Tropical Storm CHOI-WAN Advisory Cts, 03.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (CHOI-WAN)
WARNING NR 02//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 23W (CHOI-WAN), LOCATED APPROXIMATELY 42 NM
SOUTH OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT 01 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
POSITION AND TRACK MOTION. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY INDICATES IMPROVED DEEP CONVECTIVE BANDING
WRAPPING INTO A 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 020934Z ASCAT IMAGE STILL SHOWS AN
EXPANSIVE GALE-FORCE WIND FIELD, WHICH SUPPORTS THE LARGE 34-KNOT
RADII ANALYSIS AND FORECASTS. THE INITIAL INTENSITY OF 35 KNOTS IS
BASED ON ASCAT DATA (SHOWING 30 TO 35 KNOTS) DUE TO THE LOW DVORAK
INTENSITY ESTIMATES. AS PREVIOUSLY MENTIONED, THE INITIAL POSITION
IS UNCERTAIN WITH A 021705Z SSMIS 37 GHZ IMAGE SHOWING A BROAD LLCC
AND THE SSMIS WIND PRODUCT SHOWINGS AN ELONGATED CORE OF LIGHT
WINDS. THE INITIAL POSITION IS BASED ON THIS IMAGERY WITH FAIR
CONFIDENCE. 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