预报理由 WDPN31 PGTW 030900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (NEPARTAK) WARNING NR 02// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER WITH CURVED CONVECTIVE BANDING WRAPPING INTO THE SYSTEM. A 020454Z 37 GHZ SSMI IMAGE REVEALS THIS BANDING IS MAINLY CONFINED ALONG THE SOUTHERN AND EASTERN PERIPHERY OF THE SYSTEM, AND SUPPORTS THE JTWC BEST TRACK POSITION WITH GOOD CONFIDENCE. THE CURRENT INTENSITY IS ASSESSED AT 35 KNOTS BASED ON A 030021Z ASCAT PASS SHOWING A BAND OF 30 KNOT WINDS WITH ISOLATED 35 KNOT WINDS WITHIN DEEP CONVECTION IN THE EASTERN QUADRANT. ENVIRONMENTAL CONDITIONS ARE CURRENTLY CONDUCIVE FOR INTENSIFICATION WITH RADIAL OUTFLOW ALOFT, LOW (10 TO 15 KNOTS) VERTICAL WIND SHEAR, AND WARM SSTS. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 02W WILL REMAIN UNDER A WEAK STEERING ENVIRONMENT OVER THE NEXT 12 TO 24 HOURS AS A TUTT CELL POSITIONED TO THE NORTH MOVES OFF TO THE WEST. A SUBTROPICAL RIDGE IS EXPECTED TO BUILD IN FROM THE NORTHEAST TAKING NEPARTAK ON A NORTHWESTERN TRACK. GRADUAL INTENSIFICATION IS ANTICIPATED DURING THIS TIME AS OUTFLOW STEADILY IMPROVES AND THE SYSTEM CONTINUES TO CONSOLIDATE OVER WARM WATER. C. IN THE EXTENDED PERIOD NEPARTAK IS FORECAST TO INTENSIFY TO TYPHOON STRENGTH AT A STEADY RATE. ITS SPEED OF ADVANCE IS ALSO FORECAST TO INCREASE AS IT CONTINUES ON A NORTHWESTERN TRACK UNDER THE INFLUENCE OF THE SUBTROPICAL RIDGE, WITH RELATIVELY LOW VWS AND EXCELLENT UPPER-LEVEL OUTFLOW. BY TAU 120 A TROUGH IS EXPECTED TO MOVE INTO THE REGION WEAKENING THE STEERING RIDGE AND CAUSING A SHIFT NORTHWARD. AVAILABLE DYNAMICAL MODEL GUIDANCE IS IN GOOD AGREEMENT, DIFFERING SLIGHTLY IN THE EXTENDED TAU TRACKS, GIVING HIGH CONFIDENCE TO THE JTWC FORECAST.// NNNN