Post-Tropical MELISSA Discussion Thread

Up to 50%.

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
700 PM EST SUN NOV 17 2013

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A NON-TROPICAL LOW PRESSURE SYSTEM LOCATED OVER THE CENTRAL ATLANTIC
OCEAN ABOUT 850 MILES EAST-SOUTHEAST OF BERMUDA IS PRODUCING WINDS
TO GALE FORCE. ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR THIS
LOW TO ACQUIRE SUBTROPICAL OR TROPICAL CHARACTERISTICS DURING THE
NEXT FEW DAYS WHILE IT MOVES SLOWLY NORTH-NORTHWESTWARD TO
NORTHWARD. THIS SYSTEM HAS A MEDIUM CHANCE...50 PERCENT... OF
BECOMING A SUBTROPICAL OR TROPICAL CYCLONE DURING THE NEXT 48
HOURS...AND A HIGH CHANCE...70 PERCENT...OF BECOMING A SUBTROPICAL
OR TROPICAL CYCLONE DURING THE NEXT 5 DAYS. ADDITIONAL INFORMATION
ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY THE
NATIONAL WEATHER SERVICE.

&&
HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE ARE
FOUND UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.

FIVE-DAY FORMATION PROBABILITIES ARE EXPERIMENTAL IN 2013. COMMENTS
ON THE EXPERIMENTAL FORECASTS CAN BE PROVIDED AT...

WWW.NWS.NOAA.GOV/SURVEY/NWS-SURVEY.PHP?CODE=ETWO

$$
FORECASTER BROWN

Yes!  It'll be a fish, and it gets some energy out of the tropics.  It'll be fun to watch while we shiver in mid-70's temps here!! 

BULLETIN
SUBTROPICAL STORM MELISSA ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013
500 PM AST MON NOV 18 2013

...MELLISSA STRENGTHENS OVER THE OPEN CENTRAL ATLANTIC...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...29.8N 54.2W
ABOUT 650 MI...1045 KM ESE OF BERMUDA
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NW OR 325 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...987 MB...29.15 INCHES



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

SUBTROPICAL STORM MELISSA ADVISORY NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013
1100 AM AST TUE NOV 19 2013

...MELISSA STILL MOVING NORTHWARD OVER THE CENTRAL ATLANTIC...
...EXPECTED TO TRANSITION TO A TROPICAL STORM LATER TODAY...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...31.9N 54.6W
ABOUT 595 MI...960 KM E OF BERMUDA
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...N OR 10 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...982 MB...29.00 INCHES

BULLETIN
SUBTROPICAL STORM MELISSA ADVISORY NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013
500 PM AST TUE NOV 19 2013

...MELISSA TURNS NORTHEASTWARD OVER THE CENTRAL ATLANTIC...
...COULD STILL TRANSITION TO A TROPICAL STORM TONIGHT...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...33.0N 53.7W
ABOUT 645 MI...1040 KM E OF BERMUDA
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...NE OR 40 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...982 MB...29.00 INCHES


SUBTROPICAL STORM MELISSA DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013
500 PM AST TUE NOV 19 2013

MELISSA APPEARS TO BE ON THE CUSP OF MAKING THE TRANSITION FROM A
SUBTROPICAL TO A TROPICAL CYCLONE. TWO EARLIER ASCAT OVERPASSES
CAPTURED THE WIND FIELD IN THE EASTERN SEMICIRCLE...WHICH INDICATED
THAT THE OUTER WIND FIELD HAD WEAKENED AND THAT THE INNER-CORE WIND
FIELD HAD CONTRACTED INWARD WITH THE RADIUS OF MAXIMUM WINDS NOW AT
ABOUT 40-50 NMI. IN ADDITION...AN 1119 UTC AMSU OVERPASS SHOWED
THAT A PRONOUNCED UPPER-LEVEL WARM CORE HAD DEVELOPED OVER THE
LOW-LEVEL CENTER. THESE SATELLITE INDICATORS WOULD SUGGEST THAT
MELISSA WAS NOW A TROPICAL CYCLONE. HOWEVER...THE AMSU DATA ALSO
REVEALED THAT THERE WAS STILL A STRATOSPHERIC CONNECTION TO THE
WARM CORE. THIS...PLUS THE LACK OF ANY DEEP CONVECTION NEAR THE
WELL-DEFINED LOW-LEVEL CENTER...ARGUES FOR KEEPING MELISSA A
SUBTROPICAL STORM. SINCE THE ASCAT PASSES MISSED THE WESTERN
SEMICIRCLE WHERE THE STRONGEST WINDS WERE LIKELY OCCURRING IN SOME
VIGOROUS CONVECTION...THE INTENSITY IS BEING MAINTAINED AT 55 KT
BASED ON A SUBTROPICAL SATELLITE CLASSIFICATION FROM TAFB...AND
EARLIER 53-56 KT AMSU INTENSITY ESTIMATES FROM CIRA AND CIMSS.

THE INITIAL MOTION ESTIMATE IS NOW 040/14 KT. MELISSA HAS FINALLY
MADE THE MUCH ANTICIPATED TURN TO THE NORTHEAST AHEAD OF A STRONG
COLD FRONT AND ASSOCIATED DEEP-LAYER TROUGH. NHC MODEL GUIDANCE IS
IN EXCELLENT AGREEMENT ON THE CYCLONE ACCELERATING NORTHEASTWARD
OVER THE NEXT 2-3 DAYS BEFORE TURNING NORTHWARD AND MERGING WITH A
FRONTAL SYSTEM IN 4-5 DAYS OVER THE FAR NORTH ATLANTIC. THE
OFFICIAL FORECAST TRACK WAS SHIFTED TO THE RIGHT OF THE PREVIOUS
ADVISORY TRACK AFTER 36 HOURS...AND LIES CLOSE TO THE MULTI-MODEL
CONSENSUS TVCA AND THE FLORIDA STATE SUPERENSEMBLE MODEL.

THE VERTICAL SHEAR HAS DROPPED SHARPLY TO ABOUT 7 KT...WHICH HAS
ALLOWED THE LOW- AND MID-/UPPER-LEVEL CIRCULATION CENTERS TO
FINALLY BECOME VERTICALLY ALIGNED. THE ONLY THING PREVENTING
MELISSA FROM MAKING THE TRANSITION TO A TROPICAL CYCLONE IS THE
LACK OF SIGNIFICANT DEEP CONVECTION ORGANIZING AROUND THE LOW-LEVEL
CENTER. HOWEVER...SHALLOW TO MODERATE CONVECTION HAS BEEN
DEVELOPING NEAR THE CENTER AND IN THE DRY SLOT IN THE EASTERN
SEMICIRCLE DURING THE PAST COUPLE OF HOURS...AND ONLY A SLIGHT
INCREASE IN THE DEPTH AND COVERAGE OF THE CONVECTION WOULD ALLOW
MELISSA TO STRENGTHEN SLIGHTLY AND ALSO QUICKLY TRANSITION TO A
TROPICAL STORM. THE CYCLONE IS EXPECTED TO MOVE OVER COOLER WATER
AND INTO A DRIER AND MORE STABLE AIRMASS IN 24-36 HOURS...WHICH
SHOULD INDUCE STEADY WEAKENING. BY 48 HOURS...INCREASING VERTICAL
WIND SHEAR SHOULD ENHANCE THE WEAKENING PROCESS AND ALSO CAUSE
MELISSA TO TRANSITION TO A POST-TROPICAL EXTRATROPICAL CYCLONE.
THE FORECAST CLOSELY FOLLOWS THE INTENSITY CONSENSUS MODEL ICON.

TRACK...INTENSITY... AND WIND RADII FORECASTS DURING THE
EXTRATROPICAL STAGE WERE COORDINATED WITH THE NOAA OCEAN PREDICTION
CENTER.

FORECAST POSITIONS AND MAX WINDS

INIT 19/2100Z 33.0N 53.7W 55 KT 65 MPH
12H 20/0600Z 34.9N 51.4W 60 KT 70 MPH
24H 20/1800Z 37.4N 46.7W 55 KT 65 MPH
36H 21/0600Z 40.1N 41.1W 50 KT 60 MPH
48H 21/1800Z 42.4N 35.4W 50 KT 60 MPH...POST-TROP/EXTRATROP
72H 22/1800Z 47.0N 26.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
96H 23/1800Z 53.5N 24.5W 40 KT 45 MPH...POST-TROP/EXTRATROP
120H 24/1800Z...DISSIPATED

$$
FORECASTER STEWART