WDXS31 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 26S (TWENTYSIX) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.6S 108.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 407 NM NORTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH DEEP
CONVECTION IN THE WESTERN HEMISPHERE BEING SHEARD WESTWARD. THE
LLCC HAS LOST SOME DEFINITION OVER THE LAST 12 HOURS UNDER THE
EFFECTS OF STRONG EASTERLY SHEAR AND DRY AIR ENTRAINMENT. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LLCC IN ANIMATED EIR IMAGERY. THE INITIAL
INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
HIGH END OF THE AGENCY DVORAK FIXES AND CIMSS INTENSITY ESTIMATES
LISTED BELOW. TC 26S IS NOW ANALYZED TO BE WITHIN AN UNFAVORABLE
ENVIRONMENT CHARACTERIZED BY MODERATE WESTWARD OUTFLOW AND WARM
(27-28 C) SEA SURFACE TEMPERATURES (SST) GREATLY OFFSET BY STRONG
EASTERLY SHEAR AND SIGNIFICANT DRY AIR ENTRAINMENT.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 071130Z
   CIMSS AIDT: 35 KTS AT 071130Z
   CIMSS D-MINT: 25 KTS AT 071157Z
   CIMSS D-PRINT: 26 KTS AT 071130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST

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: TC 26S WILL CONTINUE WEST-SOUTHWESTWARD UNDER
THE INFLUENCE OF THE DEEP-LAYER SUBTROPICAL RIDGE TO THE SOUTHEAST.
THE CYCLONE HAS ACCELERATED OVER THE PAST 12 HOURS AND IS EXPECTED
TO APPROACH THE 26 C SST ISOTHERM BY TAU 24. THE COMBINATION OF
COOLER SST, PERSISTENT EASTERLY WIND SHEAR, AND DRY AIR ENTRAINMENT
ARE EXPECTED TO OVERCOME ANY SUPPORT FROM REMAINING WESTWARD
OUTFLOW AND CAUSE DISSIPATION BY TAU 24.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH A 45 NM CROSS-TRACK SPREAD AT TAU 24 AND MINIMAL
ALONG-TRACK SPREAD. NAVGEM REMAINS THE SOUTHERNMOST MODEL WHILE THE
GOOGLE DEEPMIND ENSEMBLE MEAN IS THE NORTHERNMOST. THE JTWC TRACK
FORECAST FOLLOWS CLOSELY TO THE CONSENSUS WITH HIGH CONFIDENCE.
INTENSITY GUIDANCE GENERALLY AGREES ON GRADUAL WEAKENING, WITH ALL
MODELS EXCEPT DECAY SHIPS SUGGESTING DECAY BELOW 35 KNOTS WITHIN
THE NEXT 24 HOURS. THE JTWC INTENSITY FORECAST FOLLOWS CLOSELY TO
THE CONSENSUS WITH HIGH CONFIDENCE.

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