Tropical Storm OTIS

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TROPICAL STORM OTIS DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2 PM PDT THU SEP 29 2005
 
A WELL-DEFINED PARTIALLY EXPOSED LOW-LEVEL CIRCULATION HAS BEEN
ROTATING NORTH AND WESTWARD AT 20-25 KT AROUND THE EAST AND NORTH
SIDE OF THE MID-LEVEL CENTER DURING THE PAST 6 HOURS. THE INITIAL
POSITION AND RESULTANT MOTION ARE BASED MAINLY ON THE LOCATION OF
THE MID-LEVEL CIRCULATION NOTED IN MICROWAVE IMAGERY. THE INITIAL
INTENSITY OF 45 KT IS BASED ON A BLEND OF SATELLITE INTENSITY
ESTIMATES OF 55 KT FROM SAB... 45 KT FROM TAFB... AND 35 KT FROM
SAB... RESPECTIVELY. THIS INTENSITY IS ALSO SUPPORTED BY AN
UW-CIMSS AMSU INTENSITY ESTIMATE OF 996 MB AND 52 KT AT 29/1545Z.
 
THE INITIAL MOTION ESTIMATE IS 310/11. THE LAST FEW VISIBLE
SATELLITE IMAGES SUGGEST THAT THE LOW-LEVEL CENTER MAY BE STARTING
TO PULL UNDERNEATH THE MID- AND UPPER-LEVEL CIRCULATION CENTERS. AS
SUCH... A DECREASE IN FORWARD SPEED IS EXPECTED TO RESUME DURING
THE NEXT 6-12 HOURS. OVERALL... THE FORECAST TRACK AND REASONING
REMAIN UNCHANGED FROM THE PREVIOUS SEVERAL FORECAST DISCUSSIONS.
OTIS IS FORECAST TO MOVE NORTHWESTWARD AROUND THE SOUTHWESTERN
PERIPHERY OF A LARGE MID-LEVEL RIDGE LOCATED OVER NORTHERN MEXICO
AND BAJA CALIFORNIA. ALL OF THE GLOBAL MODELS CONTINUE TO FORECAST
A SHOTWAVE TROUGH TO DROP SOUTHWARD AND ERODE THE WESTERN PORTION
OF THE RIDGE OVER BAJA CALIFORNIA... WHICH IS EXPECTED TO ALLOW
OTIS TO TURN NORTHWARD BY 72 HOURS AND POSSIBLY MAKE LANDFALL ALONG
THE WEST-CENTRAL COAST OF BAJA CALIFORNIA BETWEEN 96-120 HOURS. THE
NHC MODEL GUIDANCE IS IN STRONG AGREEMENT ON THIS SCENARIO... AND 
THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS TRACK AND IS
NEAR THE MIDDLE OF THE TIGHTLY PACKED GUIDANCE ENVELOPE.
 
NORTHEASTERLY UPPER-LEVEL SHEAR CONTINUES TO DECREASE AND... AS A
RESULT... THE OUTFLOW PATTERN HAS IMPROVED AND BECOME MORE
CIRCULAR. A 25/1545Z SSMI OVERPASS INDICATED A 60 PERCENT MID-LEVEL
EYEWALL HAD FORMED...SO AT LEAST AN AVERAGE RATE OF INTENSIFICATION
SHOULD OCCUR FOR THE NEXT 36 HOURS OR SO. HOWEVER...GIVEN THAT OTIS
WILL BE OVER 28.5-29C SSTS FOR AT LEAST THE NEXT 24 HOURS... A
BRIEF PERIOD OF RAPID INTENSIFICATION COULD OCCUR. BY AROUND 72
HOURS... OTIS IS FORECAST TO BEGIN MOVING OVER SUB-26C SSTS...
WHICH SHOULD INDUCE STEADY WEAKENING... WITH FASTER WEAKENING
EXPECTED AFTER 96 HOURS WHEN SOUTHWESTERLY UPPER-LEVEL IS FORECAST
TO INCREASE TO MORE THAN 20 KT.

INTERESTS NEAR THE BOTH COASTS OF THE SOUTHERN BAJA CALIFORNIA
PENINSULA SHOULD CLOSELY MONITOR THE PROGRESS OF OTIS OVER THE NEXT
FEW DAYS.

FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/2100Z 18.9N 109.4W    45 KT
 12HR VT     30/0600Z 19.4N 110.1W    55 KT
 24HR VT     30/1800Z 20.1N 111.1W    65 KT
 36HR VT     01/0600Z 20.8N 111.8W    75 KT
 48HR VT     01/1800Z 21.5N 112.4W    70 KT
 72HR VT     02/1800Z 23.3N 113.1W    65 KT
 96HR VT     03/1800Z 26.0N 114.0W    50 KT
120HR VT     04/1800Z 29.5N 114.0W    35 KT...INLAND CENTRAL BAJA
 
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