Tropical Storm SIX Advisory 8月13日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING
NR 014//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 06W (SIX), LOCATED APPROXIMATELY 299 NM
EAST-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN HAS TRACKED WEST-
SOUTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY DEPICTS DEEP CONVECTION BUILDING OVER THE
LOW-LEVEL CIRCULATION (LLC), OBSCURING THE EXACT LOCATION OF THE
LLC. THERE ARE NO RECENT MICROWAVE IMAGES AVAILABLE TO ASSIST IN
DETERMINING THE EXACT LOCATION OF THE LLC, LEADING TO LOW CONFIDENCE
IN THE INITIAL POSITION. THE INITIAL INTENSITY IS HELD AT 25 KNOTS
BASED ON A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF 1.5 (25 KNOTS).
THE SYSTEM REMAINS EMBEDDED WITHIN AN EXPANSIVE REGION OF ENHANCED
EASTERLIES BETWEEN THE UPPER-LEVEL RIDGE AND A TUTT CELL TO THE
SOUTHEAST WITH LOW TO MODERATE (15 TO 20 KNOTS) VERTICAL WIND SHEAR,
DRY AIR ENTRAINMENT AND WEAK DIFFLUENCE ALOFT. TD 06W IS TRACKING
WEST-SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF A LOW-LEVEL
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH AND NORTHWEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TD 06W IS FORECAST TO TRACK WESTWARD WITH A SLIGHT SOUTHERLY
COMPONENT THROUGH TAU 12. AS IT APPROACHES THE RYUKYU ISLANDS, THE
SYSTEM SHOULD TURN WESTWARD AS IT TRACKS ALONG THE SOUTHWEST
PERIPHERY OF THE STR. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO
REMAIN MARGINAL WITH LOW VWS AND DRY AIR ENTRAINMENT (700-500MB RH
VALUES OF 50-55%). THEREFORE, THE SYSTEM SHOULD REMAIN SHALLOW AND
WEAK, LIKELY DISSIPATING BY TAU 36 WITH SOME POTENTIAL FOR
DISSIPATION EARLIER IN THE FORECAST PERIOD. NUMERICAL MODEL GUIDANCE
IS IN TIGHT AGREEMENT THROUGH TAU 12 AND MOST MODELS ARE IN
AGREEMENT THROUGH TAU 36, WITH GFS BEING THE OUTLIER TURNING THE
SYSTEM SOUTHWESTWARD AFTER TAU 12. THEREFORE, THE JTWC FORECAST
TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH
CONFIDENCE.//
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