Tropical Storm ROSA

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TROPICAL STORM ROSA DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172012
200 AM PDT THU NOV 01 2012
 
THE STRUCTURE OF ROSA HAS ESSENTIALLY BEEN UNCHANGED FOR AT LEAST
THE LAST 24 HOURS AS MICROWAVE IMAGES CONTINUE TO SHOW THE
LOW-LEVEL CENTER ON THE WESTERN EDGE OF THE DEEP CONVECTION. 
CURRENT INTENSITY ESTIMATES ARE 45 KT FROM SAB AND 55 KT FROM TAFB
WHILE THE UW-CIMSS ADT ESTIMATE IS BETWEEN 50 AND 55 KT.  THE
INTENSITY IS HELD AT 50 KT BASED ON THESE DATA.

THERE HAS BEEN A NOTICEABLE SHIFT IN THE TRACK GUIDANCE...ALTHOUGH
IN THE GRAND SCHEME OF THINGS IT IS NOT VERY SIGNIFICANT SINCE ROSA
IS NOT EXPECTED TO GET VERY FAR DURING NEXT 3 DAYS.  THE CURRENT
MOTION ESTIMATE IS 260/2 KT.  ROSA IS LOCATED IN A WEAK STEERING
REGIME AT THE MOMENT...BUT IT APPEARS AS THOUGH A MID-LEVEL
ANTICYCLONE TO THE WEST WILL EXERT JUST ENOUGH INFLUENCE TO CAUSE
ROSA TO DRIFT SOUTHWESTWARD DURING THE NEXT COUPLE OF DAYS.  BY DAY
3...THE GLOBAL MODELS INDICATE THAT A DEEP-LAYER TROUGH OR CUTOFF
LOW WILL DEVELOP JUST TO THE WEST OF THE BAJA PENINSULA...AND THAT
FEATURE SHOULD CAUSE ROSA TO TURN TOWARD THE NORTH-NORTHWEST AND
MOVE A LITTLE FASTER BY DAY 5.  THE DETERMINISTIC GFS CONTINUES TO
BE THE EASTERNMOST OUTLIER...BUT ITS ENSEMBLE MEAN AND ABOUT 3/4 OF
THE ENSEMBLE MEMBERS ARE ON THE WEST SIDE OF THE PACK.  THE UPDATED
NHC TRACK FORECAST THEREFORE STILL FAVORS A MORE WESTERN
SOLUTION...AND IT ENDS UP IN THE VICINITY OF THE ECMWF AND TVCE
MODEL CONSENSUS BY DAY 5.

WITH THE SOUTHWARD MOTION FORECAST DURING THE NEXT COUPLE OF
DAYS...ROSA MAY BE ABLE TO ESCAPE THE STRONG UPPER-LEVEL WINDS TO
ITS NORTH FOR A LITTLE WHILE LONGER.  THE INTENSITY MODELS APPEAR
TO BE RESPONDING TO THIS AND ARE UNANIMOUS IN WEAKENING ROSA AT A
SLOWER RATE DURING THE FIRST 48 HOURS...WHICH IS REFLECTED IN THE
OFFICIAL FORECAST.  INCREASING SOUTHWESTERLY SHEAR SHOULD BE
UNAVOIDABLE AFTER 48 HOURS...AND ROSA IS STILL EXPECTED TO WEAKEN
TO A TROPICAL DEPRESSION BY DAY 3 AND A REMNANT LOW BY DAY 4.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0900Z 14.1N 118.3W   50 KT  60 MPH
 12H  01/1800Z 14.0N 118.4W   50 KT  60 MPH
 24H  02/0600Z 13.9N 118.5W   45 KT  50 MPH
 36H  02/1800Z 13.5N 118.6W   45 KT  50 MPH
 48H  03/0600Z 13.4N 118.8W   40 KT  45 MPH
 72H  04/0600Z 14.0N 119.0W   30 KT  35 MPH
 96H  05/0600Z 15.0N 119.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  06/0600Z 17.0N 120.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BERG
 
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