Tropical Storm KROSA Advisory 8月13日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR
029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 291 NM
WEST-NORTHWEST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 13 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS A VERY EXPANSIVE SYSTEM WITH FRAGMENTED CONVECTIVE
BANDS SPIRALING IN FROM THE SOUTHWEST INTO A LARGE, RAGGED AND FULLY
EXPOSED LOW-LEVEL CIRCULATION (LLC).
THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE
CENTER OF THE LLC SEEN IN EIR THAT LINES UP WITH THE BROAD LLC IN THE
121705Z ATMS MICROWAVE IMAGE. THE INITIAL INTENSITY OF 50 KNOTS IS
SET BETWEEN THE MULTI-AGENCY DVORAK CURRENT ESTIMATES RANGING FROM
T3.0-4.0 (45-65 KNOTS). THIS INTENSITY IS FURTHER SUPPORTED BY A
121614Z SATCON ESTIMATE OF 52 KNOTS. UPPER LEVEL ANALYSIS INDICATES A
MARGINAL ENVIRONMENT WITH A LOW DIRECTLY OVER THE LLC WHICH IS
INHIBITING CONVECTION. SEA SURFACE TEMPERATURE (SST) REMAINS
CONDUCIVE (29-30 DEGREES CELSIUS). THE CYCLONE IS TRACKING ALONG THE
SOUTHWESTERN PERIPHERY OF A BUILDING SUBTROPICAL RIDGE (STR) TO THE
NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. OVER THE NEXT 36 HOURS, TS 11W WILL CONTINUE ON ITS CURRENT
TRACK UNDER THE INFLUENCE OF THE AFOREMENTIONED STR. NEAR TAU 36, IT
WILL TURN POLEWARD AROUND THE STR AXIS, MAKING LANDFALL OVER WESTERN
SHIKOKU NEAR TAU 48. THE MARGINAL CONDITIONS WILL SUSTAIN THE CURRENT
INTENSITY UP TO TAU 24. AFTERWARD, INCREASING POLEWARD OUTFLOW AHEAD
OF A MID-LATITUDE TROUGH WILL PROMOTE A SLIGHT INTENSIFICATION TO A
PEAK OF 60 KNOTS BY TAU 48. LAND INTERACTION, INCREASING VWS, AND
COOLER SST (24-26 DEGREES CELSIUS) IN THE SEA OF JAPAN (SOJ) WILL
COMBINE TO GRADUALLY WEAKEN THE SYSTEM DOWN TO 50KTS BY TAU 72 AS IT
EXITS INTO THE SOJ. NUMERICAL MODELS ARE IN GOOD AGREEMENT, WITH THE
EXCEPTION OF NAVGEM, WHICH IS EXPECTING AN EARLIER RECURVE, LENDING
HIGH CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.
   C. AFTER TAU 72, COOLER SST IN THE SOJ WILL COMBINE WITH INCREASED
SHEAR TO RAPIDLY WEAKEN THE SYSTEM DOWN TO 40KTS BY TAU 96 AS IT
ACCELERATES INTO THE NORTHERN SOJ WEST OF HOKKAIDO. TS 11W WILL BEGIN
EXTRA-TROPICAL TRANSITION AS IT ENTERS THE BAROCLINIC ZONE, BECOMING
A COLD CORE LOW WITH AN EXPANSIVE WIND FIELD BY TAU 96. NUMERICAL
MODEL DIFFERENCE SPREADS OUT TO 320 NM, MOSTLY DUE TO TRACK SPEED
DIFFERENCE, BY TAU 96. THERE IS OVERALL MODERATE CONFIDENCE IN THE
JTWC FORECAST TRACK FOR THIS PORTION OF THE FORECAST THAT IS LAID
JUST TO THE LEFT OF CONSENSUS TO OFFSET THE UNLIKELY NAVGEM/JGSM
SOLUTION THAT DRIVES THE VORTEX INTO THE STR.//
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