Tropical Depression FIFTEEN-E

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TROPICAL DEPRESSION FIFTEEN-E DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 PM PDT WED SEP 28 2005
 
TROPICAL DEPRESSION FIFTEEN-E IS ALMOST TO TROPICAL STORM STRENGTH. 
BURSTS OF CONVECTION ARE OCCURRING WEST THROUGH SOUTH OF THE
EXPOSED LOW-LEVEL CENTER...WITH ENOUGH ORGANIZATION TO PRODUCE
SATELLITE INTENSITY ESTIMATES OF 35 KT FROM TAFB AND 30 KT FROM SAB
AND AFWA.  ADDITIONALLY...A SHIP 125 N MI SOUTH-SOUTHEAST OF THE
CENTER REPORTED 30 KT.  SINCE THE CONSENSUS OF THE INTENSITY
ESTIMATES IS BELOW TROPICAL STORM STRENGTH...THE SYSTEM REMAINS A
30 KT DEPRESSION FOR THIS ADVISORY.

THE INITIAL MOTION IS A SOMEWHAT UNCERTAIN 275/5.  THE CYCLONE IS ON
THE SOUTH SIDE OF A MID/UPPER-LEVEL RIDGE THAT CURRENTLY EXTENDS
WESTWARD FROM NORTHERN MEXICO ALONG 26N.  THE GFS...GFDL...NOGAPS...
AND CANADIAN MODELS INDICATE THIS RIDGE SHOULD WEAKEN IN 36-48 HR
AS A MID/UPPER-LEVEL LOW FORMS WEST OF SOUTHERN CALIFORNIA.  THESE
MODELS CALL FOR THE DEPRESSION TO GRADUALLY TURN NORTHWEST AND
NORTHWARD DURING THE NEXT FIVE DAYS...PASSING NEAR OR OVER BAJA
CALIFORNIA.  ON THE OTHER HAND...THE UKMET...THE ECMWF... AND THE
GFDN KEEP ENOUGH OF A RIDGE BETWEEN THE DEPRESSION AND THE TROUGH
TO MOVE THE DEPRESSION MORE TOWARD THE WEST-NORTHWEST AWAY FROM
LAND.  SINCE EVEN THE UKMET AND ECMWF SHOW A SIGNIFICANT TROUGH OFF
THE CALIFORNIA COAST...THE FORECAST TRACK WILL LEAN TOWARD THE GFS/
GFDL/NOGAPS/CANADIAN SOLUTION...CALLING FOR A NORTHWESTWARD MOTION
BY 24-36 HR AND A NORTHWARD MOTION BY 96-120 HR.  THE NEW FORECAST
TRACK IS CLOSE TO THE PREVIOUS PACKAGE AND ALONG THE LEFT SIDE OF
THE NORTHWARD-POINTING GUIDANCE IN BEST AGREEMENT WITH THE NOGAPS.
 
ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SHOW 15-20 KT OF
EASTERLY VERTICAL SHEAR HINDERING DEVELOPMENT.  LARGE-SCALE MODELS
AGREE THAT THE SHEAR WILL DECREASE AS THE DEPRESSION APPROACHES THE
AXIS OF THE UPPER-LEVEL RIDGE...WHICH SHOULD ALLOW STRENGTHENING
BEFORE THE CYCLONE REACHES COOLER SEA SURFACE TEMPERATURES IN 72 HR
OR SO.  THE GFDL BRINGS THE SYSTEM TO HURRICANE STRENGTH IN 24
HR...WHICH LOOKS A LITTLE UNLIKELY GIVEN CURRENT TRENDS.  THE SHIPS
MODEL CALLS FOR MUCH LESS INTENSIFICATION...WITH A PEAK INTENSITY
OF ABOUT 50 KT IN 60-72 HR.  THE INTENSITY FORECAST WILL BLEND THE
GFDL AND SHIPS...CALLING FOR THE DEPRESSION TO BECOME A TROPICAL
STORM IN 12 HR AND A HURRICANE IN 72 HR.  AFTER 72 HR...COOL SSTS
ALONG THE FORECAST TRACK SHOULD CAUSE WEAKENING.  AS MENTIONED IN
THE PREVIOUS PACKAGE...AFTER 72 HR THE CYCLONE WILL BE MOVING
ALMOST PARALLEL TO THE SST ISOTHERMS.  THUS...ANY DEVIATION FROM
THE FORECAST TRACK COULD MAKE A LARGE DIFFERENCE IN HOW WARM/COOL
THE WATER IS UNDER THE CYCLONE.

THE 12 FT SEAS RADII WERE REVISED IN THE SOUTHEASTERN QUADRANT BASED
ON THE SHIP REPORT.
 

 
FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0300Z 17.1N 107.1W    30 KT
 12HR VT     29/1200Z 17.5N 108.2W    35 KT
 24HR VT     30/0000Z 18.3N 109.5W    40 KT
 36HR VT     30/1200Z 19.2N 110.7W    45 KT
 48HR VT     01/0000Z 20.1N 111.6W    55 KT
 72HR VT     02/0000Z 22.0N 113.0W    65 KT
 96HR VT     03/0000Z 24.0N 114.0W    55 KT
120HR VT     04/0000Z 26.5N 114.5W    45 KT
 
 
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