Tropical Storm KROSA Advisory 8月11日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (KROSA) WARNING NR
021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 11W (KROSA), LOCATED APPROXIMATELY 822 NM
SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED WESTWARD AT 02 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS SLIGHTLY IMPROVED CONVECTIVE BANDING WRAPPING INTO A DEFINED
LOW-LEVEL CIRCULATION CENTER (LLCC). HOWEVER, DEEP CONVECTION OVER
THE CORE AND NORTHWEST QUADRANT REMAIN WEAK DUE TO THE PRESENCE OF
CYCLONIC FLOW AND CONVERGENCE ALOFT WHILE STRONG DIFFLUENCE OVER THE
EASTERN AND SOUTHERN FLANK CONTINUE TO FUEL DEEP CONVECTIVE BANDING.
A 101750Z SSMI 37GHZ IMAGE INDICATES TIGHTLY-CURVED BANDING
WRAPPING INTO A DEFINED, ELONGATED LLCC, WHICH SUPPORTS THE INITIAL
POSITION WITH GOOD CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT
60 KNOTS, HEDGED SLIGHTLY BELOW DVORAK CURRENT INTENSITY ESTIMATES
OF 4.0 (65 KNOTS), BASED ON THE BROAD CONVECTIVE STRUCTURE. WITH THE
EXCEPTION OF THE COMPLEX, MARGINALLY-FAVORABLE OUTFLOW, VERTICAL
WIND SHEAR AND SST VALUES REMAIN FAVORABLE. TS 11W IS LOCATED WITHIN
A WEAK STEERING ENVIRONMENT WITH A NORTH-SOUTH SUBTROPICAL RIDGE
POSITIONED TO THE EAST, A WEAK STR OVER CENTRAL JAPAN AND A BREAK TO
THE NORTH-NORTHEAST. THEREFORE, TS 11W IS TRACKING ERRATICALLY.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEXT 72 HOURS, THE PRIMARY STEERING FOR TS 11W WILL
GRADUALLY TRANSITION TO THE BUILDING STR TO THE NORTH OF TS 11W AND
THE TRACK WILL SLOWLY SHIFT NORTHWESTWARD TOWARD JAPAN. SLIGHTLY
DIMINISHED OUTFLOW, WEAK SUBSIDENCE AND POSSIBLE UPWELLING COOLER
WATER WILL MAKE THE ENVIRONMENT SOMEWHAT UNFAVORABLE THROUGH TAU 24
WITH GRADUAL WEAKENING TO ABOUT 55 KNOTS. AFTER TAU 24, AS THE
SYSTEM BEGINS TO ACCELERATE WEST-NORTHWESTWARD TO NORTHWESTWARD OVER
WARM SST, GRADUAL INTENSIFICATION IS EXPECTED. TS 11W SHOULD
RE-INTENSIFY TO A PEAK INTENSITY OF 70 KNOTS BY TAU 72 AS POLEWARD
OUTFLOW IMPROVES.
   C. AFTER TAU 72, TS 11W WILL RECURVE POLEWARD ALONG THE SOUTHWEST
PERIPHERY OF THE STR, WHICH IS EXPECTED TO WEAKEN AND REORIENT WITH
THE APPROACH OF A DEEP MIDLATITUDE SHORTWAVE TROUGH. SST VALUES WILL
REMAIN CONDUCIVE (28-29C) THROUGH TAU 96. NUMERICAL MODEL GUIDANCE
DIVERGES WITH A 160NM SPREAD IN SOLUTIONS AT TAU 96. BASED ON THE
ERRATIC SHORT-TERM MOTION AND UNCERTAINTY IN THE LATER TAUS, THERE
IS OVERALL MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK.//
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