Tropical Storm NADINE

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TROPICAL STORM NADINE DISCUSSION NUMBER  60
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
1100 AM AST THU SEP 27 2012

SATELLITE IMAGERY SHOWS THAT THE CONVECTION ASSOCIATED WITH NADINE
HAS MOVED CLOSER TO THE CIRCULATION CENTER.  HOWEVER...THE OVERALL
CONVECTIVE PATTERN IS A LITTLE RAGGED AT THIS TIME.  SATELLITE
INTENSITY ESTIMATES FROM TAFB AND SAB ARE UNCHANGED SINCE 6 HR
AGO...SO THE INITIAL INTENSITY REMAINS 50 KT.  THE CIRRUS OUTFLOW
IS FAIR IN THE NORTHERN SEMICIRCLE AND POOR ELSEWHERE.

NADINE HAS TURNED WEST-SOUTHWESTWARD DURING THE PAST SEVERAL HOURS
WITH THE INITIAL MOTION NOW 240/6.  THE STORM IS ON THE SOUTH SIDE
OF A DEEP-LAYER RIDGE...WHICH IS FORECAST TO MOVE EASTWARD DURING
THE NEXT 48-72 HR.  THIS WILL ALLOW NADINE TO TURN NORTHWESTWARD
AND NORTHWARD AS IT MOVES BETWEEN THE RIDGE AND A MID/UPPER-LEVEL
LOW CURRENTLY SEEN IN WATER VAPOR IMAGERY NEAR 29N48W.  THE TRACK
GUIDANCE IS IN GOOD AGREEMENT DURING THIS PART OF THE FORECAST
PERIOD.  AFTER THAT...THE GUIDANCE BECOMES VERY DIVERGENT.  THE
GFS...GFS ENSEMBLE MEAN...GFDL...AND HWRF FORECAST NADINE TO MOVE
SLOWLY EASTWARD TO NORTHEASTWARD ALONG THE SOUTHERN EDGE OF THE
WESTERLIES AS A TROUGH PASSES NORTH OF THE STORM.  THE UKMET...
ECMWF...CANADIAN...AND NOGAPS FORECAST A RIDGE TO BUILD NORTH AND
NORTHWEST OF NADINE IN THE WAKE OF THE WESTERLY TROUGH...WHICH
WOULD STEER THE STORM BACK TOWARD THE SOUTH OR SOUTHWEST.  THE
TRACK FORECAST CONTINUES TO SPLIT THE DIFFERENCE BETWEEN THESE
EXTREMES AND SHOWS A SLOW MOTION AT 96-120 HR.  THE NEW FORECAST
TRACK LIES NEAR THE VARIOUS CONSENSUS MODELS THROUGH 72 HR...AFTER
WHICH IT LIES WEST OF THE CONSENSUS MODELS.

THE GLOBAL MODELS FORECAST NADINE TO INTERACT WITH THE
MID/UPPER-LEVEL LOW NEAR 29N48W DURING THE FORECAST PERIOD...WITH
THE TWO SYSTEMS POSSIBLY MERGING BY 96-120 HR.  IN ADDITION...SMALL
SHORTWAVE TROUGHS ROTATING AROUND THE LOW COULD ALSO INTERACT WITH
THE STORM.  WHILE THE GLOBAL MODELS FORECAST INCREASING UPPER-LEVEL
WINDS NEAR NADINE...IT IS POSSIBLE THAT THE SHORTWAVE TROUGHS COULD
PARTLY SHIELD NADINE FROM THE RESULTING SHEAR.  THE STATISTICAL
INTENSITY GUIDANCE IS FORECASTING A STRONGER STORM THAN IT DID
DURING THE LAST ADVISORY CYCLE...WITH THE SHIPS AND LGEM MODELS NOW
5-10 KT HIGHER THAN THEY WERE 6 HR AGO.  DUE TO THE UNCERTAINTY IN
THE AMOUNT OF SHEAR...AND THE LIKELIHOOD THAT NADINE WILL MOVE OVER
COOLER SEA SURFACE TEMPERATURES AFTER 36 HR...THE NEW INTENSITY
FORECAST CONSERVATIVELY STAYS CLOSE TO THE PREVIOUS FORECAST.  THE
NEW FORECAST IS STRONGER THAN THE FLORIDA STATE SUPERENSEMBLE...BUT
IS WEAKER THAN SHIPS...LGEM...AND THE INTENSITY CONSENSUS.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/1500Z 28.7N  32.4W   50 KT  60 MPH
 12H  28/0000Z 28.6N  33.4W   55 KT  65 MPH
 24H  28/1200Z 29.0N  34.5W   55 KT  65 MPH
 36H  29/0000Z 30.1N  35.3W   55 KT  65 MPH
 48H  29/1200Z 31.5N  35.9W   55 KT  65 MPH
 72H  30/1200Z 34.5N  36.5W   50 KT  60 MPH
 96H  01/1200Z 35.5N  37.0W   50 KT  60 MPH
120H  02/1200Z 36.0N  37.0W   45 KT  50 MPH
 
$$
FORECASTER BEVEN
 
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