WDPN31 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (CONSON) WARNING NR 
020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.7N 110.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 145 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP
CONVECTION SITUATED TO THE WEST OF THE PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION AND INTENSITY OF 45
KTS ARE ASSESSED WITH MEDIUM CONFIDENCE BASED ON MULTIPLE AGENCY
DVORAK FIXES AND THE AFOREMENTIONED EIR IMAGERY. DESPITE WARM SEA
SURFACE TEMPERATURES, THE WEAK EQUATORWARD OUTFLOW AND MODERATE
VERTICAL WIND SHEAR MAINTAIN AN ONLY MARGINALLY FAVORABLE
ENVIRONMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 45 KTS AT 101750Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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 CONSON WILL CONTINUE TO TRACK GENERALLY
WESTWARD THROUGH TAU 12 UNDER THE STR UNDER A WEAK EQUATORWARD 
OUTFLOW CHANNEL. AFTERWARD, IT WILL TURN MORE WEST-NORTHWESTWARD AS 
THE STR IS WEAKENED BY AN UPPER-LEVEL TROUGH. BY TAU 12, THERE WILL 
BE A SHORT PERIOD OF DECREASED VWS, WHICH WILL FUEL A SLIGHT 
INTENSIFICATION TO A PEAK OF 50 KTS. AFTER TAU 12, VWS WILL INCREASE 
ONCE AGAIN. IN ADDITION, TS 18W WILL BEGIN TO FEEL THE EFFECTS OF 
LAND INTERACTION WITH THE MOUNTAINOUS TERRAIN OF VIETNAM. AS A 
RESULT, A DECREASE IN INTENSITY TO 40 KTS WILL BE EXPECTED BY TAU 
24. BY TAU 36, TS 18W WILL BE MAKING LANDFALL JUST SOUTH OF DA NANG, 
VIETNAM WITH A DECREASED INTENSITY OF 35 KTS. BY TAU 48, TS 18W WILL 
UNDERGO DISSIPATION OVER LAND AND WILL BECOME FULLY DISSIPATED BY 
TAU 72.

MODEL DISCUSSION: MODEL GUIDANCE HAS COME INTO TIGHTER AGREEMENT 
THAN THE PREVIOUS MODEL RUNS, WITH NAVGEM AND UKMET BEING THE 
OUTLIERS WITH ERRATIC MOVEMENT TO THE SOUTHWEST JUST BEFORE 
LANDFALL. AS A RESULT, THE FORECAST TRACK IS PLACED WITH MEDIUM 
CONFIDENCE JUST TO THE RIGHT OF THE JTWC CONSENSUS (CONW). IN
ADDITION, THE INTENSITY GUIDANCE HAS ALSO COME INTO BETTER AGREEMENT 
OVER THE PAST SIX HOURS. THE INTENSITY FORECAST IS HEDGED SLIGHTLY 
HIGHER THAN THE JTWC INTENSITY CONSENSUS (ICNW) TO MAKE UP FOR THE 
AFOREMENTIONED SLIGHT WEAKENING IN VWS BEFORE LAND INTERACTION.

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