378 
 WTNT44 KNHC 290858
 TCDAT4
  
 TROPICAL STORM NADINE DISCUSSION NUMBER  67
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
 500 AM AST SAT SEP 29 2012
  
 IT APPEARS THAT VERTICAL SHEAR IS STARTING TO WEAKEN NADINE. ALMOST
 ALL OF DEEP CONVECTION IS NOW LOCATED NORTH OF THE CENTER...AND
 MICROWAVE IMAGES SHOW AN INCREASING SEPARATION BETWEEN THE LOW AND
 MID-LEVEL CENTERS.  WITH THE DEGRADATION IN THE CLOUD PATTERN...THE
 INITIAL WIND SPEED IS REDUCED TO 60 KT...A BLEND OF THE T AND CI
 NUMBERS FROM TAFB AND SAB.  WHILE THE SHEAR IS EXPECTED TO REMAIN
 MODERATE OVER THE NEXT DAY OR TWO...SSTS SHOULD DECREASE AS NADINE
 GAINS LATITUDE.  NORMALLY THIS PATTERN WOULD CALL FOR ADDITIONAL
 WEAKENING...BUT UPPER-LEVEL TEMPERATURES ARE ALSO FORECAST TO
 COOL...WHICH COULD HELP THE CYCLONE KEEP ITS STRENGTH.  VERY LITTLE
 CHANGE WAS MADE TO THE PREVIOUS FORECAST AFTER ACCOUNTING FOR THE
 SLIGHTLY WEAKER INITIAL STATE. 
 
 A SERIES OF MICROWAVE PASSES GIVE A CONFIDENT INITIAL MOTION OF
 340/10.  THIS GENERAL MOTION IS EXPECTED FOR A DAY OR SO UNTIL
 STEERING CURRENTS BREAK DOWN TO THE NORTHWEST OF A SUBTROPICAL
 RIDGE.  MODEL GUIDANCE OVERNIGHT IS GENERALLY SHOWING MORE
 INTERACTION BETWEEN NADINE AND A MID- TO UPPER-LEVEL TROUGH OVER
 THE CENTRAL ATLANTIC...WHICH CAUSES NADINE TO UNDERGO A CYCLONIC
 LOOP IN 2 TO 4 DAY TIME FRAME.  THE ECMWF MODEL HAS BEEN FAIRLY
 CONSISTENTLY SHOWING THIS LOOP...AND NOW MOST OF THE MODELS SHOW IT
 BESIDES THE GFS AND GFS ENSEMBLE.  THE OFFICIAL FORECAST IS TRENDED
 TOWARD THE MODEL CONSENSUS...SHOWING LITTLE CHANGE IN THE FIRST DAY
 OR SO...AND A SMALL SOUTHWARD LOOP IN THE MEDIUM RANGE.  A RATHER
 LARGE TROUGH IS EXPECTED TO DEVELOP OVER THE NORTHERN ATLANTIC
 OCEAN AT BY DAY 5...WHICH WILL HOPEFULLY CAUSE NADINE TO FINALLY
 LEAVE THE SUBTROPICS.  MOST OF THE MODELS ARE NOW SHOWING THE STORM
 BECOMING POST-TROPICAL BY DAY 5 DUE TO COLDER WATERS AND STRONGER
 SHEAR...BUT GIVEN PAST EXPERIENCE...I HAVE ELECTED NOT TO SHOW THIS
 TRANSITION YET.  
  
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  29/0900Z 31.9N  35.9W   60 KT  70 MPH
  12H  29/1800Z 33.5N  36.5W   60 KT  70 MPH
  24H  30/0600Z 35.4N  37.2W   60 KT  70 MPH
  36H  30/1800Z 36.4N  37.8W   60 KT  70 MPH
  48H  01/0600Z 36.2N  38.0W   55 KT  65 MPH
  72H  02/0600Z 35.5N  37.5W   50 KT  60 MPH
  96H  03/0600Z 35.5N  36.5W   45 KT  50 MPH
 120H  04/0600Z 37.5N  33.5W   40 KT  45 MPH
  
 $$
 FORECASTER BLAKE