WDXS31 PGTW 220900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HORACIO) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.2S 69.9E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 625 NM SOUTH-SOUTHWEST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT SYSTEM, WITH A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) AND MODERATE CONVECTION IN THE WESTERN SEMICIRCLE. DRY MID-LEVEL AIR IS APPARENT ALONG THE EASTERN FLANK OF THE CIRCULATION, WHICH REMAINS DEVOID OF SIGNIFICANT CONVECTIVE ACTIVITY. VORTICAL HOT TOWERS (VHTS) ARE PERSISTENT IN THE SOUTHWESTERN QUADRANT OF THE INNER CORE, BUT HAVE YET TO PROPAGATE UPSHEAR, INHIBITED BY A PERSISTENT EASTERLY SHEAR VECTOR AND ENTRAINMENT OF DRY AIR ON THE EASTERN SIDE OF THE VORTEX. A 220707Z GMI 89GHZ IMAGE REVEALED A WELL-DEFINED UPPER-LEVEL ROTATIONAL CENTER, AND DEEP CONVECTION BEGINNING TO ORGANIZE INTO BANDS EXTENDING FROM WEST TO NORTH OF THE LLCC. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 36GHZ GMI IMAGE, WHICH REVEALED A NASCENT, SLIGHTLY ELONGATED MICROWAVE EYE FEATURE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, CONSISTENT WITH T3.0 DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW, DEMS AND FIMP. ENVIRONMENTAL CONDITIONS ARE IMPROVING AND CHARACTERIZED AS OVERALL FAVORABLE. VERTICAL WIND SHEAR (VWS) HAS SUBSIDED SOMEWHAT OVER THE PAST 12 HOURS, AS INDICATED BY THE STEADILY IMPROVING CONVECTIVE STRUCTURE SEEN IN THE ANIMATED MSI. SSTS REMAIN WARM, OHC IS MODERATELY HIGH, AND UPPER-LEVEL OUTFLOW IS MODERATE WITH A POLEWARD COMPONENT. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS DEMS: T3.0 - 45 KTS FMEE: T3.5 - 55 KTS FIMP: T3.0 - 45 KTS CIMSS SATCON: 42 KTS AT 220330Z CIMSS ADT: 34 KTS AT 220600Z CIMSS AIDT: 34 KTS AT 220600Z CIMSS D-MINT: 45 KTS AT 220702Z CIMSS D-PRINT: 36 KTS AT 220600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE POLEWARD OTHER FACTORS: VORTEX MISALIGNMENT AND DRY AIR ENTRAINMENT IN THE EASTERN SEMICIRCLE. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: TROPICAL CYCLONE (TC) 22S WILL TRANSIT ALONG A RECURVING TRACK OVER THE NEXT 72 HOURS, TURNING SOUTHWEST THEN SOUTH AND EVENTUALLY SOUTHEASTWARD AS IT ROUNDS THE WESTERN AXIS OF THE STR TO THE SOUTHEAST. THE SYSTEM IS FORECAST TO REACH THE RIDGE AXIS BY TAU 48, DECELERATING TO A MINIMUM TRANSLATIONAL SPEED, BEFORE ACCELERATING BEYOND TAU 72. BEYOND TAU 72, A TRANSIENT RIDGE DEVELOPS TO THE SOUTH IN THE LEE OF A MID-LATITUDE TROUGH; CONSEQUENTLY, TC 22S WILL TURN SHARPLY WEST-SOUTHWESTWARD AFTER TAU 96, TRANSITING ALONG THE NORTHERN PERIPHERY OF THIS RIDGE. REGARDING INTENSITY, SHEAR IS DECREASING, AND THIS TREND IS FORECAST TO CONTINUE OVER THE SHORT-TERM, FACILITATING THE ONSET OF RAPID VORTEX ALIGNMENT AND SYMMETRIZATION. THE SYSTEM WILL GRADUALLY INTENSIFY OVER THE NEXT 12 HOURS AS ENVIRONMENTAL CONDITIONS STEADILY IMPROVE. BEGINNING AT TAU 12, HOWEVER, TC 22S IS EXPECTED TO UNDERGO RAPID INTENSIFICATION (RI) AS CONDITIONS OPTIMIZE, REACHING A PEAK INTENSITY OF 100 KNOTS BY TAU 48. IMMEDIATELY FOLLOWING TAU 48, SHEAR IS FORECAST TO INCREASE SHARPLY, AND THE SYSTEM WILL BEGIN A WEAKENING TREND. DRY MID-LEVEL AIR IS EXPECTED TO INTRUDE FROM THE NORTHWEST AFTER TAU 72, COINCIDENT WITH NORTHWESTERLY SHEAR REACHING A MAGNITUDE OF OVER 45 KNOTS, MARKING THE ONSET OF A PERIOD OF RAPID WEAKENING WHICH CONTINUES THROUGH TAU 96. AFTER TAU 96, THE SYSTEM WILL CONTINUE TO WEAKEN, THOUGH AT A REDUCED PACE AS SHEAR SUBSIDES AS THE SYSTEM PASSES UNDER A JET MAXIMUM, TRANSITIONS UNDER AN UPPER-LEVEL LOW, AND BEGINS EXTRATROPICAL TRANSITION (ET). MODEL DISCUSSION: DETERMINISTIC, ENSEMBLE AND ARTIFICIAL INTELLIGENCE (AI) TRACK GUIDANCE ARE IN GOOD AGREEMENT REGARDING THE OVERALL TRACK SCENARIO, WITH MINIMAL (LESS THAN 100NM) CROSS- OR ALONG-TRACK UNCERTAINTY THROUGH TAU 72. CROSS-TRACK SPREAD INCREASES MARGINALLY BY TAU 96, BUT SUBSEQUENTLY CONVERGES TO JUST 135NM BY TAU 120. THE NAVGEM MODEL DEFINES THE WESTERN-MOST BOUNDARY OF THE TRACK ENVELOPE THROUGH THE FORECAST PERIOD, WHILE THE EC-AIFS AND FGNI AI MODELS DEFINE THE EASTERN PERIPHERY. THE JTWC FORECAST IS CONSISTENT WITH THE ECMWF AND AI CONSENSUS TRACKER THROUGH TAU 120 WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS MIXED, WITH THE GLOBAL-MODEL BASED SHIPS (GFS AND NAVGEM) CONTINUING TO DEPICT A GENERALLY FLAT INTENSITY TREND, LIMITING PEAK INTENSITY TO 55 KNOTS BY TAU 48. THE MESOSCALE MODELS (HWRF, HAFS-A, COAMPS-TC) MEANWHILE ARE TIGHTLY CONSTRAINED, RAPIDLY INTENSIFYING THE SYSTEM THROUGH TAU 48 TO A PEAK BETWEEN 100-105 KNOTS. ADDITIONALLY, THE DTOP AND RIDE RAPID INTENSIFICATION (RI) AIDS ARE TRIGGERED, AND THE COAMPS-TC, ECEPS AND FGNI ENSEMBLE INTENSIFICATION PROBABILITIES INDICATE 40-60 PERCENT CHANCES OF RI THROUGH TAU 48, PROVIDING ADDITIONAL CONFIDENCE TO THE EXPLICIT FORECAST OF RI. THE JTWC FORECAST IS ALIGNED NEAR THE DTOP AND HAFS-A TREND LINE THROUGH TAU 48 AND THE HAFS-A THROUGH THE END OF THE FORECAST WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN