WDXS31 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27S (COURTNEY) WARNING 
NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8S 105.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 565 NM WEST-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN
INCREASINGLY MORE SYMMETRICAL CONVECTIVE CANOPY OF TROPICAL CYCLONE
(TC) 27S (COURTNEY). THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON A 252330Z F16 SSMIS MICROWAVE PASS, SHOWING
CONSOLIDATING CONVECTIVE BANDING, WRAPPING INTO THE LOW-LEVEL 
CIRCULATION CENTER (LLCC), IDENTIFIED THROUGH 91 GHZ AND 37 GHZ 
CHANNELS. THE SYSTEM REMAINS VERTICALLY TILTED, HOWEVER UPPER-LEVEL 
CONSOLIDATION INDICATES SIGNIFICANT IMPROVEMENT IN THE STRUCTURE OF 
THE VORTEX. ENVIRONMENTAL ANALYSIS REVEALS ENVIRONMENT CONDUCIVE TO 
FURTHER INTENSIFICATION, WITH LOW (10-15 KTS) NORTHEASTERLY VERTICAL 
WIND SHEAR (VWS), WARM (28-29 C) SEA SURFACE TEMPERATURES (SST), 
MODERATE EQUATORWARD AND POLEWARD OUTFLOW, AMPLIFIED BY PLENTY OF 
AVAILABLE MOISTURE. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND OBJECTIVE INTENSITY 
ESTIMATES LISTED BELOW, AS WELL AS RECENT IMPROVEMENT IN THE STRUCTURE 
OF THE SYSTEM.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T3.5 - 55 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS SATCON: 53 KTS AT 260000Z
   CIMSS ADT: 53 KTS AT 260000Z
   CIMSS AIDT: 41 KTS AT 260000Z
   CIMSS D-MINT: 44 KTS AT 252330Z
   CIMSS D-PRINT: 48 KTS AT 260000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: SIGNIFICANTLY IMPROVED STRUCTURE OF
THE VORTEX LEADING TO PEAK INTENSITY INCREASE TO 85 KTS.

FORECAST DISCUSSION: TC COURTNEY IS FORECAST TO GENERALLY TRACK
WESTWARD, UNDER THE STEERING INFLUENCE OF A STR TO THE SOUTH. AN
UPPER-LEVEL TROUGH IS ABOUT TO PASS TO THE SOUTH OF THE SYSTEM, BUT
IS NOT FORECAST TO HAVE A SIGNIFICANT EFFECT, AS ANOTHER STR QUICKLY 
BUILDS BEHIND IT AND ASSUMES THE STEERING. TC 27S WILL THEN TRANSIT 
ALONG THE NORTHERN AND NORTHWESTERN PERIPHERY OF THE RIDGE, EVENTUALLY 
MAKING A POLEWARD TURN, ROUNDING THE AXIS OF THE STR. INTENSITY 
FORECAST REMAINS A CHALLENGE, AS THE AVAILABLE MODEL GUIDANCE OFFERS A 
SIGNIFICANTLY INCREASED SPREAD OF ESTIMATED WIND SPEED MAXIMA. TC 27S 
IS FORECAST TO CONTINUE DEVELOPING AND INTENSIFYING THROUGH TAU 96, 
WHILE REACHING PEAK INTENSITY OF 85-90 KTS. CONTRIBUTING FACTORS 
INCLUDE STRUCTURAL IMPROVEMENTS IDENTIFIED WITH THE AFOREMENTIONED F16 
SSMIS MICROWAVE IMAGERY, COMBINED WITH THE DEEP MONSOONAL MOISTURE, 
WHICH CAN BE OBSERVED ON THE 251800Z GFS DETERMINISTIC MODEL RUN, AS 
FAR OUT AS TAU 96. AFTERWARDS, TC COURTNEY IS FORECAST TO ENCOUNTER 
COOLER SST, WHICH COMBINED WITH INCREASING DRY AIR ENTRAINMENT WILL 
CONTRIBUTE TOWARD WEAKENING.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS ASSESSED WITH
MEDIUM CONFIDENCE THROUGHOUT THE FORECAST PERIOD. THE CROSS-TRACK
SPREAD AT TAU 72 IS LESS THAN 60 NM, INCREASING TO 130 NM BY THE
END OF THE FORECAST PERIOD, INDICATING GOOD AGREEMENT AMONG THE
MODELS IN REGARD TO THE DOMINATING STEERING MECHANISM. GOOD
CROSS-TRACK CONSENSUS IS OFFSET HOWEVER BY SIGNIFICANT INCREASE IN
ALONG-TRACK SPREAD OF 220 NM AT TAU 72, AND 270 NM AT TAU 120. THE
SLOWEST MODEL REMAINS NAVGEM AND JTWC TRACK IS LAID CLOSE, BUT
SLIGHTLY FASTER THAN THE MULTI-MODEL CONSENSUS, IN AN EFFORT TO
OFFSET THE LESS LIKELY GUIDANCE, AS THE FASTER MODELS VERIFIED
BETTER OVER THE LAST 12 HOURS. AS PREVIOUSLY MENTIONED, INTENSITY
ASSESSMENT REMAINS THE MAJOR CHALLENGE WITH A CURRENT PEAK
INTENSITY SPREAD OF 55 KTS, WITH COAMPS-TC PREDICTING 60 KTS AT TAU
12, AND HAFS GOING AS HIGH AS 115 KTS. JTWC INTENSITY FORECAST IS
ASSESSED ON THE HIGHER END OF THE MULTI-MODEL CONSENSUS, AS THE
ENVIRONMENTAL ANALYSIS REVEALS STRUCTURAL IMPROVEMENT OF THE VORTEX. 
ADDITIONALLY, ONE OF THE RAPID INTENSIFICATION (RI) AIDS (FRIA) 
INDICATES 67 PERCENT PROBABILITY FOR 25 KT INCREASE OVER THE NEXT
24 HOURS. GIVEN THE SIGNIFICANT GUIDANCE DISAGREEMENT THROUGHOUT
THE FORECAST PERIOD, JTWC INTENSITY FORECAST IS ASSESSED WITH LOW
CONFIDENCE.

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