TC 13S(DJOUNGOU) peaks as a powerful CAT 4 US//TCFA issued for INVEST 95S//10 Day ECMWF Storm Tracks//1809utc

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 13S. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON INVEST 95S, ON THE REMNANTS OF SUBTROPICAL 15P AND ON THE OVERLAND REMNANTS OF TC 14P.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL CYCLONE (TC) 13S (DJOUNGOU) EXHIBITING A TIGHTENING SYMMETRIC EYE OF 20NM DIAMETER AND SMOOTH CIRRUS CANOPY ALOFT (168NM DIAMETER). ROBUST SPIRAL BANDING PERSISTS THROUGHOUT THE EASTERN PERIPHERY OF THE SYSTEM WITH INTERMITTENT OVERSHOOTING CLOUD TOPS THROUGHOUT. A 180406Z MHS 89GHZ SATELLITE MICROWAVE IMAGE CAPTURED A SLIGHT OFFSET OF THE LOW LEVEL CIRCULATION CENTER (LLCC) AND UPPER LEVEL EYE FEATURE, SHOWING THE EYE FEATURE TO BE 30NM EAST OF THE LLCC AND SUGGESTING AN EASTWARD TILTING VORTEX WITH HEIGHT. THE ENVIRONMENT IS ASSESSED AS HIGHLY FAVORABLE HAVING SIGNIFICANT DIVERGENCE ALOFT, WARM (29-30C) SEAS SURFACE TEMPERATURES (SST) OFFSET BY MODERATE (15- 20KTS) VERTICAL WIND SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE SYMMETRIC EYE FEATURE OBSERVED IN A GOES-IO VISIBLE SATELLITE IMAGE. THE INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 13S IS FORECAST TO TRACK ALONG THE SOUTHWESTERN PERIPHERY OF THE NEAR EQUATORIAL RIDGE TO THE NORTHEAST OF THE SYSTEM THROUGHOUT THE FORECAST PERIOD, STEERING THE SYSTEM SOUTHEASTWARD THROUGH TAU 48 AND THEN GRADUALLY TURNING TO AN EASTWARD TRACK BY TAU 72. IN GENERAL, THE FAVORABLE ENVIRONMENT BEGINS TO GRADUALLY BECOME UNFAVORABLE, STARTING WITH A RISE IN VWS (25-30KTS BY TAU 12). SST IS ANTICIPATED TO STEADILY DROP FROM 30C (TAU 00) TO 22C (TAU 72). UPPER LEVEL DIVERGENCE IS FORECAST TO SHARPLY CUT OFF BETWEEN TAU 36 AND TAU 48, ATTRIBUTED TO SIGNIFICANT DRY AIR ENTRAINMENT STARTING NEAR TAU 24. IN SUCH, A RAPID WEAKENING TREND IS FORECAST FROM TAU 12 TO TAU 72. THE SYSTEM IS FORECAST TO BEGIN SUBTROPICAL TRANSITION NEAR TAU 48 AND BE SUBTROPICAL BY TAU 72.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN EXCEPTIONAL AGREEMENT REGARDING BOTH TRACK AND INTENSITY. THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE WITH A CROSS-TRACK SPREAD AT TAU 72 OF JUST 107 NM. INTENSITY GUIDANCE SUGGESTS THE SYSTEM HAS LIKELY REACHED PEAK INTENSITY, WITH ONLY ONE JTWC CONSENSUS MEMBER (COAMPS-TC) SUGGESTING A POSSIBLE SLIGHT (5 KTS) RISE FROM TAU 00 TO TAU 12. FOR THE REMAINDER OF THE FORECAST PERIOD, GUIDANCE INDICATES A RAPID WEAKENING TREND BUT WITH A 30 KT SPREAD IN GUIDANCE BY TAU 72. FOR THIS REASON, THE JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE.

THE AREA OF CONVECTION (INVEST 95S) PREVIOUSLY LOCATED NEAR 17.9S 51.8E IS NOW LOCATED NEAR 16.7S 51.7E, APPROXIMATELY 397 NM WEST-NORTHWEST OF MAURITIUS. INVEST 95S WILL NOT STOP UNTIL IT GETS ENOUGH, SHOWING GREAT STRUCTURAL IMPROVEMENT AS IT HAS RAPIDLY CONSOLIDATED OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY AND AN 180019Z SSMIS 91GHZ MICROWAVE IMAGE DEPICT A LOW LEVEL CIRCULATION (LLC) WITH DEEP FLARING CONVECTION CONCENTRATED OVER AND NORTHEAST OF THE PERCEIVED LOW LEVEL CIRCULATION CENTER (LLCC) AND FRAGMENTED BANDING MAINLY ON THE SOUTHERN PERIPHERY OF THE SYSTEM. THE ENVIRONMENT IS HIGHLY FAVORABLE FOR FURTHER DEVELOPMENT WITH LOW (5-10KT) VWS, GOOD POLEWARD OUTFLOW ALOFT, AND WARM (29-30 C) SST. GLOBAL DETERMINISTIC AND ENSEMBLE MODELS ARE IN TIGHT AGREEMENT ON THE DEVELOPMENT OF INVEST 95S AND TRACKING IT NORTHEASTWARD OVER THE NEXT 24-36 HOURS, BUT HAVE DIFFERENCES WHEN IT COMES TO SPEED OF THE SYSTEM AS IT FLATTENS OUT ON AN EASTWARD TRAJECTORY. INTENSITY GUIDANCE SHOWS GOOD CONSENSUS ON INVEST 95S TRACKING OVER A PATCH OF 32C WATER WITHIN THE NEXT 12-24 HOURS, WHICH WILL FUEL RAPID AND STEADY INTENSIFICATION BEFORE MAKING A SOUTHWARD TURN TOWARDS THE MASCARENE ISLANDS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 23 TO 28 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO HIGH.

GLOBAL DETERMINISTIC AND ENSEMBLE MODELS ARE IN TIGHT AGREEMENT ON THE DEVELOPMENT OF INVEST 95S AND TRACKING IT NORTHEASTWARD OVER THE NEXT 24-36 HOURS, BUT HAVE DIFFERENCES WHEN IT COMES TO SPEED OF THE SYSTEM AS IT FLATTENS OUT ON AN EASTWARD TRAJECTORY. INTENSITY GUIDANCE SHOWS GOOD CONSENSUS ON INVEST 95S TRACKING OVER A PATCH OF 32C WATER WITHIN THE NEXT 12-24 HOURS, WHICH WILL FUEL RAPID AND STEADY INTENSIFICATION BEFORE MAKING A SOUTHWARD TURN TOWARDS THE MASCARENE ISLANDS.