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Tropical Storm NADINE (Text)

ZCZC MIATCDAT4 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM NADINE DISCUSSION NUMBER  39
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
1100 PM AST THU SEP 20 2012
 
SATELLITE IMAGES INDICATE THAT RELATIVELY DEEP CONVECTION HAS BEEN
INCREASING NORTHWEST OF THE CENTER OF NADINE DURING THE PAST
SEVERAL HOURS.  THE INCREASE IN CONVECTION...HOWEVER...IS LIKELY
RELATED TO BAROCLINIC INFLUENCES SINCE SURFACE OBSERVATIONS FROM
THE AZORES AND AN 2224 UTC ASCAT PASS INDICATE A FRONTAL ZONE
IMPINGING ON THE CORE OF THE TROPICAL CYCLONE.  THE INITIAL
INTENSITY ESTIMATE IS INCREASED TO 55 KT IN AGREEMENT WITH THE
EARLIER ASCAT DATA WHICH SHOWED SEVERAL 50 KT UNCONTAMINATED WIND
BARBS NORTHWEST OF THE CENTER.  THESE STRONGER WINDS ARE PRESUMABLY
RELATED TO AN INCREASE IN THE PRESSURE GRADIENT ON THE NORTHWEST
SIDE OF THE STORM.
 
SATELLITE AND MICROWAVE DATA SUGGEST THAT THE TRACK OF NADINE MAY BE
VEERING MORE SOUTHEASTERLY...BUT A LONGER-TERM INITIAL MOTION
ESTIMATE IS 120/08.  LARGE-SCALE MODELS ARE IN REASONABLY GOOD
AGREEMENT THAT NADINE WILL BE STEERED SOUTHEASTWARD AND SLOW DOWN
THROUGH 36-48 HOURS.  AFTER THIS TIME...THERE REMAINS A LARGE
SPREAD IN THE TRACK GUIDANCE.  AS IN THE LAST FEW RUNS...THE GFS
SHOWS MORE INTERACTION WITH THE MID- TO UPPER-LEVEL TROUGH PASSING
NORTH OF THE STORM WHICH RESULTS IN NADINE MOVING MORE RAPIDLY
EAST-NORTHEASTWARD. ON THE OTHER HAND...THE ECMWF/UK MET HAVE A
SLIGHTLY MORE PROGRESSIVE TROUGH WITH LESS AMPLITUDE AND EITHER
KEEP NADINE MEANDERING OR MOVING MORE SLOWLY TOWARD THE NORTHEAST
THAN THE GFS. SINCE THERE CONTINUES TO BE A STARK DICHOTOMY IN THE
GFS/ECMWF ENSEMBLE MEMBERS...ONLY A SLOW MOVEMENT TOWARD THE EAST
IS DEPICTED DURING THE 3 TO 5 DAY TIME FRAME.
 
GLOBAL MODELS SHOW NADINE ATTEMPTING TO OUTRUN THE BAROCLINIC ZONE
ENCROACHING ON IT DURING THE NEXT DAY OR TWO...BUT THIS MAY BE
OPTIMISTIC GIVEN THE CURRENT SEPARATION BETWEEN THESE TWO FEATURES.
THE TRANSITION TO A POST-TROPICAL LOW COULD NOW BE MORE
IMMINENT...AND POST-TROPICAL STATUS IS FORECAST TO OCCUR SOONER
THAN IN THE PREVIOUS ADVISORY. THEN AGAIN...NADINE COULD TEMPORARILY
FIND ITSELF SECLUDED FROM THE BAROCLINIC ENVIRONMENT...OVER
RELATIVELY WARMER WATERS...AND IN A MORE UNSTABLE ENVIRONMENT
DUE TO A STEEPENING OF LAPSE RATES. GIVEN THE CURRENT SATELLITE
APPEARANCE OF NADINE...THE LATTER POSSIBILITY IS TREATED AS A LOWER
PROBABILITY ALTERNATE SCENARIO.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0300Z 35.4N  28.0W   55 KT  65 MPH
 12H  21/1200Z 34.5N  27.1W   55 KT  65 MPH
 24H  22/0000Z 33.2N  26.1W   55 KT  65 MPH...POST-TROPICAL
 36H  22/1200Z 32.5N  25.1W   50 KT  60 MPH...POST-TROPICAL
 48H  23/0000Z 32.4N  24.3W   50 KT  60 MPH...POST-TROPICAL
 72H  24/0000Z 32.4N  24.0W   50 KT  60 MPH...POST-TROPICAL
 96H  25/0000Z 32.4N  23.9W   50 KT  60 MPH...POST-TROPICAL
120H  26/0000Z 32.4N  23.8W   50 KT  60 MPH...POST-TROPICAL
 
$$
FORECASTER KIMBERLAIN/BROWN
 
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