Tropical Storm NADINE

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TROPICAL STORM NADINE DISCUSSION NUMBER  31
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
1100 PM AST TUE SEP 18 2012
 
THE CONVECTION NEAR THE CENTER OF NADINE HAS DISSIPATED THIS EVENING
AND THE CYCLONE NOW HAS ONE RAGGED BAND OF CONVECTION OVER THE
NORTHERN PORTION OF THE CIRCULATION. DVORAK DATA T-NUMBERS HAVE
DECREASED AND A BLEND OF THE FINAL T- AND CI-NUMBERS YIELDS AN
INITIAL INTENSITY OF 45 KT. NADINE IS CURRENTLY OVER SSTS OF AROUND
25 DEGREES CELSIUS AND IT SHOULD MOVE OVER SLIGHTLY COOLER WATERS
DURING THE NEXT COUPLE OF DAYS. THE PREDICTED SLOW MOTION OF NADINE
COULD ALSO CAUSE SOME UPWELLING...WHICH IS LIKELY TO REDUCE THE
SSTS A LITTLE MORE. ONE WOULD EXPECT THE COOL WATER AND MODERATE
SOUTHWESTERLY SHEAR TO CAUSE NADINE TO WEAKEN. HOWEVER...MUCH OF
THE INTENSITY GUIDANCE SHOWS LITTLE CHANGE IN STRENGTH DURING THE
NEXT COUPLE OF DAYS. THE GLOBAL MODELS ACTUALLY PREDICT SOME
INCREASE IN WINDS OVER THE NORTHWESTERN PORTION OF THE CYCLONE AS A
LARGE HIGH PRESSURE SYSTEM BUILDS SOUTHEASTWARD DURING THE NEXT
COUPLE OF DAYS. AS A RESULT...THE NHC FORECAST CALLS FOR LITTLE
CHANGE IN INTENSITY FOR MOST OF THE FORECAST PERIOD. NADINE COULD
BECOME POST-TROPICAL IF IT LOSES MOST OF ITS DEEP CONVECTION DURING
THE FORECAST PERIOD...AND THERE IS GREAT UNCERTAINTY AS TO THE
TIMING OF WHEN THIS COULD OCCUR.

NADINE IS MOVING NORTH-NORTHEASTWARD AT ABOUT 6 KT. THE FORECAST
TRACK REMAINS A SIGNIFICANT CHALLENGE AS DIFFERENCES EXIST IN THE
MODELS AS TO HOW THE STORM WILL INTERACT WITH A LARGE MID-LATITUDE
TROUGH THAT AMPLIFIES OVER THE NORTHEASTERN ATLANTIC IN A COUPLE OF
DAYS. NADINE IS FORECAST SLOW DOWN AND MEANDER SOUTHWEST OF THE
AZORES DURING THE NEXT DAY OR SO. AFTER THAT TIME...THE TRACK
GUIDANCE DIFFERS ON WHETHER THE CYCLONE WILL MOVE SOUTHEASTWARD AND
THEN EASTWARD AROUND THE BASE OF THE TROUGH...OR TURN SOUTHWESTWARD
AROUND A STRONG DEEP-LAYER RIDGE OVER THE NORTH-CENTRAL ATLANTIC.
THE 12Z ECMWF SHOWED THE LATTER SCENARIO...BUT MOST OF THE OTHER
GUIDANCE HAS BEEN TRENDING TOWARD A FASTER EASTWARD SOLUTION. THE
NEW NHC TRACK FORECAST FAVORS THE EASTWARD SOLUTION AND IS A LITTLE
FASTER THAN THE PREVIOUS TRACK...BUT NOT AS FAST AS MUCH OF THE
GUIDANCE AND THE TVCA CONSENSUS. THIS MAINTAINS SOME CONTINUITY
WITH THE PREVIOUS TRACK AND SHOWS SOME RESPECT FOR THE ECMWF
SOLUTION.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/0300Z 35.8N  32.2W   45 KT  50 MPH
 12H  19/1200Z 36.5N  32.0W   45 KT  50 MPH
 24H  20/0000Z 36.9N  31.6W   45 KT  50 MPH
 36H  20/1200Z 36.4N  30.6W   45 KT  50 MPH
 48H  21/0000Z 35.3N  29.0W   45 KT  50 MPH
 72H  22/0000Z 34.4N  26.5W   45 KT  50 MPH...POST-TROPICAL
 96H  23/0000Z 34.0N  25.0W   45 KT  50 MPH...POST-TROPICAL
120H  24/0000Z 34.0N  24.0W   40 KT  45 MPH...POST-TROPICAL
 
$$
FORECASTER BROWN
 
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