WDXS31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 26S (TWENTYSIX) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.9S 112.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 390 NM NORTH OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) OF TROPICAL
CYCLONE (TC) 26S AS IT IS BEGINNING TO YET AGAIN ACCELERATE
WESTWARD. AFTER A BRIEF PERIOD OF REDUCED TRANSLATIONAL SPEEDS, AS
THE SYSTEM INTERACTED WITH THE REMNANTS OF TROPICAL CYCLONE 25S, IT
IS NOW AGAIN UNDER THE INFLUENCE OF A LARGE-SCALE, DEEP-LAYER
SUBTROPICAL RIDGE CENTERED OVER WESTERN AUSTRALIA. OVER THE LAST
FEW HOURS, TC 26S MANAGED TO ALIGN VERTICALLY AND PRODUCE PERSISTENT 
CENTRAL CONVECTION, WHICH IS NOW HEAVILY SHEARED BY THE 25-30 KT 
EASTERLY VERTICAL WIND SHEAR (VWS). OUTFLOW REMAINS MODERATE TO STRONG, 
PRIMARILY IN THE WESTWARD DIRECTION, WITH AN ADDITIONAL POLEWARD 
COMPONENT. SEA SURFACE TEMPERATURES (SST) REMAIN FAVORABLE AND WARM 
(29-30 C), WHILE ADDITIONAL ENVIRONMENTAL ANALYSIS REVEALS PATCHY AREAS 
OF DRY MID-LEVEL AIR ENTERING THE CORE OF THE VORTEX PRIMARILY FROM THE 
SOUTHEAST. OVERALL THE RIVALING CHARACTERISTICS RESULT IN AN OVERALL 
MARGINAL ENVIRONMENT WITH SOME POTENTIAL FOR SLIGHT INTENSIFICATION. 
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE 
EXTRAPOLATION FROM A 061047Z RCM-3 SAR PASS. THE INITIAL INTENSITY OF 
35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE DATA FROM THE SAME 
SAR PASS, CORROBORATED BY THE AGENCY DVORAK AND OBJECTIVE ESTIMATES 
LISTED BELOW.

INITIAL WIND RADII BASIS: 061047Z RCM-3 SAR PASS

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED OVER WESTERN AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 061130Z
   CIMSS AIDT: 35 KTS AT 061130Z
   CIMSS D-MINT: 30 KTS AT 060912Z
   CIMSS D-PRINT: 27 KTS AT 061300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG WESTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT PRIMARY WITHIN THE
SOUTHEASTERN QUADRANT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TC 26S IS FORECAST TO CONTINUE TRACKING ALONG
THE NORTHWESTERN PERIPHERY OF THE STR CENTERED TO THE SOUTHEAST
THROUGHOUT THE CURRENT FORECAST PERIOD. AS THE SYSTEM IS BATTLING
HIGH (30+ KTS) VWS AND CONTINUOUS DRY AIR ENTRAINMENT, ITS ABILITY
TO MAINTAIN VERTICAL STRUCTURE AND UTILIZE WARM SEA SURFACE 
TEMPERATURES ALONG THE WAY WILL ALLOW IT TO MAINTAIN INTENSITY OF
AROUND 35 KTS UNTIL TAU 48. AROUND THAT TIME, AND AS THE SYSTEM
MOVES FURTHER POLEWARD, IT WILL BEGIN TO TRANSIT OVER COOLER (25-26
C) SEAS AND ENCOUNTER MORE DRY AIR CONTRIBUTING TO THE EROSION OF
ITS VORTEX AND RESULTING IN OVERALL WEAKENING. TC 26S IS FORECAST
TO FULLY DISSIPATE BY OR PRIOR TO TAU 72.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGHOUT THE FORECAST WITH ALL AVAILABLE GUIDANCE
AGREEING ON THE STEERING PATTERN, AS WITNESSED BY A CROSS-TRACK
SPREAD OF 50 NM AT TAU 24, EXPANDING ONLY TO ABOUT 100 NM BY THE
END OF THE FORECAST. THEREFORE JTWC OFFICIAL TRACK PREDICTION IS
LAID WITH HIGH CONFIDENCE. INTENSITY FORECAST IS ASSESSED WITH
MEDIUM CONFIDENCE AS IT CARRIES A BIT MORE UNCERTAINTY THROUGHOUT
THE CURRENT WARNING PERIOD. WHILE THE GUIDANCE ENVELOPE AMONG THE 
CONSENSUS MEMBERS IS NO LARGER THAN 20 KTS, THE PROGRESSION VARIES 
THROUGHOUT THE CURRENT FORECAST TIMES AND BEYOND. STATISTICAL-DYNAMICAL 
MODELS DEPICT CONTINUOUS WEAKENING AND FULL DISSIPATION AS SOON AS TAU 
24. NAVGEM-DRIVEN COAMPS-TC AND DETERMINISTIC GFS INDICATE
SLIGHT WEAKENING OR STEADY INTENSITY FOR THE INITIAL 48-60 HOURS,
FOLLOWED BY SLIGHT INTENSIFICATION. MEANWHILE, HAFS AND GFS-DRIVEN
COAMPS-TC PROJECT SLIGHT INITIAL INTENSIFICATION, WITH TC 26S
POTENTIALLY REACHING 40-45 KTS WITHIN 24-36 HOURS, FOLLOWED BY
WEAKENING AND DISSIPATION AFTERWARDS. OVERALL, THE INTENSITY ESTIMATE 
AND DISSIPATION TIMELINE WILL BE DRIVEN BY SEA SURFACE TEMPERATURES, 
DRY AIR ENTRAINMENT AND VWS INTENSITY, WHICH ALL WILL HEAVILY DEPEND ON 
HOW FAR SOUTH TC 26S WILL BE LOCATED BETWEEN TAUS 48-72. JTWC OFFICIAL 
INTENSITY PREDICTION IS ASSESSED CLOSE TO THE MULTI MODEL CONSENSUS 
GUIDANCE AT EACH OF THE FORECASTED TAUS.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM//
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