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Tropical Storm NADINE


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TROPICAL STORM NADINE DISCUSSION NUMBER  30
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
500 PM AST TUE SEP 18 2012
 
NADINE CONTINUES TO MAINTAIN SOME DEEP CONVECTION NEAR THE CENTER
AND OVER THE NORTHERN SEMICIRCLE.  ALTHOUGH DVORAK DATA T-NUMBERS
HAVE DECREASED SOMEWHAT...AN EARLIER ASCAT PASS OVER THE SYSTEM
SUPPORTED AN INTENSITY OF 50 KT.  SINCE THE CONVECTION HAS NOT
CHANGED MUCH SINCE THAT OVERPASS...THE ADVISORY INTENSITY WILL
REMAIN AT 50 KT.  BASED ON THE FORECAST TRACK...NADINE SHOULD NOT
MOVE OVER MUCH COOLER WATERS...AND THESE HIGHER-LATITUDE CYCLONES
TEND TO BE MORE RESILIENT TO VERTICAL SHEAR.  THE OFFICIAL
INTENSITY FORECAST IS THE SAME AS THE PREVIOUS ONE AND IS VERY
SIMILAR TO THE STATISTICAL-DYNAMICAL LGEM GUIDANCE.  THE SYSTEM
COULD BECOME POST-TROPICAL IF IT LOSES MOST OF ITS DEEP CONVECTION
DURING THE FORECAST PERIOD...AND THE OFFICIAL FORECAST SHOWS THIS
TRANSITION OCCURRING BY DAY 4.  HOWEVER THERE IS GREAT UNCERTAINTY
AS TO THE SPECIFIC TIMING OF THIS EVENT AND NADINE COULD LOSE
TROPICAL CHARACTERISTICS MUCH SOONER...OR MUCH LATER.
 
THE STORM APPEARS TO HAVE TURNED TOWARD THE NORTH-NORTHEAST AND THE
MOTION IS NEAR 030/7.  FORECASTING THE TRACK OF THIS CYCLONE
CONTINUES TO BE A GREAT CHALLENGE.  A HIGHLY ANOMALOUS BLOCKING
PATTERN IS PREDICTED BY THE GLOBAL MODELS TO DEVELOP AROUND NADINE
IN THE LATTER PART OF THE FORECAST PERIOD...LEADING TO A STRONG
MID-LEVEL ANTICYCLONE OVER THE NORTH-CENTRAL ATLANTIC AND AN
INTENSE TROUGH/CYCLONE TO THE EAST OF THIS HIGH.  THE TRACK
GUIDANCE MODELS HAVE BEEN FLIP-FLOPPING ON WHETHER NADINE...OR ITS
POST-TROPICAL COUNTERPART...WILL BE STEERED AROUND THE SOUTHEASTERN
PERIPHERY OF THE HIGH OR BE DRAWN EASTWARD BY THE TROUGH IN 3-5
DAYS.  THE LATEST MODEL RUNS ARE FAVORING THE LATTER
SCENARIO...ALTHOUGH THE NEW ECMWF FORECAST SHOWS THE INTENSE
TROUGH/CYCLONE ABSORBING NADINE WITHIN 3-4 DAYS.  THE OFFICIAL
TRACK FORECAST HAS BEEN SHIFTED TO THE EAST OF THE PREVIOUS ONE
BUT...IN AN ATTEMPT TO MAINTAIN CONTINUITY...IS NOT NEARLY AS FAR
EAST AS THE NEW MODEL CONSENSUS.

THE TROPICAL STORM FORCE WIND RADII WERE ADJUSTED OUTWARD BASED ON
THE AFOREMENTIONED ASCAT PASS.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/2100Z 35.2N  32.6W   50 KT  60 MPH
 12H  19/0600Z 36.2N  32.3W   50 KT  60 MPH
 24H  19/1800Z 36.9N  32.1W   50 KT  60 MPH
 36H  20/0600Z 36.8N  31.2W   50 KT  60 MPH
 48H  20/1800Z 36.1N  30.0W   50 KT  60 MPH
 72H  21/1800Z 34.8N  28.0W   50 KT  60 MPH
 96H  22/1800Z 34.0N  27.0W   50 KT  60 MPH...POST-TROPICAL
120H  23/1800Z 33.5N  25.5W   45 KT  50 MPH...POST-TROPICAL
 
$$
FORECASTER PASCH
 
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