Tropical Storm VONGFONG Advisory 5月14日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (VONGFONG) WARNING
NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 01W (VONGFONG), LOCATED APPROXIMATELY 381 NM
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD
AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY INDICATES THE RAPID INTENSIFICATION TREND HAS
CONTINUED OVER THE PAST SIX HOURS, WITH TY 01W NOW MAINTAINING AN 8
NM EYE, WHILE THE CDO HAS EXPANDED AND OVERALL SYMMETRY IMPROVED.
EARLIER PASSES FROM SMAP AND SMOS INDICATED A VERY COMPACT CORE.
DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND RJTD ARE T5.0 (90
KNOTS), AS WAS THE 131840Z ADT, HOWEVER, DATA-T VALUES WERE HIGHER.
BASED ON THE OBSERVED STRUCTURAL IMPROVEMENT AND COMPACT CORE, THE
INITIAL INTENSITY WAS HEDGED HIGHER TO 105 KNOTS TOWARDS THE DATA-T.
HOWEVER, A 131806Z GPM PARTIAL PASS ARRIVED SHORTLY AFTER THE
ANALYSIS TIME THAT INDICATES AN EYEWALL REPLACEMENT CYCLE (ERC) MAY
BE UNDERWAY, SO INTENSITY IS LIKELY BEGINNING TO FALL. THE INITIAL
POSITION WAS PLACED WITH HIGH CONFIDENCE BASED ON THE EIR AND GPM
MICROWAVE EYE FEATURE, AND INDICATES THAT VONGFONG HAS TRACKED MORE
WESTWARD THAN PREVIOUSLY ANTICIPATED. THE ENVIRONMENT REMAINS VERY
FAVORABLE FOR ADDITIONAL INTENSIFICATION AFTER ERC COMPLETES, WITH
LOW (5-10 KTS) VWS, WARM SSTS (29-30 C) AND ROBUST RADIAL OUTFLOW
ALOFT. TY VONGFONG IS BEING STEERED BY A DEEP-LAYER SUBTROPICAL RIDGE
POSITIONED TO THE EAST NEAR GUAM WHICH IS EXTENDING WEST TOWARD THE
LUZON STRAIT.
3. FORECAST REASONING.
   A. THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS FORECAST BULLETIN.
   B. TY VONGFONG IS EXPECTED TO GRADUALLY SHIFT TO A WEST-NORTHWEST
AND THEN NORTHWESTWARD TRACK OVER THE NEXT 36 HOURS AS THE EXTENSION
OF THE STEERING RIDGE RECEDES BACK TO THE EAST. AS A RESULT OF THE
ADDITIONAL WESTWARD MOTION OVER THE PAST SIX HOURS, THE TRACK HAS
BEEN SHIFTED SLIGHTLY WESTWARD. BY TAU 36, TY 01W SHOULD BEGIN TO
ROUND THE RIDGE AND TURN MORE NORTHWARD. A PEAK OF 115 KNOTS IN 12
HOURS WAS MAINTAINED AS OVERALL CONDITIONS REMAIN FAVORABLE ONCE ERC
COMPLETES PRIOR TO LANDFALL. AFTER LANDFALL, THE INTENSITIES WERE
MODIFIED LOWER DUE TO THE MORE INLAND FORECAST TRACK. NUMERICAL
MODELS ARE COMING INTO TIGHTER AGREEMENT DURING THE LAST GUIDANCE
UPDATE, WITH ECMWF NOW FALLING IN-LINE WITH THE PREDOMINANT CLUSTER,
WHILE UKMET AND MOGREPS REMAIN WESTWARD OUTLIERS. THE OFFICIAL JTWC
FORECAST TRACK IS HEDGED TO THE EAST OF THE CONSENSUS TRACK, CLOSE TO
THE TIGHT PACKING OF THE EASTERN MODEL SOLUTIONS. HOWEVER, DUE TO
UNCERTAINTY OF WHEN THE NORTHWARD TURN WILL OCCUR AND TO WHAT DEGREE
LANDFALL WILL IMPACT THE SYSTEM, OVERALL CONFIDENCE IS POOR FOR THIS
PORTION OF THE FORECAST.
   C.AFTER TAU 72, TY VONGFONG WILL COMPLETE RECURVATURE AND BEGIN A
NORTHEAST TRACK AFTER ENTERING THE LUZON STRAIT. INCREASING VWS
(25-30 KNOTS) AS TY 01W NEARS A BAROCLINIC BOUNDARY, ALONG WITH
COOLING SSTS WILL LEAD TO FURTHER WEAKENING OF THE SYSTEM TO 45 KTS
BY TAU 96. AT THIS TIME, INTERACTION WITH WESTERLY FLOW TO THE NORTH
WILL CAUSE THE SYSTEM TO BEGIN EXTRATROPICAL TRANSITION AND FURTHER
WEAKENING TO A 35 KTS SYSTEM BY TAU 120 AS IT IS FULLY ABSORBED INTO
THE BAROCLINIC ZONE. THERE IS SIGNIFICANT ALONG TRACK SPREAD OF MODEL
SOLUTIONS AFTER TAU 72. AS ECMWF SHIFTED EASTWARD, THE CONSENSUS AT
TAUS 96 AND 120 SHIFTED SEVERAL HUNDRED MILES TO THE NORTHEAST OF THE
PREVIOUS RUN. AS THE FORECAST DISCOUNTS THE WESTWARD UKMET SOLUTION,
TAU 96 AND 120 FORECAST POSITIONS WERE SHIFTED NORTHEAST. THE LARGE
SPREAD IN MODEL GUIDANCE LENDS HIGH UNCERTAINTY DURING THIS PERIOD
AND THUS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.//
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