Typhoon 14W(KOINU) to reach CAT 3 US by 36h// TS 17L(PHILIPPE)// TS 18L(RINA)// 0109utc updates

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

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY CONSOLIDATING TYPHOON STRENGTH TROPICAL CYCLONE. DEEP CONVECTIVE BANDING IS NOW FULLY WRAPPING THE CIRCULATION AND A POSSIBLE TRANSIENT EYE FEATURE IS NOW OBSERVABLE. A RECENT 010455Z ATMS 165GHZ MICROWAVE IMAGE SHOWS A NEARLY COMPLETE MICROWAVE EYE FEATURE WITH DEEP CONVECTIVE BANDINGS PRIMARILY TO THE SOUTH OF THE LLCC. A 010515Z AMSR2 MICROWAVE RADIOMETRY PARTIAL PASS REVEALS A THICK BAND OF 50-60KT WINDS EVIDENT IN THE WESTERN REGION OF THE FORMING EYE WALL. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI AND ATMS IMAGERY. THE INITIAL INTENSITY OF 65 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A GROWING RANGE OF DVORAK AND AUTOMATED INTENSITY ESTIMATES. WEAK TYPHOON STRENGTH TROPICAL CYCLONES ARE NOTORIOUS FOR THE WIDE RANGE OF INTENSITY ESTIMATES THEY GARNER, DUE TO THE VARIOUS DVORAK METHODS THAT CAN BE USED. UNTIL A DEFINED EYE FEATURE FORMS, INTENSITY ESTIMATES MAY FLUCTUATE, THUS OVERALL MEDIUM CONFIDENCE.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: HAVING RECENTLY ACHIEVED TYPHOON STRENGTH, TY 14W (KOINU) IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE NORTHEAST. BY TAU 24, THIS STR BEGINS TO BUILD BACK UP AND MIGRATE WESTWARD, RESULTING IN A GRADUAL WESTWARD ARC TOWARD THE SOUTHERN TIP OF TAIWAN. IN TERMS OF INTENSITY, 14W WILL RAPIDLY SURGE TO 100KTS BY TAU 36, FUELED BY WARM SSTS (30C), LOW VERTICAL WIND SHEAR AND IMPROVING OUTFLOW ALOFT. BY TAU 72, 14W IS FORECAST TO REACH ITS PEAK INTENSITY OF 110KTS AND POSSIBLY HIGHER BEFORE VWS INCREASES AND FAVORABLE OUTFLOW IS LOST. THE SYSTEM IS FORECAST TO MAKE LANDFALL OVER SOUTHERN TAIWAN NEAR 110KTS AND PROCEED WESTWARD GRADUALLY WEAKENING THROUGH THE FORECAST PERIOD. IT IS IMPORTANT TO NOTE THAT IF THE STR TO THE NORTHEAST BUILDS UP MORE RAPIDLY OR EXTENDS POLEWARD OF 14W AS ECMWF AND COAMPS-TC INDICATE. THIS WOULD CAUSE A MORE DRAMATIC WESTWARD COURSE, KEEPING THE SYSTEM OVER OPEN WATERS AND MORE IMPORTANTLY AWAY FROM THE TAIWANESE MOUNTAIN RANGE, ALL OF WHICH COULD ALLOW FOR ADDITIONAL INTENSIFICATION THROUGH THE FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT WITH A MAJORITY OF THE MEMBERS CLOSELY FOLLOWING THE JTWC FORECAST TRACK. AS PREVIOUSLY MENTIONED ABOVE, ECMWF AND COAMPS-TC INDICATE A MORE DRAMATIC WESTWARD COURSE OVER OPEN WATERS AND INTO THE NORTHERN REGIONS OF THE SOUTH CHINA SEA. FOR THIS REASON THE JTWC TRACK FORECAST IS PLACED INITIALLY WITH HIGH CONFIDENCE AND WITH MEDIUM CONFIDENCE THEREAFTER. RELIABLE MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH ALL MEMBERS QUICKLY INTENSIFYING THE SYSTEM THROUGH TAU 72, AFTER WHICH GRADUAL WEAKENING THROUGH THE FORECAST PERIOD. AS SOME MEMBERS ARE INDICATING LANDFALL AND OTHERS REMAIN OVER OPEN WATER, THERE IS A MODERATE SPREAD IN THE MEMBERS BY TAU 120. THEREFOR, THE JTWC INTENSITY FORECAST REMAINS SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS WITH OVERALL MEDIUM CONFIDENCE.