007 
 WTPZ45 KNHC 291405
 TCDEP5
 TROPICAL STORM OTIS DISCUSSION NUMBER   6
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
 8 AM PDT THU SEP 29 2005
  
 A LARGE BURST OF CONVECTION WITH CLOUD TOPS COLDER THAN -80C
 DEVELOPED EARLY THIS MORNING OVER AND SOUTHWEST OF THE CENTER. A
 29/0912Z AMSR-E MICROWAVE OVERPASS INDICATED A LARGE CURVED BAND
 THAT WRAPPED MORE THAN HALF WAY AROUND THE MID-LEVEL CIRCULATION
 CENTER... WITH AN EXPOSED LOW-LEVEL CENTER LOCATED NEAR THE
 SOUTHERN TIP OF THE CONVECTIVE BAND. DVORAK INTENSITY ESTIMATES AT
 12Z WERE 45 KT FROM TAFB AND SAB... AND 35 KT FROM AFWA. SINCE THAT
 TIME... HOWEVER... CLOUD TOPS HAVE WARMED AND THE BANDING FEATURES
 HAVE BECOME LESS DISTINCT. THEREFORE... THE INTENSITY HAS ONLY BEEN
 INCREASED TO 40 KT FOR THIS ADVISORY.
  
 THE INITIAL MOTION ESTIMATE IS 305/08. AS MENTIONED IN PREVIOUS
 DISCUSSIONS... THE EXACT CENTER REMAINS DIFFICULT TO DETERMINE. THE
 AFOREMENTIONED AMSR-E OVERPASS DID DEPICT A NICE LOW-LEVEL
 CIRCULATION... BUT OVER THE PAST 24 HOURS THERE HAVE BEEN MULTIPLE
 SWIRLS GENERATED IN THE DEEP CONVECTION TO THE WEST THAT HAVE THEN
 ROTATED CYCLONICALLY AROUND THE MID-LEVEL CIRCULATION CENTER. THE
 ADVISORY POSITION IS BASED ON A BLEND OF THE MID-LEVEL AND
 LOW-LEVEL CENTERS NOTED IN MICROWAVE DATA... WHICH ALSO MAINTAINS
 CONTINUITY WITH THE PREVIOUS MOTION AND FORECAST TRACK. OTIS IS
 EXPECTED TO GRADUALLY MOVE WEST-NORTHWESTWARD AROUND THE
 SOUTHWESTERN PERIPHERY OF A LARGE MID-LEVEL SUBTROPICAL RIDGE
 ORIENTED EAST-WEST ACROSS NORTHERN MEXICO AND BAJA CALIFORNIA. THE
 WESTERN PORTION OF THE RIDGE OVER BAJA CALIFORNIA IS FORECAST BY
 ALL THE MODELS TO BE ERODED BY A SOUTHWARD-MOVING SHORTWAVE TROUGH
 AFTER 72 HOURS... WHICH SHOULD ALLOW OTIS TO TURN NORTHWARD ACROSS
 BAJA BY 120 HOURS. ONLY THE 29/00Z ECMWF MODEL TURNS OTIS AWAY FROM
 THE BAJA PENINSULA. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE
 PREVIOUS TRACK AND THE NHC MODEL CONSENSUS... MINUS THE ECMWF.
  
 NORTHEASTERLY UPPER-LEVEL SHEAR CONTINUES TO SLOWLY ABATE ACROSS
 OTIS AND THIS TREND IS FORECAST TO CONTINUE THROUGH 72 HOURS.
 HOWEVER... SOME MID-LEVEL SHEAR UNDERCUTTING THE IMPROVING OUTFLOW
 LAYER APPEARS TO BE AFFECTING THE CYCLONE AND LIKELY WILL NOT
 WEAKEN FOR ANOTHER 24 HOURS. BUT WITH THE IMPROVING OUTFLOW PATTERN
 ...WEAK VERTICAL SHEAR... AND SSTS OF 28-29C BENEATH THE STORM...
 AT LEAST MODEST STRENGTHENING SHOULD OCCUR UNTIL COOLER WATER IS
 REACHED AFTER 72 HOURS. THE OFFICIAL INTENSITY FORECAST IS A BLEND
 OF THE SHIPS AND GFDL MODELS... WHICH BRING OTIS UP TO 63 KT AND 74
 KT... RESPECTIVELY... BY 48 HOURS.
  
 FORECASTER STEWART
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      29/1500Z 17.9N 108.2W    40 KT
  12HR VT     30/0000Z 18.7N 109.2W    45 KT
  24HR VT     30/1200Z 19.5N 110.5W    55 KT
  36HR VT     01/0000Z 20.1N 111.3W    65 KT
  48HR VT     01/1200Z 20.8N 111.9W    70 KT
  72HR VT     02/1200Z 21.9N 112.5W    65 KT
  96HR VT     03/1200Z 24.5N 113.5W    50 KT
 120HR VT     04/1200Z 28.5N 114.0W    35 KT...INLAND OVER BAJA
 
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