Tropical Storm PHANFONE Advisory 12月24日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (PHANFONE)
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 30W (PHANFONE), LOCATED APPROXIMATELY 547 NM
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 14
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY REVEALS AN AREA OF SUSTAINED DEEP CENTRAL
CONVECTION OBSCURING THE LOW LEVEL CIRCULATION CENTER. THERE IS
FAIR CONFIDENCE IN THE INITIAL POSITION WITH ONLY A LOWER
RESOLUTION 231715Z ATMS 88.2GHZ MICROWAVE IMAGE AVAILABLE TO
SUPPORT POSITIONING. THE INITIAL INTENSITY IS CONSISTENT WITH
MULTI-AGENCY DVORAK ESTIMATES OF T3.5 (55 KTS). THE ENVIRONMENT IS
FAVORABLE FOR DEVELOPMENT WITH LOW (10-15 KT) VERTICAL WIND SHEAR
(VWS), GOOD POLEWARD AND WESTWARD OUTFLOW AND WARM (28-29 CELSIUS)
SEA SURFACE TEMPERATURES (SSTS). TS 30W IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS A SLIGHT ADJUSTMENT TO THE FORECAST PHILOSOPHY,
DECREASING THE INTENSITY OF THE SYSTEM SLIGHTLY BETWEEN TAUS 12 TO
48 DUE TO LAND INTERACTION AS IT PASSES THROUGH THE PHILIPPINES.
   B. TS 30W WILL TRACK GENERALLY WEST-NORTHWESTWARD THROUGHOUT
THE FORECAST. THE ENVIRONMENT REMAINS FAVORABLE ALLOWING TS 30W TO
INTENSIFY TO 70 KTS BY TAU 12. THE SYSTEM IS ANTICIPATED TO MAKE
LANDFALL BETWEEN TAUS 12 AND 24 CAUSING A SLIGHT DECREASE IN
INTENSITY TO 65 KTS BY TAU 24. BETWEEN TAUS 24 AND 48 THE
FAVORABLE ENVIRONMENT IS EXPECTED TO PARTIALLY OFFSET THE LAND
INTERACTION ALLOWING THE SYSTEM TO MAINTAIN INTENSITY. ONCE TS 30W
EMERGES IN THE SOUTH CHINA SEA IT WILL INCREASE TO A MAXIMUM
INTENSITY OF 80 KTS AT TAU 72. HOWEVER, DUE TO THE COMPLICATED
NATURE OF THE LAND INTERACTION IN THIS FORECAST THERE IS HIGH
UNCERTAINTY IN THE INTENSITY FORECAST. THERE IS STRONG AGREEMENT
IN THE MODEL TRACK GUIDANCE THROUGH TAU 48. AFTER TAU 48, THE
SPREAD INCREASES SLIGHTLY BUT REMAINS TIGHT, THEREFORE THERE IS
HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, TS 30W WILL BEGIN TO ENCOUNTER DECREASING
SSTS, INCREASING VWS AND RELATIVELY COOL, DRY AIR. AS A RESULT,
THE INTENSITY IS EXPECTED TO FALL RAPIDLY, REACHING 30 KTS BY TAU
120. FURTHERMORE, THE SYSTEM WILL SLOW AS IT APPROACHES A COL
BETWEEN THE STEERING STR AND A LESS PRONOUNCED STR TO THE WEST.
MODEL GUIDANCE SPREAD INCREASES FOR THIS PORTION OF THE FORECAST,
ALTHOUGH IN BETTER AGREEMENT THAN AT THE 23/12Z FORECAST.
THEREFORE, THE FORECAST TRACK CLOSELY FOLLOWS THE MULTI-MODEL
CONSENSUS WITH FAIR CONFIDENCE AS THE MODELS COME INTO BETTER
AGREEMENT.//
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