WDXS31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (TWENTYTWO) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.5S 76.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 490 NM SOUTH-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
OBSCURED BUT CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC) WITH
DEEP CONVECTION PERSISTING PRIMARILY ON THE WESTERN HALF OF THE
CIRCULATION DUE TO NORTHEASTERLY SHEAR. CLOUD TOP TEMPERATURES HAVE
CONTINUED TO COOL WITHIN THE PAST 6 HOURS AS DEEP CONVECTION
INTENSIFIES AND BEGINS TO EXPAND INTO UPSHEAR QUADRANTS AS THE
SHEAR WEAKENS. MODERATE OUTFLOW IS EVIDENT POLEWARD AND WESTWARD.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON AN
EARLIER 192006Z AMSR2 PASS AND AGENCY FIXES. THE INITIAL INTENSITY
OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 191930Z
OCEANSAT-3 OSCAT SCATTEROMETER DATA AND AVAILABLE OBJECTIVE AND
SUBJECTIVE SATELLITE ESTIMATES.

INITIAL WIND RADII BASIS: 191930Z OCEANSAT-3 OSCAT SCATTEROMETER
DATA 

CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF THE SUBTROPICAL
RIDGE (STR) CENTERED TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS D-MINT: 28 KTS AT 192006Z
   CIMSS D-PRINT: 31 KTS AT 200000Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 22S WILL CONTINUE TRACKING
SOUTHWESTWARD UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGE
POSITIONED TO THE SOUTHEAST. ENVIRONMENTAL CONDITIONS WILL REMAIN
GENERALLY FAVORABLE OVER THE NEXT 24 HOURS, AND WITH A SYMMETRIC
INNER CORE NOT YET FORMED, THIS WILL LIKELY RESULT IN A GRADUAL
INCREASE IN INTENSITY DURING THAT PERIOD. DURING THE 24 TO 72 HOUR
PERIOD, AN INCREASE IN EASTERLY FLOW ALOFT IS EXPECTED TO RAISE
VERTICAL SHEAR TO 15-25 KTS, SLOWING THE RATE OF INTENSIFICATION.
NUMERICAL MODELS CURRENTLY DISAGREE ON THE MAGNITUDE AND DURATION
OF THIS SHEAR, WITH THE ECMWF SHOWING SIGNIFICANTLY STRONGER SHEAR
THAN GFS-BASED MODELS, AND ACCORDINGLY SHOWS MORE DISRUPTION TO THE
STORM'S INNER CORE STRUCTURE. THE JTWC FORECAST ASSUMES SHEAR WILL
BE STRONG ENOUGH TO CAP THE RATE OF INTENSIFICATION AT A
CLIMATOLOGICAL PACE. AS 22S ROUNDS THE AXIS OF THE SUBTROPICAL
RIDGE AT 72 TO 96 HOURS AND APPROACHES A JET STREAK TO ITS SOUTH,
VERTICAL SHEAR IS EXPECTED TO RELAX FOR A BRIEF PERIOD,
SIMULTANEOUS WITH A SIGNIFICANT INCREASE IN POLEWARD OUTFLOW. AS A
RESULT, THE SYSTEM IS EXPECTED TO INTENSIFY MORE QUICKLY DURING THE
72 TO 96 HOUR PERIOD, REACHING A PEAK OF 100 KTS AT TAU 96.
THEREAFTER, DUE TO ITS FORECASTED PROXIMITY TO THE JET AND DRY AIR
ENTRAINMENT FROM THE WESTERN SIDE, TC 22S IS FORECASTED TO BEGIN
EXTRATROPICAL TRANSITION AND A WEAKENING TREND BY TAU 120.  

MODEL DISCUSSION: CROSS TRACK SPREAD AMONGST MODEL GUIDANCE IS
FAIRLY TIGHT THROUGH 72 HOURS, WITH GFS FARTHEST NORTH AND ECMWF
ENSEMBLE FARTHEST SOUTH. THE JTWC FORECASTED TRACK IS PLACED CLOSE
TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE FOR THE FIRST 72
HOURS. AFTER TAU 72 THE TRACK IS PLACED WITH MEDIUM CONFIDENCE
ACCOUNTING FOR UNCERTAINTY IN REGARDS TO THE SPEED AT WHICH THE
CIRCULATION WILL RECURVE AROUND THE SUBTROPICAL RIDGE OVER THE
INDIAN OCEAN, AND THE FORECASTED JET INTERACTION. REGARDING THE
INTENSITY GUIDANCE, THE MAJORITY OF MODELS AGREE ON STEADY
INTENSIFICATION WITH SOME RAPID INTENSIFICATION INDICATORS,
PRIMARILY AFTER TAU 48. HAFS-A IS THE STRONGEST AID WITH A MAXIMUM
INTENSITY OF 125 KTS AROUND TAU 96. THE JTWC INTENSITY FORECAST IS
CLOSE TO THE MULTI-MODEL CONSENSUS WITH A PEAK OF 100 KTS AT 96
HOURS WITH MEDIUM CONFIDENCE THROUGHOUT THE FORECAST PERIOD,
INHERITING SOME UNCERTAINTY FROM TRACK GUIDANCE FACTORS AND MODEL
DISAGREEMENT ON SHEAR MAGNITUDE DURING THE 24 TO 72 HOUR PERIOD.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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