Tropical Storm PHANFONE Advisory 12月22日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 30W (THIRTY)
WARNING
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 30W (THIRTY), LOCATED APPROXIMATELY 324
NM EAST-SOUTHEAST OF KOROR, PALAU, HAS TRACKED WESTWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS EXPLOSIVE FLARING CENTRAL CONVECTION OFFSET
NORTHWESTWARD OF THE LOW LEVEL CIRCULATION (LLC). THE INITIAL
POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON A PARTLY-EXPOSED
LLC IN THE 211618Z AMSR2 89GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 30KTS IS BASED ON THE DVORAK ESTIMATE OF T2.0/30KTS
FROM PGTW AND IS CONSISTENT WITH A RECENT ASCAT PASS. ANALYSES
INDICATE AN OVERALL FAVORABLE ENVIRONMENT WITH MODERATE (20-25KT)
RELATIVE VERTICAL WIND SHEAR ALONG THE NORTHERN HALF THAT IS MOSTLY
OFFSET BY ROBUST RADIAL OUTFLOW WITH A STRONG POLEWARD BIAS AND VERY
WARM (>30C) SEA SURFACE TEMPERATURE (SST) IN THE PHILIPPINE SEA. THE
CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE NORTH WITH A WEST-EAST ORIENTED AXIS
OVER 20N LATITUDE.
3. FORECAST REASONING.
   A.  THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 30W WILL TRACK MORE ON A WEST-NORTHWESTWARD TRAJECTORY OVER
THE NEXT FIVE DAYS AS THE STR REORIENTS. THE FAVORABLE ENVIRONMENT
WILL FUEL STEADY INTENSIFICATION REACHING TYPHOON STRENGTH BY TAU 48
BEFORE MAKING LANDFALL OVER THE ISLAND OF LEYTE, PHILIPPINES.
   C. AFTER TAU 72, TD 30W WILL DRAG ACROSS THE VISAYAN ISLANDS,
ACROSS THE SULU SEA AND EXIT INTO THE SOUTH CHINA SEA SHORTLY AFTER
TAU 96. THE SYSTEM WILL CONTINUE TO GRADUALLY INTENSIFY, IMPEDED
ONLY BY ISLAND INTERACTION, REACHING 85KTS BY TAU 120. THE NUMERICAL
MODELS ARE IN GOOD AGREEMENT TO THE FORECAST TRACK, HOWEVER, GIVEN
THE FORMATIVE STAGE OF THE CYCLONE AND THE POSSIBLE ERRATIC STORM
MOTION ASSOCIATED WITH IT, THERE IS OVERALL LOW CONFIDENCE IN THE
JTWC TRACK FORECAST.//
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