Tropical Storm CHOI-WAN Advisory 03.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (CHOI-WAN)
WARNING NR 03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 23W (CHOI-WAN), LOCATED APPROXIMATELY 32 NM
SOUTH-SOUTHWEST OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT 03 KNOTS
OVER THE PAST SIX HOURS. DUE TO THE BROAD NATURE OF THE SYSTEM,
THERE IS A LARGE DEGREE OF UNCERTAINTY (APPROXIMATELY 60 NM) IN THE
INITIAL (MSI) POSITION AND TRACK MOTION. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY DEPICTS A BROAD, EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH MULTIPLE MESOVORTICES ROTATING CYCLONICALLY ABOUT
A CENTROID. ANIMATED INFRARED IMAGERY CONTINUES TO DEPICT IMPROVED
DEEP CONVECTIVE BANDING WRAPPING INTO THE BROAD LOW-LEVEL
CIRCULATION CENTER (LLCC). ALTHOUGH TS 23W IS STILL A VERY LARGE
SYSTEM, IT APPEARS TO BE GAINING CHARACTERISTICS TYPICAL OF A
TROPICAL STORM E.G., MORE CENTRALIZED DEEP CONVECTION AND A
CONTRACTING WIND FIELD WITH A RADIUS OF MAXIMUM WINDS OF 90 NM. THE
INITIAL INTENSITY OF 35 KNOTS IS BASED ON ASCAT DATA (SHOWING 30 TO
35 KNOTS) DUE TO THE LOW DVORAK INTENSITY ESTIMATES. UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE UPPER-LEVEL ENVIRONMENT WITH GOOD
OUTFLOW, LOW VERTICAL WIND SHEAR (VWS) AND WARM SST. TS 23W IS QUASI-
STATIONARY AS IT SLOWLY CONSOLIDATES WITHIN A COMPETING STEERING
INFLUENCE.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TS 23W IS EXPECTED TO ACCELERATE WESTWARD BY TAU 12 AS THE STR
BUILDS TO THE NORTH AND BECOMES THE DOMINANT STEERING INFLUENCE.
AFTER TAU 24, TS 23W SHOULD INTENSIFY AT A FASTER RATE DUE TO
FAVORABLE ENVIRONMENTAL CONDITIONS.
   C. IN THE EXTENDED TAUS, TS CHOI-WAN WILL BEGIN TO ROUND THE STR
AND TRACK MORE POLEWARD. AS IT GAINS LATITUDE, VWS WILL INCREASE AND
SSTS WILL DECREASE. HOWEVER, INCREASED POLEWARD OUTFLOW WILL OFFSET
THESE NEGATIVE EFFECTS, VENTILATING THE CYCLONE TO A PEAK OF 85
KNOTS. AVAILABLE MODEL GUIDANCE IS IN GOOD AGREEMENT, HOWEVER, GIVEN
THE UNCERTAINTY IN THE CURRENT STORM MOTION AND THE INITIAL PORTION
OF THE FORECAST TRACK, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST
TRACK.//
NNNN
NNNN