WDPN31 PGTW 130300 MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W WARNING NR 13// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 130000Z TO 180000Z SEP 2006. A. TYPHOON (TY) 14W (SHANSHAN), LOCATED APPROXIMATELY 360 NM SOUTH-SOUTHEAST OF NAHA, OKINAWA, HAS TRACKED WEST- WARD AT 10 KNOTS OVER THE PAST SIX HOURS. B. TY 14W HAS INCREASED ITS SPEED OF ADVANCE AS IT CONTINUES TO TRACK WESTWARD ALONG THE SOUTHERN PERIPHERY OF A SUBTROPICAL RIDGE SITUATED SOUTH OF WESTERN JAPAN. TY 14W WILL BEGIN TO TRACK NORTHWESTWARD AFTER TAU 24 AND WILL TURN NORTHWARD BETWEEN TAUS 36 AND 48 AS THE SYSTEM TRACKS INTO A WEAKNESS IN THE SUBTROPICAL RIDGE CREATED BY AN APPROACHING MIDLATITUDE TROUGH. THE AVAILABLE DYNAMIC AIDS ARE IN GOOD AGREEMENT WITH THIS SCENARIO, BUT THERE CONTINUES TO BE DISAGREEMENT AS TO THE TIMING AND THE DEGREE OF THE RECURVATURE. THE MAJORITY OF THE MODELS FORECAST A SHARP TURN OVER OKINAWA WHILE JTYM AND WBAR INDICATE A MORE GRADUAL TURN NORTHWARD ALONG 124 DEGREES EAST LONGITUDE. THE CURRENT FORECAST IS BASED ON A CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS. C. TY 14W HAS MAINTAINED INTENSITY OVER THE PAST 06 HOURS. UPPER LEVEL CONVERGENCE CONTINUES TO SUPPRESS OUTFLOW ALOFT NORTH OF THE SYSTEM, WHILE EQUATORWARD OUTLFOW REMAINS FAVOR- ABLE. TY 14W IS FORECAST TO INTENSIFY AT A LESS THAN CLIMAT- LOGICAL RATE THROUGH TAU 36 AS THE EQUATORWARD OUTFLOW REMAINS STRONG AND THE BROAD-SCALE CONVERGENCE DECREASES SOMEWHAT. THE SYSTEM WILL WEAKEN SLOWLY THROUGH TAU 72 AS IT ENCOUNTERS INCREASING VERTICAL WIND SHEAR ASSOCIATED WITH THE APPROACHING MIDLATITUDE TROUGH. D. CURRENT WIND RADII ARE BASED ON A 122045Z QUIKSCAT IMAGE AND A 122156Z SSM/I IMAGE. FORECAST WIND RADII ARE BASED ON CLIMA- TOLOGY FOR AN AVERAGE-SIZED SYSTEM. E. AFTER TAU 72, TY 14W IS FORECAST TO WEAKEN AS IT ACCELERATES NORTHEASTWARD AND INTERACTS WITH THE MIDLATITUDE WESTERLIES. EXTRA- TROPICAL TRANSITION WILL BEGIN BY TAU 96. FORECAST TEAM: CHARLIE// NNNNHTTP/1.1 200 OK Date: Wed, 13 Sep 2006 08:53:18 GMT Server: Apache Content-Length: 0 Connection: close Content-Type: text/plain; charset=UTF-8