Tropical Storm PHANFONE Advisory sáb, 28-12

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (PHANFONE) WARNING
NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 30W (PHANFONE), LOCATED APPROXIMATELY 479 NM
EAST OF DA NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT 04 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY REVEALS AN ISOLATED CONVECTIVE CELL THAT IS OBSCURING THE
LOW LEVEL CIRCULATION CENTER. A 270507Z ATMS 88 GHZ MICROWAVE IMAGE
PROVIDES FAIR CONFIDENCE IN THE INITIAL POSITION. THE INITIAL
INTENSITY FALLS BETWEEN A PGTW DVORAK FIX OF T4.0 (65 KTS) AND A
270143Z CIMSS SATCON ESTIMATE OF 57 KTS. DESPITE A GOOD POLEWARD
OUTFLOW CHANNEL, THE ENVIRONMENT IS UNFAVORABLE DUE TO MODERATE-TO-
HIGH (20-25 KT) VERTICAL WIND SHEAR (VWS), MARGINAL (26-27 CELSIUS)
SEA SURFACE TEMPERATURE, AND DRY AIR WRAPPING IN FROM THE WEST. TS
30W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 30W WILL CONTINUE TO TRACK GENERALLY WESTWARD AND DISSIPATE
UNDER INCREASINGLY UNFAVORABLE ENVIRONMENTAL CONDITIONS. BY TAU 48,
THE SYSTEM SHOULD FALL BELOW WARNING THRESHOLD. NAVGEM AND GFS ARE
NORTHERN OUTLIERS. THE REMAINING MODELS FOLLOW A SIMILAR TRACK, JUST
SOUTH OF THE JTWC TRACK FORECAST. THE STEERING OVER THE SHORT
DURATION OF THE FORECAST IS COMPLEX. AS THE INTENSITY WEAKENS, THE
STEERING INFLUENCES TRANSITIONS TO LOWER LEVELS AND THE ORIENTATION
OF THE STR WILL CHANGE. THIS LIKELY EXPLAINS THE DISPARITY BETWEEN
THE NAVGEM/GFS AND THE OTHER MODELS. BASED ON THE HIGH SPREAD AND
COMPLEX STEERING ENVIRONMENT, THERE IS LOW CONFIDENCE IN THE JTWC
TRACK FORECAST.//
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