Tropical Storm HALONG Advisory 11月7日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (HALONG) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 24W (HALONG), LOCATED APPROXIMATELY 552 NM EAST-
SOUTHEAST OF IWO TO, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 07
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED SATELLITE IMAGERY
(EIR)SHOWS THE SYSTEM HAS BEGUN TO WEAKEN AS EVIDENCED BY WARMING
CLOUD TOPS AND STRIATIONS ALONG THE NORTHEAST FLANK. A PINHOLE EYE
HAS ALSO BECOME OBSCURED OVER THE LAST FEW FRAMES IN THE EIR
ANIMATION. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED
ON THE PINHOLE EYE, ADJUSTED FOR A SLIGHT POLEWARD SLANT. THE
INITIAL INTENSITY OF 120KTS IS BASED ON THE HIGH END OF AGENCY AND
OBJECTIVE DVORAK ESTIMATES AND REFLECTS THE WEAKENING TREND. TY 24W
HAS DRIFTED INTO AN AREA OF MEDIUM (15-20KT) VERTICAL WIND SHEAR
(VWS) THAT IS PARTIALLY OFFSET BY A ROBUST POLEWARD OUTFLOW INTO THE
PREVAILING WESTERLIES. ALONG-TRACK SEA SURFACE TEMPERATURES (SST)
ARE NOW BELOW 28C AND LESS CONDUCIVE. OVERALL, THE ENVIRONMENT HAS
BECOME UNFAVORABLE. THE CYCLONE IS TRACKING THE POLEWARD SIDE OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY HALONG 24W WILL ACCELERATE AND TRACK ON A MORE
NORTHEASTWARD TRAJECTORY UNDER THE WESTERLY JET WINDS. THE
ENVIRONMENT WILL BECOME MORE UNFAVORABLE WITH INCREASING VWS AND
COOLING SSTS. ADDITIONALLY, BY TAU 24, THE SYSTEM WILL ENTER THE
BAROCLINIC ZONE AND BEGIN EXTRA-TROPICAL TRANSITION (ETT). THESE
COMBINED DYNAMICS WILL CONTRIBUTE TO ITS RAPID DECAY, AND BY TAU 48
WILL BE REDUCED TO A STORM-FORCE COLD CORE LOW WITH AN EXPANSIVE
WIND FIELD AS IT COMPLETES ETT. THE NUMERICAL MODELS ARE IN GOOD
AGREEMENT WITH MODERATE SPREADING, LENDING FAIR CONFIDENCE IN THE
JTWC TRACK FORECAST.//
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