Tropical Storm OTIS

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TROPICAL STORM OTIS DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 AM PDT THU SEP 29 2005
 
A QUIKSCAT PASS AT 0130Z SUPPORTED AT LEAST 30 KT...WITH A COUPLE OF
UNCERTAIN 35 KT VECTORS IN CONVECTION TO THE WEST OF THE CENTER. 
SINCE THAT TIME THERE HAS BEEN AN INCREASE IN DEEP CONVECTION OVER
OR VERY NEAR THE CIRCULATION CENTER...AND THE 6Z CLASSIFICATIONS
FROM TAFB AND SAB WERE T2.5...OR 35 KT.  BASED ON THE ABOVE...THE
DEPRESSION IS UPGRADED TO A TROPICAL STORM.  

THE CENTER REMAINS DIFFICULT TO LOCATE.  THERE HAVE BEEN SEVERAL
MICROWAVE PASSES THAT SUGGEST A CENTER TO THE NORTH AND EAST OF MY
ESTIMATED POSTION...BUT THESE MAY BE REFLECTING SWIRLS GENERATED IN
THE CONVECTION THAT THEN ROTATE COUNTERCLOCKWISE AROUND A BROADER
CIRCULATION.  AT NIGHT I WOULD PREFER TO MAINTAIN MORE CONTINUITY
WITH THE PREVIOUS TRACK THAN JUMP ON ONE OF THESE SWIRLS.  EVEN
SO...THE TRACK DOES APPEAR TO HAVE TURNED TO THE RIGHT AND THE
INITIAL MOTION IS ESTIMATED TO BE 300/5.  OTIS REMAINS ON
THE SOUTH SIDE OF A MID- TO UPPER-LEVEL RIDGE THAT CURRENTLY EXTENDS
WESTWARD FROM NORTHERN MEXICO ACROSS BAJA CALIFORNIA. GLOBAL MODEL
GUIDANCE IS IN PRETTY GOOD AGREEMENT THAT THIS RIDGE WILL BE
REPLACED BY A TROUGH OR CUTOFF LOW OFF OF SOUTHERN CALIFORNIA OVER
THE NEXT 48 HOURS...AND THAT OTIS WILL TURN NORTHWARD ALONG THE
EAST SIDE OF THIS TROUGH.  THERE IS CONSIDERABLE SPREAD IN THE
FORWARD SPEED OF OTIS AMONG THE DYNAMICAL MODELS...ESPECIALLY LATE
IN THE FORECAST PERIOD...AND THERE HASN'T BEEN MUCH CONSISTENCY
FROM RUN TO RUN.  THE NOGAPS...WHICH HAD BEEN ONE OF THE SLOWER
MODELS PREVIOUSLY...IS NOW ONE OF THE FASTEST...WHILE THE
GFDL...WHICH HAD BEEN THE FASTEST...IS NOW IN THE MIDDLE OF THE
PACK.  SUCH ERRATIC BEHAVIOR IS A GOOD REASON TO STAY NEAR THE
DYNAMICAL MODEL CONSENSUS.  ONLY THE 12Z EUROPEAN MODEL TURNS OTIS
AWAY FROM THE BAJA PENINSULA.  

NORTHEASTERLY SHEAR CONTINUES TO AFFECT OTIS...ALTHOUGH THIS SHEAR
IS FORECAST TO LESSEN OVER THE NEXT 36 HOURS.  SLOW STRENGTHENING
IS EXPECTED OVER THE NEXT DAY OR SO WITH A SOMEWHAT FASTER PACE
AFTER THAT.  BY LATE IN THE FORECAST PERIOD...INCREASING SOUTHERLY
SHEAR AND/OR COOLER SSTS ARE EXPECTED TO RESULT IN A WEAKENING
TREND.  THE OFFICIAL FORECAST IS A BLEND OF THE SHIPS AND GFDL
GUIDANCE.  

 
FORECASTER FRANKLIN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0900Z 17.5N 107.6W    35 KT
 12HR VT     29/1800Z 18.0N 108.6W    40 KT
 24HR VT     30/0600Z 18.9N 110.0W    45 KT
 36HR VT     30/1800Z 19.7N 111.0W    55 KT
 48HR VT     01/0600Z 20.5N 111.7W    65 KT
 72HR VT     02/0600Z 22.1N 112.6W    65 KT
 96HR VT     03/0600Z 24.5N 113.5W    50 KT
120HR VT     04/0600Z 27.5N 114.0W    35 KT...INLAND
 
 
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