TC 18S(NEVILLE) peaked at CAT 4 US well above forecast//INVEST 95S// ECMWF 10 Day Storm Tracks// 2215utc

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 18S

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) DEPICTS TROPICAL CYCLONE (TC) 18S (NEVILLE) WITH A DEGRADING RAGGED-EYE THAT HAS NEARLY FILLED AS THE SYSTEM WEAKENS. THE CURRENT ENVIRONMENT IS ASSESSED AS MARGINALLY UNFAVORABLE CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT AND WARM (27-28 C) SEA SURFACE TEMPERATURES GREATLY OFFSET BY MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR (VWS) AND DRY AIR BEGINNING TO ENTRAIN INTO THE SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 221200Z HIMAWARI-9 INFRARED SATELLITE IMAGE. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES LISTED BELOW. THE CURRENT INTENSITY (CI) DVORAK ESTIMATES ARE ASSESSED AS POTENTIALLY TOO HIGH DUE TO THE COMPACT NATURE AND SIZE OF THE SYSTEM. FINAL-T NUMBERS RANGING FROM 4.5-5.0 ARE ASSESSED TO BE MORE REPRESENTATIVE AND WERE LEVIED MORE WHEN DETERMINING SYSTEM INTENSITY.

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 WEST-SOUTHWESTWARD TRACK THROUGH TAU 48 AS IT TRACKS ALONG THE NORTHWESTERN PERIPHERY OF THE STR TO THE SOUTH. AFTER TAU 48, THE SYSTEM IS FORECAST TO TURN MORE POLEWARD (SOUTHWESTWARD) AS 18S ROUNDS THE WESTERN EXTENT OF THE STR. REGARDING INTENSITY, TC 18S IS EXPECTED TO CONTINUE TO WEAKEN AS VWS VALUES REMAIN HIGH, SEA SURFACE TEMPERATURES DECREASE, AND DRY AIR ENTRAINS THE SYSTEM. ADDITIONALLY, A PRONOUNCED SHORTWAVE TROUGH IS POSITIONED TO THE WEST AND WILL AID IN DISSIPATION AS 18S ENCROACHES THE TROUGH. THE SYSTEM IS FORECAST TO WEAKEN TO 70 KTS NEAR TAU 12, 60 KTS NEAR TAU 24, 50 KTS NEAR TAU 36, AND 40 KTS NEAR TAU 48. BY TAU 72, TC 18S IS ANTICIPATED TO HAVE ENTIRELY DISSIPATED.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN CLOSE AGREEMENT WITH A 90 NM CROSS-TRACK SPREAD AT TAU 72. AS A RESULT, THE JTWC FORECAST TRACK WAS PLACED WITH HIGH CONFIDENCE THROUGH THE FORECAST PERIOD. INTENSITY GUIDANCE IS IN FAIR AGREEMENT, WITH ALL MODELS SUGGESTING A WEAKENING TREND AND DISSIPATION BY TAU 72. HWRF SLIGHTLY DIFFERS BY MAINTAINING 90 KTS THROUGH TAU 12 BEFORE STARTING THE WEAKENING TREND. HAFS-A DEPICTS A QUICKER ONSET OF DISSIPATION, REACHING 25 KTS BY TAU 48. THE JTWC INTENSITY FORECAST IS THEREFORE PLACED WITH MEDIUM CONFIDENCE THROUGH THE FORECAST PERIOD.