WDPN31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (CONSON) WARNING NR 
016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.1N 113.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 311 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
DISORGANIZED SYSTEM WITH FLARING CONVECTION OBSCURING AN ASSESSED LOW
LEVEL CIRCULATION (LLC) TRACKING WESTWARD OVER THE PAST SIX HOURS.
THE INITIAL INTENSITY OF 45 KTS IS BASED ON THE MULTI-AGENCY DVORAK
INTENSITY ESTIMATES. THE SYSTEM IS CURRENTLY TRACKING WESTWARD IN A
MARGINALLY FAVORABLE ENVIRONMENT WITH MODERATE VERTICAL WIND SHEAR,
WARM SEA SURFACE TEMPERATURES, AND WEAK RADIAL OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 45 KTS AT 091726Z
   CIMSS ADT: 49 KTS AT 091740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: INCREASE TO STORM INTENSITY AS IT
MAKES LANDFALL OVER CENTRAL VIETNAM.

FORECAST DISCUSSION: TROPICAL STORM (TS) 18W IS CURRENTLY TRACKING
WESTWARD UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGE TO THE
NORTHEAST. TS 18W IS FORECAST TO REMAIN ON THIS WESTERLY TRACK
THROUGH TAU 24. BY TAU 36, THE SYSTEM WILL REACH A MAX INTENSITY
OF 70 KTS AS IT MAKES A SLIGHT TURN TO THE WEST-NORTHWEST AS A
MID-LATITUDE TROUGH BEGINS TO DEEPEN TO THE NORTH, CREATING A WEAK
STEERING ENVIRONMENT. BY TAU 72, TS 18W IS EXPECTED TO MAKE
LANDFALL JUST NORTH OF HUE, VIETNAM WITH A SLIGHT DECREASE IN
INTENSITY OF 60 KTS. THE SYSTEM WILL THEN STEADILY DECREASE TO 30
KTS BY TAU 96, AND 20 KTS BY TAU 120, AS IT TRANSITS DEEPER OVER
THE INDOCHINA PENINSULA.

MODEL DISCUSSION: MODEL GUIDANCE DEPICTS A GENERALLY WESTWARD OR
WEST-NORTHWESTWARD TRACK TOWARDS THE COAST OF VIETNAM. HOWEVER,
THERE IS STILL A FAIR DEGREE OF UNCERTAINTY REGARDING THE POSITION OF
LANDFALL. CURRENT MODEL SOLUTIONS DEPICT A ROUGHLY 320 NM SPREAD 
ACROSS
THE COAST OF VIETNAM AND A MAJORITY OF THE CONSENSUS MEMBERS SHOW A
WESTERLY TRACK WITH LANDFALL OVER CENTRAL VIETNAM. THIS LENDS MEDIUM
CONFIDENCE IN THE JTWC FORECAST TRACK. MULTIMODEL INTENSITY GUIDANCE 
(ICNW) IS IN FAIR AGREEMENT, WITH ALL MODELS DEPICTING AN 
INTENSIFICATION PHASE WHICH PEAKS NEAR 70 KTS AROUND TAU 48, 
FOLLOWED 
BY A STEADY WEAKENING TREND BEFORE LANDFALL, HOWEVER THE JTWC 
INTENSITY
FORECAST IS HEDGED HIGHER THAN ICNW BEFORE LANDFALL DUE TO THE 
FORECASTED FAVORABLE ENVIRONMENTAL CONDITION WITH LOW TO MODERATE VWS
AND VERY WARM SSTS.

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