Tropical Storm NAMTHEUN Advisory Sáb, 01-10

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN)
WARNING NR 02//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 15W (FIFTEEN), LOCATED APPROXIMATELY 216 NM
SOUTH-SOUTHWEST OF KADENA AB, HAS TRACKED NORTH-NORTHEASTWARD AT
12 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY DEPICTS AN AREA OF FLARING CENTRAL CONVECTION WITH
FRAGMENTED BANDING WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER.
THE INITIAL POSITION IS BASED ON RECENT SATELLITE FIXES FROM PGTW
AND RJTD WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS ASSESSED AT
25 AND IS BASED ON THE CURRENT CONVECTIVE STRUCTURE AND DVORAK
ESTIMATES FROM PGTW AND RJTD REPORTING T1.5 (25 KNOTS). UPPER-LEVEL
ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH LOW VERTICAL WIND
SHEAR BEING OFFSET BY WEAK DIFFLUENCE AND DOMINANT WESTERLY FLOW.
SEA SURFACE TEMPERATURES ARE VERY FAVORABLE, NEAR 30 CELSIUS.
CURRENTLY TD 15W IS TRACKING NORTHEAST ALONG THE PERIPHERY OF A MID
TO LOW LEVEL NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR-TERM TD 15W WILL CONTINUE TO TRACK NORTHWEST UNDER
THE INFLUENCE OF THE STEERING RIDGE FOR THE FIRST 24 HOURS. FROM TAU
24 TO 48 TD 15W WILL ENTER A WEAK STEERING ENVIRONMENT AS THE NER
MOVES OFF TO THE SOUTHWEST AND A SUBTROPICAL RIDGE BUILDS IN FROM
THE NORTHEAST. SLIGHT INTENSIFICATION IS EXPECTED WHILE IN A QUASI-
STATIONARY SCENARIO AS UPPER-LEVEL CONDITIONS IMPROVE OVER FAVORABLE
WATERS. THIS PERIOD OF INTENSIFICATION WILL BE SHORT LIVED ONCE THE
SUBTROPICAL RIDGE BUILDS SUFFICIENTLY TO STEER TD 15W NORTH-
NORTHWESTWARD INTO A DEEPENING TROUGH POSITIONED OVER THE EAST CHINA
SEA. HIGH VERTICAL WIND SHEAR WILL WEAKEN TD 15W TO A WEAK TROPICAL
STORM BY TAU 72.
   C. IN THE EXTENDED FORECAST BEYOND TAU 72, TD 15W WILL FURTHER
WEAKEN UNDER THE INFLUENCE OF THE UPPER-LEVEL TROUGH BELOW TROPICAL
STORM STRENGTH. DYNAMIC MODEL GUIDANCE IS NOT HANDLING THE SYSTEM
VERY WELL DUE TO THE RELATIVELY WEAK INTENSITY OVER THE LIFE-CYCLE
OF THE SYSTEM. GFS IS SHOWING THE SYSTEM NEARLY DISSIPATED BEYOND
TAU 72 WHILE ALL OTHER MODEL GUIDANCE IS SHOWING TD 15W REMAINING AT
OR NEAR TROPICAL STORM STRENGTH AND SUPPORT THE GENERAL FORECAST
PHILOSOPHY. DUE TO THE UNCERTAINTY IN THE STEERING ENVIRONMENT THERE
IS LOW CONFIDENCE IN THE FORECAST TRACK.//
NNNN
NNNN