GALE WARNING 022 ISSUED FROM RSMC NADI Apr 200104 UTC.
TROPICAL DEPRESSION TD17F CENTRE 998HPA WAS LOCATED NEAR 12.5S 178.4W AT
200000UTC. POSITION FAIR. TD17F MOVING NORTHWEST AT 09 KNOTS.
EXPECT CLOCKWISE WINDS UPTO 35 KNOTS WITHIN 60 TO 90 NAUTICAL MILES AWAY FROM
THE CENTRE IN THE SECTORS FROM NORTHWEST THROUGH NORTH TO EAST IN THE NEXT 12 TO
24 HOURS.
AREA OF GALES MOVING WITH THE DEPRESSION.
THIS IS THE FIRST WARNING ON THIS SYSTEM.
WTPS31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE WARNING//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI//180351ZAPR2016//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT.//
RMKS/
1. TROPICAL CYCLONE 20P (TWENTY) WARNING NR 001
01 ACTIVE TROPICAL CYCLONE IN SOUTHPAC
MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
WIND RADII VALID OVER OPEN WATER ONLY
---
WARNING POSITION:
200000Z --- NEAR 13.1S 178.2W
MOVEMENT PAST SIX HOURS - 285 DEGREES AT 10 KTS
POSITION ACCURATE TO WITHIN 060 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
REPEAT POSIT: 13.1S 178.2W
---
FORECASTS:
12 HRS, VALID AT:
201200Z --- 12.9S 179.0W
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 24 HR POSIT: 295 DEG/ 03 KTS
---
24 HRS, VALID AT:
210000Z --- 12.6S 179.6W
MAX SUSTAINED WINDS - 040 KT, GUSTS 050 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
045 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 060 DEG/ 04 KTS
---
36 HRS, VALID AT:
211200Z --- 12.2S 178.9W
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 055 NM NORTHEAST QUADRANT
045 NM SOUTHEAST QUADRANT
040 NM SOUTHWEST QUADRANT
045 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 080 DEG/ 06 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
220000Z --- 12.0S 177.6W
MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 050 KT WINDS - 015 NM NORTHEAST QUADRANT
015 NM SOUTHEAST QUADRANT
015 NM SOUTHWEST QUADRANT
015 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 065 NM NORTHEAST QUADRANT
055 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
065 NM NORTHWEST QUADRANT
VECTOR TO 72 HR POSIT: 100 DEG/ 06 KTS
---
72 HRS, VALID AT:
230000Z --- 12.4S 175.2W
MAX SUSTAINED WINDS - 060 KT, GUSTS 075 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 050 KT WINDS - 025 NM NORTHEAST QUADRANT
030 NM SOUTHEAST QUADRANT
025 NM SOUTHWEST QUADRANT
025 NM NORTHWEST QUADRANT
RADIUS OF 034 KT WINDS - 065 NM NORTHEAST QUADRANT
065 NM SOUTHEAST QUADRANT
060 NM SOUTHWEST QUADRANT
070 NM NORTHWEST QUADRANT
VECTOR TO 96 HR POSIT: 125 DEG/ 08 KTS
---
LONG RANGE OUTLOOK:
---
96 HRS, VALID AT:
240000Z --- 14.2S 172.6W
MAX SUSTAINED WINDS - 055 KT, GUSTS 070 KT
WIND RADII VALID OVER OPEN WATER ONLY
VECTOR TO 120 HR POSIT: 125 DEG/ 07 KTS
---
120 HRS, VALID AT:
250000Z --- 15.8S 170.1W
MAX SUSTAINED WINDS - 050 KT, GUSTS 065 KT
WIND RADII VALID OVER OPEN WATER ONLY
---
REMARKS:
200300Z POSITION NEAR 13.0S 178.4W. TROPICAL CYCLONE 20P (TWENTY),
LOCATED APPROXIMATELY 316 NM WEST OF AVATA SAMOA, HAS TRACKED WEST-
NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY DEPICTS DEEP CONVECTION
CONSOLIDATING AROUND A LOW-LEVEL CIRCULATION CENTER (LLCC) WHICH IS
CURRENTLY COVERED BY A CENTRAL DENSE OVERCAST (CDO). A 192043Z AMSU-
B 89GHZ IMAGE SHOWS THAT THE DEEP CONVECTION IS RESTRICTED TO THE
NORTHEASTERN QUADRANT OF THE SYSTEM WITH SOME MODERATE CONVECTIVE
BANDS BEGINNING TO FORM TO THE SOUTHEAST OF THE LLCC. THE
CORRESPONDING 192043Z ASCAT-B PASS INDICATES BROAD AREAS OF 20-25
KNOT WINDS BOTH NORTH AND SOUTH OF THE LLCC, WHILE AN EARLIER
191747Z WINDSAT PASS SHOWED A FEW 30-35 KNOT UNFLAGGED PLOTS. THE
INITIAL INTENSITY IS ASSESSED AT 30 KNOTS BASED ON DVORAK ESTIMATES
BETWEEN 30 AND 35 KNOTS FROM KNES AND PGTW RESPECTIVELY. UPPER-LEVEL
ANALYSIS INDICATES TC 20P IS CURRENTLY IN A MARGINALLY FAVORABLE
ENVIRONMENT WITH LOW-MODERATE (10 TO 20 KNOTS) VERTICAL WIND SHEAR
(VWS), MODERATE POLEWARD OUTFLOW AND SEA SURFACE TEMPERATURES (SSTS)
OF 30 DEG CELSIUS. TC 18P IS CURRENTLY TRACKING WEST-NORTHWESTWARD
UNDER THE INFLUENCE A TRANSIENT RIDGE TO THE SOUTH. BY TAU 24, THIS
RIDGE WILL WEAKEN AND SHIFT EASTWARD, ALLOWING THE NEAR EQUATORIAL
RIDGE (NER) TO BECOME THE DOMINATE STEERING MECHANISM, RESULTING IN
A TURN OF TC 20P BACK TO AN EASTWARD TRACK BY TAU 36. THROUGH THE
REMAINDER OF THE FORECAST PERIOD THE SYSTEM IS FORECAST TO TRACK
EAST THEN SOUTHEASTWARD UNDER THE INFLUENCE OF THE NER. TC 20P IS
FORECAST TO SLOWLY INTENSIFY OVER THE NEXT 24 HOURS, AS THE UPPER-
LEVEL ENVIRONMENT REMAINS MARGINAL DUE TO MODERATE VWS AND THE
ENTRAINMENT OF RELATIVELY DRY AIR FROM THE WEST. AFTER TAU 24, THE
MOISTURE ENVELOPE WILL IMPROVE, VWS WILL DECREASE AND OUTFLOW WILL
IMPROVE AS THE SYSTEM TAPS INTO THE UPPER-LEVEL WESTERLIES, ALLOWING
FURTHER INTENSIFICATION, BEFORE PEAKING AT 60 KNOTS BY TAU 72.
THROUGH THE REMAINDER OF THE FORECAST PERIOD, TC 20P WILL SLOWLY
WEAKEN AS IT ENCOUNTERS HIGHER VWS. DYNAMIC MODEL GUIDANCE IS IN
FAIRLY TIGHT AGREEMENT IN THE OVERALL TRACK BUT THERE IS HIGH
UNCERTAINTY IN THE TIMING AND LOCATION OF THE TURN BACK TOWARDS THE
EAST, THEREFORE, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK.
MAXIMUM SIGNIFICANT WAVE HEIGHT AT 200000Z IS 8 FEET. NEXT WARNINGS
AT 200900Z, 201500Z, 202100Z AND 210300Z. THIS CANCELS AND
SUPERSEDES REF A (WTPS22 PGTW 190400).//
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