Subject: Pacific-EN: Tropical Storm Jimena Discussion Number 4

From: SIU Weather Processor <[email-masked]>
Date: Tue, 26 Aug 1997 09:33:04 +1900

190
WTPZ42 KNHC 261433
TCDEP2
TROPICAL STORM JIMENA DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT TUE AUG 26 1997

SATELLITE IMAGES INDICATE THAT THE CYCLONE HAS MAINTAINED ITS
ORGANIZATION WITH A FAIRLY SYMMETRICAL MASS OF CONVECTION AROUND THE
CENTER.  DVORAK INTENSITY ESTIMATES ARE AT TROPICAL STORM STRENGTH
SO THE SYSTEM IS BEING NAMED.  THERE IS AN ELONGATED UPPER-LEVEL
ANTICYCLONE OVER THE STORM.  ALTHOUGH THERE IS A LARGE MID- TO
UPPER-LEVEL TROUGH TO THE NORTH AND NORTHWEST OF THE SYSTEM...THIS
TROUGH DOES NOT SEEM TO BE SHEARING THE TROPICAL CYCLONE.  INSTEAD
IT APPEARS TO BE ASSISTING THE OUTFLOW TO THE NORTHEAST.  SOME
ADDITIONAL STRENGTHENING IS FORECAST...BUT LATER IN THE PERIOD
SHEARING COULD LIMIT DEVELOPMENT.

MOTION IS SLOWER AND MORE TO THE RIGHT OF PREVIOUS ESTIMATES.
OBJECTIVE GUIDANCE IS COMPLICATED BY THE AVN INITIALIZATION OF A
FALSE VORTEX ABOUT 10 DEG WEST-SOUTHWEST OF JIMENA.  THIS MODEL
VORTEX APPEARS STRONGER THAN THE TROPICAL CYCLONE BUT IS NOT EVIDENT
IN SATELLITE IMAGERY OR SURFACE OBSERVATIONS.  THUS THE AVN AND GFDL
MODELS MAY HAVE AN UNREALISTIC STEERING FLOW.  THE CURRENT NHC
FORECAST IS ADJUSTED A BIT TO THE RIGHT AND SLOWER THAN THE PREVIOUS
ONE...BASED MAINLY ON THE INITIAL MOTION.  THIS IS ALSO FAIRLY CLOSE
TO THE LATEST NOGAPS RUN...WHICH DOES NOT CONTAIN THE SPURIOUS
VORTEX IN ITS INITIAL STATE.

PASCH

FORECAST POSITIONS AND MAX WINDS

INITIAL     26/1500Z 12.2N 135.6W    35 KTS
12HR VT     27/0000Z 12.5N 136.5W    40 KTS
24HR VT     27/1200Z 13.2N 138.1W    45 KTS
36HR VT     28/0000Z 13.9N 139.7W    50 KTS
48HR VT     28/1200Z 14.8N 141.4W    50 KTS
72HR VT     29/1200Z 16.5N 144.5W    50 KTS

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