TC 18S(NEVILLE) +45 knots last 24H may reach CAT 3 US within 24H//ECMWF 10 Day Storm Tracks//2109utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 18S

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS TROPICAL CYCLONE (TC) 18S WITH PERSISTENT DEEP CONVECTION OVER ASSESSED LOW-LEVEL CIRCULATION CENTER (LLCC) ALONG WITH A DIMPLED RAGGED EYE FEATURE AND WELL-DEFINED CONVECTIVE BANDING WRAPPING INTO THE SYSTEM. THE CURRENT ENVIRONMENT IS ASSESSED AS FAVORABLE CHARACTERIZED BY MODERATE RADIAL OUTFLOW ALOFT, LOW (0-5 KTS) VERTICAL WIND SHEAR (VWS), AND WARM (27- 28 C) SEA SURFACE TEMPERATURES. MODELS SUGGEST THAT THE CORE OF THE VORTEX HAS REMAINED MOIST AND IS SUCCESSFULLY RESISTING DRY AIR ENTRAINMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 210600Z HIMAWARI-9 VISIBLE (1KM) SATELLITE IMAGE. THE INITIAL INTENSITY 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 18S IS FORECAST TO CONTINUE ON A WESTWARD TRACK UNTIL TAU 24 AS IT TRACKS ALONG THE NORTHERN PERIPHERY OF THE STR TO THE SOUTH. AFTER TAU 24, THE SYSTEM IS FORECAST TO BEGIN A SOUTHWESTWARD TRACK AS IT STARTS TO ROUND THE NORTHWESTERN PERIPHERY OF THE STR. THE SYSTEM IS EXPECTED TO CONTINUE THE SOUTHWESTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST INTERVAL. REGARDING THE JTWC INTENSITY FORECAST, TC 18S IS FORECAST TO INTENSIFY TO A PEAK OF 95 KTS AROUND TAU 12 AND MAINTAIN THAT INTENSITY THROUGH TAU 24 DUE PRIMARILY TO AN INCREASE IN OUTFLOW ALOFT AND THE PERSISTENCE OF LOW VWS. AFTER TAU 24, VWS VALUES BEGIN TO RISE TO AROUND 15 KTS AND THE SYSTEM IS EXPECTED TO START DEGRADING. TC 18S IS, AS A RESULT, FORECAST TO BE 90 KTS NEAR TAU 36 AND 85 KTS NEAR TAU 48. AFTER TAU 48, DRY AIR BEGINS TO ENTRAIN INTO THE SYSTEM AND VWS IS EXPECTED TO INCREASE TO 25-30 KTS DUE TO PROXIMITY TO THE UPPER-LEVEL JET WHICH WILL AID TO QUICKLY WEAKEN THE SYSTEM. TC 18S IS FORECAST TO WEAKEN TO 60 KTS NEAR TAU 72 AND EVENTUALLY DISSIPATE TO 30 KTS BY TAU 96.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A 250 NM CROSS-TRACK SPREAD AT TAU 72. GUIDANCE BEGINS TO SPREAD AFTERWARDS AND THE CROSS-TRACK SPREAD INCREASES TO 350 NM AT TAU 96 AS THE MODELS VARY ON THE SHARPNESS OF THE TURN AROUND THE STR. THEREFORE, THE JTWC TRACK FORECAST IS ASSESSED WITH HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE FOR THE REMAINDER OF THE FORECAST. THE JTWC INTENSITY FORECAST IS ASSESSED WITH OVERALL LOW CONFIDENCE DUE TO TECHNICAL DIFFICULTIES PREVENTING RECENT DATA FROM GFS, HWRF, AND HAFS-A BEING INCORPORATED INTO THE MODEL GUIDANCE FOR THIS WARNING.