WTPS31 PGTW 030900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE 18P (DONNA) WARNING NR 002// RMKS/ 1. TROPICAL CYCLONE 18P (DONNA) WARNING NR 002 01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE WIND RADII VALID OVER OPEN WATER ONLY --- WARNING POSITION: 030600Z --- NEAR 12.7S 171.2E MOVEMENT PAST SIX HOURS - 280 DEGREES AT 05 KTS POSITION ACCURATE TO WITHIN 040 NM POSITION BASED ON CENTER LOCATED BY SATELLITE PRESENT WIND DISTRIBUTION: MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 050 KT WINDS - 025 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT 080 NM SOUTHEAST QUADRANT 070 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT REPEAT POSIT: 12.7S 171.2E --- FORECASTS: 12 HRS, VALID AT: 031800Z --- 12.7S 170.4E MAX SUSTAINED WINDS - 065 KT, GUSTS 080 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 010 NM NORTHEAST QUADRANT 015 NM SOUTHEAST QUADRANT 015 NM SOUTHWEST QUADRANT 015 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 035 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 040 NM SOUTHWEST QUADRANT 035 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT 100 NM SOUTHEAST QUADRANT 095 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 24 HR POSIT: 255 DEG/ 05 KTS --- 24 HRS, VALID AT: 040600Z --- 13.0S 169.4E MAX SUSTAINED WINDS - 075 KT, GUSTS 090 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 025 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 025 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 040 NM NORTHEAST QUADRANT 055 NM SOUTHEAST QUADRANT 050 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 075 NM NORTHEAST QUADRANT 115 NM SOUTHEAST QUADRANT 115 NM SOUTHWEST QUADRANT 090 NM NORTHWEST QUADRANT VECTOR TO 36 HR POSIT: 245 DEG/ 05 KTS --- 36 HRS, VALID AT: 041800Z --- 13.5S 168.4E MAX SUSTAINED WINDS - 085 KT, GUSTS 105 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 025 NM NORTHEAST QUADRANT 025 NM SOUTHEAST QUADRANT 030 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 045 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 090 NM NORTHEAST QUADRANT 120 NM SOUTHEAST QUADRANT 125 NM SOUTHWEST QUADRANT 085 NM NORTHWEST QUADRANT VECTOR TO 48 HR POSIT: 230 DEG/ 05 KTS --- EXTENDED OUTLOOK: 48 HRS, VALID AT: 050600Z --- 14.1S 167.6E MAX SUSTAINED WINDS - 095 KT, GUSTS 115 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 035 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT 055 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 040 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 095 NM NORTHEAST QUADRANT 125 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 085 NM NORTHWEST QUADRANT VECTOR TO 72 HR POSIT: 180 DEG/ 03 KTS --- 72 HRS, VALID AT: 060600Z --- 15.2S 167.6E MAX SUSTAINED WINDS - 105 KT, GUSTS 130 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 030 NM SOUTHEAST QUADRANT 035 NM SOUTHWEST QUADRANT 025 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 050 NM NORTHEAST QUADRANT 060 NM SOUTHEAST QUADRANT 065 NM SOUTHWEST QUADRANT 050 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 095 NM NORTHEAST QUADRANT 125 NM SOUTHEAST QUADRANT 120 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 96 HR POSIT: 150 DEG/ 04 KTS --- LONG RANGE OUTLOOK: --- 96 HRS, VALID AT: 070600Z --- 16.6S 168.4E MAX SUSTAINED WINDS - 110 KT, GUSTS 135 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 035 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 055 NM NORTHEAST QUADRANT 065 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 045 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 100 NM NORTHEAST QUADRANT 125 NM SOUTHEAST QUADRANT 115 NM SOUTHWEST QUADRANT 080 NM NORTHWEST QUADRANT VECTOR TO 120 HR POSIT: 150 DEG/ 05 KTS --- 120 HRS, VALID AT: 080600Z --- 18.4S 169.5E MAX SUSTAINED WINDS - 105 KT, GUSTS 130 KT WIND RADII VALID OVER OPEN WATER ONLY RADIUS OF 064 KT WINDS - 030 NM NORTHEAST QUADRANT 035 NM SOUTHEAST QUADRANT 035 NM SOUTHWEST QUADRANT 020 NM NORTHWEST QUADRANT RADIUS OF 050 KT WINDS - 055 NM NORTHEAST QUADRANT 065 NM SOUTHEAST QUADRANT 060 NM SOUTHWEST QUADRANT 045 NM NORTHWEST QUADRANT RADIUS OF 034 KT WINDS - 105 NM NORTHEAST QUADRANT 125 NM SOUTHEAST QUADRANT 115 NM SOUTHWEST QUADRANT 085 NM NORTHWEST QUADRANT --- REMARKS: 030900Z POSITION NEAR 12.7S 171.0E. TROPICAL CYCLONE 18P (DONNA), LOCATED APPROXIMATELY 344 NM NORTH-NORTHEAST OF PORT VILA, VANUATU, HAS TRACKED WESTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON A LOW-LEVEL CENTER FEATURE EVIDENT IN A 030412Z SSMIS IMAGE AND RECENT SATELLITE POSITION FIXES FROM KNES AND PGTW. THE INTENSITY OF 55 KNOTS IS CONSISTENT WITH DVORAK SATELLITE INTENSITY ESTIMATES OF T=3.5 FROM THE SAME REPORTING AGENCIES. TC 18P HAS TURNED WESTWARD OVER THE PAST SIX HOURS UNDER THE INFLUENCE OF A DEVELOPING SUBTROPICAL STEERING RIDGE TO THE SOUTH. THE SYSTEM HAS STEADILY INTENSIFIED, AND BECOME INCREASINGLY ORGANIZED, UNDER THE FAVORABLE INFLUENCES OF STRONG POLEWARD OUTFLOW ALOFT, LOW VERTICAL WIND SHEAR (5-10 KNOTS) AND PASSAGE OVER VERY WARM WATER (29-30C). TC 18P IS EXPECTED TO TRACK WESTWARD TO SOUTHWESTWARD OVER THE NEXT 48 HOURS UNDER THE CONTINUED INFLUENCE OF THE SUBTROPICAL STEERING RIDGE. STEADY INTENSIFICATION IS ANTICIPATED AS ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE, WITH SOME GUIDANCE SUGGESTING THAT A MORE RAPID INTENSIFICATION RATE THAN INDICATED IN THE CURRENT FORECAST IS POSSIBLE. BY TAU 48, A BREAK IS EXPECTED TO DEVELOP IN THE STEERING RIDGE IN RESPONSE TO AN APPROACHING MID-LATITUDE TROUGH, ALLOWING TC 18P TO TURN SHARPLY POLEWARD AROUND THE STEERING RIDGE PERIPHERY. ADDITIONAL INTENSIFICATION IS EXPECTED INTO THE EXTENDED PERIOD, AS POLEWARD OUTFLOW IS ENHANCED AHEAD OF THE DEVELOPING MID-LATITUDE TROUGH. BY TAU 120, INCREASING VERTICAL WIND SHEAR ASSOCIATED WITH UPPER-LEVEL FLOW AHEAD OF THE TROUGH SHOULD INITIATE A WEAKENING TREND. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT REGARDING THE OVERALL FORECAST SCENARIO OF A WESTWARD TO SOUTHWESTWARD TRACK IN THE NEAR-TERM, FOLLOWED BY A POLEWARD TRACK IN THE MEDIUM TO EXTENDED RANGE. HOWEVER, THERE IS CONSIDERABLE DISAGREEMENT REGARDING THE EXACT PATH THE SYSTEM WILL FOLLOW. THE CURRENT JTWC OFFICIAL FORECAST IS SHIFTED SLIGHTLY WESTWARD FROM THE PREVIOUS FORECAST AND LIES WITHIN THE MODEL FORECAST ENVELOPE NOT FAR FROM THE MULTI-MODEL CONSENSUS, WHICH HAS CONSISTENTLY INDICATED A TRACK RUNNING PARALLEL AND NEAR TO THE VANUATU ISLAND CHAIN. CONSIDERING THE LARGE MODEL SPREAD, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 030600Z IS 18 FEET. NEXT WARNINGS AT 032100Z AND 040900Z.//