WDXS32 PGTW 040900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 13S (VINCE) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 17.8S 90.1E INITIAL INTENSITY: 100 KTS GEOGRAPHIC REFERENCE: 518 NM SOUTHWEST OF THE COCOS ISLANDS MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 37 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT SYSTEM, WITH A CLOUD-FILLED PINHOLE EYE. ANIMATED ENHANCED INFRARED (EIR) IMAGERY SHOWS THAT THE PINHOLE EYE REACHED ITS MOST INTENSE RIGHT AROUND 040600Z, BUT SUBSEQUENT IMAGERY SHOWS THE EYE ALREADY STARTED TO FILL IN, THOUGH IT REMAINS PRESENT. A 040332Z AMSU-B 89GHZ MICROWAVE IMAGE SHOWED WELL-DEFINED SPIRAL BANDS OF DEEP CONVECTION WRAPPING INTO THE SMALL EYE FEATURE. HOWEVER, THE MICROWAVE IMAGERY ALSO INDICATED THE SYSTEM IS HIGHLY ASYMMETRICAL IN TERMS OF CONVECTION, WITH THE SOUTHEASTERN HALF OF THE CIRCULATION BEING RATHER SHALLOW OVERALL. HAFS-A SHOWS A GENERAL LACK DEEP MOISTURE IN THE SOUTHEASTERN PORTION OF THE CIRCULATION, WHICH IS VERIFIED BY THE AMSU-B DEPICTION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PINHOLE EYE IN THE MSI AND EIR. THE INITIAL INTENSITY IS HEDGED SLIGHTLY HIGHER THAN THE HIGHEST AGENCY DVORAK FIX (T5.5 FROM KNES) BASED ON THE FACT THAT DVORAK OFTEN STRUGGLES WITH PINHOLE EYES. ADDITIONAL SUPPORT FOR THE INITIAL INTENSITY COMES FROM A 032332Z RCM-2 SAR PASS WHICH REVEALED 100 KNOT WINDS SIX HOURS AGO. THE ENVIRONMENT IS FAVORABLE, WITH WARM SSTS, GOOD DIVERGENT OUTFLOW ALOFT THOUGH THE PRESENCE OF PERSISTENT MODERATE EASTERLY SHEAR WILL LIKELY HINDER THINGS GOING FORWARD. INITIAL WIND RADII BASIS: SAR DATA CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.5 - 77 KTS KNES: T5.5 - 102 KTS DEMS: T4.5 - 77 KTS APRF: T4.5 - 77 KTS CIMSS SATCON: 91 KTS AT 040545Z CIMSS ADT: 82 KTS AT 040600Z CIMSS AIDT: 85 KTS AT 040600Z CIMSS D-PRINT: 84 KTS AT 040600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 26-27 CELSIUS OUTFLOW: STRONG EQUATORWARD OTHER FACTORS: MESOSCALE RADIAL OUTFLOW AND SHEAR BLOCKING. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE INITIAL INTENSITY WAS RAISED TO 100 KNOTS, WHICH RESULTS IN SIGNIFICANT INCREASE IN FORECAST INTENSITY THROUGH THE ENTIRE FORECAST PERIOD. FORECAST DISCUSSION: TC 13S (VINCE) WILL TRACK SOUTHWESTWARD ALONG THE NORTHWEST SIDE OF THE DEEP STR TO THE SOUTHEAST FOR THE FIRST 36 HOURS OF THE FORECAST. A RELATIVELY DEEP MID-LATITUDE TROUGH WILL PASS BY TO THE SOUTH AROUND TAU 48. WHILE THIS TROUGH WILL BE STRONG ENOUGH TO BREAK THE RIDGE, IT IS NOT EXPECTED TO REACH FAR ENOUGH EQUATORWARD TO INDUCE TC 13S SOUTHWARD. HOWEVER, TRACK SPEEDS WILL SLOW DOWN BRIEFLY AS THE STEERING GRADIENT WEAKENS AND A VERY SLIGHT DIP POLEWARD IS LIKELY. DEEP RIDGING WILL RAPIDLY BUILD IN BEHIND THE TROUGH AFTER TAU 60, AND SLIDE TO A POSITION NEAR 25S 80E AND ENHANCING THE STEERING GRADIENT ONCE MORE. TC 13S WILL SPEED UP A KNOT OR TWO WHILE CONTINUING ON ITS SOUTHWESTWARD TREK THROUGH THE END OF THE FORECAST PERIOD. A SLIGHT TURN MORE POLEWARD WILL START AROUND TAU 120, AS THE SYSTEM WILL BE IN THE VERY EARLY PHASES OF ROUNDING THE RIDGE AT THIS POINT. IN TERMS OF INTENSITY, THE SYSTEM HAS RAPIDLY INTENSIFIED OVER THE LAST DAY, LIKELY AS A RESULT OF A DEEP CONVECTIVE BURST PUSHING BACK AGAINST THE MODERATE EASTERLY SHEAR AND REDUCING THE LOCALIZED SHEAR OVER TOP OF THE SYSTEM. UPSHEAR CONVECTION HAS DISSIPATED BUT NEW CONVECTION IS STARTING TO APPEAR ON THE NORTHERN SIDE OF THE EYE. WHETHER THIS CAN STICK AND ROTATE UPSHEAR WILL BE THE DETERMINANT FACTOR GOING FORWARD. THE SYSTEM IS VERY COMPACT, THUS RAPID AND LARGE DEVIATIONS IN INTENSITY CAN BE EXPECTED. THE OVERALL TREND IS FOR A SLOW WEAKENING TREND OVER THE NEXT TWO DAYS AS THE SYSTEM EXPERIENCES A LESSER AMOUNT OF POLEWARD OUTFLOW DURING THIS TIMEFRAME. HOWEVER, BY TAU 72, TC 13S WILL MOVE INTO WARMER WATERS AND BEGIN TO TAP INTO A ROBUST POLEWARD OUTFLOW CHANNEL, WHICH SHOULD ALLOW FOR A REINTENSIFICATION THROUGH THE END OF THE FORECAST. MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE ARE IN GOOD AGREEMENT WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD. IN FACT, THE SPREAD IS SOMEWHAT REMARKABLE, BEING ON 80NM AT TAU 120 BETWEEN ALL DETERMINISTIC CONSENSUS MEMBERS. ENSEMBLE GUIDANCE (GEFS AND ECENS) SHOW MORE SPREAD BETWEEN MEMBERS, BUT THE BULK OF THE MEMBERS ARE CONFINED TO A VERY TIGHT ENVELOPE ABOUT THE MEAN. THE JTWC FORECAST IS ALIGNED WITH THE CONSENSUS MEAN AND WITH SUCH STRONG AGREEMENT, IS SET WITH HIGH CONFIDENCE. INTENSITY GUIDANCE ON THE OTHER HAND IS EXTREMELY UNCERTAIN, WITH A VERY WIDE RANGE OF POTENTIAL OUTCOMES. THE HWRF AND COAMPS-TC FOR INSTANCE DROP THE SYSTEM TO 50-60 KNOTS WITHIN THE NEXT 36 HOURS BUT REINTENSIFY IT THROUGH AFTER. MEANWHILE THE HAFS-A INTENSIFIES THE SYSTEM AFTER TAU 12, ALL THE WAY UP TO 130 KNOTS. THE CONSENSUS MEAN IS SOMEWHERE IN THE MIDDLE, AND THE JTWC FORECAST CLOSELY TRACKS THE CONSENSUS, WITH LOW CONFIDENCE IN LIGHT OF THE EXTREMELY LARGE SPREAD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN