Tropical Storm SIX Advisory 8月12日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR
010//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 531 NM EAST
OF KADENA AB, OKINAWA, HAS TRACKED WESTWARD AT 16 KNOTS (KTS) OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A
PARTIALLY-EXPOSED, WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC) WITH
FLARING DEEP CONVECTION IN THE WESTERN SEMICIRCLE, LEADING TO HIGH
CONFIDENCE IN THE INITIAL POSITION. AN 111648Z AMSR2 89 GHZ MICROWAVE
IMAGE SHOWS ISOLATED POCKETS OF DEEP CONVECTION LOCATED TO THE SOUTH AND
WEST OF THE DEFINED LLCC. THE INITIAL INTENSITY REMAINS ASSESSED AT 25
KTS BASED ON A DVORAK CURRENT INTENSITY ESTIMATE OF T1.5 (25 KTS) AND
PREVIOUS ASCAT DATA. FAVORABLE SST (NEAR 30 CELSIUS) AND FAIR
EQUATORWARD OUTFLOW ARE OFFSET BY PERSISTENT, MODERATE (15-20 KT)
EASTERLY VERTICAL WIND SHEAR (VWS). ADDITIONALLY, LOW 700-500 MB
RELATIVE HUMIDITY VALUES OF 40-45% ARE CAUSING THE SYSTEM TO CONTINUE TO
STRUGGLE. TD 06W IS TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF A
LOW LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. DUE TO THE WSW-ENE ORIENTATION OF THE LOW-LEVEL STR, TD 06W IS
FORECAST TO TRACK WEST-SOUTHWESTWARD AS IT NEARS THE RYUKYU ISLANDS.
THERE IS POTENTIAL FOR SLIGHT INTENSIFICATION TO A PEAK INTENSITY OF 30
KTS THROUGH TAU 12. HOWEVER, TD 06W IS EXPECTED TO REMAIN SHALLOW AND
RELATIVELY WEAK DUE TO A CONTINUED MARGINAL ENVIRONMENT OF LOW TO
MODERATE EAST-NORTHEASTERLY VWS. NUMERICAL MODELS ARE IN GOOD AGREEMENT
THROUGH TAU 48 AND THEN FAIR AGREEMENT THROUGH TAU 72. THE SOLE OUTLIER,
THE GFS ENSEMBLE SOLUTION, TRACKS FURTHER TO THE SOUTH AFTER TAU 24 THAN
THE MAJORITY OF THE OTHER SOLUTIONS. AFTER TAU 48, THE MODEL SOLUTIONS
BEGIN TO DIVERGE AND CROSS-TRACK SPREAD INCREASES FROM 50NM TO 180NM BY
TAU 72. THEREFORE, THERE IS MODERATE CONFIDENCE IN THE JTWC FORECAST
TRACK WHICH IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS.//
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