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Tropical Storm ROSA (Text)

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TROPICAL STORM ROSA DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP172012
800 PM PDT TUE OCT 30 2012
 
SATELLITE IMAGERY SHOWS THAT THE CONVECTIVE PATTERN OF ROSA HAS NOT
CHANGED MUCH OVER THE PAST FEW HOURS. THE COLDEST CLOUD TOPS ARE
SEEN IN A CDO-LIKE FEATURE EAST OF THE LOW-LEVEL CENTER...WHILE
THERE IS LITTLE CONVECTIVE BANDING ELSEWHERE. DVORAK ESTIMATES
REMAIN 45 KT FROM SAB AND 35 KT FROM TAFB...AND THE INITIAL
INTENSITY REMAINS 40 KT BASED ON A BLEND OF THESE VALUES. WESTERLY
FLOW ALOFT TO THE NORTH OF ROSA APPEARS TO BE ENHANCING THE OUTFLOW
IN THAT SEMICIRCLE...BUT THE SHEAR IS DISPLACING THE CONVECTION
EAST OF THE LOW-LEVEL CENTER. GLOBAL MODEL FIELDS AND THE SHIPS
GUIDANCE SHOW WESTERLY SHEAR INCREASING OVER THE NEXT 24 HOURS...
WHICH SHOULD ALLOW FOR ONLY LIMITED STRENGTHENING IN THE SHORT
TERM. AFTER 24 HOURS...A CONTINUED INCREASE IN SHEAR SHOULD LEAD TO
WEAKENING AND REMNANT LOW STATUS IN ABOUT 4 DAYS. 
 
A 2231 UTC AMSU PASS SHOWED THAT ROSA IS LOCATED A LITTLE TO THE
EAST OF EARLIER ESTIMATES...AND THE INITIAL MOTION ESTIMATE IS
275/04. ROSA IS CURRENTLY SITUATED ON THE SOUTHEASTERN FLANK OF A
MID-LEVEL RIDGE....WHICH SHOULD RESULT IN A SLOW WESTWARD MOTION
FOR THE NEXT DAY OR SO. THEN...AS A DEEP-LAYER TROUGH MOVES INTO
THE EASTERN PACIFIC TO THE NORTH OF THE TROPICAL CYCLONE...THE
TRACK MODEL GUIDANCE BECOMES QUITE DIVERGENT. THE ECMWF...UKMET...
AND NOGAPS SHOW A WEAKENING ROSA TURNING WEST-SOUTHWESTWARD BY DAY
4. ALTERNATIVELY...THE GFS AND GFDL SHOW A DEEPER REPRESENTATION OF
ROSA TURNING NORTHEASTWARD AT DAYS 4 AND 5 IN RESPONSE TO A MID-
LEVEL CUTOFF LOW THAT FORMS OFF THE COAST OF THE BAJA PENINSULA.
GIVEN THAT ROSA IS NOT EXPECTED TO BE IN AN ENVIRONMENT CONDUCIVE
FOR MUCH STRENGTHENING...THE GFS/GFDL SEENARIO SEEMS A LITTLE
LESS LIKELY...ALTHOUGH THIS SOLUTION NOW HAS THE SUPPORT OF A FEW
OF THE GEFS ENSEMBLE MEMBERS. GIVEN THAT THE TVCE MULTI-MODEL
CONSENSUS AND THE GEFS ENSEMBLE MEAN SHOW VERY LITTLE MOTION AT
DAYS 3 THROUGH 5...THE NHC FORECAST HAS BEEN SLOWED DOWN
CONSIDERABLY...BUT STILL SHOWS A WEST-SOUTHWESTWARD MOTION TO
PROVIDE SOME CONTINUITY WITH THE PREVIOUS NHC FORECAST. FURTHER
ADJUSTMENTS TO THE TRACK MAY BE NECESSARY IN THE NEXT CYCLE.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0300Z 14.5N 117.0W   40 KT  45 MPH
 12H  31/1200Z 14.6N 117.6W   45 KT  50 MPH
 24H  01/0000Z 14.7N 118.3W   45 KT  50 MPH
 36H  01/1200Z 14.8N 118.8W   40 KT  45 MPH
 48H  02/0000Z 14.9N 119.3W   40 KT  45 MPH
 72H  03/0000Z 14.5N 120.5W   35 KT  40 MPH
 96H  04/0000Z 14.2N 121.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  05/0000Z 14.0N 123.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BRENNAN
 
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