WDXS31 PGTW 060900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (ELEVEN) WARNING 
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.2S 118.6E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 401 NM NORTH-NORTHWEST OF BROOME,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT
SYSTEM, WHICH HAS RAPIDLY DEVELOPED OVER THE PAST 12 HOURS. MSI
INDICATES THE SYSTEM REMAINS SOMEWHAT ASYMMETRIC, WITH A BALL OF
DISORGANIZED CONVECTION AND VORTICAL HOT TOWERS BEGINNING TO WRAP
INTO THE CORE OF THE CIRCULATION, AND AN ELONGATED AREA OF
FRAGMENTED CONVECTION EXTENDING OFF TO TH EAST IN A STATIONARY
BANDING COMPLEX (SBC). A 060538Z AMSR2 SHOWED THE SBC TO GOOD
EFFECT, WRAPPING UP THE WEST SIDE OF THE LOW LEVEL CIRCULATION
CENTER (LLCC), AND FRAGMENTED, FORMATIVE BANDING ON THE EASTERN
SIDE OF THE LLCC. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE AMSR2 36GHZ IMAGE NOTED ABOVE, WHICH SHOWED
A WELL-DEFINED LOW EMISSIVITY REGION (LER) SURROUNDED BY SHARP
CYCLONICALLY CURVED BANDING. THE INITIAL INTENSITY IS ASSESSED WITH
MEDIUM CONFIDENCE, SLIGHTLY BELOW THE AGGRESSIVE PGTW AND KNES T3.0
(45 KTS) DVORAK CURRENT INTENSITY ESTIMATES, HEDGED A BIT LOWER
BASED ON AN AMSR2 WIND ESTIMATE SHOWING A MAXIMUM OF 35 KNOTS.
CIMSS ANALYSIS SUGGESTS MODERATE (NEAR 20 KTS) EASTERLY SHEAR,
BUT JTWC HAND ANALYSIS AND MODEL SOUNDINGS SUGGEST A MESOSCALE
POINT SOURCE OVER TOP OF THE SYSTEM AND SIGNIFICANTLY LOWER VWS
(0-10 KTS). SSTS ARE VERY WARM (29-30C) AND UPPER-LEVEL OUTFLOW
IS RADIAL, THOUGH CONSTRAINED TO A SMALL AREA DUE TO THE SMALL SIZE
OF POINT SOURCE ALOFT. OVERALL CONDITIONS ARE NEAR-OPTIMUM FOR
RAPID INTENSIFICATION.

INITIAL WIND RADII BASIS: SMAP AND AMSR2 WIND DATA 

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF DEVELOPING
SUBTROPICAL RIDGE (STR) OVER WESTERN AUSTRALIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TROPICAL CYCLONE 11S (ELEVEN) HAS RAPIDLY
CONSOLIDATED AND INTENSIFIED OVER THE PAST 12 HOURS AS IT TURNED
SHARPLY POLEWARD. OVER THE NEXT 48 HOURS, THE SYSTEM IS EXPECTED TO
CONTINUE ON A RATHER LEISURELY SOUTHWESTWARD TRACK (AVERAGE TRACK
SPEED JUST SIX KNOTS) ALONG A RELATIVELY WEAK GRADIENT ON THE
NORTHWEST SIDE OF A BUILDING STR CENTER OVER WESTERN AUSTRALIA.
BEYOND TAU 48, THE RIDGE EXPANDS AND STRENGTHENS, ULTIMATELY
MERGING WITH ANOTHER STR CENTER FAR TO THE WEST INTO A LARGE RIDGE
COMPLEX WITH AN AXIS LYING NEAR 25S. THIS WILL PUSH TC 11S ONTO A
WESTWARD TRACK FROM TAU 72 THROUGH THE END OF THE FORECAST
PERIOD. AS NOTED ABOVE, ENVIRONMENTAL CONDITIONS ARE HIGHLY
FAVORABLE, IN FACT, NEARLY OPTIMAL FOR RAPID INTENSIFICATION
THROUGH THE NEXT 48 HOURS. THE SYSTEM IS EXPECTED TO REMAIN IN A
VERY LOW SHEAR ENVIRONMENT THROUGH TAU 48 AND WILL RETAIN THE
UPPER-LEVEL POINT SOURCE PROVIDING GOOD, THOUGH SMALL-SCALE,
OUTFLOW ALOFT. THE FORECAST TRACK TAKES THE SYSTEM OVER A POOL OF
HIGH OHC WATERS, WITH HEAT CONTENT APPROACHING 90 KJ PER CM2,
BETWEEN TAUS 36 AND 48 WHICH WILL PROVIDE ADDITIONAL ENERGY TO
SUPPORT RAPID INTENSIFICATION (RI). THE FORECAST CALLS FOR THE
SYSTEM TO RI OVER THE NEXT 48 HOURS, REACHING A PEAK OF AT LEAST
100 KNOTS BY TAU 48. THE COMBINATION OF INCREASED EASTERLY SHEAR
AND DECREASING SSTS (ESPECIALLY WEST OF 111E) WILL SERVE TO WEAKEN
THE SYSTEM SLIGHTLY THROUGH TAU 96, THOUGH CONDITIONS ONCE AGAIN
IMPROVE AFTER TAU 96, ALLOWING THE SYSTEM TO MAINTAIN ITS INTENSITY
THROUGH TAU 120. DUE TO THE COMPACT NATURE OF THE SYSTEM,
SHORT-TERM INTENSITY FLUCTUATIONS AND RAPID EYEWALL REPLACEMENT
CYCLES (EWRC) ARE LIKELY, WHICH WILL HAVE A LARGE EFFECT ON THE
OVERALL INTENSITY TRENDS. 

MODEL DISCUSSION: THE BULK OF THE DETERMINISTIC AND ENSEMBLE TRACK
GUIDANCE IS IN FAIRLY GOOD AGREEMENT, WITH TWO NOTABLE OUTLIERS IN
THE NAVGEM AND HWRF. THE MAJORITY OF THE TRACK GUIDANCE SUPPORTS
THE JTWC FORECAST AND LIES WITHIN A TIGHT, 60NM ENVELOPE AT TAU 72,
WHICH DOUBLES IN SIZE BY TAU 120. THE OUTLIERS NOTED ABOVE HOWEVER,
SEPARATE FROM THE PACK AFTER TAU 36 AND DRIVE THE SYSTEM INTO THE
RIDGE, AND KEEP THE TRACK QUITE A BIT FURTHER SOUTH THAN THE
REMAINDER OF THE GUIDANCE. AFTER TAU 96, THE GFS AND THE GFS
ENSEMBLE ALSO TREND A BIT MORE POLEWARD THAN THE REMAINDER OF THE
GUIDANCE PACKAGE, LEADING TO INCREASED UNCERTAINTY IN THE LATER
FORECAST TAUS. INTENSITY GUIDANCE IS IN VERY GOOD AGREEMENT THAT
THE SYSTEM IS LIKELY TO RI IN THE FIRST 48 HOURS, WITH CTR1, RIPA,
FRIA AND RICN AIDS ALL TRIGGERED. ADDITIONALLY, THE COAMPS-TC
ENSEMBLE INTENSITY PROBABILITIES INDICATE A 100 PERCENT PROBABILITY
OF RI BETWEEN TAU 24 AND 48. THE HWRF AND COAMPS-TC PEAK THE SYSTEM
AT 100 KNOTS AT TAU 48, THEN SUGGESTS MARGINAL WEAKENING TO TAU 72
FOLLOWED BY A FLAT INTENSITY TREND OR MARGINAL REINTENSIFICATION
THROUGH THE END OF THE FORECAST PERIOD. THE JTWC FORECAST TAKES THE
BAIT AND CLOSELY FOLLOWS THE RI, HWRF AND COAMPS-TC TREND LINE TO
TAU 48, THEN REMAINS ELEVATED ABOVE THE CONSENSUS MEAN, WHICH IS
BEING PULLED DOWN BY THE UNREALISTIC DECAY-SHIPS GUIDANCE, THROUGH
THE REMAINDER OF THE FORECAST. 

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