Tropical Storm HALONG Advisory 11月5日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (HALONG) WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 24W (HALONG), LOCATED APPROXIMATELY 428 NM EAST-
NORTHEAST OF SAIPAN, HAS TRACKED NORTHWESTWARD AT 06 KNOTS OVER
THE PAST SIX HOURS. TY 24W HAS DEVELOPED AN EYE APPARENT IN ENHANCED
INFRARED (EIR) SATELLITE IMAGERY AND IN A 041658Z SSMI 37GHZ
MICROWAVE IMAGE, SUPPORTING THE INITIAL POSITION WITH HIGH
CONFIDENCE. THE CURRENT INTENSITY IS ASSESSED AT 105 KNOTS BASED ON
DVORAK INTENSITY ESTIMATES RANGING FROM T5.0-6.0 (90-115 KNOTS),
SUPPORTED BY A 041549Z SATCON ESTIMATE OF 107 KTS. UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH ROBUST POLEWARD
OUTFLOW AND LOW (5-10 KT) VERTICAL WIND SHEAR (VWS). HOWEVER, THERE
IS UPPER LEVEL CONVERGENCE TO THE SOUTH OF THE SYSTEM. SST VALUES
NEAR 29C ARE ALSO CONDUCIVE FOR FURTHER DEVELOPMENT. TY 24W IS
TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL
RIDGE (STR) POSITIONED TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. A MIDLATITUDE TROUGH IS DIGGING DOWN AND ERODING THE STEERING
STR TO THE EAST OF TY 24W. TY 24W WILL TRACK NORTH-NORTHWESTWARD TO
NORTHWARD THROUGH TAU 36 THEN GRADUALLY RECURVE AS IT ROUNDS THE STR
AXIS AFTER TAU 36. BY TAU 72, TY 24W WILL ACCELERATE NORTH-
NORTHEASTWARD AND WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) WHEN IT
INTERACTS WITH THE MIDLATITUDE WESTERLIES AND BAROCLINIC ZONE. THE
SYSTEM WILL INTENSIFY UNDER FAVORABLE CONDITIONS TO A PEAK OF 125
KNOTS BY TAU 24 DUE, IN PART, TO THE ENHANCED POLEWARD OUTFLOW THAT
IS TAPPING INTO THE PASSING MIDLATITUDE TROUGH TO THE NORTH. TY 24W
WILL BEGIN TO WEAKEN AFTER TAU 36 DUE TO INCREASING VWS AND SLOW
TRACK MOTION OVER WATERS WITH LOW OCEAN HEAT CONTENT (OHC). THE
FORECAST TRACK HAS BEEN SLOWED AND ADJUSTED WESTWARD FROM THE
PREVIOUS TRACK FORECAST, TOWARDS THE ECMWF SOLUTION AND THE MULTI-
MODEL CONSENSUS.
   C. IN THE EXTENDED PERIOD, TY 24W WILL ACCELERATE NORTHEASTWARD
AS IT TRACKS WITHIN THE MIDLATITUDE WESTERLIES AND IS EXPECTED TO
COMPLETE ETT BY TAU 120 AS IT GAINS FRONTAL CHARACTERISTICS.
HOWEVER, THE SYSTEM IS FORECAST TO MAINTAIN ATYPICALLY SLOW TRACK
SPEEDS AFTER TAU 96 DUE TO THE PRESENCE OF A STRONG, LOW-LEVEL
MIDLATITUDE HIGH TO THE NORTHEAST. AFTER TAU 72, TY 24W WILL WEAKEN
RAPIDLY DUE TO INCREASING VWS UNDER THE MIDLATITUDE WESTERLIES AND
COOLING SSTS. NAVGEM IS THE EASTERN OUTLIER SHOWING A TIGHTER
RECURVE. OTHERWISE, THE NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH
THE TRACK AND TIMING OF THE RECURVE, THEREFORE, THERE IS HIGH
OVERALL CONFIDENCE IN THE JTWC TRACK FORECAST.//
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