INDICATED NEAR 30 KNOTS OF WIND AT 100 FT...WHICH TRANSLATES TO AROUND 20-25 KNOTS AT SURFACE TO PROMPT ISSUANCE OF SMALL CRAFT ADVISORY. SEAS WILL CONTINUE TO INCREASE AS DURATION OVER FETCH INCREASES AND SWELL TRAIN AUGMENTS LOCAL WIND WAVES. THE NEAR SHORE WATERS AND TIDAL LAKES WILL LIKELY BECOME QUITE DANGEROUS TO NAVIGATE TODAY THROUGH THE WEEKEND AND SHOULD LIKELY BE AVOIDED FOR THIS HOLIDAY WEEKEND. THIS FORECAST IS BASED ON ANTICIPATION OF SOME TROPICAL CYCLONE DEVELOPMENT THOUGH THE SYSTEM CURRENTLY HAS BAROCLINIC STRUCTURE AND TRANSFORMATION TO A MORE BAROTROPIC REGIME WILL BE A LITTLE SLOW TO OCCUR...AT LEAST NOT UNTIL THE STRONG WESTERLIES RELAX IN THE NORTH GULF. WATER VAPOR CLEARLY SHOWS UPPER SHEAR ZONE ALONG THE LA COAST THAT WILL BE AN INHIBITOR UNTIL IT MOVES FARTHER WEST. NONETHELESS...A VERY CHAOTIC WEATHER PATTERN IS EXPECTED THROUGH THE WEEKEND INTO EARLY NEXT WEEK THAT MAY EMULATE THE ECCENTRICITY AND PERSISTENCE OF HURRICANE JUAN OF 1985 OR TROPICAL STORM ALLISON OF 2001. 24/RR && .PRELIMINARY POINT TEMPS/POPS... MCB 92 72 89 71 / 30 20 30 40 BTR 93 76 89 72 / 40 30 50 50 ASD 91 77 85 75 / 50 40 60 60 MSY 92 80 84 77 / 60 40 70 70 GPT 92 77 85 75 / 50 40 70 70 PQL 90 76 86 74 / 60 40 70 70 && .LIX WATCHES/WARNINGS/ADVISORIES... LA...FLASH FLOOD WATCH UNTIL 7 PM SUNDAY FOR THE FOLLOWING ZONES: ASSUMPTION...LOWER JEFFERSON...LOWER LAFOURCHE...LOWER PLAQUEMINES...LOWER ST. BERNARD...LOWER TERREBONNE...ORLEANS...ST. CHARLES...ST. JAMES...ST. JOHN THE BAPTIST...UPPER JEFFERSON...UPPER LAFOURCHE...UPPER PLAQUEMINES...UPPER ST. BERNARD...AND UPPER TERREBONNE. GM...SMALL CRAFT ADVISORY UNTIL 1 AM FRIDAY FOR THE FOLLOWING ZONES: BRETON SOUND...CHANDELEUR SOUND...COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60 NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA OUT 20 NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA RIVER OUT 20 NM...COASTAL WATERS FROM STAKE ISLAND LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO 60 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND MISSISSIPPI SOUND. MS...FLASH FLOOD WATCH UNTIL 7 PM SUNDAY FOR THE FOLLOWING ZONES: HANCOCK...HARRISON...AND JACKSON. GM...SMALL CRAFT ADVISORY UNTIL 1 AM FRIDAY FOR THE FOLLOWING ZONES: BRETON SOUND...CHANDELEUR SOUND...COASTAL WATERS FROM BOOTHVILLE LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER OUT 20 NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA FROM 20 TO 60 NM...COASTAL WATERS FROM PASCAGOULA MS TO STAKE ISLAND LA OUT 20 NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM PORT FOURCHON TO LOWER ATCHAFALAYA RIVER OUT 20 NM...COASTAL WATERS FROM STAKE ISLAND LA TO THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER FROM 20 TO 60 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON FROM 20 TO 60 NM...COASTAL WATERS FROM THE SOUTHWEST PASS OF THE MISSISSIPPI RIVER TO PORT FOURCHON OUT 20 NM...LAKE BORGNE...LAKE PONTCHARTRAIN AND LAKE MAUREPAS...AND MISSISSIPPI SOUND. && $$