WDPN31 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SANBA) WARNING NR 
009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.9N 109.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 174 NM EAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 16W (SANBA) RAPIDLY ACCELERATING ALONG TRACK OVER THE PAST
SIX HOURS AND TAKING ADVANTAGE OF WARM SSTS ALONG THE WAY.  A
ROBUST FLARE OF CONVECTION COLLOCATED WITH THE LOW LEVEL
CIRCULATION CENTER (LLCC) OCCURRED AROUND 190900Z WITH OVERSHOOTING
TOPS DISPERSING RADIALLY ALOFT. THIS CREATED AN IMPRESSIVE
CONVECTIVE CANOPY ON EIR THAT FULLY OBSCURED THE LLCC WITH A 373NM
DIAMETER (EAST TO WEST) AT 191200Z. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON A HIMAWARI-9 EIR IMAGE. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW, AS WELL
AS SURFACE OBSERVATION REPORTS FROM NEARBY ZHANJIANG REPORTING
31KTS SOUTHEASTERLY WINDS AT 191200Z.

INITIAL WIND RADII BASIS: PERSISTENCE AND SCATTEROMETRY

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST AND
EXTENSION OF RIDGING TO WEST


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS ADT: 39 KTS AT 191130Z
   CIMSS AIDT: 36 KTS AT 191230Z
   CIMSS DPRINT: 37 KTS AT 191200Z
   CIMSS DMINT: 34 KTS AT 191112Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 16W RAPIDLY ACCELERATED TO A 6-HOUR TRACK
SPEED OF 11 KNOTS.  DESPITE THE ACCELERATED TRACK SPEED, THE
GENERAL THEME AMONG MODEL GUIDANCE IS THAT THE SYSTEM WILL SLOW
TRACK SPEED AND EVENTUALLY COME TO A NEAR RECIPROCAL COURSE
SOUTHWESTWARD AROUND TAU 12. THIS STALL IN VELOCITY WILL ENABLE
UPWELLING OF COOLER OCEAN WATERS TO OCCUR. BETWEEN THE UPWELLING
AND INCREASING VERTICAL WIND SHEAR, THE SYSTEM IS ANTICIPATED TO
WEAKEN SIGNIFICANTLY BY TAU 48 TO AND COMPLETELY DISSIPATE OVER
WATER BY TAU 72.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE CONTINUES TO
INDICATE AND BE OF GOOD AGREEMENT THAT TS 16W WILL TRACK GENERALLY
NORTHEASTWARD THROUGH TAU 12, AND THEN TRACK BACK ON A NEAR
RECIPROCAL COURSE TO THE SOUTHWEST THROUGH THE FORECAST PERIOD.
SINCE THE PREVIOUS WARNING (008), MOGREPS HAS COME INTO AGREEMENT
WITH THE OTHER CONSENSUS MEMBERS.  TRACK SPEED CONTINUES TO PRESENT
GREAT UNCERTAINTY AMONG THE JTWC CONSENSUS WITH AN ALONG TRACK
ERROR OF APPROXIMATELY 294NM BETWEEN GALWEM AND GFS AT TAU 72. THIS
UNCERTAINTY OF TRACK SPEED CONTRIBUTES TO AN OVERALL FORECAST
CONFIDENCE OF MEDIUM.

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