Western North Pacific: 01W named DUJUAN, forecast to intensify next 36h if wind shear decreases, 18/09utc update

01W(DUJUAN).ANIMATED MULTISPECTRAL SATELLITE IMAGERY REVEALS A FULLY EXPOSED, WELL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC), WITH FLARING DEEP CONVECTION WITH OVERSHOOTING TOPS SHEARED TO THE WEST OF THE LLCC, LENDING HIGH CONFIDENCE TO THE INITIAL POSITION.

01W(DUJUAN). WARNING 5 ISSUED AT 18/09UTC.UPPER-LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH MODERATE (15-20 KNOTS) EASTERLY VERTICAL WIND SHEAR (VWS) OFFSET BY ROBUST DIFFLUENT POLEWARD OUTFLOW. SST VALUES REMAIN CONDUCIVE AT 29-30C. TS 01W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT SOUTH OF A BREAK IN THE SUBTROPICAL RIDGE (STR) RESULTING FROM THE PRESENCE OF A MAJOR SHORTWAVE TROUGH EXTENDING FROM JAPAN TO EAST OF TAIWAN. OVER THE NEXT 36 HOURS, THE SHORTWAVE TROUGH WILL MOVE TO THE NORTHEAST AND FILL, ALLOWING FOR THE STR TO THE EAST TO BUILD IN TO THE NORTHEAST OF TS 01W, ALLOWING THE SYSTEM TO MOVE SLOWLY WESTWARD THROUGH 36H. AFTER 48H, THE STR AXIS REORIENTS SLIGHTLY TO A MORE NORTHWEST-SOUTHEAST ORIENTATION, AND IN RESPONSE TS 01W WILL TURN TO A MORE WEST-NORTHWEST TRACK THROUGH 72H. LANDFALL IS EXPECTED NEAR 60H ALONG THE FAR NORTHEAST COAST OF MINDANAO. WIND SHEAR IS CURRENTLY DOMINATING THE SYSTEM. HOWEVER, WIND SHEAR IS EXPECTED TO WEAKEN SLIGHTLY OVER THE NEXT DAY OR SO, WHICH WILL ALLOW THE SYSTEM TO REESTABLISH CORE CONVECTION, ENABLING A SLOW BUT STEADY INTENSIFICATION TO A PEAK OF 50 KNOTS BY 48H. THERE IS CONSIDERABLE UNCERTAINTY HOWEVER IN THE INTENSIFICATION FORECAST DUE TO THE STEADY EASTERLY WIND SHEAR AND HOW MUCH THE STRONG POLEWARD OUTFLOW WILL OFFSET THIS SHEAR. THE SYSTEM IS FORECAST TO CONTINUE TRACKING ALONG THE WESTERN BOUNDARY OF THE DEEP-LAYER STR LOCATED TO THE EAST THROUGH THE EXTENDED FORECAST PERIOD. BY 72H THE SYSTEM IS EXPECTED TO BE IN THE BOHOL SEA, AND WILL TRACK NORTHWESTWARD OVER THE MAJOR ISLANDS OF THE SOUTHWEST PHILIPPINES, REEMERGING INTO THE NORTHERN SULU SEA BY 96H, AND INTO THE SOUTH CHINA SEA BEFORE 120H.INCREASING WIND SHEAR, DECREASED UPPER-LEVEL OUTFLOW AND THE ENTRAINMENT OF DRIER AIR WILL WEAKEN THE SYSTEM TO 25 KNOTS BY 120H.

01W(DUJUAN).NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT THROUGH 48H, WITH INCREASING UNCERTAINTY BY 72H. THE UKMET DETERMINISTIC AND ENSEMBLE SOLUTIONS CONTINUE TO SHOW AN UNLIKELY POLEWARD TRACK TO THE EAST OF THE PHILIPPINES, WHILE THE GFS SOLUTION SHOWS AN EQUALLY UNLIKELY DUE TO WEST TRACK. DISCOUNTING THE OUTLIERS, THE REMAINDER OF THE CONSENSUS MEMBERS LIE CLOSE TO THE CONSENSUS MEAN, WITH A 280KM SPREAD IN SOLUTIONS AT 72H.EVEN WHEN DISCOUNTING THE UKMET, UKMET ENSEMBLE SHOWING THE UNLIKELY POLEWARD TRACK, AND THE GFS DEPICTING A STRAIGHT WESTERLY TRACK, NUMERICAL MODEL GUIDANCE IS IN POOR AGREEMENT AFTER 72H, WITH A 830KM SPREAD IN MODEL SOLUTIONS BY 120H. THE JTWC FORECAST TRACK REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND LIES NEAR THE ECMWF SOLUTION. OVERALL, THERE IS POOR CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH LIES SOUTH OF THE MULTI-MODEL CONSENSUS, NEAR THE ECMWF SOLUTION.

01W(DUJUAN). 18/0430UTC. NOAA-20.

18/06UTC. JTWC IS ISSUING 6HOURLY WARNINGS ON 01W AND 12HOURLY WARNINGS ON 21S. 3 HOURLY SATELLITE BULLETINS ARE ISSUED FOR BOTH SYSTEMS.