WDPN31 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.7N 109.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 86 NM EAST-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS REVEALED IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 
172254Z SSMIS 91 GHZ COLOR COMPOSITE MICROWAVE IMAGE, TROPICAL 
DEPRESSION (TD) 16W HAS CONSOLIDATED OVER THE PAST SIX HOURS WITH 
IMPROVED CONVECTIVE BANDING OVER THE NORTHERN SEMICIRCLE WRAPPING 
INTO THE WESTERN QUADRANT OF A PARTIALLY EXPOSED LOW-LEVEL 
CIRCULATION CENTER. THE INITIAL POSITION IS SOMEWHAT OBSCURED BUT IS 
PLACED WITH MEDIUM CONFIDENCE. THE INITIAL INTENSITY OF 30 KTS IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGENCY DVORAK AND 
AUTOMATED FIXES WHICH RANGE FROM 25 TO 33 KNOTS.

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

CURRENT STEERING MECHANISM: LOW-LEVEL REFLECTION OF THE SUBTROPICAL
RIDGE (STR) POSITIONED TO THE EAST AND NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 172330Z
   CIMSS AIDT: 30 KTS AT 180030Z
   CIMSS DPRINT: 33 KTS AT 180000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   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 TRACK GENERALLY NORTH-
NORTHWESTWARD THROUGH TAU 48 ALONG THE WESTERN PERIPHERY OF THE
LOW-LEVEL STR. THE SYSTEM IS EXPECTED TO MAINTAIN TD STRENGTH THROUGH
TAU 24 WITH GRADUAL INTENSIFICATION AFTER THE SYSTEM TRACKS PAST 
HAINAN ISLAND TO A PEAK INTENSITY OF 45 KNOTS BY TAU 48. DURING THIS 
SHORT PERIOD OF INTENSIFICATION, ENVIRONMENTAL CONDITIONS ARE 
EXPECTED TO IMPROVE, WITH ENHANCED POLEWARD OUTFLOW AND WARM SST. 
AFTER TAU 48, A WEAK STR IS EXPECTED TO BUILD TO THE NORTH AND 
NORTHWEST EFFECTIVELY BLOCKING POLEWARD PROGRESSION AND PRODUCING A 
PROLONGED PERIOD OF SLOW, QUASI-STATIONARY TRACK MOTION NORTHWEST OF 
HAINAN ISLAND. AFTER TAU 72, THE SYSTEM WILL LIKELY DRIFT SOUTHWARD 
WHILE WEAKENING DUE TO DRY AIR ENTRAINMENT AND WEAK DIVERGENCE ALOFT. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT 
THROUGH TAU 24 THEN FAIR AGREEMENT THROUGH TAU 72 THUS THERE IS 
MEDIUM OVERALL CONFIDENCE IN THE JTWC TRACK FORECAST THROUGH TAU
72. THE 171800Z COAMPS-TC ENSEMBLE (CTCXEPS) INTENSITY PROBABILITY
CHART SHOWS A 70 TO 80 PERCENT PROBABILITY OF MODERATE 
INTENSIFICATION FROM TAU 24 TO TAU 48. AFTER TAU 72, NUMERICAL MODEL 
GUIDANCE IS IN POOR AGREEMENT WITH A LARGE SPREAD IN TRACK FORECASTS. 
THE 171200Z ECMWF AND 171800Z GEFS PROBABILISTIC GUIDANCE INDICATES 
HIGH UNCERTAINTY IN THE TRACK OVER THE GULF OF TONKIN, REFLECTING THE 
WEAK, COMPETING STEERING ENVIRONMENT. IN GENERAL, BOTH THE 
DETERMINISTIC AND PROBABILISTIC GUIDANCE SUPPORT A STEADY WEAKENING 
TREND AFTER TAU 72.   

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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