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Excerpts from the Morning AFDs at various NWS Offices around the GOM. Slidell,La AFD LIX FARTHER SOUTH...ANOTHER MORE DIFFUSE SURFACE BOUNDARY/TROUGH IS EVIDENT JUST SOUTH OF THE FLORIDA PANHANDLE TO COASTAL SOUTHEAST LOUISIANA. AT 4 AM...A 1015 MB LOW PRESSURE AREA IS ANALYZED ALONG THE SURFACE TROUGH OVER THE EXTREME NORTHEAST GULF OF MEXICO. WATER VAPOR SHOWS DRIER AIR WORKING SOUTH INTO THE EASTERN GULF COAST AREA AS A MID/UPPER TROUGH AMPLIFIES OVER THE EASTERN SEABOARD. THE SOUTHERN PORTION OF THE UPPER LEVEL TROUGH APPEARS TO HAVE A BIT OF A KINK/NOTCH THAT COULD SIGNAL THE POSSIBLE DEVELOPMENT OF A MID LEVEL LOW IN THE VICINITY OF THE SURFACE LOW...BUT WILL HAVE TO WATCH THIS THE NEXT 3 TO 6 HOURS AND ANALYZE THE 12Z RAOB/UPPER AIR DATA AND FUTURE SATELLITE DATA TO HAVE A GOOD HANDLE ON THE SHORT TERM DEVELOPMENT THAT THE MODELS KEEP ADVERTISING OVER THE NORTHEAST GULF. Key West,FL AFD KEY .SHORT TERM (TODAY THROUGH SUNDAY)... CYCLONIC FLOW OVER THE BAHAMAS SOUTH OF 24N AND WEST OF 74W SEEMS TO BE ASSOCIATED WITH A TROUGH OF LOW PRESSURE BETWEEN HAITI AND THE EASTERN TIP OF CUBA. THIS TROUGH OF LOW PRESSURE IS LOCATED AMONG ENHANCED...DEEP LAYERED...ATMOSPHERIC MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. THE TROUGH OF LOW PRESSURE WILL MOVE WESTWARD ACROSS EASTERN CUBA TODAY...BEFORE PROGRESSING THROUGH THE FLORIDA STRAITS TONIGHT INTO SATURDAY MORNING. Tampa Bay,FL AFD TBW AT THE SURFACE A FRONTAL BOUNDARY WILL STALL ACROSS THE NORTHERN GULF COAST AND CONTINUE TO PROVIDE A FOCUS FOR DAILY CONVECTION AS WELL AS POSSIBLY LEAD TO SURFACE CYCLOGENESIS ACROSS THE NORTHERN GULF EARLY IN THE PERIOD. THIS WILL KEEP A WARM AND MOIST AIRMASS IN PLACE ACROSS THE PENINSULA AND SO WILL CONTINUE CLIMATOLOGICALLY HIGH POPS. THE BIG QUESTION IS HOW FAR SOUTH THIS BOUNDARY WILL ACTUALLY MAKE IT AND WHETHER OR NOT LOW PRESSURE WILL DEVELOP OFF THE WEST COAST OF FLORIDA AND MOVE WESTWARD INTO THE GULF OF MEXICO. THE 00Z NAM DOES DEVELOP A WEAK LOW OFFSHORE OF TAMPA LATE FRIDAY AND PUSHES IT WESTWARD. IN THIS SCENARIO DRY ENE FLOW MAKES IT INTO THE FL PANHANDLE AND PRECIP IS MAINLY CONFINED TO THE OFFSHORE WATERS. COMPARED TO THE 18Z RUN...THE LOW MOVES WESTWARD AT A FASTER PACE AND IS SLIGHTLY WEAKER. THE 00Z GFS ALSO DEVELOPS A LOW OFFSHORE OF TAMPA ON FRIDAY BUT MOVES IT MUCH SLOWER TO THE WEST...RESULTING IN HIGHER MOISTURE ACROSS THE FL PANHANDLE ON SATURDAY AND SUNDAY. THIS IS SIMILAR TO PREVIOUS GFS RUNS. HOWEVER...A CLOSER LOOK AT THE 00Z GFS PRECIPITATION FIELDS SHOWS THAT A DISPROPORTIONATE AMOUNT OF THE PRECIP FORECAST BY THE GFS WITH THIS LOW IS NON-CONVECTIVE PRECIP...WHICH SUGGESTS CONVECTIVE FEEDBACK AND MAKES ITS SOLUTION SUSPECT. MEANWHILE...THE 00Z RGEM HAS A 1009 MB LOW WELL SOUTH OF APALACHICOLA BY SATURDAY EVENING WITH PRECIP CHANCES REMAINING OVER THE FL PANHANDLE. THE PREVIOUS 12Z ECMWF HAD ONLY A VERY WEAK LOW DEVELOPING WITH MOST OF THE SIGNIFICANT PRECIP OFFSHORE OR JUST BARELY TOUCHING THE BEACHES ON SATURDAY. THE 21Z SREF HAD SEVERAL MEMBERS DEVELOPING LOWS OF VARIOUS INTENSITIES PUSHING WESTWARD AS WELL. Tallahassee, FL AFD TAE SO...WHAT TO BELIEVE? THERE SEEMS TO BE FAIRLY STRONG MODEL SUPPORT OF AT LEAST A WEAK LOW DEVELOPING LATE TODAY AND PUSHING WESTWARD INTO THE GULF. MORE IMPORTANTLY...LATE NIGHT RADAR SEEMS TO SUPPORT THE IDEA OF SMALL SCALE MESO-LOW OVER DIXIE COUNTY DRIFTING VERY SLOWLY SOUTHWARD WITH EVEN A FEW BANDING FEATURES OCCASIONALLY PRESENT. AS A RESULT...AM BUYING INTO THE IDEA OF A WEAK LOW MOVING WESTWARD INTO THE GULF OVER THE WEEKEND...BUT AM NOT CURRENTLY BUYING THE GFS PRECIPITATION FIELDS DUE TO THE CONVECTIVE FEEDBACK ISSUE MENTIONED ABOVE. Mobile,AL AFD MOB (SATURDAY THROUGH SUNDAY NIGHT)...FRONTAL BOUNDARY WILL MOVE OFF THE COAST BY SATURDAY AND JUST ABOUT ALL OF THE COMPUTER MODEL GUIDANCE DEVELOPS A LOW PRESSURE AREA ALONG IT IN SOME FORM OR THE OTHER. GFS STRONGER WITH THE LOW MOVING IT VERY SLOWLY TO THE WEST AND ESSENTIALLY STALLS IT OVER THE MOBILE AREA THROUGH SUNDAY...WHERAS THE NAM TAKES IT WESTWARD MORE QUICKLY THROUGH SUNDAY. THE ECMWF IS WEAKER AND FARTHER SOUTH WITH THE LOW...PASSING IT TO THE WEST BY SUNDAY. WE WENT CLOSER TO THE FASTER AND WEAKER ECMWF GIVEN SOMEWHAT BETTER PERFORMANCE ON LOCATING LARGER SCALE FEATURES OVER THE PAST WEEK...BRINGING IN A LITTLE DRIER AIR TOWARDS SUNDAY FROM THE NORTHEAST AND TAKING THE LOW MORE QUICKLY TO THE WEST THROUGH SUNDAY. Jackson,MS AFD JAN .LONG TERM...SUNDAY THROUGH FRIDAY...MANY MANY QUESTIONS IN THE LONG TERM AND ALL REALLY REVOLVE AROUND THE DEVELOPING LOW OVER THE GULF FORECASTED BY SOME MODELS. AT 12Z SUNDAY...MOST ALL MODELS AGREE IN A 1010-1012MB LOW IN THE NORTHERN GULF GENERALLY SOUTH OF THE MISSISSIPPI COAST/NEAR NEW ORLEANS. THIS IS ABOUT THE ONLY THING THEY AGREE ON AND FROM THIS POINT...SOLUTIONS DIVERGE. THE NAM TRACKS THIS FEATURE TO THE WEST. THE GFS...WHICH HAS BEEN THE ONE TO CONSISTENTLY DEVELOP THIS FEATURE...MEANDERS THIS FEATURE IN THE SAME LOCATION UNTIL TUESDAY AFTERNOON BEFORE IT LOSES ITS UPPER SUPPORT AND BEGINS TO OPEN INTO A TROUGH. IT THEN MOVES NORTH ACROSS EASTERN MISSISSIPPI AND LINGERS. THE ECMWF NEVER REALLY DEVELOPS THE FEATURE MUCH INTO A LOW...BUT RATHER A WEAK LOW/OPEN WAVE TYPE FEATURE AND TRACKS IT PROGRESSIVELY WEST. WHILE I CANNOT COMPLETELY RULE OUT THE POSSIBILITY OF SOMETHING DEVELOPING IN THIS REGION GIVEN THAT WATER TEMPS ARE RATHER WARM AND DISTURBANCES CAN ORIGINATE OFF OLD FRONTAL BOUNDARIES...FEEL THAT THE ECMWF HAS BEEN A LITTLE MORE ON TARGET WITH REGARD TO CURRENT TROPICAL LIKE SYSTEMS AND WILL CONTINUE TO TREND MORE IN THIS DIRECTION THROUGH THE LONG TERM BUT OVERALL CONFIDENCE REMAINS VERY LOW. MODEL DIAGNOSTIC DISCUSSION ...CLOSED UPPER LOW MIGRATING WESTWARD ACROSS THE N. GULF... FINAL PREFERENCE: 00Z/12Z ECMWF OR 00Z NAM/GFS WITH A DAMPENED SOLN THIS MID-LEVEL DISTURBANCE SEEMS TO EMERGE SOMEWHERE ACROSS FLORIDA WITH SOME MODELS DEPICTING THIS ENERGY DRIFTING WESTWARD IN TIME. BY SAT. EVENING...THE 00Z/18Z/12Z VERSIONS OF THE NAM FORECAST THE WEAK CLOSED LOW TO BE ALONG THE EASTERN GULF COAST. THE DETAILS BECOME A LITTLE BIT VAGUE BY THE END OF THE WEEKEND...BUT THE NAM FORECASTS A SOLN WHICH FEATURES THE UPPER/SFC LOW NEAR NEW ORLEANS BY SUN. EVENING/NIGHT. THE GFS HAS ALSO SHOWN DECENT CONTINUITY WITH THIS DISTURBANCE ALTHOUGH THE MOST RECENT RUN PLACES IT FARTHER TO THE SOUTH OF THE FL PANHANDLE AT 04/00Z WITH THE SFC LOW BEING BEST DEFINED WITH THE 00Z/12Z GFS MODEL RUNS. THIS GENERAL SOLN IS ALSO SUPPORTED BY THE 00Z NAM...BUT IT SEEMS FEW OTHER GLOBAL MODELS FAVOR SUCH AN EVOLUTION. TO A LESSER EXTENT...THE 00Z/12Z ECMWF SUGGESTS AN ELONGATED UPPER TROF OVER A SIMILAR REGION WHICH THE 00Z NAM/GFS DEPICT A STRONG CLOSED LOW CENTER. MEANWHILE...AMONG OTHER GLOBAL GUIDANCE...THE 00Z UKMET AND 12Z CMC/UKMET FORECAST AN H5/SFC LOW AS WELL...BUT FOCUSED CLOSER TO THE WESTERN PENINSULA OF FL. WITH RESPECT TO THE ENSEMBLES...THERE IS MEAGER SUPPORT FOR ANY SIGNIFICANT CYCLONES ACROSS THE GULF AS ONLY A COUPLE ENSEMBLE MEMBERS DEPICT THE FEATURE. THEREFORE...THE POSITION SUPPORTED BY THE 00Z NAM/GFS/ECMWF AND 12Z ECMWF WILL BE PREFERRED...EXCEPT THE NCEP MODELS ARE MUCH TOO DEEP WITH THE SYSTEM. |