WDPN32 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (NAMTHEUN) 
WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.2N 157.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 175 NM EAST OF MINAMI TORI SHIMA, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A MEDIUM-SIZED
SYSTEM WITH PERSISTENT CONVECTION OVER THE CENTRAL DENSE OVERCAST
(CDO) THAT IS TRAILING A FEEDER BAND SOUTHWARD. THE INITIAL POSITION 
IS PLACED WITH MEDIUM CONFIDENCE BASED ON LOW CLOUD LINE TRACING 
INTO THE OBSCURED LOW LEVEL CIRCULATION (LLC) AND EXTRAPOLATION FROM 
A WEAK LLC FEATURE IN THE 140232Z AMSR MICROWAVE IMAGE THE INITIAL 
INTENSITY OF 30KTS IS ASSIGNED WITH MEDIUM CONFIDENCE BASED ON AN 
OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND 
REFLECTS THE 6-HR PERSISTENT CONVECTIVE SIGNATURE OF THE SYSTEM. 
ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH STRONG EQUATORWARD 
OUTFLOW AND WARM SST OFFSET BY STRONG VWS. THE SYSTEM HAS BEGUN TO 
EXHIBIT SUBTROPICAL CHARACTERISTICS, I.E., ASYMMETRIC WIND FIELD AND 
VORTICITY SIGNATURE AND THE CDO OFFSET EASTWARD AND POLEWARD OF THE 
LLC. THE CYCLONE IS TRACKING ON THE POLEWARD SIDE OF THE STR TO THE 
SOUTH.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 26-28 CELSIUS
   OUTFLOW: STRONG EQUATORWARD

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 NAMTHEUN WILL CONTINUE ON ITS CURRENT TRACK
FOR THE DURATION OF THE FORECAST UNDER THE STEERING INFLUENCE OF
THE STR. THE MARGINAL ENVIRONMENT WILL SUSTAIN THE CURRENT INTENSITY
FOR UP TO TAU 24. AFTERWARD, INCREASING VWS AND COOLING SSTS WILL
GRADUALLY ERODE THE SYSTEM TOWARD DISSIPATION BY TAU 48, POSSIBLY
SOONER. CONCURRENTLY, THE CYCLONE WILL CONTINUE TO GAIN MORE
SUBTROPICAL CHARACTERISTICS. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN VERY TIGHT AGREEMENT,
GRADUALLY SPREADING TO 96NM AT TAU 48, LENDING HIGH CONFIDENCE TO
THE JTWC TRACK FORECAST. HOWEVER, THERE IS ONLY MEDIUM CONFIDENCE
THE INTENSITY FORECAST GIVEN THE UNCERTAINTY IN THE SUBTROPICAL
TRANSITION. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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