352  
WTNT44 KNHC 080851  
TCDAT4  
 
TROPICAL STORM RINA DISCUSSION NUMBER 9  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192017  
500 AM AST WED NOV 08 2017  
 
SATELLITE IMAGERY OVER THE PAST 6 HOURS INDICATES THAT RINA HAS  
TAKEN ON A TIGHT COMMA-CLOUD APPEARANCE, MORE INDICATIVE OF A  
SUB-TROPICAL CYCLONE THAN A TROPICAL SYSTEM. ALTHOUGH AN EYE-LIKE  
FEATURE HAS RECENTLY DEVELOPED, IT APPEARS TO BE TILTED ABOUT 20-30  
NMI TO THE NORTH OF THE LOW-LEVEL CENTER. DVORAK SATELLITE INTENSITY  
ESTIMATES WERE ST3.0/45-50 KT FROM TAFB AND T3.5 FROM SAB. DATA  
FROM A LATE-ARRIVING, PARTIAL ASCAT-B SCATTEROMETER PASS AT 0029Z  
INDICATED 46-KT SURFACE WINDS WELL EAST OF THE CENTER, AND THE CLOUD  
PATTERN HAS IMPROVED SINCE THAT TIME. BASED THESE DATA, THE  
INTENSITY OF RINA HAS BEEN INCREASED TO 50 KT.  
 
RINA IS MOVING NORTHWARD OR 010/17 KT. RINA IS LOCATED JUST NORTH  
OF THE AXIS OF A DEEP-LAYER RIDGE, WHICH IS LOCATED TO THE EAST OF  
THE CYCLONE. AS A RESULT, A NORTHWARD TO NORTH-NORTHEASTWARD MOTION  
IS EXPECTED FOR THE NEXT 12-24 H. THEREAFTER, A SHORTWAVE TROUGH  
SITUATED TO THE SOUTHWEST OF RINA SHOULD INDUCE ACCELERATION TOWARD  
THE NORTHEAST ON THURSDAY, FOLLOWED BY A MORE RAPID MOTION OF 30-35  
KT BY THURSDAY NIGHT AND FRIDAY AS WESTERLY FLOW ON THE EAST SIDE OF  
A DEEP-LAYER TROUGH CAPTURES THE SYSTEM. THE LATEST NHC MODEL  
GUIDANCE HAS SHIFTED TO THE WEST SOME, BUT THE OFFICIAL FORECAST  
TRACK HAS ONLY BEEN NUDGED SLIGHTLY IN THAT DIRECTION DUE TO A  
DISTINCT WESTWARD BIAS NOTED IN THE MODEL GUIDANCE DURING THE PAST  
48 HOURS.  
 
ALTHOUGH SOME SIGHT STRENGTHENING COULD OCCUR DURING THE NEXT 6-12  
HOURS, THE OVERALL INTENSITY TREND IS FORECAST TO CHANGE LITTLE  
DURING THE PERIOD DUE TO THE COMBINATION OF COLD SSTS OF LESS THAN  
20 DEG C BY 18 H AND INCREASING VERTICAL WIND SHEAR OF MORE THAN 35  
KT BY 36 HOURS. BY 24 H, RINA SHOULD BECOME A POST-TROPICAL CYCLONE  
OVER THE COLD WATERS OF THE FAR NORTH ATLANTIC AND BECOME  
EXTRATROPICAL AND MERGE WITH A FRONT BY 48-72 H.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 08/0900Z 37.1N 48.4W 50 KT 60 MPH  
12H 08/1800Z 39.7N 47.7W 50 KT 60 MPH  
24H 09/0600Z 43.6N 45.7W 50 KT 60 MPH...POST-TROPICAL  
36H 09/1800Z 48.7N 40.6W 50 KT 60 MPH...POST-TROP/EXTRATROP  
48H 10/0600Z 53.3N 32.0W 45 KT 50 MPH...POST-TROP/EXTRATROP  
72H 11/0600Z...DISSIPATED  
 

 
FORECASTER STEWART  
 
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