####018001602####
WTNT43 KNHC 070857

TCDAT3

TROPICAL STORM HANNA DISCUSSION NUMBER  42

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082008

500 AM EDT SUN SEP 07 2008

 

THE CLOUD PATTERN ASSOCIATED WITH HANNA IS SPREADING OUT WELL AHEAD

OF THE SURFACE CENTER...WITH THE CLOSEST DEEP CONVECTION NOW

DISPLACED ABOUT 125 NMI TO THE NORTH AND NORTHEAST.  THE

CIRCULATION IS ALSO CLOSE TO...BUT NOT QUITE ENTANGLED WITH...A

FRONTAL BOUNDARY.  BASED ON THE LOSS OF CONVECTION NEAR THE

CORE...HANNA IS NO LONGER CONSIDERED TO BE A TROPICAL CYCLONE AND

THIS WILL BE THE LAST ADVISORY.



MAXIMUM WINDS ARE ESTIMATED TO BE 45 KT BASED ON SHIP REPORTS...AND

HANNA IS EXPECTED TO REMAIN A VIGOROUS EXTRATROPICAL CYCLONE DURING

ITS PASSAGE OVER THE NORTH ATLANTIC.  THE OFFICIAL FORECAST IS IN

GOOD AGREEMENT WITH THE GFS.

 

FUTURE INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS

FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE OCEAN PREDICTION

CENTER...UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.



 

FORECAST POSITIONS AND MAX WINDS

 

INITIAL      07/0900Z 42.6N  70.0W    45 KT...EXTRATROPICAL

 12HR VT     07/1800Z 45.4N  64.5W    45 KT...EXTRATROPICAL

 24HR VT     08/0600Z 48.4N  57.1W    45 KT...EXTRATROPICAL

 36HR VT     08/1800Z 50.0N  50.0W    45 KT...EXTRATROPICAL

 48HR VT     09/0600Z 51.0N  43.0W    45 KT...EXTRATROPICAL

 72HR VT     10/0600Z 53.5N  27.0W    45 KT...EXTRATROPICAL

 96HR VT     11/0600Z 58.0N  16.0W    40 KT...EXTRATROPICAL

120HR VT     12/0600Z...ABSORBED WITHIN EXTRATROPICAL LOW

 

$$

FORECASTER FRANKLIN

 ####018002000####
WTPZ43 KNHC 070857

TCDEP3

TROPICAL STORM LOWELL DISCUSSION NUMBER   2

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP132008

200 AM PDT SUN SEP 07 2008

 

MICROWAVE PASSES SUGGEST THAT THE CENTER OF LOWELL IS A LITTLE

NORTHEAST OF EARLIER ESTIMATES...NEAR THE NORTHEASTERN EDGE OF A

MASS OF CONVECTION THAT IS VERY COLD BUT RELATIVELY SHAPELESS.  THE

SYSTEM IS EXPERIENCING NORTHEASTERLY SHEAR OF ABOUT 20 KT...BUT

THIS SHEAR IS FORECAST TO LESSEN SOMEWHAT OVER THE NEXT 24-36

HOURS.  THE GFDL SHOWS LITTLE DEVELOPMENT...BUT THE HWRF AND SHIPS

MODELS BRING LOWELL UP TO ABOUT 60 KT AND THE OFFICIAL FORECAST

FOLLOWS THE LATTER TWO MODELS.  NEAR THE END OF THE FORECAST PERIOD

COOLER WATERS AND SOUTHWESTERLY SHEAR ARE EXPECTED TO INDUCE

WEAKENING.



LOWELL IS CURRENTLY MOVING AROUND THE PERIPHERY OF A SUBTROPICAL

RIDGE EXTENDING WESTWARD FROM MEXICO.  THE MODEL GUIDANCE HAS

CHANGED SUBSTANTIALLY WITH THE 00Z RUNS...WITH ALL THE DYNAMICAL

MODELS NOW SHOWING A MID- TO UPPER LEVEL TROUGH EXTENDING SOUTHWARD

FROM CALIFORNIA THAT TURNS LOWELL NORTHWARD AND NORTHEASTWARD BY DAY

THREE.  IN FACT...THE GFDL AND ECMWF TURN LOWELL SO SHARPLY THAT IT

RECURVES SOUTH OF THE BAJA CALIFORNIA PENINSULA.  THE OFFICIAL

FORECAST IS ADJUSTED TO THE RIGHT OF THE PREVIOUS ADVISORY BUT

STILL LIES ON THE EXTREME LEFT OF THE GUIDANCE ENVELOPE.  THERE ARE

SOME HINTS IN THE MODELS THAT THE LOW AND MID-LEVEL CIRCULATIONS

COULD SEPARATE BY DAY THREE...AND THIS LOWERS CONFIDENCE IN THE

LONGER TERM TRACK FORECAST. 



 

FORECAST POSITIONS AND MAX WINDS

 

INITIAL      07/0900Z 16.6N 107.2W    35 KT

 12HR VT     07/1800Z 17.3N 108.6W    40 KT

 24HR VT     08/0600Z 18.2N 110.5W    50 KT

 36HR VT     08/1800Z 18.7N 112.0W    60 KT

 48HR VT     09/0600Z 19.4N 113.4W    60 KT

 72HR VT     10/0600Z 20.5N 114.5W    55 KT

 96HR VT     11/0600Z 21.5N 115.0W    45 KT

120HR VT     12/0600Z 22.5N 114.5W    35 KT

 

$$

FORECASTER FRANKLIN