WDXS31 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 01S (ONE) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.3S 87.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 559 NM WEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED SHEARED LOW LEVEL CIRCULATION WITH DEEP
CONVECTION DISPLACED TO THE SOUTHWEST. THE PARTIALLY EXPOSED LOW
LEVEL CIRCULATION CENTER (LLCC) IS ALSO IDENTIFIABLE ON A 171536Z
METOP-C MHS 89GHZ MICROWAVE IMAGE. WATER VAPOR IMAGERY HIGHLIGHTS
STRONG POLEWARD DIFFLUENCE ALOFT FEEDING INTO THE SUBTROPICAL JET
(STJ) TO THE SOUTH. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE AFOREMENTIONED MICROWAVE AND EIR IMAGERY.
THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: STEERED BY A SUBTROPICAL RIDGE (STR) TO
THE WEST-SOUTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   FMEE: T2.0 - 30 KTS
   CIMSS SATCON: 36 KTS AT 171537Z
   CIMSS ADT: 32 KTS AT 171815Z

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: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 01S WILL TRACK
WEST-SOUTHWESTWARD ON THE NORTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) TO THE SOUTH FOR THE REMAINDER OF THE FORECAST PERIOD.
VERTICAL WIND SHEAR WILL DECREASE FAVORABLY WITHIN THE NEXT 12
HOURS, ALLOWING FOR A PERIOD OF SLIGHT INTENSIFICATION IN THE
NEAR-TERM TO 40KTS. VERTICAL WIND SHEAR WILL INCREASE SIGNIFICANTLY
AS THE SYSTEM TRACKS CLOSER TO THE SUBTROPICAL JET (STJ) TO THE
SOUTH AROUND TAU 24-36. ADDITIONALLY, TC 01S WILL LOSE FAVORABLE
HEAT AND MOISTURE AS THE SYSTEM PASSES INTO COOL SEA SURFACE
TEMPERATURES BELOW 26C, INITIATING A PHASE OF WEAKENING AFTER TAU
24. TC 01S WILL DISSIPATE BELOW WARNING THRESHOLD BY TAU 48 AS
VERTICAL WIND SHEAR ERODES THE CIRCULATION STRUCTURE.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN STRONG
AGREEMENT THAT TC 01S WILL TRACK WEST-SOUTHWESTWARD WHILE DRIVEN BY
A SUBTROPICAL RIDGE TO THE SOUTH. ENSEMBLE GUIDANCE IS ALSO IN GOOD
AGREEMENT, DESPITE A SLIGHTLY LARGER SPREAD IN THE NEAR-TERM BY
ECENS. THE JTWC INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT TC 01S
WILL HAVE A PEAK INTENSITY OF APPROXIMATELY 40KTS WITHIN THE NEXT
12-24 HOURS. THE ENSEMBLE GUIDANCE CAPTURES PEAK INTENSITIES OF
35-40KTS AS WELL, WITH ECENS LEANING TOWARDS THE HIGHER END.

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