TROPICAL DISTURBANCE ADVISORY NUMBER A5 ISSUED FROM RSMC NADI
Feb 202316 UTC.
TROPICAL CYCLONE VICKY CATEGORY 1 CENTRE 995HPA WAS LOCATED NEAR
14.5S 171.1W AT 202230 UTC. POSITION POOR BASED ON HR HIMAWARI-8
IR/VIS IMAGERY AND PERIPHERAL SURFACE REPORTS. CYCLONE MOVING
EAST-SOUTHEAST AT ABOUT 6 KNOTS. MAXIMUM 10-MINUTE AVERAGE WINDS NEAR
THE CENTRE ESTIMATED AT ABOUT 35 KNOTS.
DEEP CONVECTION CONTINUES TO PERSIST OVER THE LLCC WITH PRIMARY BANDS
WRAPPING ONTO THE LLCC. OGANISATION IMPROVED. SYSTEM LIES UNDER AN
UPPER DIVERGENT AREA IN A LOW SHEARED ENVIRONMENT. CYCLONIC
CIRCULATION EXTENDS UP TO 500HPA. SST AROUND
30 DEGREES CELSIUS. GLOBAL MODELS HAVE PICKED UP THE SYSTEM AND MOVE
IT SOUTHEASTWARDS INITIALLY AND SOUTHWARDS THEREAFTER WITH FURTHER
INTENSIFICATION.
DVORAK ANALYSIS BASED ON 0.6 WRAP ON LOG10 SPIRAL YIELDING DT=3.0.
MET AND PT AGREE. FT BASED ON DT THUS, YIELDING T3.0/3.0/D0.5/24HRS.
FORECASTS :
AT 12 HRS VALID AT 211030 UTC 16.2S 170.2W MOV SSE AT 09 KT WITH 45
KT CLOSE TO CENTRE
AT 24 HRS VALID AT 212230 UTC 17.3S 169.7W MOV SSE AT 08 KT WITH 50
KT CLOSE TO CENTRE
OUTLOOK :
AT 36 HRS VALID AT 221030 UTC 18.0S 169.4W MOV SSE AT 07 KT WITH 55
KT CLOSE TO CENTRE
AT 48 HRS VALID AT 222230 UTC 18.6S 169.1W MOV SSE AT 06 KT WITH 55
KT CLOSE TO CENTRE
THE NEXT TROPICAL DISTURBANCE ADVISORY ON TROPICAL CYCLONE VICKY WILL
BE ISSUED AROUND 210200 UTC.
WTPS31 PGTW 202300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 17P (SEVENTEEN) WARNING NR 001//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/200351ZFEB2020//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT.//
RMKS/
1. TROPICAL CYCLONE 17P (SEVENTEEN) 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:
201800Z --- NEAR 14.3S 171.5W
MOVEMENT PAST SIX HOURS - 125 DEGREES AT 11 KTS
POSITION ACCURATE TO WITHIN 020 NM
POSITION BASED ON CENTER LOCATED BY SATELLITE
PRESENT WIND DISTRIBUTION:
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 070 NM NORTHEAST QUADRANT
070 NM SOUTHEAST QUADRANT
015 NM SOUTHWEST QUADRANT
055 NM NORTHWEST QUADRANT
REPEAT POSIT: 14.3S 171.5W
---
FORECASTS:
12 HRS, VALID AT:
210600Z --- 16.0S 170.4W
MAX SUSTAINED WINDS - 045 KT, GUSTS 055 KT
WIND RADII VALID OVER OPEN WATER ONLY
RADIUS OF 034 KT WINDS - 050 NM NORTHEAST QUADRANT
050 NM SOUTHEAST QUADRANT
015 NM SOUTHWEST QUADRANT
045 NM NORTHWEST QUADRANT
VECTOR TO 24 HR POSIT: 165 DEG/ 08 KTS
---
24 HRS, VALID AT:
211800Z --- 17.6S 170.0W
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
020 NM SOUTHWEST QUADRANT
030 NM NORTHWEST QUADRANT
VECTOR TO 36 HR POSIT: 190 DEG/ 05 KTS
---
36 HRS, VALID AT:
220600Z --- 18.6S 170.2W
MAX SUSTAINED WINDS - 035 KT, GUSTS 045 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATING AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
RADIUS OF 034 KT WINDS - 040 NM NORTHEAST QUADRANT
040 NM SOUTHEAST QUADRANT
010 NM SOUTHWEST QUADRANT
010 NM NORTHWEST QUADRANT
VECTOR TO 48 HR POSIT: 235 DEG/ 06 KTS
---
EXTENDED OUTLOOK:
48 HRS, VALID AT:
221800Z --- 19.3S 171.2W
MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
WIND RADII VALID OVER OPEN WATER ONLY
DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
---
REMARKS:
202100Z POSITION NEAR 14.7S 171.2W.
20FEB20. TROPICAL CYCLONE (TC) 17P (SEVENTEEN), LOCATED APPROXIMATELY
47 NM WEST OF PAGO PAGO, HAS TRACKED SOUTHEASTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. THIS IS A LATE CYCLE 201800Z WARNING BEING ISSUED
AT 202300Z. ANIMATED MULTISPECTRAL IMAGERY INDICATES A COMPACT CIRCULATION
WITHIN THE SPCZ HAS RAPIDLY CONSOLIDATED OVER THE PAST SIX HOURS.
SCATTEROMETRY DATA AS THE SYSTEM APPROACHED WESTERN SAMOA INDICATED 30
KNOTS, AND OBSERVATIONS AT MAOTA AND FALEOLO AIRPORTS SUPPORTED THIS ESTIMATE.
ADDITIONALLY, DVORAK ESTIMATES AT 18Z RANGED FROM T1.5 TO T2.0 (25-30 KNOTS).
HOWEVER, A 201937Z OBSERVATION FROM PAGO PAGO FOUND 40 KNOTS SUSTAINED WITH
GUSTS TO 65 KNOTS. THE DVORAK ESTIMATE IS LIKELY UNDER-REPRESENTING THE ACTUAL PEAK
INTENSITY DUE TO THE COMPACT NATURE OF THE CONVECTIVE CORE. THEREFORE, THE
INTENSITY IS NOW ASSESSED AT 45 KNOTS. TC 17P IS TRACKING SOUTHEASTWARD ALONG A
PERSISTENT TROUGH AND IS IN A FAVORABLE ENVIRONMENT WITH WARM (27-28 CELSIUS) SEA
SURFACE TEMPERATURES, LOW (10-15KTS) VERTICAL WIND SHEAR (VWS) AND ESTABLISHED
POLEWARD OUTFLOW. THE SYSTEM IS EXPECTED TO BEGIN A GENERALLY SOUTH-SOUTHEASTWARD
TRACK AT TAU 12, BECOMING SOUTHWARD AFTER TAU 24. AS THE TRACK BEGINS TO TURN
SOUTH-SOUTHWESTWARD AFTER TAU 24, TC 17P WILL BEGIN TO DISSIPATE OVER WATER DUE TO
INCREASING VWS AND COOLER SST, WEAKENING TO 35 KTS BY TAU 36. INCREASINGLY UNFAVORABLE
CONDITIONS WILL LEAD TO FULL DISSIPATION OVER WATER BY TAU 48. NUMERICAL MODEL
SOLUTIONS ARE IN POOR AGREEMENT WITH A 184 NM SPREAD AT TAU 12 INCREASING TO 295 NM AT
TAU 48. ADDITIONALLY, SOME NUMERICAL MODEL SOLUTIONS DEPICT 17P INTERACTING WITH 96P
AFTER TAU 48. THE COMBINATION OF POTENTIAL SYSTEM INTERACTION AND HIGH DEGREE OF
SPREAD YIELDS LOW CONFIDENCE TO THE OVERALL JTWC FORECAST TRACK. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 202300Z IS 15 FEET. NEXT
WARNINGS AT 210300Z, 210900Z, 211500Z AND 212100Z.
2. THIS CANCELS AND SUPERSEDES REF A (WTPS21 PGTW 190400).//
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