WTPS31 PGTW 290900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 04P (TUNI) WARNING NR 007// RMKS/ 1. TROPICAL CYCLONE 04P (TUNI) WARNING NR 007 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 290600Z --- NEAR 16.5S 170.6W MOVEMENT PAST SIX HOURS - 130 DEGREES AT 13 KTS POSITION ACCURATE TO WITHIN 060 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 034 KT WINDS - 035 NM NORTHEAST QUADRANT 070 NM SOUTHEAST QUADRANT 085 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT REPEAT POSIT: 16.5S 170.6W --- FORECASTS: 12 HRS, VALID AT: 291800Z --- 17.6S 169.5W MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING EXTRATROPICAL RADIUS OF 034 KT WINDS - 045 NM NORTHEAST QUADRANT 080 NM SOUTHEAST QUADRANT 090 NM SOUTHWEST QUADRANT 060 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 140 DEG/ 07 KTS --- 24 HRS, VALID AT: 300600Z --- 18.7S 168.5W MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT WIND RADII VALID OVER OPEN WATER ONLY BECOMING EXTRATROPICAL RADIUS OF 034 KT WINDS - 055 NM NORTHEAST QUADRANT 090 NM SOUTHEAST QUADRANT 090 NM SOUTHWEST QUADRANT 065 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 135 DEG/ 08 KTS --- 36 HRS, VALID AT: 301800Z --- 19.8S 167.4W MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT WIND RADII VALID OVER OPEN WATER ONLY EXTRATROPICAL --- REMARKS: 290900Z POSITION NEAR 16.8S 170.3W. TROPICAL CYCLONE (TC) 04P (TUNI), LOCATED APPROXIMATELY 132 NM SOUTH OF PAGO PAGO, AMERICAN SAMOA HAS TRACKED SOUTHEASTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN ELONGATED AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH ASSOCIATED CONVECTION SHEARED TO THE SOUTHEAST DUE TO PERSISTENT 20 TO 25 KNOT NORTHWESTERLY VERTICAL WIND SHEAR (VWS). A STRONG POLEWARD OUTFLOW CHANNEL, ASSOCIATED WITH A MID-LATITUDE TROUGH, IS PROVIDING SUFFICIENT VENTILATION FOR THE PERSISTENT CONVECTION. THE CURRENT POSITION IS BASED ON THE EXPOSED LLCC IN THE EIR LOOP AND IN A 290628Z SSMIS 91GHZ MICROWAVE IMAGE WITH FAIR CONFIDENCE. THE INTENSITY HAS BEEN HELD AT 40 KNOTS BASED ON PREVIOUS SCATTEROMETER PASSES AND IS SUPPORTED BY DVORAK INTENSITY ESTIMATES RANGING FROM 35 TO 45 KNOTS. TC TUNI IS MOVING SOUTHEASTWARD UNDER THE STEERING INFLUENCE A SUB-TROPICAL RIDGE (STR) TO THE EAST. THIS STR WILL REMAIN THE DOMINANT STEERING MECHANISM THROUGHOUT THE FORECAST PERIOD. AS THE CYCLONE MOVES POLEWARD, VWS WILL CONTINUE TO INCREASE AND SEA SURFACE TEMPERATURES WILL DECREASE LEADING TO A SLOW WEAKENING TREND. IN ADDITION, NEAR TAU 12, TC 04P WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE WEAK BAROCLINIC ZONE. THE SYSTEM WILL FULLY EMBED WITHIN THE MID-LATITUDE WESTERLY FLOW AND COMPLETE ETT BY THE END OF THE FORECAST PERIOD. DYNAMIC MODEL GUIDANCE REMAINS CONSISTENT WITH MOST TRACKERS SHOWING A SOUTHEASTWARD TRACK; HOWEVER, THE BROAD ELONGATED NATURE OF THE SYSTEM CREATES A POSITIONAL UNCERTAINTY THAT LEADS TO LOW CONFIDENCE IN THE JTWC FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 290600Z IS 14 FEET. NEXT WARNINGS AT 292100Z AND 300900Z.//