Tropical Storm TWENTYTHREE Advisory 10月10日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (TWENTYTHREE)
WARNING NR 05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 23W (TWENTYTHREE), LOCATED APPROXIMATELY
128 NM NORTH-NORTHWEST OF DA NANG, VIETNAM, HAS TRACKED WEST-
NORTHWESTWARD AT 19 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS RAGGED BANDS OF DEEP
CONVECTION WRAPPING AROUND AN ILL-DEFINED LOW LEVEL CIRCULATION
CENTER (LLCC). DETERMINING THE EXACT CENTER HAS BEEN CHALLENGING,
HIGHLIGHTED BY THE LARGE SPREAD IN AVAILABLE FIX ESTIMATES. RECENT
PASSES BY ASCAT AND OSCAT (STILL UNDER TESTING AND EVALUATION)
PROVIDED SOME DETAIL OF THE OVERALL STRUCTURE, WITH ENHANCED (25-30
KNOT) EASTERLIES TO THE NORTH ALONG THE CHINESE COAST, AND WEAK (5-
10 KNOT) WESTERLY FLOW TO THE SOUTH OF THE LLCC. THE TRACK WAS
SHIFTED SLIGHTLY SOUTH BASED ON THIS DATA. THE INITIAL POSITION IS
BASED ON THE EIR LOOP, AND SUPPORTED BY OBSERVATIONS FROM STATION
48846 (12 KNOTS FROM 50 DEGREES AND 1001.5 MB MSLP) AND STATION
48848 FURTHER SOUTH (1-2 KNOTS FROM 230 DEGREES AND 1000.2 MB MSLP).
THE INITIAL INTENSITY OF 30 KNOTS IS HEDGED ABOVE PGTW AND RJTD
DVORAK ESTIMATES OF T1.5 (25 KNOTS) BASED ON THE AFOREMENTIONED
SCATTEROMETRY DATA, HOWEVER, THE PEAK WINDS ARE CONSTRAINED TO THE
NORTHERN GULF OF TONKIN. UPPER LEVEL ANALYSIS REVEALS WELL
ESTABLISHED OUTFLOW, HOWEVER, FURTHER DEVELOPMENT HAS BEEN
CONSTRAINED DUE TO 20+ KNOT VERTICAL WIND SHEAR VALUES. SEA SURFACE
TEMPERATURES REMAIN FAVORABLE (28-29 CELSIUS). TD 23W IS TRACKING
WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE MID-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TD 23W WILL CONTINUE TRACKING WEST-NORTHWESTWARD AND MAKE
LANDFALL OVER CENTRAL VIETNAM IN THE NEXT FEW HOURS. THE SYSTEM WILL
WEAKEN RAPIDLY AS IT MOVES AWAY FROM THE ENHANCED MARITIME WINDS.
MODEL GUIDANCE IS IN GOOD AGREEMENT FOR BOTH TRACK AND INTENSITY.
OVERALL CONFIDENCE FOR THE JTWC FORECAST IS HIGH.//
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