WDPN31 PGTW 201500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SANBA) WARNING 
NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.3N 109.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 190 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 16W (SANBA) HAVING PERSISTED IN A MARGINAL
ENVIRONMENT OVER THE PAST SIX HOURS.  THOUGH THE LOW LEVEL
CIRCULATION CENTER IS COMPLETELY OBSCURED, MID LEVEL CLOUDS ARE
OBSERVED ROTATING CYCLONICALLY ABSENT OF ANY DEEP CONVECTION. 
MARGINAL SST (27-28 C), MODERATE TO HIGH VWS (20-25 KTS), AND DRY
AIR (RELATIVE HUMIDITY LESS THAN 50 PERCENT) CONTINUE TO WEAKEN TD
16W. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON
201200Z HIMAWARI-9 CIRA PROXYVIS IMAGE. THE INITIAL INTENSITY OF 30
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE AND
OBJECTIVE INTENSITY ESTIMATES LISTED BELOW, AS WELL AS SHIPBOARD
SURFACE OBSERVATIONS IVO 20.1N 107.7E REPORTING 32KTS NORTHERLY
WINDS AT 200900Z.

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

CURRENT STEERING MECHANISM: LOW TO MID-LEVEL NORTHEASTERLY FLOW

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 201140Z
   CIMSS AIDT: 33 KTS AT 201300Z
   CIMSS DPRINT 32 KTS AT 201300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK POLEWARD

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 16W IS FORECAST TO GRADUALLY WEAKEN OVER
THE NEXT 24 HOURS.  COMPLETE DISSIPATION IS ANTICIPATED PRIOR TO
TAU 24. MODERATE TO HIGH VERTICAL WIND SHEAR (20-25 KTS), MARGINAL
SST (27C TO 28C), LOW RELATIVE HUMIDITY (LESS THAN 50 PERCENT) WILL
SLOWLY DIMINISH WHAT IS LEFT OF THE LOW-LEVEL VORTEX.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT TD 16W WILL TRACK IN A GENERAL SOUTHWESTWARD DIRECTION
OVER THE NEXT 24 HOURS.  INTENSITY GUIDANCE SUGGESTS A SLOW
DISSIPATION OCCURRING OVER THE SAME INTERVAL, FROM 30 TO 20 KNOTS. 
A CROSS-TRACK SPREAD OF 98NM AND ALONG-TRACK SPREAD OF 168NM
PRESENT UNCERTAINTY IN TRACK SPEED AND DIRECTION.  HENCEFORTH, THE
JTWC FORECAST CONFIDENCE IS MEDIUM.

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