WDPN31 PGTW 120300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (BANYAN) WARNING NR 05// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 14W (BANYAN), LOCATED APPROXIMATELY 56 NM WEST-SOUTHWEST OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON RECENT MICROWAVE SATELLITE IMAGERY, INCLUDING AN 112216Z GMI PASS, AND SCATTEROMETER DATA, INCLUDING AN 112259Z ASCAT PASS. THE INTENSITY OF 50 KNOTS IS BASED ON MULTI-AGENCY DVORAK FIX VALUES AND THE AFOREMENTIONED ASCAT DATA. TS 14W IS TURNING POLEWARD ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL STEERING RIDGE TOWARD THE BASE OF AN APPROACHING MID-LATITUDE TROUGH TO THE NORTHWEST. THE CYCLONE HAS BECOME INCREASINGLY ORGANIZED DURING THE PAST SIX HOURS, WITH TIGHTLY-WRAPPED DEEP CONVECTION PERSISTING OVER THE CENTER. THE UPPER-LEVEL OUTFLOW PATTERN AND HIGH ALONG-TRACK HEAT CONTENT ARE SUPPORTIVE OF FURTHER DEVELOPMENT IN THE NEAR-TERM. 3. FORECAST REASONING. A. THE OVERALL FORECAST PHILOSOPHY FOR TS 14W IS UNCHANGED FROM THE PREVIOUS WARNING. FORECAST INTENSITIES IN THE MEDIUM-RANGE HAVE INCREASED SLIGHTLY BASED ON ANTICIPATED FAVORABLE ENVIRONMENTAL CONDITIONS. B. TS 14W WILL TURN POLEWARD AND APPROACH THE BASE OF AN UPPER-LEVEL TROUGH CURRENTLY ANALYZED TO THE NORTHWEST OF THE SYSTEM. GENERALLY POLEWARD MOTION IS EXPECTED TO CONTINUE THROUGH TAU 72, WHEN THE SYSTEM WILL BEGIN TO INTERACT DIRECTLY WITH A SECOND TROUGH APPROACHING FROM THE NORTHWEST. STEADY INTENSIFICATION IS EXPECTED FOR THE NEXT 36 TO 48 HOURS AS THE CYCLONE PASSES OVER VERY WARM WATER AND THROUGH A SUPPORTIVE UPPER- LEVEL FLOW PATTERN. ALTHOUGH CURRENT NUMERICAL MODEL GUIDANCE SUGGESTS A STEADY TREND, INTENSIFICATION ABOVE THE CURRENT FORECAST IS POSSIBLE GIVEN FAVORABLE ENVIRONMENTAL CONDITIONS. WEAKENING IS EXPECTED BY BEGIN BY TAU 72 AS TS 14W INTERACTS WITH THE AFOREMENTIONED SECOND TROUGH. C. TS 14W WILL ACCELERATE POLEWARD AND COMPLETE EXTRATROPICAL TRANSITION BY TAU 96. ALTHOUGH NUMERICAL MODEL GUIDANCE REMAINS IN FAIR AGREEMENT WITH THE OVERALL TRACK SCENARIO, MODEL SPREAD INCREASES AFTER TAU 24 AS EACH MODEL DEPICTS THE SHARPNESS AND SPEED OF THE POLEWARD AND EVENTUAL NORTHEASTWARD TURNS DIFFERENTLY. GIVEN THIS PATTERN, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST THROUGH TAU 24, AND LOW CONFIDENCE THEREAFTER.// NNNN