TC 21S(OLGA) intensifying and peaking within 24H may reach CAT 2 US// ECMWF 10 Day Storm Tracks, 0615utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 21S(OLGA)

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING SYSTEM, WITH A DEVELOPING CENTRAL DENSE OVERCAST AND WEAK DEVELOPING EYE. A 061053Z SSMIS 91 GHZ MICROWAVE IMAGE REVEALS DEEP CONVECTIVE BANDING WRAPPING TIGHTLY INTO A DEFINED LOW-LEVEL CIRCULATION CENTER, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. ALTHOUGH THERE IS DRY AIR PRESENT OVER THE WESTERN PERIPHERY OF THE SYSTEM, THERE IS A DEEP MOIST CORE AS WELL AS ROBUST POLEWARD OUTFLOW, LOW VERTICAL WIND SHEAR AND WARM SST VALUES. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON SUBJECTIVE DVORAK INTENSITY ESTIMATES OF 55 KNOTS FROM ALL AGENCIES. CIMSS OBJECTIVE INTENSITY ESTIMATES HAVE INCREASED MARKEDLY, WITH ADT AND AIDT ESTIMATES RANGING FROM 49 TO 59 KNOTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 21S IS TRACKING SLOWLY SOUTHWARD ALONG THE WESTERN PERIPHERY OF THE STR BUT IS EXPECTED TO TURN SOUTHWESTWARD TO WEST-SOUTHWESTWARD AFTER TAU 24 ALONG AN EXTENSION OF THE STR POSITIONED OVER NORTHWESTERN AUSTRALIA. TC OLGA WILL CONTINUE TRACKING GENERALLY WEST-SOUTHWESTWARD THROUGH TAU 96, WITH A STRONG HIGH BUILDING TO THE SOUTH. ENVIRONMENTAL CONDITIONS WILL REMAIN CONDUCIVE THROUGH TAU 24 ALLOWING FOR A SHORT PERIOD OF MODERATE INTENSIFICATION, WITH A PEAK INTENSITY OF 80 KNOTS BY TAU 24. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO DEGRADE QUICKLY AFTER TAU 24, WITH INCREASING VERTICAL WIND SHEAR (VWS) OF 25 KNOTS NEAR TAU 24 TO 45 KNOTS BY TAU 72. MID- TO UPPER-LEVEL DRY AIR ENTRAINMENT WILL INCREASE SIGNIFICANTLY OVER THE NEXT TWO DAYS, WITH THE SYSTEM EMBEDDED WITHIN A VERY DRY, HOSTILE ENVIRONMENT BY TAU 72, WHICH WILL LEAD TO RAPID WEAKENING AND DISSIPATION BY TAU 96.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH SHOWS A TRACK RECURVING INTO NORTHWEST AUSTRALIA, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH A 140 NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 72 AND 206 NM AT TAU 96. BOTH THE 060000Z ECMWF ENSEMBLE (EPS) AND THE 060600Z GFS ENSEMBLE (GEFS) INDICATE A SIMILAR TRACK SPREAD. RELIABLE INTENSITY GUIDANCE CONSISTENTLY INDICATES A SHARP INTENSIFICATION TREND THROUGH TAU 24 WITH PEAK INTENSITIES RANGING FROM 60 TO 80 KNOTS THEN A PERIOD OF RAPID WEAKENING THROUGH TAU 96. RAPID INTENSIFICATION GUIDANCE HAS CONTINUED TO TRIGGER SUPPORTING THE SHARP INTENSIFICATION PHASE. THE 060600Z COAMPS-TC INTENSITY ENSEMBLE NO LONGER INDICATES RAPID INTENSIFICATION BUT DOES SHOW A 40 TO 50 PERCENT PROBABILITY OF MODERATE INTENSIFICATION THROUGH TAU 24.