WDXS32 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (THIRTEEN) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.6S 101.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 328 NM SOUTHEAST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A DEVELOPING
SYSTEM WITH THE CENTRAL DENSE OVERCAST SHEARED WESTWARD, PARTIALLY
EXPOSING A DEFINED LOW LEVEL CIRCULATION (LLC). THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTLY EXPOSED
LLC AND LINED UP WITH A BULLSEYE FEATURE IN THE 011433Z ASCAT PASS.
THE INITIAL INTENSITY OF 35KTS, HELD HIGHER THAN AGENCY DVORAK 
ESTIMATES, IS ALSO PLACED WITH HIGH CONFIDENCE BASED ON A WIDE PATCH OF 
35-KT WIND BARBS ALONG THE SE-SW QUADRANTS IN THE ASCAT PASS. ANALYSIS 
INDICATES A FAVORABLE ENVIRONMENT WITH WARM SST AND STRONG POLEWARD 
OUTFLOW SLIGHTLY OFFSET BY MODERATE VWS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SSE.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   DEMS: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 13S WILL TRACK WEST-SOUTHWESTWARD UNDER THE
STEERING STR. THE FAVORABLE ENVIRONMENT WILL FUEL STEADY 
INTENSIFICATION TO A PEAK OF 65KTS BY TAU 72. AFTERWARD, INCREASING
VWS AND COOLING SST WILL GRADUALLY WEAKEN THE SYSTEM DOWN TO 55KTS
BY TAU 120. 

MODEL DISCUSSION: AVAILABLE NUMERICAL MODELS ARE IN VERY TIGHT
AGREEMENT WITH A GRADUAL AND EVEN SPREAD TO 102NM BY TAU 72 THEN TO
155NM BY TAU 120. HOWEVER, GIVEN THE UNCERTAINTIES ASSOCIATED WITH
A DEVELOPING SYSTEM, THERE IS ONLY MEDIUM CONFIDENCE IN THE JTWC
TRACK AND INTENSITY FORECASTS. 

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