328  
WTNT44 KNHC 070236  
TCDAT4  
 
TROPICAL STORM RINA DISCUSSION NUMBER 4  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192017  
1100 PM AST MON NOV 06 2017  
 
DESPITE THE LOW-LEVEL CENTER BEING EXPOSED TO THE WEST OF THE DEEP  
CONVECTION, A PAIR OF ASCAT-A AND ASCAT-B PASSES BETWEEN 00Z AND  
01Z SHOWED AN AREA OF 30-35 KT WINDS EAST OF THE CYCLONE'S CENTER.  
BASED ON THE ASCAT DATA, THE DEPRESSION IS UPGRADED TO A TROPICAL  
STORM WITH THE INITIAL INTENSITY SET AT 35 KT. THE RATHER  
DISORGANIZED CLOUD PATTERN IS CONSISTENT WITH THE APPROXIMATELY 20  
KT OF WESTERLY SHEAR ANALYZED BY UW-CIMSS AND THE SHIPS MODEL. THE  
ENVIRONMENT IS ONLY EXPECTED TO BE MARGINALLY CONDUCIVE FOR  
INTENSIFICATION VIA DIABATIC PROCESSES, WITH THE SHEAR EXPECTED TO  
REMAIN NEAR 20 KT AND THE SSTS COOLING ALONG THE FORECAST TRACK.  
AFTER 24 TO 36 HOURS, COOLING UPPER-TROPOSPHERIC TEMPERATURES AND  
INCREASING UPPER-LEVEL DIVERGENCE SUGGEST THAT RINA WILL MAINTAIN  
ITS INTENSITY AS IT BEGINS EXTRATROPICAL TRANSITION, WHICH SHOULD BE  
COMPLETE BETWEEN BY 72 HOURS. THE NEW NHC INTENSITY FORECAST IS  
SIMILAR TO THE PREVIOUS ONE AND IS CLOSE TO THE HWRF AND HCCA AIDS.  
THE OFFICIAL FORECAST SHOWS RINA DISSIPATING BY 96 HOURS IN  
AGREEMENT WITH GLOBAL MODEL FIELDS.  
 
THE EXPOSED LOW-LEVEL CENTER AND ASCAT PASSES RESULT IN HIGH  
CONFIDENCE IN THE INITIAL POSITION, AND RINA HAS BEGUN TO MOVE  
MORE STEADILY, WITH AN INITIAL MOTION ESTIMATE OF 010/06. RINA  
SHOULD CONTINUE TO ACCELERATE NORTHWARD AND NORTH-NORTHEASTWARD  
DURING THE NEXT 36 TO 48 HOURS BETWEEN A MID-LEVEL RIDGE TO THE EAST  
AND AN UPPER-LEVEL TROUGH TO THE WEST. AFTER 48 HOURS, RINA IS  
FORECAST TO ACCELERATE FURTHER AS IT ENTERS THE MID-LATITUDE  
WESTERLIES. THE TRACK MODEL GUIDANCE HAS SHIFTED LEFT THIS CYCLE,  
AND THE ALONG-TRACK SPREAD IS QUITE LARGE BY 72 HOURS, WITH THE GFS  
MORE THAN 500 N MI NORTHEAST OF THE ECMWF AT THAT TIME. THE NEW NHC  
TRACK FORECAST HAS BEEN ADJUSTED WESTWARD AND A BIT SLOWER, AND LIES  
CLOSE TO A BLEND OF THE GFS AND ECMWF SOLUTIONS TO THE EAST OF THE  
TVCA MULTI-MODEL CONSENSUS. CONFIDENCE IN THE DETAILS OF THE TRACK  
FORECAST IS LOWER THAN USUAL GIVEN THE LARGE MODEL SPREAD.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 07/0300Z 30.4N 49.9W 35 KT 40 MPH  
12H 07/1200Z 32.4N 49.6W 40 KT 45 MPH  
24H 08/0000Z 35.4N 49.0W 45 KT 50 MPH  
36H 08/1200Z 39.0N 48.0W 45 KT 50 MPH  
48H 09/0000Z 42.3N 46.2W 45 KT 50 MPH  
72H 10/0000Z 51.0N 36.0W 40 KT 45 MPH...POST-TROP/EXTRATROP  
96H 11/0000Z...DISSIPATED  
 

 
FORECASTER BRENNAN  
 
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