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Subtropical Storm MELISSA Forecast Discussion Number 4

2013-11-19 09:49:35| National Hurricane Center (Atlantic)

Issued at 500 AM AST TUE NOV 19 2013 000 WTNT44 KNHC 190849 TCDAT4 SUBTROPICAL STORM MELISSA DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013 500 AM AST TUE NOV 19 2013 MELISSA APPEARS TO HAVE STRENGTHENED A LITTLE OVERNIGHT. ALTHOUGH THE CYCLONE IS NOT PRODUCING WIDESPREAD DEEP CONVECTION...A FEW BANDS HAVE BECOME BETTER ESTABLISHED TO THE NORTH OF THE CENTER DURING THE LAST FEW HOURS. THE INITIAL WIND SPEED IS NUDGED UPWARD TO 55 KT...IN AGREEMENT WITH THE LATEST SATELLITE INTENSITY ESTIMATE FROM TAFB. THE CIRCULATION OF THE CYCLONE IS GRADUALLY BECOMING MORE CIRCULAR AND THE CLOUD PATTERN APPEARS TO BE CONTRACTING WHILE IT SEPARATES FROM THE NEARBY FRONTAL BOUNDARY. A DECREASE IN SHEAR DURING THE NEXT 12 TO 24 HOURS COULD ALLOW MELISSA TO STRENGTHEN A LITTLE AND TRANSITION TO A TROPICAL CYCLONE. ANY STRENGTHENING SHOULD COME TO AN END IN 24 TO 36 HOURS WHEN THE STORM IS EXPECTED TO MOVE OVER SIGNIFICANTLY COLDER WATER AND INTO A DRIER AIRMASS. MELISSA IS ANTICIPATED TO BECOME POST-TROPICAL IN ABOUT 48 HOURS WHEN IT IS FORECAST TO BE OVER SEA SURFACE TEMPERATURES OF ABOUT 18 C. THE SUBTROPICAL STORM HAS TURNED TO THE NORTH...WITH THE LATEST INITIAL MOTION ESTIMATE BEING 360/8 KT. A DEEP-LAYER TROUGH AND ASSOCIATED COLD FRONT LOCATED OVER THE WESTERN ATLANTIC WILL BE MOVING CLOSER TO MELISSA...AND WILL HELP ACCELERATE THE CYCLONE NORTHEASTWARD DURING THE NEXT COUPLE OF DAYS. BEYOND A COUPLE OF DAYS...THERE IS A NOTABLE DISAGREEMENT IN HOW THE POST-TROPICAL REMNANT OF MELISSA INTERACTS WITH THE DEEP-LAYER TROUGH. THE GFS CONTINUES TO SHOW THE CYCLONE ROTATING AROUND THE EASTERN SIDE OF THE TROUGH OR LOW...WHILE THE ECMWF AND UKMET SHOW THE CYCLONE MOVING MORE EASTWARD IN THE WESTERLIES. THE NHC FORECAST IS ADJUSTED A LITTLE TO THE EAST OF THE PREVIOUS ONE...AND LIES CLOSE TO THE FLORIDA STATE SUPERENSEMBLE...WHICH IS IN BETWEEN THE AFOREMENTIONED SCENARIOS. FORECAST POSITIONS AND MAX WINDS INIT 19/0900Z 31.2N 54.6W 55 KT 65 MPH 12H 19/1800Z 32.6N 53.5W 60 KT 70 MPH 24H 20/0600Z 35.3N 50.3W 60 KT 70 MPH 36H 20/1800Z 38.4N 45.5W 55 KT 65 MPH 48H 21/0600Z 41.3N 39.5W 55 KT 65 MPH...POST-TROPICAL 72H 22/0600Z 46.5N 30.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 23/0600Z 52.0N 27.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 24/0600Z...DISSIPATED $$ FORECASTER CANGIALOSI

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Subtropical Storm MELISSA Forecast Discussion Number 3

2013-11-19 03:58:03| National Hurricane Center (Atlantic)

Issued at 1100 PM AST MON NOV 18 2013 000 WTNT44 KNHC 190257 TCDAT4 SUBTROPICAL STORM MELISSA DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013 1100 PM AST MON NOV 18 2013 DEEP CONVECTION IN MELISSA REMAINS QUITE ASYMMETRIC WITH A NARROW BAND WRAPPING AROUND THE CENTER AT A RADIUS OF ABOUT 60-90 NM ALONG WITH A LARGER BAND IN THE EASTERN SEMI-CIRCLE A FEW HUNDRED MILES FROM THE CENTER. WATER VAPOR IMAGERY INDICATES THAT MELISSA REMAINS INTERTWINED WITH AN UPPER-LEVEL LOW...THUS A SUBTROPICAL STORM STATUS STILL APPEARS WARRANTED AT THIS TIME. A TIMELY 0030 UTC PARTIAL ASCAT-A PASS PROVIDED PEAK WINDS OF ABOUT 45 KT. THIS ALONG WITH THE TAFB HEBERT-POTEAT SUBTROPICAL CLASSIFICATION OF 3.0...45-50 KT...HELPED TO DETERMINE THE INITIAL INTENSITY OF 50 KT. MELISSA IS MOVING AT 325 DEGREES AT 7 KT. THE CYCLONE SHOULD VEER TOWARD THE NORTHEAST AND ACCELERATE DURING THE NEXT TWO DAYS AS A SHORTWAVE TROUGH OVER EASTERN CANADA CURRENT HELPS KICK OUT MELISSA INTO THE MID-LATITUDE WESTERLIES. THE TRACK GUIDANCE IS TIGHTLY CLUSTERED THROUGH 72 HR...BUT THEN DIVERGES DEPENDING IN PART ON HOW MUCH EXTRATROPICAL TRANSITION OCCURS. THE GFS AND DEPENDENT MESOSCALE HURRICANE MODELS INDICATE AN EARLIER TRANSITION...WHICH THEN WRAPS MELISSA NORTHWARD QUICKER. THE ECMWF AND NAVGEM KEEP MELISSA FARTHER EAST IN THE WARM SECTOR OF THE APPROACHING EXTRATROPICAL LOW AND DISSIPATE IT BEFORE EXTRATROPICAL TRANSITION. THE OFFICIAL FORECAST IS A BLEND OF THESE SOLUTIONS AND IS CLOSE TO THE PREVIOUS ADVISORY THROUGH THREE DAYS...BUT THEN FASTER AND FARTHER EAST THEREAFTER. THE EXTRATROPICAL TRACK IS BASED IN LARGE PART UPON INPUT FROM THE OCEAN PREDICTION CENTER. MELISSA HAS A SHORT WINDOW OF OPPORTUNITY FOR FURTHER INTENSIFICATION. THE SHEAR IS PROJECTED TO LESSEN FOR ABOUT A DAY WHILE THE CYCLONE REMAINS OVER LUKEWARM WATERS. THIS SHOULD ALLOW ENOUGH CONVECTION TO FORM OVER THE CENTER AND A DEEP WARM CORE TO DEVELOP FOR TROPICAL TRANSITION TO OCCUR...AS ALSO INDICATED BY THE FSU CYCLONE PHASE SPACE DIAGRAMS. IN ABOUT 36 TO 48 HOURS...THE RAPIDLY DROPPING SSTS THAT MELISSA WILL ENCOUNTER COUPLED WITH MUCH STRONGER VERTICAL SHEAR SHOULD CAUSE THE DEEP CONVECTION TO CEASE. THUS A TRANSITION TO A POST-TROPICAL LOW IS INDICATED AT 48 HOURS...EVEN THOUGH A FULL EXTRATROPICAL STAGE IS PREDICTED TO OCCUR AROUND THREE DAYS. BY DAY FIVE...MELISSA IS ANTICIPATED TO BECOME ABSORBED BY THE LARGER EXTRATROPICAL LOW. THE AFOREMENTIONED ASCAT PASS ALSO ALLOWED FOR A MORE CONFIDENT ASSESSMENT OF THE 34 AND 50 KT WIND RADII. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 30.3N 54.7W 50 KT 60 MPH 12H 19/1200Z 31.3N 54.5W 50 KT 60 MPH 24H 20/0000Z 33.6N 52.4W 55 KT 65 MPH 36H 20/1200Z 36.4N 48.5W 60 KT 70 MPH 48H 21/0000Z 39.8N 43.4W 55 KT 65 MPH...POST-TROPICAL 72H 22/0000Z 46.0N 33.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 96H 23/0000Z 53.5N 33.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 24/0000Z...DISSIPATED $$ FORECASTER LANDSEA

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Subtropical Storm MELISSA Forecast Discussion Number 2

2013-11-18 21:54:01| National Hurricane Center (Atlantic)

Issued at 500 PM AST MON NOV 18 2013 000 WTNT44 KNHC 182053 TCDAT4 SUBTROPICAL STORM MELISSA DISCUSSION NUMBER 2 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013 500 PM AST MON NOV 18 2013 DEEP CONVECTION HAS PERSISTED NEAR THE CENTER OF MELISSA...ALBEIT SOMEWHAT FRAGMENTED. WEAK ANTICYCLONIC OUTFLOW HAS BECOME ESTABLISHED IN THE SOUTHERN SEMICIRCLE OF THE INNER-CORE REGION... SUGGESTING THAT MELISSA IS TRYING TO MAKE THE TRANSITION TO A TROPICAL STORM. IN ADDITION...EARLIER ASCAT OVERPASSES AT 1314Z AND 1408Z INDICATED THAT THE RADIUS OF MAXIMUM WINDS HAS CONTRACTED DOWN TO LESS THAN 80 NMI AND MAXIMUM WINDS WERE 50-51 KT IN THE SOUTHWESTERN QUADRANT. HOWEVER...BOTH OVERPASSES MISSED THE INNER CORE WIND FIELD...WHICH MEANS THAT THE RADIUS OF MAXIMUM WINDS COULD BE SMALLER AND THE PEAK WINDS COULD BE STRONGER. AFTER MELISSA PASSED JUST EAST OF DRIFTING BUOY 41999 AT 1000Z...WHICH REPORTED A PRESSURE OF 989.4 MB...THE PRESSURE AT THE BUOY HAS REMAINED AT OR BELOW 993 MB SINCE ABOUT 1400Z AS MELISSA HAS MOVED FARTHER AWAY...WHICH SUGGESTS THAT THE CYCLONE COULD STILL BE DEEPENING. THE INITIAL MOTION ESTIMATE IS 325/08 KT. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING THROUGH 36 H. NHC MODEL GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON MELISSA MOVING SLOWLY NORTHWESTWARD AND NORTHWARD OVER THE NEXT 24 HOURS...AND THEN ACCELERATING NORTHEASTWARD BY 36 H. MELISSA WILL LIKELY REMAIN A SEPARATE ENTITY THROUGH 120 H AND NOT BE ABSORBED BY AN APPROACHING FRONTAL SYSTEM UNTIL NEAR OR AFTER THE FORECAST PERIOD. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND LIES CLOSE TO THE MULTI-MODEL CONSENSUS TVCA. THE EXTRATROPICAL TRACK IS BASED ON INPUT FROM THE NOAA OCEAN PREDICTION CENTER. MELISSA HAS ABOUT 36 HOURS OR SO TO STRENGTHEN SOME MORE WHILE THE CYCLONE REMAINS OVER RELATIVELY WARM WATER. ALTHOUGH SSTS WILL BE DECREASING FROM THE CURRENT 27C TO AROUND 22-23C BY 36-48 H...THE 500 MB TEMPERATURES ARE NEAR -13C...WHICH IS MUCH COLDER THAN A TYPICAL TROPICAL ATMOSPHERE...AND THAT SHOULD HELP TO MAINTAIN UNSTABLE CONDITIONS AND THE FORMATION OF ADDITONAL CONVECTION IN THE INNER CORE REGION. AS A RESULT...MELISSA IS EXPECTED TO TRANSITION TO A TROPICAL CYCLONE ON TUESDAY. IN ADDITION...THE GFS-BASED SHIPS INTENSITY MODEL IS NOW INDICATING THAT THE 850-200 MB VERTICAL WIND SHEAR WILL DROP SHARPLY FROM THE CURRENT 30 KT TO LESS THAN 10 KT IN THE 18-24 H TIME FRAME...AND THAT IS WHEN THE CYCLONE COULD REACH ITS PEAK INTENSITY...AND POSSIBLY EVEN OBTAIN HURRICANE STRENGTH. GRADUAL WEAKENING IS FORECAST AFTER 48 HOURS AS MELISSA MOVES OVER SSTS LESS THAN 20C...INTO A DRIER AND MORE STABLE AIRMASS...AND EXPERIENCE STRONG SOUTHWESTERLY WIND SHEAR AHEAD OF A DEEP-LAYER TROUGH THAT WILL MOVE OFF OF THE EAST COAST OF NORTH AMERICA DURING THE NEXT DAY OR SO. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 29.8N 54.2W 50 KT 60 MPH 12H 19/0600Z 30.7N 54.5W 55 KT 65 MPH 24H 19/1800Z 32.3N 53.5W 60 KT 70 MPH 36H 20/0600Z 34.9N 50.6W 60 KT 70 MPH 48H 20/1800Z 38.0N 46.5W 60 KT 70 MPH 72H 21/1800Z 44.5N 36.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 22/1800Z 50.0N 34.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 23/1800Z 57.0N 39.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ FORECASTER STEWART

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Subtropical Storm MELISSA Forecast Discussion Number 1

2013-11-18 16:01:01| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT MON NOV 18 2013 000 WTNT44 KNHC 181500 TCDAT4 SUBTROPICAL STORM MELISSA DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013 1100 AM EDT MON NOV 18 2013 DEEP CONVECTION HAS DEVELOPED DURING THE PAST SEVERAL HOURS NEAR THE WELL-DEFINED CENTER OF A LARGE GALE-AREA LOCATED OVER THE CENTRAL ATLANTIC WELL TO THE EAST-SOUTHEAST OF BERMUDA. FRONTAL BOUNDARIES NEAR THE CENTER APPEAR TO HAVE DISSIPATED AND SO ADVISORIES ARE BEING INITIATED AT THIS TIME. ALTHOUGH THERE ARE HINTS OF ANTICYCLONIC OUTFLOW HAVING RECENTLY DEVELOPED OVER THE INNER CORE CONVECTION...THE SYSTEM IS STILL WELL-EMBEDDED WITHIN AN UPPER-LEVEL LOW AND THE MOST RECENT SCATTEROMETER WIND DATA SUGGEST THAT THE CYCLONE MAY STILL HAVE A LARGE RADIUS OF MAXIMUM WINDS. AS A RESULT...THE SYSTEM IS BEING DESIGNATED AS A SUBTROPICAL STORM RATHER THAN A TROPICAL STORM...AT LEAST FOR NOW. THE INITIAL MOTION ESTIMATE IS NORTHWESTWARD...OR 320/08 KT. NHC MODEL GUIDANCE IS IN EXCELLENT AGREEMENT ON MELISSA MOVING NORTHWESTWARD AND GRADUALLY SLOWING DOWN OVER THE NEXT 24 HOURS OR SO AS IT MOVES AROUND THE WESTERN PERIPHERY OF A HIGH-AMPLITUDE RIDGE LOCATED BETWEEN THE CYCLONE AND THE AZORES. THE CYCLONE COULD POSSIBLY BECOME STATIONARY FOR A BRIEF PERIOD ON TUESDAY WHEN THE SYSTEM MOVES UNDERNEATH A 200 MB LOW/TROUGH. HOWEVER...BY 48 HORUS AND BEYOND...A DEEP-LAYER TROUGH LOCATED OVER THE EASTERN PORTIONS OF CANADA AND THE UNITED SATES IS EXPECTED TO ACCELERATE MELISSA TO THE NORTHEAST. BY DAYS 4 AND 5...MELISSA IS FORECAST OT INTERACT WITH THE AFOREMENTIONED DEEPENING TROUGH AND TURN BACK TOWARD THE NORTH AND NORTHWEST OVER THE FAR NORTH ATLANTIC. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE MULTI-MODEL CONSENSUS TVCA. MELISSA HAS ABOUT 48 HOURS OR SO TO STRENGTHEN...AND THE SHIPS INTENSITY MODEL INDICATES THAT THE VERTICAL SHEAR IS EXPECTED TO DECREASE TO LESS THAN 10 KT BY 36 HOURS. THE WEAKENING SHEAR SHOULD ALLOW FOR AT LEAST SOME MODEST STRENGTHENING TO OCCUR WHILE THE CYCLONE REMAINS OVER RELATIVELY WARM WATER...BUT ALSO ALLOW FOR THE TRANSITION TO A TROPICAL CYCLONE. THE NHC INTENSITY FORECAST IS SIMILAR TO THE ICON INTENSITY FORECAST MODEL. HOWEVER...IT IS NOT OUT OF THE QUESTION THAT MELISSA COULD ATTAIN HURRICANE STATUS IN 36-48 HOURS WHEN THE VERTICAL SHEAR IS AT A MINIMUM. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 29.3N 53.6W 45 KT 50 MPH 12H 19/0000Z 30.2N 54.4W 50 KT 60 MPH 24H 19/1200Z 31.3N 54.3W 55 KT 65 MPH 36H 20/0000Z 33.6N 52.3W 60 KT 70 MPH 48H 20/1200Z 36.6N 48.9W 60 KT 70 MPH 72H 21/1200Z 42.8N 39.4W 55 KT 65 MPH...POST-TROP/EXTRATROP 96H 22/1200Z 50.0N 35.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 23/1200Z 55.0N 39.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ FORECASTER STEWART

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Central Reach Existing Policies and Conditions Report - Discussion Draft

2013-11-12 18:26:29| PortlandOnline

January 2011 draft

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