Tropical Storm NADINE

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TROPICAL STORM NADINE DISCUSSION NUMBER  29
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
1100 AM AST TUE SEP 18 2012
 
THE STORM HAS BEEN MAINTAINING SOME...NOT MUCH...DEEP CONVECTION
NEAR AND JUST NORTH OF THE CENTER. THE CURRENT INTENSITY IS 50 KT
BASED ON A DVORAK CLASSIFICATION FROM TAFB. ALTHOUGH THE DYNAMICAL
GUIDANCE INDICATES QUITE A BIT OF SHEAR OVER NADINE DURING THE NEXT
FEW DAYS...THESE HIGHER-LATITUDE SYSTEMS ARE KNOWN TO BE MORE
RESILIENT TO SHEAR. THIS IS CONSISTENT WITH THE LATEST LGEM
GUIDANCE WHICH MORE OR LESS MAINTAINS THE CURRENT INTENSITY FOR THE
NEXT SEVERAL DAYS. AS INDICATED BELOW...NADINE IS NOT EXPECTED TO
MOVE MUCH FARTHER NORTH OVER THE PERIOD. THEREFORE IT IS NOT LIKELY
TO ENCOUNTER ENOUGH BAROCLINICITY TO UNDERGO AN EXTRATROPICAL
TRANSFORMATION. HOWEVER...SINCE THE SYSTEM IS MOVING OVER
MARGINALLY WARM WATERS IT COULD...AT SOME POINT...LOSE ENOUGH DEEP
CONVECTION SO THAT IT NO LONGER WOULD QUALIFY AS A TROPICAL
CYCLONE. THIS IS REFLECTED IN THE OFFICIAL FORECAST WHICH SHOWS
POST-TROPICAL STATUS BY DAY 3. HOWEVER...IT SHOULD BE NOTED THAT
THE SPECIFIC TIMING OF SUCH A TRANSITION IS HIGHLY UNCERTAIN.

THE TRACK FORECAST REMAINS COMPLICATED AS A HIGHLY ANOMALOUS
BLOCKING PATTERN IS FORECAST TO EVOLVE AT MID-TROPOSPHERIC LEVELS
OVER THE NORTH ATLANTIC. THE GFS AND ECMWF MODELS...HOWEVER...HAVE
COME INTO BETTER AGREEMENT IN THE LATTER PART OF THE FORECAST
PERIOD. THE GFS 3-5 DAY PREDICTIONS NOW SHOW NADINE...OR ITS
POST-TROPICAL COUNTERPART...BEING DRIVEN SOUTHWARD BY THE FLOW
BETWEEN AN INTENSE 500 MB TROUGH TO THE WEST OF EUROPE AND A VERY
STRONG ANTICYCLONE CENTERED NORTH OF 40N OVER THE CENTRAL ATLANTIC.
BY THE END OF THE PERIOD...THE GFS SHOWS THE CYCLONE MOVING
SOUTHWESTWARD ON THE SOUTHEASTERN PERIPHERY OF THE ANTICYCLONE. THE
ECMWF SHOWS A SIMILAR BEHAVIOR...BUT TAKES THE SYSTEM FARTHER WEST
AT DAYS 4 AND 5. THE OFFICIAL FORECAST SHIFTS THE SYSTEM SOUTHWARD
AT DAYS 3-5 BUT DOES NOT YET COMMIT TO THE WESTWARD TURN. THIS IS A
LITTLE SOUTH OF THE PREVIOUS FORECAST...BUT NOT AS FAR SOUTH AS THE
LATEST MODEL CONSENSUS.

FORECAST POSITIONS AND MAX WINDS
 
INIT  18/1500Z 34.4N  32.9W   50 KT  60 MPH
 12H  19/0000Z 35.4N  32.7W   50 KT  60 MPH
 24H  19/1200Z 36.4N  32.5W   50 KT  60 MPH
 36H  20/0000Z 36.7N  32.0W   50 KT  60 MPH
 48H  20/1200Z 36.5N  31.0W   50 KT  60 MPH
 72H  21/1200Z 35.5N  28.5W   50 KT  60 MPH...POST-TROPICAL
 96H  22/1200Z 34.0N  28.0W   50 KT  60 MPH...POST-TROPICAL
120H  23/1200Z 33.0N  28.0W   45 KT  50 MPH...POST-TROPICAL
 
$$
FORECASTER PASCH
 
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