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Tropical Storm JERRY Forecast Discussion Number 7

2013-09-30 16:32:12| National Hurricane Center (Atlantic)

Issued at 1100 AM AST MON SEP 30 2013 000 WTNT41 KNHC 301432 TCDAT1 TROPICAL STORM JERRY DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112013 1100 AM AST MON SEP 30 2013 DEEP CONVECTION HAS BECOME MORE PERSISTENT...AND VISIBLE SATELLITE IMAGES INDICATE THAT THE LOW-LEVEL CENTER IS NEAR THE WESTERN EDGE OF THE MAIN AREA OF CONVECTION. DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB ARE BOTH 35 KT...AND THE CYCLONE IS BEING UPGRADED TO A TROPICAL STORM ON THIS ADVISORY. WATER VAPOR IMAGERY SHOWS DIFFLUENT UPPER-LEVEL FLOW OVER THE AREA...HOWEVER THE DYNAMICAL GUIDANCE INDICATES THAT WESTERLY TO NORTHWESTERLY VERTICAL SHEAR SHOULD CONTINUE TO AFFECT THE STORM FOR THE NEXT SEVERAL DAYS. AT THIS TIME...THE ENVIRONMENT IS NOT EXPECTED TO BE HOSTILE ENOUGH TO PREVENT AT LEAST A LITTLE STRENGTHENING DURING THE NEXT DAY OR SO. IN THE LATTER PART OF THE FORECAST PERIOD...THERE IS QUITE A BIT OF SPREAD IN THE NUMERICAL INTENSITY GUIDANCE...AND THEREFORE THE WIND SPEED FORECAST FOR THAT TIME IS OF LOW CONFIDENCE. CENTER FIXES FROM VISIBLE SATELLITE IMAGES INDICATE THAT THE STORM HAS MOVED A LITTLE MORE TO THE EAST THAN EARLIER ESTIMATED...AND THE INITIAL MOTION IS NEAR 090/6. THE DYNAMICAL MODELS CONTINUE TO PREDICT AN AMPLIFYING MID-TROPOSPHERIC RIDGE TO THE NORTHWEST AND NORTH OF JERRY OVER THE NEXT SEVERAL DAYS. THIS STEERING SCENARIO SHOULD RESULT IN THE STORM DECELERATING AND MOVING IN A CLOCKWISE LOOP DURING THE NEXT 48-72 HOURS...AS SHOWN IN THE OFFICIAL TRACK FORECAST. IN THE LATTER PART OF THE PERIOD...THE GLOBAL MODELS ARE SUGGESTING THAT JERRY MAY NOT GET PICKED UP BY THE NEXT TROUGH IN THE WESTERLIES...AND THIS IS ALSO REFLECTED IN THE CURRENT OFFICIAL FORECAST. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 27.0N 45.7W 35 KT 40 MPH 12H 01/0000Z 26.6N 45.5W 35 KT 40 MPH 24H 01/1200Z 26.3N 45.5W 40 KT 45 MPH 36H 02/0000Z 26.2N 46.5W 40 KT 45 MPH 48H 02/1200Z 26.3N 47.9W 40 KT 45 MPH 72H 03/1200Z 27.3N 49.8W 40 KT 45 MPH 96H 04/1200Z 28.5N 49.0W 35 KT 40 MPH 120H 05/1200Z 30.5N 46.0W 35 KT 40 MPH $$ FORECASTER PASCH

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Tropical Depression ELEVEN Forecast Discussion Number 5

2013-09-30 04:35:10| National Hurricane Center (Atlantic)

Issued at 1100 PM AST SUN SEP 29 2013 000 WTNT41 KNHC 300235 TCDAT1 TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112013 1100 PM AST SUN SEP 29 2013 THE CLOUD PATTERN ASSOCIATED WITH THE DEPRESSION HAS IMPROVED SLIGHTLY OVER THE LAST SEVERAL HOURS. ALTHOUGH DEEP CONVECTION REMAINS CONFINED TO THE NORTHERN PORTION OF THE CIRCULATION...IT HAS LESS OF A SHEARED APPEARANCE. THE LATEST DVORAK CLASSIFICATIONS FROM TAFB AND SAB SUPPORT MAINTAINING THE INITIAL WIND SPEED AT 30 KT. THE GLOBAL MODELS SHOW THE UPPER-LEVEL WINDS DECREASING SOME DURING THE NEXT FEW DAYS WHILE DRIER AIR IMPINGES ON THE SYSTEM. THESE MIXED SIGNALS SUGGEST THAT ONLY A LITTLE STRENGTHENING IS LIKELY DURING THAT TIME FRAME. BY THE END OF THE WEEK...AN INCREASE IN SOUTHWESTERLY SHEAR IS FORECAST AND THAT SHOULD INDUCE SOME WEAKENING. THE OFFICIAL FORECAST LIES CLOSER TO THE LOW END OF THE GUIDANCE. SATELLITE FIXES SUGGEST THAT THE DEPRESSION HAS TURNED TO THE RIGHT...AS FORECAST...AND THE LATEST INITIAL MOTION ESTIMATE IS 065/8. A LARGE DEEP-LAYER TROUGH OVER THE NORTH ATLANTIC IS GRADUALLY MOVING EASTWARD...ALLOWING A RIDGE TO AMPLIFY TO THE WEST OF THE TROPICAL CYCLONE. THIS PATTERN WILL CAUSE THE DEPRESSION TO SLOW DOWN AND THEN MEANDER OVER THE CENTRAL ATLANTIC DURING THE NEXT COUPLE OF DAYS. A MORE SUBSTANTIAL NORTHEASTWARD MOTION IS EXPECTED TO BEGIN IN 3 TO 4 DAYS WHEN ANOTHER TROUGH APPROACHES THE SYSTEM. THE NHC TRACK FORECAST IS FAIRLY CLOSE TO THE PREVIOUS ONE AND LIES NEAR THE MIDDLE OF THE GUIDANCE ENVELOPE. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 27.0N 47.0W 30 KT 35 MPH 12H 30/1200Z 27.1N 46.1W 35 KT 40 MPH 24H 01/0000Z 26.9N 45.9W 35 KT 40 MPH 36H 01/1200Z 26.6N 46.0W 40 KT 45 MPH 48H 02/0000Z 26.4N 46.8W 40 KT 45 MPH 72H 03/0000Z 27.0N 48.5W 40 KT 45 MPH 96H 04/0000Z 29.5N 48.0W 35 KT 40 MPH 120H 05/0000Z 31.5N 45.0W 35 KT 40 MPH $$ FORECASTER CANGIALOSI

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Tropical Depression ELEVEN Forecast Discussion Number 3

2013-09-29 16:32:33| National Hurricane Center (Atlantic)

Issued at 1100 AM AST SUN SEP 29 2013 000 WTNT41 KNHC 291432 TCDAT1 TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112013 1100 AM AST SUN SEP 29 2013 THE DEPRESSION HAS A POORLY ORGANIZED PRESENTATION ON SATELLITE IMAGES THIS MORNING. THE LOW-LEVEL CENTER IS NOT WELL DEFINED AND DEEP CONVECTION IS LIMITED TO A FEW CLUSTERS OF SHOWERS AND THUNDERSTORMS OVER THE NORTHERN SEMICIRCLE AND A NARROW BAND OVER THE EASTERN PORTION OF THE CIRCULATION. DVORAK CLASSIFICATIONS SUPPORT AN INTENSITY OF NO MORE THAN 25-30 KT...SO THE CURRENT INTENSITY IS HELD AT 30 KT. AN UPPER-LEVEL LOW JUST TO THE NORTHWEST OF THE DEPRESSION CONTINUES TO IMPART SOUTHWESTERLY SHEAR...AND THE GLOBAL MODELS SUGGEST THAT THIS REGIME SHOULD CONTINUE FOR THE NEXT 12-24 HOURS. LATER ON...THE DYNAMICAL GUIDANCE INDICATES SOME RELAXATION OF THE SHEAR SO SOME STRENGTHENING IS FORECAST IN A DAY OR SO. THE LATEST GFS RUN DOES NOT SHOW THE SYSTEM WEAKENING IN THE LATTER PART OF THE FORECAST PERIOD...AND THE NEW OFFICIAL FORECAST CALLS FOR THE CYCLONE TO MAINTAIN ITSELF FOR THE NEXT 5 DAYS. THIS IS VERY CLOSE TO THE LATEST INTENSITY MODEL CONSENSUS. THERE IS CONSIDERABLE SPREAD IN CENTER FIXES...AND THE INITIAL MOTION IS AN UNCERTAIN 050/8. A MID-LEVEL RIDGE IS PREDICTED BY THE GLOBAL MODELS TO AMPLIFY TO THE WEST OF THE CYCLONE WITHIN THE NEXT COUPLE OF DAYS...WHICH SHOULD CAUSE THE SYSTEM TO SLOW DOWN AND TURN TOWARD THE RIGHT. THE GFS AND ECMWF GLOBAL MODELS AS WELL AS THE HFIP STREAM 1.5 MODEL CONSENSUS SHOW THE TROPICAL CYCLONE EXECUTING A SMALL CLOCKWISE LOOP DURING THE NEXT FEW DAYS...AND SO DOES THE OFFICIAL TRACK FORECAST. BY LATE IN THE FORECAST PERIOD...A LARGE MID-LEVEL TROUGH APPROACHING FROM THE WEST SHOULD CAUSE THE CYCLONE TO MOVE NORTHEASTWARD. THE NEW NHC TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE...ALBEIT SHIFTED SLIGHTLY EASTWARD. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 26.0N 48.6W 30 KT 35 MPH 12H 30/0000Z 26.7N 47.7W 30 KT 35 MPH 24H 30/1200Z 26.8N 46.8W 35 KT 40 MPH 36H 01/0000Z 26.5N 46.3W 40 KT 45 MPH 48H 01/1200Z 26.5N 47.0W 40 KT 45 MPH 72H 02/1200Z 26.5N 47.5W 40 KT 45 MPH 96H 03/1200Z 27.5N 47.5W 40 KT 45 MPH 120H 04/1200Z 29.5N 45.0W 40 KT 45 MPH $$ FORECASTER PASCH

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Tropical Depression ELEVEN Forecast Discussion Number 2

2013-09-29 10:48:14| National Hurricane Center (Atlantic)

Issued at 500 AM AST SUN SEP 29 2013 000 WTNT41 KNHC 290847 TCDAT1 TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112013 500 AM AST SUN SEP 29 2013 NIGHTTIME VISIBLE IMAGERY INDICATES THE DEPRESSION HAS A ROBUST LOW-LEVEL CIRCULATION...BUT THE ASSOCIATED DEEP CONVECTION IS SHEARED WELL TO THE NORTH AND NORTHEAST OF THE CENTER. SOME WEAK CURVED BAND FEATURES HAVE DEVELOPED RECENTLY IN THE EASTERN SEMICIRCLE...SUGGESTING THAT THE SYSTEM IS TRYING TO GET BETTER ORGANIZED. FOR NOW...HOWEVER...AN INTENSITY OF 30 KT IS BEING MAINTAINED BASED ON A SATELLITE INTENSITY ESTIMATE OF 30 KT FROM TAFB AND UW-CIMSS ADT. THE INITIAL MOTION ESTIMATE IS 040/08 KT. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. THE SMALL DEPRESSION IS EXPECTED TO MOVE NORTHEASTWARD AND SLOW DOWN AS IT MOVES AROUND THE NORTH SIDE OF A WEAKENING MID-LEVEL RIDGE WHILE A SHORTWAVE TROUGH TO THE NORTH GRADUALLY LIFTS OUT. THIS SHOULD RESULT IN VERY WEAK STEERING FLOW FOR THE NEXT COUPLE OF DAYS. A NEW RIDGE IS THEN FORECAST BY THE MODELS TO BUILD IN AND BECOME HIGHLY AMPLIFIED TO THE WEST AND NORTH OF THE CYCLONE BY 48 HOURS...WHICH SHOULD ACT TO TURN THE CYCLONE WESTWARD THROUGH 72 HOURS...COMPLETING A SMALL CLOCKWISE LOOP IN THE PROCESS. AFTER THAT...A SECOND AND STRONGER MID-/UPPER-LEVEL TROUGH WILL MOVE EASTWARD FROM THE UNITED STATES...AND ACT TO LIFT OUT THE CYCLONE AND ACCELERATE IT TO THE NORTHEAST ON DAYS 4 AND 5. THE NEW NHC FORECAST TRACK IS ALMOST IDENTICAL TO THE PREVIOUS TRACK...AND LIES CLOSE TO A BLEND OF THE GFS AND ECMWF MODELS. ALTHOUGH THE GFS-BASED SHIPS INTENSITY MODEL IS ONLY INDICATING 9 KT OF SOUTH-SOUTHWESTERLY VERTICAL SHEAR ACROSS THE DEPRESSION...WHICH IS SIGNIFICANTLY LOWER THAN IT WAS ON THE PREVIOUS ADVISORY... SATELLITE IMAGERY AND THE ASSOCIATED CONVECTIVE CLOUD PATTERN OF THE DEPRESSION SUGGESTS THAT THE SHEAR IS CONSIDERABLY STRONGER... LIKELY DUE TO THE PRESENCE OF A MID-/UPPER-LEVEL LOW LOCATED ONLY ABOUT 300 NMI TO THE NORTHWEST OF THE CYCLONE. THAT LOW IS FORECAST BY MOST OF THE MODELS...ESPECIALLY THE GFS AND ECMWF...TO MOVE IN TANDEM WITH THE CYCLONE OVER THE NEXT 72 HOURS OR SO AS IT MAKES A CLOCKWISE LOOP. AS A RESULT...THIS SYSTEM WILL LIKELY BE PLAGUED BY AT LEAST MODERATE SHEAR FOR THE NEXT 2 TO 3 DAYS...WHICH SHOULD PREVENT ANY SIGNIFICANT STRENGTHENING FROM OCCURRING. THE NHC INTENSITY FORECAST IS IDENTICAL TO THE PREVIOUS PACKAGE AND REMAINS CLOSE TO THE INTENSITY CONSENSUS MODEL...ICON. HOWEVER...IF THE AFOREMENTIONED UPPER-LEVEL SHOULD DISSIPATE OR MOVE AWAY FROM THE CYCLONE SOONER THAN CURRENTLY EXPECTED...THEN THE SYSTEM COULD BE SOMEWHAT STRONGER THAN CURRENTLY FORECAST ON DAYS 4 AND 5. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 25.6N 49.7W 30 KT 35 MPH 12H 29/1800Z 26.4N 48.8W 35 KT 40 MPH 24H 30/0600Z 27.0N 47.6W 40 KT 45 MPH 36H 30/1800Z 26.8N 46.8W 40 KT 45 MPH 48H 01/0600Z 26.4N 46.6W 40 KT 45 MPH 72H 02/0600Z 26.3N 47.8W 35 KT 40 MPH 96H 03/0600Z 27.7N 48.6W 35 KT 40 MPH 120H 04/0600Z 30.0N 47.0W 30 KT 35 MPH $$ FORECASTER STEWART

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Tropical Depression ELEVEN Forecast Discussion Number 1

2013-09-29 04:34:02| National Hurricane Center (Atlantic)

Issued at 1100 PM AST SAT SEP 28 2013 000 WTNT41 KNHC 290233 TCDAT1 TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112013 1100 PM AST SAT SEP 28 2013 THE WELL-DEFINED AREA OF LOW PRESSURE OVER THE CENTRAL ATLANTIC HAS DEVELOPED ENOUGH ORGANIZED DEEP CONVECTION TO BE CLASSIFIED AS A TROPICAL DEPRESSION...THE ELEVENTH ONE OF THE ATLANTIC HURRICANE SEASON. THE INITIAL WIND SPEED IS SET AT 30 KT BASED ON EARLIER SCATTEROMETER DATA. THE DEPRESSION IS MOVING NORTHWARD AT ABOUT 8 KT ON THE WEST SIDE OF A DEEP-LAYER RIDGE. THIS SUBTROPICAL RIDGE IS EXPECTED TO WEAKEN SOON AS A LARGE TROUGH AMPLIFIES OVER THE NORTH ATLANTIC...CAUSING THE CYCLONE TO TURN NORTHEASTWARD OVERNIGHT AND THEN EASTWARD LATE SUNDAY. THE TROUGH IS NOT EXPECTED TO ABSORB OR PICK UP THE DEPRESSION...INSTEAD THE MODELS ARE IN GOOD AGREEMENT IN SHOWING THE CYCLONE BEING LEFT BEHIND IN WEAK STEERING CURRENTS FOR AT LEAST A FEW DAYS. THE NEXT SUBSTANTIAL INFLUENCE ON THE STEERING FLOW WILL LIKELY BE ANOTHER TROUGH THAT WILL BE APPROACHING THE DEPRESSION AROUND THE MIDDLE PORTION OF NEXT WEEK. THE NHC FORECAST SHOWS THE SYSTEM MAKING A CLOCKWISE LOOP AND LIES CLOSE TO THE DYNAMICAL MODEL CONSENSUS THROUGH THE FORECAST PERIOD. THE DEPRESSION IS CURRENTLY BEING AFFECTED BY ABOUT 15 KT OF SOUTHERLY SHEAR...WHICH HAS DISPLACED MUCH OF THE ASSOCIATED CONVECTION TO THE NORTH OF THE CENTER. THE SHEAR IS EXPECTED TO LESSEN DURING THE NEXT 24 HOURS...WHICH SHOULD ALLOW THE DEPRESSION STRENGTHEN A LITTLE. AFTER THAT TIME...HOWEVER...AN INCREASE IN NORTHWESTERLY SHEAR AND DRIER AIR ARE EXPECTED TO END THE STRENGTHENING TREND AND LIKELY INDUCE WEAKENING. THE NHC WIND SPEED FORECAST IS NEAR THE INTENSITY MODEL CONSENSUS IN THE SHORT TERM AND THEN LIES ON THE LOW SIDE OF THE GUIDANCE GIVEN THE ANTICIPATED HOSTILE ENVIRONMENTAL CONDITIONS. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 25.2N 50.2W 30 KT 35 MPH 12H 29/1200Z 26.1N 49.4W 35 KT 40 MPH 24H 30/0000Z 27.0N 48.3W 40 KT 45 MPH 36H 30/1200Z 27.1N 47.0W 40 KT 45 MPH 48H 01/0000Z 26.6N 46.5W 40 KT 45 MPH 72H 02/0000Z 26.2N 47.5W 35 KT 40 MPH 96H 03/0000Z 27.2N 49.0W 35 KT 40 MPH 120H 04/0000Z 29.5N 47.5W 30 KT 35 MPH $$ FORECASTER CANGIALOSI

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