000
WTNT44 KNHC 130844
TCDAT4
 
TROPICAL STORM NADINE DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL142012
500 AM AST THU SEP 13 2012

THE OVERALL APPEARANCE OF NADINE IN INFRARED IMAGERY HAS CHANGED
LITTLE DURING THE PAST SEVERAL HOURS.  A RECENT AMSU IMAGE SHOWS A
MID-LEVEL EYE DISPLACED TO THE EAST-NORTHEAST OF OF THE APPARENT
LOW-LEVEL CENTER.  THIS MAY BE DUE TO 10-20 KT OF SOUTHWESTERLY
VERTICAL WIND SHEAR DIAGNOSED BY THE SHIPS MODEL AND ANALYSES FROM
CIMSS.  SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM TAFB AND
SAB...AND A ASCAT OVERPASS RECEIVED JUST AFTER THE PREVIOUS
ADVISORY SUPPORTS WINDS OF AT LEAST 55-60 KT.  BASED ON THESE
DATA...THE INITIAL INTENSITY REMAINS 60 KT.  THE INITIAL WIND RADII
HAVE BEEN REVISED A LITTLE BASED ON THE ASCAT DATA.

THE INITIAL MOTION IS 305/14.  NADINE IS MOVING TOWARD A BREAK IN
THE SUBTROPICAL RIDGE...AND DURING THE NEXT 48 HR THE GUIDANCE IS
IN GOOD AGREEMENT THAT THE CYCLONE SHOULD RECURVE AROUND THE
WESTERN END OF THE RIDGE INTO THE WESTERLIES.  THIS PART OF THE
FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK.  AFTER 48 HR...THE
GUIDANCE BECOMES SERIOUSLY DIVERGENT.  THE GFDL FORECASTS A
NORTHWARD MOVEMENT TOWARD NEWFOUNDLAND...WHILE THE GFS AND ECMWF
FORECAST A GENERALLY EASTWARD MOTION.  THE OTHER DYNAMICAL AND
CONSENSUS MODELS ARE SPREAD BETWEEN THESE EXTREMES.  THIS SPREAD
SEEMS TO RESULT FROM HOW THE MODELS HANDLE THE INTERACTIONS BETWEEN
NADINE...A DEEP-LAYER LOW FORECAST TO BE TO ITS EAST...AND A
MID/UPPER-LEVEL TROUGH FORECAST TO BE IN THE WESTERLIES NEAR
NEWFOUNDLAND.  AT THIS TIME...IT IS NOT CLEAR WHICH OF THE MODELS
HAS THE BEST HANDLE ON THESE INTERACTIONS.  THEREFORE...THE
FORECAST TRACK IS NUDGED ONLY SLIGHTLY NORTHWARD...AND IT LIES NEAR
THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE IN BEST AGREEMENT WITH
THE GFS...ECMWF...AND FLORIDA STATE SUPERENSEMBLE.  ADDITIONAL
ADJUSTMENTS OF THIS PART OF THE TRACK MAY BE NECESSARY WHEN THE
MODELS COME INTO BETTER AGREEMENT.

THE WINDOW FOR NADINE TO STRENGTHEN MAY BE CLOSING.  IN ADDITION TO
THE CURRENT INCREASE IN SHEAR...WATER VAPOR IMAGERY SHOWS
MID/UPPER-LEVEL DRY AIR IMPINGING ON THE CYCLONE FROM THE
SOUTHWEST.  DESPITE THE LESS FAVORABLE ENVIRONMENT...MOST OF THE
INTENSITY GUIDANCE SHOWS SOME STRENGTHENING DURING THE NEXT 24
HR...AND THE NEW FORECAST CALLS FOR NADINE TO BECOME A HURRICANE
DURING THAT TIME.  AFTER 24 HR...THE DYNAMICAL MODELS ARE IN GOOD
AGREEMENT THAT NADINE WILL ENCOUNTER AT LEAST 20-30 KT OF WESTERLY
SHEAR...WHICH SHOULD CAUSE SOME WEAKENING.  THERE ARE HINTS THAT
THE SHEAR COULD SUBSIDE AFTER 72 HR...BUT DUE TO THE UNCERTAINTY OF
HOW NADINE WILL INTERACT WITH THE OTHER SYSTEMS IN THE WESTERLIES
THE FORECAST WILL NOT SHOW STRENGTHENING DURING THAT PERIOD.  THE
NEW FORECAST IS SIMILAR TO...BUT LESS INTENSE THAN...THE PREVIOUS
FORECAST USING A BLEND OF THE SHIPS...LGEM...AND INTENSITY
CONSENSUS MODELS. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0900Z 21.5N  51.3W   60 KT  70 MPH
 12H  13/1800Z 23.1N  52.7W   65 KT  75 MPH
 24H  14/0600Z 25.4N  54.0W   70 KT  80 MPH
 36H  14/1800Z 27.6N  54.2W   70 KT  80 MPH
 48H  15/0600Z 29.3N  53.3W   65 KT  75 MPH
 72H  16/0600Z 31.5N  49.5W   60 KT  70 MPH
 96H  17/0600Z 32.5N  44.0W   60 KT  70 MPH
120H  18/0600Z 34.0N  38.0W   60 KT  70 MPH
 
$$
FORECASTER BEVEN