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#47841 (Received by flhurricane at: 11:08 PM 22.Sep.2005) TCDAT3 HURRICANE RITA DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT THU SEP 22 2005 FLIGHT LEVEL WIND DATA AND RADAR OBSERVATIONS FROM THE AIR FORCE HURRICANE HUNTER AIRCRAFT INDICATE THAT THE CONCENTRIC EYEWALL CYCLE MIGHT BE NEARING COMPLETION. THERE IS NOW ONLY A SINGLE FLIGHT LEVEL WIND MAXIMUM AT A RADIUS OF ABOUT 20 N MI...ASSOCIATED WITH THE OUTER EYEWALL THAT THE AIRCRAFT RADAR INDICATE IS SLOWLY CONTRACTING... WHILE THE INNER EYEWALL CONTINUES TO DETERIORATE. RECENT GOES INFRARED IMAGERY ALSO INDICATES THAT A COMPLETE RING OF VERY COLD CONVECTIVE TOPS...COLDER THAN -70C... NOW SURROUNDS THE EYE. THE CENTRAL PRESSURE HAS ONLY RISEN SLIGHTLY TO 917 MB AS MEASURED BY THE MOST RECENT DROPSONDE. RECENT FLIGHT LEVEL AND DROPSONDE WIND DATA DO NOT SUPPORT AN INTENSITY GREATER THAN ABOUT 110 KT...BUT GIVEN THE VERY LOW PRESSURE...THE INITIAL INTENSITY IS ADJUSTED ONLY SLIGHTLY DOWNWARD TO 120 KT. RITA IS ABOUT TO PASS OVER ANOTHER EDDY OF HIGH OCEAN HEAT CONTENT. COMBINING THIS WITH THE POSSIBLE CONTRACTION OF THE OUTER EYEWALL DURING THE NEXT SEVERAL HOURS...SOME RESTRENGTHENING IS FORECAST IN THE SHORT TERM. GRADUAL WEAKENING IS POSSIBLE LATER ON FRIDAY BEFORE LANDFALL DUE TO LESSER OCEAN HEAT CONTENT CLOSER TO THE COAST...AND TO THE POSSIBILITY OF SOME INCREASE IN THE WIND SHEAR. THE BOTTOM LINE IS THAT THE INTENSITY WILL LIKELY FLUCTUATE DURING THE NEXT 36 HOURS...AND RITA IS EXPECTED TO MAKE LANDFALL AS A MAJOR HURRICANE...AT LEAST CATEGORY THREE. ALTHOUGH RITA HAS WOBBLED WESTWARD DURING THE PAST COUPLE OF HOURS...THE OVERALL MOTION DURING THE PAST SEVERAL HOURS HAS REMAINED WEST-NORTHWESTWARD...ABOUT 300/9. THERE ARE NO CHANGES TO THE OFFICIAL TRACK FORECAST...SINCE THE VARIOUS DYNAMICAL MODELS STRADDLE THE PREVIOUS ADVISORY TRACK. RITA IS EXPECTED TO GRADUALLY TURN NORTHWESTWARD AND EVENTUALLY NORTHWARD AS THE HIGH TO ITS NORTH SLIDES EASTWARD. RITA IS FORECAST TO THEN ESSENTIALLY STALL IN ABOUT THREE DAYS IN THE AREA OF NORTHEASTERN TEXAS WHERE STEERING CURRENTS ARE FORECAST TO BECOME VERY WEAK. THIS SCENARIO POSES A GREAT RISK OF VERY HEAVY RAINFALL WELL INLAND AND FOR MANY DAYS AFTER LANDFALL. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 23/0300Z 26.2N 90.3W 120 KT 12HR VT 23/1200Z 27.0N 91.5W 125 KT 24HR VT 24/0000Z 28.4N 93.0W 120 KT 36HR VT 24/1200Z 29.8N 94.2W 115 KT...INLAND 48HR VT 25/0000Z 31.1N 94.7W 65 KT...INLAND 72HR VT 26/0000Z 33.0N 95.0W 35 KT...INLAND 96HR VT 27/0000Z 33.0N 95.0W 25 KT...INLAND 120HR VT 28/0000Z 33.0N 95.0W 25 KT...INLAND |
#47834 (Received by flhurricane at: 10:58 PM 22.Sep.2005) TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 23 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT THU SEP 22 2005 DEEP CONVECTION WITH RATHER COLD CLOUD TOPS REMAIN NEAR THE ALLEGED CENTER OF PHILIPPE. A 2207 UTC SSMI OVERPASS PROVIDED SOME IDEA AS TO THE CENTER LOCATION. EVEN THOUGH IT IS NOT CLEAR THAT A CLOSED LOW-LEVEL CENTER REMAINS...ADVISORIES WILL CONTINUE UNTIL IT BECOMES CERTAIN THAT THE LOW-LEVEL CENTER NO LONGER EXISTS. BASED ON A 2.5 DVORAK CLASSIFICATION FROM TAFB...THE INITIAL INTENSITY WILL REMAIN 35 KT FOR THIS ADVISORY. PHILIPPE REMAINS A SMALL TROPICAL CYCLONE THAT IS EMBEDDED WITHIN A BROADER AREA OF LOW PRESSURE. IN FACT...BOTH SAB AND TAFB BEGAN SUBTROPICAL CLASSIFICATIONS AT 0000 UTC ON THE BROADER LOW TO THE SOUTHWEST OF PHILIPPE. THE TROPICAL CYCLONE REMAINS IN A HIGH SHEAR ENVIRONMENT WITH DRY MID-LEVEL AIR SWEEPING OVER THE CYCLONE FROM THE SOUTH. IF PHILIPPE SURVIES...A MODEST INCREASE IN STRENGTH IS POSSIBLE AS IT BECOMES EXTRATROPICAL IN ABOUT 24 TO 36 HOURS. THE INITIAL MOTION IS A HIGHLY UNCERTAIN 345/15. THERE HAS NOT BEEN MUCH CHANGE TO THE FORECAST GUIDANCE WITH THE GFS AND GFDL STILL SUGGESTING THAT PHILIPPE WILL SLOW DOWN AND NOT GET PICKED UP BY THE APPROACHING TROUGH/FRONTAL ZONE. THE NOGAPS AND UKMET ACCELERATE PHILIPPE AND/OR ITS EXTRATROPICAL LOW NORTHEASTWARD AND MERGES IT WITH THE FRONT IN ABOUT 48 HOURS. THE OFFICIAL TRACK FORECAST FOLLOWS THIS SCENARIO BUT IS NOT AS FAST WITH THE NORTHEASTWARD ACCELERATION. THE TRACK WAS ADJUSTED SLIGHTLY EASTWARD BUT IT REMAINS VERY SIMILAR TO THE PREVIOUS ADVISORY. FORECASTER BROWN/KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 23/0300Z 28.8N 58.3W 35 KT 12HR VT 23/1200Z 30.7N 59.1W 35 KT 24HR VT 24/0000Z 33.0N 59.8W 35 KT 36HR VT 24/1200Z 35.3N 58.2W 40 KT...EXTRATROPICAL 48HR VT 25/0000Z 36.5N 55.5W 40 KT...EXTRATROPICAL 72HR VT 26/0000Z...ABSORBED WITHIN FRONTAL ZONE. |
#47782 (Received by flhurricane at: 4:53 PM 22.Sep.2005) TCDAT3 HURRICANE RITA DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT THU SEP 22 2005 RITA IS GOING TROUGH THE WEAKENING PHASE OF AN EYEWALL REPLACEMENT CYCLE AND DATA FROM THE NOAA RECONNAISSANCE PLANE INDICATE THAT WINDS HAVE DECREASED TO 125 KNOTS...AND THIS MAY BE GENEROUS. HOWEVER...THE MINIMUM CENTRAL PRESSURE HAS REMAINED AROUND 913 MB...WHICH IS A VERY LOW PRESSURE TO HAVE ONLY 125 KNOTS. IN ADDITION TO THE EYEWALL REPLACEMENT CYCLE...RITA IS CURRENTLY MOVING OVER THE EDGE OF A COLD SST EDDY. THIS COULD HAVE ENHANCED THE WEAKENING TODAY. THE HURRICANE IS FORECAST TO MOVE OVER ANOTHER WARM EDDY DURING THE NEXT 12 TO 24 HOURS AND THERE IS SOME CHANCE THAT RITA COULD REGAIN SOME INTENSITY. BECAUSE THE SHEAR IS FORECAST TO INCREASE...THIS MAY COMPENSATE FOR THE STRENGTHENING THAT MAY BE CAUSED BY THE EFFECTS OF THE HIGH HEAT CONTENT. THE BEST OPTION AT THIS TIME IS TO KEEP RITA AS A 125 KT HURRICANE WITH A SLIGHT WEAKENING BEFORE LANDFALL. THE BOTTOM LINE IS THAT RITA IS EXPECTED TO MAKE LANDFALL AS A DANGEROUS HURRICANE OF AT LEAST A CATEGORY THREE INTENSITY. RITA IS MOVING TOWARD THE WEST-NORTHWEST OR 300 DEGREES AT 8 KNOTS. THE FORECAST TRACK HAS NOT CHANGED AND RITA IS EXPECTED TO BE STEERED TOWARD THE WEST-NORTHWEST AND NORTHWEST TOWARD THE UPPER-TEXAS OR THE WESTERN LOUISIANA COASTS AS THE HIGH SHIFTS EASTWARD. AFTER LANDFALL...STEERING CURRENTS ARE EXPECTED TO WEAKEN AND THE CYCLONE COULD MEANDER FOR A COUPLE OF DAYS IN THE VICINITY OF NORTHEASTERN TEXAS...PRODUCING HEAVY RAINS. BASED ON THE FORECAST TRACK AND WIND RADII...THE TROPICAL STORM WARNING HAS BEEN EXTENDED EASTWARD AND NORTHWARD ALONG THE LOUISIANA COAST. ANY TROPICAL STORM FORCE WINDS IN THE NEW ORLEANS AREA ARE EXPECTED TO BE CONFINED TO A FEW SQUALLS ASSOCIATED WITH QUICKLY MOVING RAINBANDS. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 22/2100Z 25.8N 89.5W 125 KT 12HR VT 23/0600Z 26.5N 90.7W 125 KT 24HR VT 23/1800Z 27.8N 92.4W 125 KT 36HR VT 24/0600Z 29.2N 93.8W 120 KT 48HR VT 24/1800Z 30.5N 94.5W 75 KT...INLAND 72HR VT 25/1800Z 33.0N 95.0W 40 KT...INLAND 96HR VT 26/1800Z 33.0N 95.0W 25 KT...INLAND 120HR VT 27/1800Z 33.0N 95.0W 25 KT...INLAND |
#47771 (Received by flhurricane at: 4:25 PM 22.Sep.2005) TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 22 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT THU SEP 22 2005 ALTHOUGH I AM NOT CERTAIN THAT THE LOW-LEVEL VORTICITY CENTER OF PHILIPPE ACTUALLY STILL HAS A CLOSED SURFACE WIND CIRCULATION... THERE IS ENOUGH CONVECTION AND APPARENT ROTATION TO KEEP THE SYSTEM AS A NOMINAL TROPICAL CYCLONE FOR THE TIME BEING. PHILIPPE IS A SMALL TROPICAL CYCLONE EMBEDDED WITHIN A BROAD NON-TROPICAL AREA OF LOW PRESSURE. THE INITIAL INTENSITY OF 35 KT IS BASED ON AN EARLIER QUIKSCAT PASS AND A 30 KT SHIP REPORT SOUTHEAST OF THE CENTER. THE ENVIRONMENT IS CHARACTERIZED BY HIGH SHEAR AND DRY MID-LEVEL AIR SWEEPING OVER THE CYCLONE FROM THE SOUTH. A HIGHLY DIFLUENT LARGE-SCALE UPPER FLOW IS LOCATED JUST TO THE CYCLONE'S NORTH...BUT THIS PATTERN AND PHILIPPE APPEAR TO BE MOVING MORE OR LESS IN TANDEM...SO I AM NOT EXPECTING THE CYCLONE TO BE ABLE TO TAKE ADVANTAGE. SOME INCREASE IN STRENGTH IS POSSIBLE AS PHILIPPE BECOMES EXTRATROPICAL AND ACCELERATES NORTHEASTWARD BEFORE BECOMING ABSORBED WITHIN A FRONTAL ZONE AFTER ABOUT 48 HOURS. THE INITIAL MOTION IS 350/15. PHILIPPE...WHICH IS A RELATIVELY SHALLOW SYSTEM...IS EXPECTED TO ROTATE AROUND THE BROADER LOW IN WHICH IT IS EMBEDDED FOR THE NEXT 12 TO 24 HOURS. IN ABOUT 48 HOURS A FRONTAL ZONE SHOULD BE APPROACHING PHILIPPE FROM THE NORTHWEST. ALL GUIDANCE AGREES GENERALLY WITH THIS SCENARIO. HOWEVER...AS THE FRONT APPROACHES THERE ARE SIGNIFICANT DIFFERENCES AMONG THE MODELS...WITH THE NOGAPS AND UKMET ACCELERATING PHILIPPE AND/OR THE NON-TROPICAL LOW NORTHEASTWARD...WHILE THE GFS AND GFDL LEAVE PHILIPPE BEHIND OR MOVE IT NORTHEAST ONLY SLOWLY. THE OFFICIAL FORECAST LEANS TOWARD THE FASTER SOLUTION AND IS IN BEST AGREEMENT WITH THE 12Z UKMET RUN. IT IS QUITE POSSIBLE THAT PHILIPPE WILL LOSE ITS CLOSED CIRCULATION AND DISSIPATE MUCH EARLIER THAN SHOWN BELOW. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 22/2100Z 27.5N 57.7W 35 KT 12HR VT 23/0600Z 29.5N 59.2W 35 KT 24HR VT 23/1800Z 31.3N 60.2W 35 KT 36HR VT 24/0600Z 32.8N 60.2W 40 KT...EXTRATROPICAL 48HR VT 24/1800Z 35.0N 58.0W 40 KT...EXTRATROPICAL 72HR VT 25/1800Z...ABSORBED WITHIN FRONTAL ZONE |
#47708 (Received by flhurricane at: 11:01 AM 22.Sep.2005) TCDAT3 HURRICANE RITA DISCUSSION NUMBER 20 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT THU SEP 22 2005 RITA APPEARS TO HAVE REACHED ITS PEAK INTENSITY DURING THE PAST 12 HOURS. HURRICANES TYPICALLY DO NOT MAINTAIN SUCH HIGH INTENSITY FOR A LONG TIME. INITIAL INTENSITY ESTIMATE IS 145 KNOTS. ALTHOUGH SOME FLUCTUATIONS IN INTENSITY ARE LIKELY DURING THE NEXT DAY OR TWO...DUE TO EYEWALL REPLACEMENT CYCLES...AN OVERALL GRADUAL WEAKENING TREND SHOULD TAKE PLACE. THIS WEAKENING TREND IS BASED ON LOWER OCEANIC HEAT CONTENT ALONG THE FORECAST TRACK AND INCREASING SHEAR. NEVERTHERELESS...RITA IS EXPECTED TO MAKE LANDFALL AS A DANGEROUS HURRICANE OF AT LEAST A CATEGORY THREE INTENSITY. RITA HAS BEEN MOVING TOWARD THE WEST-NORTHWEST OR 295 DEGREES AT 8 KNOTS. A STRONG HIGH PRESSURE SYSTEM CURRENTLY CENTERED OVER NORTHERN TEXAS/OKLAHOMA IS EXPECTED TO SHIFT EASTWARD ALLOWING RITA TO TAKE A MORE NORTHWESTERLY AND NORTHERLY TRACK. THE EASTWARD SHIFT OF THE HIGH IS FORECAST BY ALL GLOBAL MODELS...RESULTING IN TRACK GUIDANCE CONSISTENTLY TURNING THE HURRICANE TOWARD THE NORTHWEST AND NORTH TOWARD THE UPPER-TEXAS OR THE WESTERN LOUISIANA COASTS. AFTER LANDFALL...STEERING CURRENTS ARE EXPECTED TO WEAKEN AND THE CYCLONE COULD MEANDER FOR A COUPLE OF DAYS IN THE VICINITY OF NORTHEASTERN TEXAS...PRODUCING HEAVY RAINS. BASED ON THE FORECAST TRACK AND WIND RADII...HURRICANE WARNINGS HAVE BEEN ISSUED AT THIS TIME FROM PORT O'CONNOR TEXAS TO MORGAN CITY LOUISIANA. TROPICAL STORM WARNINGS ARE IN EFFECT ON EITHER SIDE OF THE HURRICANE WARNING. FORECASTER AVILA FORECAST POSITIONS AND MAX WINDS INITIAL 22/1500Z 25.4N 88.7W 145 KT 12HR VT 23/0000Z 25.8N 89.9W 140 KT 24HR VT 23/1200Z 26.9N 91.6W 130 KT 36HR VT 24/0000Z 28.2N 93.0W 125 KT 48HR VT 24/1200Z 30.0N 94.5W 100 KT...INLAND 72HR VT 25/1200Z 33.0N 95.0W 45 KT...INLAND 96HR VT 26/1200Z 34.0N 95.0W 30 KT...INLAND 120HR VT 27/1200Z 34.5N 94.5W 25 KT...INLAND |
#47702 (Received by flhurricane at: 10:48 AM 22.Sep.2005) TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 AM EDT THU SEP 22 2005 DETERMINING A LOW-LEVEL CIRCULATION HAS BEEN DIFFICULT THIS MORNING. THE CENTER THAT WE HAVE BEEN FOLLOWING FOR THE LAST 24 HOURS APPEARS TO BE DISSIPATING WITHIN A BROADER CYCLONIC CIRCULATION...AND SATELLITE REPRESENTATION SHOWS THE OVERALL SYSTEM OBTAINING SUBTROPICAL OR EXTRATROPICAL CHARACTERISTICS RATHER QUICKLY. DVORAK DATA T-NUMBERS ARE ARE 2.5...35 KT FROM TAFB AND 1.5...25 KT FROM SAB. BASED ON A FEW POSSIBLY RAIN CONTAMINATED 35 KT WIND BARBS FROM A RECENT QUIKSCAT PASS...THE INITIAL INTENSITY IS HELD AT 35 KT. THE INITIAL MOTION IS ESTIMATED AT 350/15. WATER VAPOR IMAGERY INDICATES PHILIPPE INTERACTING WITH A STRONG UPPER LEVEL LOW TO THE SOUTHWEST OF THE CYCLONE. GLOBAL MODELS DIFFER IN THE FUTURE TRACK OF THE PHILIPPE/EXTRATROPICAL LOW. THE UKMET MODEL ACCELERATES THE CYCLONE NORTHEASTWARD IN THREE DAYS...WHILE THE GFS MODEL FORECASTS A WEAKENING SLOW DECAY WITH LITTLE NORTHEAST MOTION. THE OFFICIAL FORECAST TAKES A MORE CONSERVATIVE APPROACH...ABSORBING PHILIPPE INTO THE LARGER EXTRATROPICAL CIRCULATION WITHIN 12 HOURS. UNLESS THE REMNANT VORTICITY OF PHILIPPE BECOMES BETTER DEFINED THIS AFTERNOON...ADVISORIES WILL BE DISCONTINUED. IT IS ALSO POSSIBLE FOR PHILIPPE TO REGAIN TROPICAL CHARACTERISTICS IF THE GFS SOLUTION PLAYS OUT. FORECASTER MAINELLI/FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 22/1500Z 26.2N 57.1W 35 KT 12HR VT 23/0000Z 28.2N 57.6W 35 KT...ABSORBED 24HR VT 23/1200Z 30.6N 58.7W 35 KT...EXTRATROPICAL 36HR VT 24/0000Z 32.6N 58.8W 40 KT...EXTRATROPICAL 48HR VT 24/1200Z 34.5N 57.0W 45 KT...EXTRATROPICAL 72HR VT 25/1200Z 36.5N 51.6W 45 KT...EXTRATROPICAL 96HR VT 26/1200Z 38.5N 45.5W 40 KT...EXTRATROPICAL 120HR VT 27/1200Z 40.0N 39.0W 40 KT...EXTRATROPICAL |
#47649 (Received by flhurricane at: 4:46 AM 22.Sep.2005) TCDAT3 HURRICANE RITA DISCUSSION NUMBER 19 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT THU SEP 22 2005 IF RITA HAS NOT PEAKED IN INTENSITY...IT LOOKS LIKE IT IS PRETTY CLOSE TO DOING SO. THE LATEST CENTRAL PRESSURE ESTIMATED FROM RECONNAISSANCE AIRCRAFT DATA IS 897 MB...WHICH SHOWS LITTLE CHANGE DURING THE PAST 8 HR. THE MAXIMUM FLIGHT-LEVEL WINDS SO FAR ARE 165 KT IN THE NE EYEWALL...WHICH IS ONLY SLIGHTLY HIGHER THAN THE 161 KT OBSERVED YESTERDAY AFTERNOON. THE AIRCRAFT DATA SHOWS A INCREASINGLY STRONG OUTER WIND MAXIMUM THAT IS LIKELY THE START OF A CONCENTRIC EYEWALL CYCLE...AND SATELLITE IMAGERY SINCE THE END OF THE ECLIPSE PERIOD SHOWS WARMING OF THE CONVECTION NEAR THE CENTER. BASED ON ALL OF THIS...THE INITIAL INTENSITY REMAINS 150 KT. RITA HAS TURNED A LITTLE TO THE RIGHT DURING THE PAST SEVERAL HOURS AND THE INITIAL MOTION IS NOW 285/8. RAWINSONDE DATA SHOWS A STRONG MID-LEVEL RIDGE CENTERED OVER TEXAS. LARGE-SCALE MODELS FORECAST THIS RIDGE TO SHIFT EASTWARD INTO THE SOUTHEASTERN STATES AND THE EASTERN GULF OF MEXICO DURING THE NEXT 48 HR. THIS SHOULD ALLOW RITA TO TURN MORE NORTHWARD WITH TIME. THE TRACK GUIDANCE IS NOW CLUSTERED AROUND A LANDFALL BETWEEN THE SABINE RIVER AND MATAGORDA TEXAS IN 48-60 HR...WITH A NET EASTWARD SHIFT OF THE GUIDANCE SINCE THE LAST PACKAGE. THE NEW FORECAST TRACK IS ALSO SHIFTED EASTWARD ABOUT 30 N MI...CALLING FOR LANDFALL NEAR THE BOLIVAR PENINSULA AND GALVESTON BAY. HOWEVER...IT SHOULD BE NOTED THAT THE NEW TRACK IS ALONG THE LEFT OR WEST SIDE OF THE ENVELOPE OF GUIDANCE. THE INTENSITY FORECAST REMAINS SOMEWHAT PROBLEMATIC. FIRST...THE MORE NORTHERLY TRACK WILL LIKELY KEEP RITA OVER THE LOOP CURRENT LONGER THAN PREVIOUSLY EXPECTED...SO THE EFFECT OF LOWER OCEAN HEAT CONTENT MAY BE SOMEWHAT LESS THAN PREVIOUSLY EXPECTED IN THE FIRST 24 HR OR SO. SECOND...THE GFS AND SHIP MODELS FORECAST SIGNIFICANT SHEAR OVER RITA AFTER 24 HR...WHICH RESULTS IN SHIPS CALLING FOR SIGNIFICANT WEAKENING. SHEAR ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SHOW ABOUT 12 KT OF SOUTHERLY SHEAR CAUSED BY AN UPPER-LEVEL ANTICYCLONE EAST OF RITA...AND THE LARGE-SCALE MODELS SUGGEST THIS PATTERN WILL CONTINUE UNTIL LANDFALL. HOWEVER...THE GFS AND SHIPS MAY BE OVERDOING THE SHEAR. FINALLY...THERE WILL BE AT LEAST ONE AND POSSIBLE MORE CONCENTRIC EYEWALL CYCLES BEFORE LANDFALL. THE INTENSITY FORECAST IS BASED ON THE PREMISE THAT SHEAR AND REDUCED OUTFLOW WILL CAUSE A GRADUAL WEAKENING... ESPECIALLY AFTER RITA MOVES WEST OF THE LOOP CURRENT IN 24-36 HR. SUPERIMPOSED ON TOP OF THIS WILL BE FLUCTUATIONS CAUSED BY CONCENTRIC EYEWALL CYCLES. THE NEW INTENSITY FORECAST IS AN UPDATE OF THE PREVIOUS FORECAST...CALLING FOR SLOW OVERALL WEAKENING BUT NOT AS MUCH AS SHOWN BY SHIPS. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 22/0900Z 24.9N 88.0W 150 KT 12HR VT 22/1800Z 25.3N 89.3W 150 KT 24HR VT 23/0600Z 26.1N 91.1W 145 KT 36HR VT 23/1800Z 27.2N 92.8W 140 KT 48HR VT 24/0600Z 28.8N 94.3W 130 KT 72HR VT 25/0600Z 32.0N 95.5W 65 KT...INLAND 96HR VT 26/0600Z 34.1N 95.0W 30 KT...INLAND 120HR VT 27/0600Z 34.5N 94.5W 25 KT...INLAND DISSIPATING |
#47638 (Received by flhurricane at: 4:31 AM 22.Sep.2005) TCDAT2 TROPICAL STORM PHILIPPE DISCUSSION NUMBER 20 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT THU SEP 22 2005 PHILIPPE REMAINS VERY DISORGANIZED...WITH THE DEEP CONVECTION IN SCATTERED CLUSTERS NEAR/AROUND THE ESTIMATED CENTER AND LITTLE EVIDENCE OF BANDING FEATURES. MY BEST GUESS IS THAT THE SYSTEM HAS WEAKENED TO A MINIMAL TROPICAL STORM. SHEARING AND SUBSIDENCE ASSOCIATED WITH A LARGE UPPER-LEVEL LOW CENTERED NEAR 23N 62W HAVE BEEN DISRUPTING THE TROPICAL CYCLONE. GLOBAL MODELS CONTINUE TO FORECAST THAT THE UPPER-LEVEL LOW WILL BE SQUEEZED INTO A CYCLONIC SHEAR AXIS...CREATING AN ANTICYCLONIC UPPER-LEVEL FLOW FIELD OVER PHILIPPE THAT WOULD ALLOW STRENGTHENING. HOWEVER I SEE NO SIGN OF THIS HAPPENING WITHIN THE NEXT DAY OR SO...AND THEREFORE NO CHANGE IN STRENGTH IS FORECAST FOR 24 HOURS WITH ONLY A MODEST INCREASE IN INTENSITY THEREAFTER. ANOTHER POSSIBILITY IS THAT...GIVEN ITS SOMEWHAT SUBTROPICAL APPEARANCE...THE SYSTEM COULD STRENGTHEN AS A HYBRID-TYPE OF CYCLONE. ASSUMING THAT PHILIPPE WILL INTERACT WITH A FRONTAL SYSTEM BY THE END OF THE PERIOD...THE FORECAST SHOWS EXTRATROPICAL TRANSFORMATION BY DAY 5. THE CENTER CANNOT BE IDENTIFIED WITH GEOSTATIONARY IMAGERY...AND I HAVE BASED THE LOCATION PRIMARILY ON A POOR FIX USING AN AMSU-B IMAGE. A RECENT AMSR-E IMAGE SUGGESTS THAT THE CENTER MAY BE LOCATED MORE TO THE NORTHEAST...BUT WE WILL WAIT FOR VISIBLE IMAGERY TO CONFIRM THIS. FOR THE TIME BEING...THE INITIAL MOTION ESTIMATE IS A HIGHLY UNCERTAIN 350/10. TRACK GUIDANCE CONTINUES TO INDICATE A MOTION AROUND THE WESTERN PERIPHERY OF A SUBTROPICAL HIGH PRESSURE CELL. THERE CONTINUES TO BE SOME UNCERTAINTY AS TO WHETHER PHILIPPE WILL BE PICKED UP BY A SHORTWAVE TROUGH MOVING OFF THE CANADIAN MARITIMES. SOME GLOBAL MODELS...E.G. THE GFS... INDICATE THAT AT LEAST A PIECE OF PHILIPPE'S VORTICITY WILL BE LEFT BEHIND IN THE SUBTROPICS. BECAUSE OF THIS UNCERTAINTY...THE OFFICIAL TRACK FORECAST IS A LITTLE SLOWER AND TO THE RIGHT OF THAT FROM THE PREVIOUS ADVISORY. FORECASTER PASCH FORECAST POSITIONS AND MAX WINDS INITIAL 22/0900Z 23.3N 57.2W 35 KT 12HR VT 22/1800Z 25.5N 57.8W 35 KT 24HR VT 23/0600Z 28.1N 59.0W 35 KT 36HR VT 23/1800Z 30.5N 60.0W 40 KT 48HR VT 24/0600Z 32.5N 59.0W 45 KT 72HR VT 25/0600Z 35.0N 54.0W 45 KT 96HR VT 26/0600Z 37.0N 48.0W 40 KT 120HR VT 27/0600Z 38.5N 41.5W 40 KT...EXTRATROPICAL |