Typhoon 14W(KOINU) to cross Southern TAIWAN after 36h// TS 17L(PHILIPPE)// Invest 98E// 0306utc updates

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TY 14W(KOINU).

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SPIRAL BANDING WRAPPING INTO A FORMATIVE, RAGGED EYE, WHICH SUPPORTS THE INITIAL POSITION WITH MEDIUM CONFIDENCE. OVERALL, THE SYSTEM HAS WEAKENED SLIGHTLY DUE TO PERSISTENT EASTERLY VERTICAL WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT. THIS IS CLEARLY EVIDENT IN A 022232Z SSMIS 91 GHZ MICROWAVE IMAGE WHICH DEPICTS A PARTIAL EYEWALL OVER THE WESTERN SEMICIRCLE AND A DRY SLOT OVER THE EASTERN SEMICIRCLE, WITH DEEP CONVECTIVE BANDING WRAPPING TIGHTLY AROUND THE ELONGATED LOW-LEVEL CIRCULATION CENTER. THE INITIAL INTENSITY IS ASSESSED AT 105 KNOTS BASED ON THE AGENCY FINAL-T (102 KTS) ESTIMATES AND CURRENT INTENSITY ESTIMATES OF 6.0 (115 KTS) AS WELL AS A 022233Z DMINT ESTIMATE OF 101 KTS. THE 030130Z AIDT ESTIMATE OF 111 KTS IS ALSO IN BETTER ALIGNMENT WITH THE INITIAL INTENSITY ASSESSMENT. A 022130Z RCM-3 SAR IMAGE REVEALS MAXIMUM WINDS OF ONLY 88 KNOTS WITH EXPANSIVE GALE-FORCE AND STORM-FORCE WINDS ESPECIALLY OVER THE SOUTHEAST QUADRANT. THE SAR IMAGE WAS USED TO ADJUST THE INITIAL WIND RADII WITH HIGH CONFIDENCE HOWEVER THE MAXIMUM WIND ESTIMATE IS TOO LOW.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TYPHOON (TY) 14W IS FORECAST TO TRACK NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH TAU 12 TOWARD A BREAK IN THE STR ASSOCIATED WITH A MIDLATITUDE SHORTWAVE TROUGH. AFTER TAU 12, THE TROUGH WILL PROPAGATE EASTWARD ALLOWING THE STR TO REBUILD TO THE NORTH, WHICH WILL TURN THE SYSTEM ON A WEST-NORTHWESTWARD TO WESTWARD TRAJECTORY THROUGH TAU 120. TY 14W SHOULD WEAKEN STEADILY DUE TO THE PERSISTENT VWS AS IT APPROACHES AND TRACKS OVER SOUTHERN TAIWAN WITH FURTHER WEAKENING AS IT TRACKS OVER THE SOUTH CHINA SEA, TAIWAN STRAIT REGION. A WEAK NORTHEAST SURGE IS EXPECTED TO BUILD INTO THE TAIWAN STRAIT WITH EXPANSIVE GALE-FORCE WINDS AND INFUSION OF COOLER, DRIER, MORE STABLE AIR.

MODEL DISCUSSION: THROUGH TAU 72, NUMERICAL MODEL GUIDANCE IS IN TIGHT AGREEMENT WITH A 67 NM CROSS-TRACK SPREAD IN SOLUTIONS LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST THROUGH TAU 72. AFTER TAU 72, THERE IS INCREASING SPREAD AND UNCERTAINTY DUE TO THE NORTHEAST SURGE THROUGH THE TAIWAN STRAIT AND ITS INFLUENCE ON A WEAKENING, SHALLOWER SYSTEM. MUCH OF THE DETERMINISTIC GUIDANCE IS TURNING THE SYSTEM WEST-SOUTHWESTWARD TO SOUTHWESTWARD NEAR TAU 120. BOTH THE GEFS AND EPS ENSEMBLES INDICATE RAPID WEAKENING NEAR THE SOUTHEAST COAST OF CHINA WITH INCREASING POTENTIAL FOR A SLOW, ERRATIC TRACK AND A SHARP SOUTHWESTWARD TURN NEAR OR JUST SOUTHEAST OF HONG KONG. AS A RESULT OF THIS COMPLEX SCENARIO, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK AFTER TAU 72. OVERALL, THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST.