WDPN32 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (NAMTHEUN) 
WARNING NR 015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.1N 153.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 66 NM SOUTH OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY-EXPOSED, BROAD LOW-LEVEL CIRCULATION (LLC) POSITIONED
SOUTHWEST OF A CIRCULAR AREA OF INTENSE DEEP CONVECTION, WHICH IS
OBSCURING THE CENTER. A 130823Z SSMIS 91GHZ MICROWAVE IMAGE
INDICATES A WEAKLY DEFINED LLCC WITH DISORGANIZED DEEP CONVECTION
SHEARED TO THE EAST. TD 23W REMAINS SITUATED UNDER VIGOROUS UPPER-
LEVEL SOUTHERLY FLOW WITH STRONG DIFFLUENCE FUELING PERSISTENT DEEP
CONVECTION OVER THE EASTERN SEMICIRCLE. DUE TO THE LACK OF RECENT
MICROWAVE IMAGERY AND THE OBSCURED, BROAD LLC, THERE IS LOW
CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY OF 30 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW DVORAK
ESTIMATE AND RECENT ASCAT DATA.

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: T2.5 - 35 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 46 KTS AT 130831Z
   CIMSS ADT: 37 KTS AT 131140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EASTWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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 IS EXPECTED TO TRACK NORTH-NORTHEASTWARD 
THROUGH THE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE STR 
TO THE SOUTHEAST. SLIGHT INTENSIFICATION IS ANTICIPATED BY TAU 12 
THEN A STEADY WEAKENING TREND THROUGH THE REMAINDER OF THE FORECAST 
AS CONDITIONS GRADUALLY DEGRADE.   

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH A 160NM SPREAD IN SOLUTIONS AT TAU 48 LENDING MEDIUM
CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE IS IN
FAIR AGREEMENT AS WELL WITH HWRF INDICATING A SLIGHT
INTENSIFICATION TO NEAR 40 KNOTS BY TAU 12 THEN A STEADY WEAKENING
TREND. COAMPS-TC AND SHIPS GUIDANCE INDICATES A PEAK NEAR 40-45
KNOTS AT TAU 48 TO TAU 60 LIKELY ASSOCIATED WITH THE INFLUENCE AND
UPPER-LEVEL SUPPORT OF SUBTROPICAL WESTERLIES.       

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