Tropical Storm NAMTHEUN Advisory Thu Oct 14

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (NAMTHEUN)
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 23.9N 156.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 133 NM EAST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EASTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CONVECTION
OBSCURING A BROAD LOW-LEVEL CIRCULATION (LLC). A 132054Z SSMIS
91GHZ MICROWAVE IMAGE INDICATES DISORGANIZED DEEP CONVECTION
SHEARED TO THE EAST OF THE MAIN LLC, LENDING TO MEDIUM CONFIDENCE
IN INITIAL POSITION. TD 23W REMAINS SITUATED UNDER VIGOROUS
UPPER-LEVEL SOUTHERLY FLOW WITH STRONG RADIAL DIFFLUENCE FUELING
PERSISTENT DEEP CONVECTION OVER THE EASTERN SEMICIRCLE. THE INITIAL
INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
MULTIPLE AGENCY DVORAK ESTIMATES. ENVIRONMENTAL ANALYSIS REVEALS A
MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE VERTICAL WIND
SHEAR OFFSET BY STRONG RADIAL OUTFLOW.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF A LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHEAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: STRONG RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TD 23W WILL CONTINUE TO TRACK NORTHEASTWARD
THROUGH THE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE STR
TO THE SOUTHEAST. THE SYSTEM WILL MAINTAIN 30 KNOTS UNTIL IT BEGINS
ENCOUNTERING COOLER SSTS NEAR TAU 36. AT THIS TIME IT WILL
GRADUALLY WEAKEN AND ALSO BEGIN TO EXPERIENCE AN INCREASE IN VWS AS
IT MOVES INTO THE HIGHER LATITUDES. THE SYSTEM IS EXPECTED TO BEGIN
DISSIPATING BY TAU 48 AND FULLY COMPLETE BY TAU 72 IF NOT SOONER.
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH A 220NM SPREAD IN SOLUTIONS AT TAU 72, LENDING TO MEDIUM
CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE IS IN
FAIR AGREEMENT AS WELL WITH MULTIPLE MODELS SHOWING THE PEAK
INTENSITY AT 30 KNOTS THROUGH TAU 36. THE SYSTEM WILL CONTINUE
MOVING NORTHEAST AND SLOWLY DECREASE INTENSITY AS IT MOVES UNDER
THE INFLUENCE OF THE SUBTROPICAL WESTERLIES WHEREBY IT BEGINS
DISSIPATING OVER THE OPEN WATER.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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