WDXS32 PGTW 020900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (THIRTEEN) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.7S 98.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 240 NM SOUTH-SOUTHEAST OF THE COCOS
ISLANDS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 13S WITH PERSISTENT CONVECTION FORMING OVER THE CENTER AND
A STRONG BANDING FEATURE EXTENDING TO THE SOUTH. ENVIRONMENTAL
ANALYSIS INDIACTES THAT 13S IS IN A FAVORABLE ENVIRONMENT
CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT, LOW (5-10 KTS)
VERTICAL WIND SHEAR, AND WARM (27-28 C) SEA SURFACE TEMPERATURES.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
LOW-LEVEL CLOUD TRACING IN THE ANIMATED MSI. THE INITIAL INTENSITY
OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY
DVORAK AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE FROM EARLIER SCATTEROMETER
DATA

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) CENTERED TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T2.5 - 35 KTS
   APRF: T2.0 - 30 KTS
   CIMSS SATCON: 46 KTS AT 020600Z
   CIMSS ADT: 33 KTS AT 020600Z
   CIMSS AIDT: 30 KTS AT 020600Z
   CIMSS DPRINT:36 KTS AT 020600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 13S IS FORECAST TO TRACK SOUTHWESTWARD, ALONG
THE NORTHWESTERN PERIPHERY OF THE STR THOUGHOUT THE FORECAST
PERIOD. REGARDING INTENSITY, 13S IS FORECAST TO STEADILY INTENSIFY
TO AROUND 70 KTS AT TAU 72. AFTER TAU 72, FURTHER INTENSIFICATION
WILL BE HALTED AS SEA SURFACE TEMPERATURES BECOME BORDERLINE.
HOWEVER, OTHER ENVIRONMENTAL FACTORS REMAIN FAVORABLE. AS A RESULT,
IS FORECAST TO MAINTAIN ITS INTENSITY AFTER TAU 72 THROUGH TAU 120.


MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 13S WITH A 205 NM CROSS TRACK SPREAD AT TAU
72 WHICH OPENS UP TO  330 NM AT TAU 120. WITH NO SIGNIFICANT
OUTLIERS, THE JTWC TRACK FORECAST IS PLACED CLOSE TO CONSENSUS
THROUGHOUT THE ENTIRETY OF THE FORECAST. THERE IS SOME DISAGREEMENT
REGARDING INTENSTY THOUGH. COAMPS-TC IS A MAJOR OUTLIER, SUGGESTING
MINIMAL INTENSIFICATION AND WEAKENING AFTER TAU 48. THE REMAINDER
OF GUIDANCE IS IN BETTER AGREEMENT, AND THE JTWC INTENSITY FORECAST
FOLLOWS CLOSELY TO THE MAIN GROUPING WITH MEDIUM CONFIDENCE.

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