WDXS31 PGTW 172100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 19S (FABIEN) WARNING NR 015// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 8.8S 73.0E INITIAL INTENSITY: 70 KTS GEOGRAPHIC REFERENCE: 106 NM SOUTH-SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 24 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN ERODING SYSTEM THAT IS NOW QUASI-STATIONARY, WITH THE LLCC BEGINNING TO DECOUPLE AND STRETCH FROM THE UPPER-LEVEL CIRCULATION CENTER (ULCC) AS THE WIND SHEAR CONTINUES TO INCREASE. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE USING BOTH THE 171614Z ASCAT METOP-B AND THE 171707Z ASCAT METOP-C IMAGES, SHOWING A SIGNIFICANT REDUCTION IN THE WIND RADII AND OVERALL INTENSITY. THE CONVECTIVE STRUCTURE IS ERODING ON THE NORTHWESTERN SIDE OF THE SYSTEM, WHICH SHOWS ON EVEN THE COARSEST OF IMAGES FROM A 171703Z AMSU METOP-C IMAGE. THE LACK OF CONVECTION IS HIGHLY INDICATIVE OF THE DRY-AIR INTRUSION AND UPWELLING PREVIOUSLY DISCUSSED ON PRIOR FORECASTS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE ASCAT IMAGE AND THE OVERALL QUASI-STATIONARY MOTION. THE INITIAL INTENSITY OF 70KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON MULTIPLE AGENCY DVORAK INTENSITY ESTIMATES REMAINING HIGH DUE TO CONSTRAINTS, WHILE THE OBJECTIVE AUTOMATED INTENSITY ESTIMATES ARE FALLING RAPIDLY DUE TO THE SCENE TYPE CHANGES DUE TO THE OVERALL STRUCTURAL BECOMING NOTICEABLY COMPROMISED. INITIAL WIND RADII BASIS: SCATTEROMETER DATA FROM A 171707Z ASCAT METOP-C. CURRENT STEERING MECHANISM: COMPLEX STEERING FROM A SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST AND A BUILDING STR FROM THE WEST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T4.5 - 77 KTS KNES: T5.0 - 90 KTS DEMS: T4.5 - 77 KTS FMEE: T4.5 - 77 KTS FIMP: T4.5 - 77 KTS CIMSS SATCON: 68 KTS AT 171704Z CIMSS ADT: 67 KTS AT 171800Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE VWS: 15-20 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: UPWELLING AND DRY AIR ENTRAINMENT. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 19S (FABIEN) WILL REMAIN QUASI-STATIONARY FOR A FEW MORE HOURS UNTIL THE SYSTEM REGAINS THE STEERING FROM THE STR TO THE SOUTH AND TRACKS WEST-SOUTHWESTWARD. THE ERODING WESTERN SECTOR OF THE SYSTEM WILL CONTINUE AS THE UPWELLING, WIND SHEAR, AND DRY AIR ENTRAINMENT HAVE INCREASED EXCESSIVELY ON THE CONVECTIVE CORE. THE SHALLOW OCEAN HEAT CONTENT (OHC) REGIONS WILL CONTINUE TO WEAKEN THE SYSTEM AS IT TRACKS TO THE SOUTHWEST OVER THE NEXT 48 HOURS. THE SYSTEM WILL TRANSITION ITS PRIMARY STEERING INFLUENCE TO A BUILDING STR OVER MADAGASCAR BETWEEN TAUS 48 AND 72. AFTER TAU 48, TC 19S WILL THEN BEGIN A MORE POLEWARD TRANSIT AS IT ENTERS A COMPLEX AND COMPETING STEERING ENVIRONMENT WHEN THE STR TO THE SOUTHWEST AND A BUILDING NEAR-EQUATORIAL RIDGE (NER) TO THE NORTH COMPETE FOR STEERING CONTROL. THE SYSTEM WILL THEN MOVE INTO A HIGH SHEAR ENVIRONMENT, WHICH WILL SIGNIFICANTLY DECREASE THE INTENSITY TO 35KTS BY TAU 120. MODEL DISCUSSION: THE MODEL OUTPUT REMAINS IN POOR AGREEMENT AS MEMBERS ATTEMPT TO RESOLVE THE COMPLEX STEERING PATTERN DISCUSSED ABOVE, AND FOR THIS REASON, THE JTWC FORECAST TRACK IS PLACED WITH MEDIUM CONFIDENCE INITIALLY AND WITH LOW CONFIDENCE IN THE EXTENDED TRACK FORECAST. RELIABLE MODEL INTENSITY GUIDANCE IS IN FAIR AGREEMENT WITH A BULK OF THE GUIDANCE, GENERALLY FOLLOWING THE TREND OF THE JTWC FORECAST INTENSITY. COAMPS-TC REMAINS THE SOLE OUTLIER INDICATING THE SYSTEM WILL REINVIGORATE TO A 75KT SYSTEM BY TAU 36 BUT QUICKLY WEAKENS THE SYSTEM BY TAU 96. ALL OTHER MODELS GRADUALLY DECLINE THE INTENSITY FROM TAU 00 THROUGH TAU 120. FOR THIS REASON, THE JTWC FORECAST INTENSITY IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH OVERALL MEDIUM CONFIDENCE IN THE NEAR TAUS AND LOW THEREAFTER. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN