Tropical Storm ATSANI Advisory 11月4日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (ATSANI)
WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 23W (ATSANI), LOCATED APPROXIMATELY 390 NM SOUTH
OF KADENA AB, HAS TRACKED EAST-NORTHEASTWARD AT 04 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR)
SHOWS A QUASI-STATIONARY SYSTEM WITH FORMATIVE DEEP CONVECTIVE BANDS
AND CYCLING CONVECTIVE ACTIVITY NEAR THE ASSESSED LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH FAIR
CONFIDENCE BASED ON THE BANDING FEATURES WHICH ARE EVIDENT IN A
031737Z ATMS MICROWAVE IMAGE. THE INITIAL INTENSITY IS ASSESSED AT
35 KNOTS WITH FAIR CONFIDENCE BASED ON PGTW AND RJTD CURRENT
INTENSITY ESTIMATES OF T2.5 AND A 031740Z ADVANCED DVORAK TECHNIQUE
(ADT) ESTIMATE OF 37 KNOTS. THE OVERALL ENVIRONMENT REMAINS
FAVORABLE FOR DEVELOPMENT WITH WARM (28 TO 29 DEGREE CELSIUS) SEA
SURFACE TEMPERATURES (SST), LOW (5-10 KNOTS) VWS, AND MODERATE
OUTFLOW OFFSET TO THE NORTHEAST. THE SYSTEM REMAINS ENTRENCHED IN A
COL REGION WITH NO DOMINANT STEERING FLOW.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 23W IS EXPECTED TO FINALLY TURN BACK WEST AND THEN WEST-
NORTHWEST UNDER A WEAK STEERING ENVIRONMENT OVER THE NEXT 24 HOURS
AS A STR LOCATED TO THE NORTHEAST BEGINS TO BUILD IN. BY TAU 36, THE
STR BUILDS EVEN FURTHER WEST, AND WILL SERVE TO ACCELERATE TS 23W
INTO THE LUZON STRAIT BY TAU 60, WITH A PEAK INTENSITY OF 60 KNOTS
EXPECTED AT TAU 72. THE ENVIRONMENT IS EXPECTED TO REMAIN FAVORABLE
THROUGH TAU 72 WITH GOOD OUTFLOW, LOW (5-10 KNOTS) VWS AND WARM (28-
29 DEGREE CELSIUS) SST VALUES. NUMERICAL MODELS ARE IN OVERALL GOOD
AGREEMENT WITH A SPREAD OF 140NM AT TAU 72 DISCOUNTING THE NAVGEM
SOLUTION, WHICH CONTINUES TO TAKE THE SYSTEM ON AN UNREALISTIC TRACK
NORTH OVER TAIWAN AND INTO THE EAST CHINA SEA. THE JTWC FORECAST
LIES NEAR THE MULTI-MODEL CONSENSUS SOLUTION THROUGH TAU 72 WITH
FAIR CONFIDENCE DUE TO THE NEAR-TERM ERRATIC MOTION AND RESULTANT
UNCERTAINTY IN THE TIMING OF THE TURN TO THE WEST.
   C. AFTER TAU 72, THE SYSTEM BEGINS TO TRACK SOUTHWESTWARD AS TS
23W TAKES STEERING FROM A SECOND STR LOCATED OVER INDOCHINA, WHICH
HAS A MORE SOUTHWEST-NORTHEAST ORIENTATION. ADDITIONALLY, THE SYSTEM
BEGINS TO FEEL THE IMPACT OF INCREASING VWS (15-30 KNOTS),
DECREASING SST AND CONVERGENT FLOW ALOFT, LEADING TO A FAIRLY RAPID
WEAKENING TREND. DYNAMIC MODEL GUIDANCE IS IN OVERALL GOOD AGREEMENT.
HOWEVER, NAVGEM TAKES THE SYSTEM INTO THE EAST CHINA SEA, WHILE THE
AFUM SOLUTION TURNS DRAMATICALLY SOUTHWARD AFTER TAU 72. BOTH
SOLUTIONS ARE CONSIDERED UNREALISTIC AND DISCOUNTED FROM THE MULTI-
MODEL CONSENSUS WHICH JTWC IS LAID ALONG. THERE IS OVERALL FAIR
CONFIDENCE IN THE LATER JTWC TRACK FORECAST DUE TO THE CURRENT QUASI-
STATIONARY STATE AND THE OVERALL SPREAD IN THE GUIDANCE.//
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