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TROPICAL DEPRESSION NINE-E DISCUSSION NUMBER 1
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT SUN AUG 25 2002
VISIBLE AND INFRARED SATELLITE IMAGERY INDICATE THE TROPICAL
DISTURBANCE LOCATED ABOUT 475 MILES SOUTHWEST OF MANZANILLO MEXICO
HAS STRENGTHENED INTO TROPICAL DEPRESSION NINE-E. BANDING FEATURES
HAVE IMPROVED SIGNIFICANTLY DURING THE PAST 6 HOURS AND THE INITIAL
INTENSITY OF 30 KT IS BASED ON A DVORAK SATELLITE INTENSITY ESTIMATE
OF T2.0...OR 30 KT...FROM TAFB. UPPER-LEVEL OUTFLOW IS FAIR IN ALL
QUADRANTS...BUT IS STEADILY IMPROVING.
THE INITIAL MOTION ESTIMATE IS 270/05. THE TROPICAL CYCLONE IS
EXPECTED TO REMAIN SOUTH OF THE SUBTROPICAL RIDGE THAT EXTENDS FROM
NORTHERN MEXICO WESTWARD TO NORTH OF HURRICANE FAUSTO. ALL OF THE
GLOBAL MODELS POORLY INITIALIZED THIS SYSTEM...AT BEST...DESPITE THE
WELL-DEFINED LOW-LEVEL CIRCULATION DEPICTED NICELY IN AN EARLIER
QUIKSCAT OVERPASS. AS SUCH...THE OFFICIAL FORECAST TRACK IS A BLEND
OF THE CLIPER... LBAR...DEEP AND MEDIUM BAM MODELS...AND ALSO USING
THE OVERALL SYNOPTIC PATTERN FOR A "STRAIGHT-RUNNER.".
THE SHIPS INTENSITY MODEL WAS FOLLOWED CLOSELY THRU 36 HOURS AND
THEN THE INTENSITY WAS INCREASED ABOVE SHIPS AFTER THAT. THE REASON
IS THAT THE SHIPS MODEL USED THE LBAR FORECAST TRACK TO DETERMINE
THE VERTICAL SHEAR...WHICH REMAINS LESS THAN 10 KT THRU 48
HOURS...BUT THEN INCREASES THE SHEAR SIGNIFICANTLY SINCE LBAR TAKES
THE CYCLONE RAPIDLY NORTHWESTWARD AFTER 48 HOURS. THE AVN MODEL IS
FORECASTING AN UPPER-LEVEL LOW IN THE VICINITY OF THE OFFICIAL 48-
AND 72-HOUR POSITIONS. HOWEVER...NOGAPS AND THE UKMET MODELS MOVE
THE UPPER-LEVEL LOW FASTER TO THE WEST AND KEEP THE CYCLONE UNDER
WEAK ANTICYCLONIC FLOW. GIVEN THE POOR INITIALIZATION OF THIS
SYSTEM BY THE AVN AND CURRENT WATER VAPOR IMAGERY INDICATING ONE
UPPER-LEVEL LOW SOUTH OF BAJA CALIFORNIA MOVING WESTWARD AND ANOTHER
ONE SOUTHWEST OF THE DEPRESSION DROPPING SOUTHWESTWARD...THEN IT
APPEARS THAT THE NOGAPS AND UKMET MODELS HAVE A BETTER HANDLE ON THE
UPPER-LEVEL FLOW PATTERN. HOWEVER...SINCE THE DEPRESSION IS EXPECTED
TO PASS BETWEEN THE TWO UPPER-LOWS...THE OUFLOW ENVIRONMENT APPEARS
TO BE CONDUCIVE FOR SIGNIFICANT INTENSIFICATION ONCE THE INNER-CORE
CONVECTION PERSISTS...AND THE OFFICIAL INTENSITY FORECAST COULD BE
TOO LOW AT 48- AND 72-HOURS.
FORECASTER STEWART
FORECAST POSITIONS AND MAX WINDS
INITIAL 26/0300Z 15.0N 110.3W 30 KTS
12HR VT 26/1200Z 15.1N 111.3W 35 KTS
24HR VT 27/0000Z 15.3N 112.7W 45 KTS
36HR VT 27/1200Z 15.5N 114.2W 55 KTS
48HR VT 28/0000Z 15.8N 115.9W 70 KTS
72HR VT 29/0000Z 16.5N 119.0W 80 KTS
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