APCEDI Alert SP/FJ Cyclone Vaianu (TD12F) #4-2006: Cyclone Vaianu Slowly Strengthens as it passes west of the main Central and Southern Tonga Groups

The RSMC-Nadi Tropical Cyclone Centre and the Joint Typhoon Warning Centre continue to issue guidance on Cyclone Vaianu.

Cyclone Vaianu is currently at Category 1 intensity on the Saffir Simpson Scale and is expected to slowly intensify over the next 24 hours.

Cyclone Vaianu continues passing roughly equidistantly between the Central and Southern Tonga Groups and the Southern Lau Group of Fiji over 200 km from either area. This continues to be good news for both countries because as it is passing between both areas, neither of them will sustain a direct hit. Therefore, only minor damage and flooding of low lying areas is likely. However, any change in direction could bring the storm closer to island areas.

Vaianu is moving southwest at about 05 knots (09 km/h) and expected to curve southward in 24 hours. Given Vaianu's forecast track to the west of the main Tonga islands it is likely that only minor damage and flooding could occur throughout much of the Vava'u, Ha'apai and Nomuka Groups for the most part. However, the western most islands in the Groups such as Late (Vava'u), Kao and Tofua (Ha'apai) and Fonuafo'ou and Hunga Tonga (Nomuka) should be particularly alert as the centre of Vaianu will be closest to these islands. Tonga's main island of Tongatapu needs to closely watch this storm as long term forecasting shows it curving south and southeast, but still passing to the west of the main island.

Also the Southern Lau Group of Fiji should maintain vigilance especially the southeastern-most islands of Ogea, Vatoa and Onoilau.

All interests in Tonga, Fiji and Niue should closely monitor the progress of this storm, and undertake any actions as advised by the local authorities. Although the storm is moving away from Wallis and Futuna and Samoa, all interests should maintain vigilance due to continuing rough seas, winds and heavy rains.

CURRENT ADVISORIES AND WARNINGS

TONGA
A GALE WARNING REMAINS IN FORCE FOR NOMUKA GROUP, HA'APAI GROUP, TONGATAPU GROUP AND NEARBY SMALLER ISLANDS.
A STRONG WIND WARNING REMAINS IN FORCE FOR NIUAS AND VAVAU GROUP.

SAMOA
WIND ADVISORY IN FORCE FOR SAMOA
FLOOD ADVISORY REMAINS IN FORCE
LANDSLIDE ADVISORY REMAINS IN EFFECT

NIUE
A STRONG WIND WARNING REMAINS IN FORCE FOR NIUE.

FIJI
A STRONG WIND WARNING REMAINS IN FORCE OVER LAND AREAS OF THE LAU GROUP.
A DAMAGING SWELL WARNING REMAINS IN FORCE FOR FIJI.
A STRONG WIND WARNING REMAINS IN FORCE FOR ALL FIJI WATERS.

WALLIS AND FUTUNA
A STRONG WIND WARNING REMAINS IN FORCE FOR WALLIS AND FUTUNA WATERS.

AMERICAN SAMOA
SMALL CRAFT ADVISORY
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From the RSMC-Nadi Tropical Cyclone Centre

Tropical Disturbance Advisory Number A11 issued from RSMC NADI
Feb 12/2002 UTC 2006 UTC.

Tropical Cyclone VAIANU [975hPa] centre was located near 19.1 South 176.9 West at 121800 UTC. Position fair and based on MTSAT/EIR with animation and peripheral surface reports. Repeat position 19.1S 176.9W at 121800 UTC. Cyclone moving southwest at about 05 knots but is expected to turn south in the next 6 to 12 hours. Cyclone intensifying. Maximum 10-minute average winds estimated at 60 knots close to the centre, increasing to 65 knots in the next 6 to 12 hours. Expect winds over 47 knots within 30 miles of centre and winds over 33 knots within 100 miles of centre in sectors from north through east to southwest and within 80 miles elsewhere.

Overall organisation improved past 24 hours though development steady past 6 hours. Warm air intrusion evident past 6 hours. Some warming of convective tops occuring. The system lies under the 250-hPa ridge in a diffluent region. Outflow good to south and north and restricted elsewhere. CIMMS indicates mininal shear over the cyclone. SST in the area is about 29-30C. Dvorak analysis based on LG embedded centre yielding DT=4.5. PT=MET=4.0, thus T4.0/4.0/D1.0/24hrs. Cyclone is being steered by a deep north to northeast steering flow. A gradual southward turn is expected in the next 6 to 12 hours. Global models generally agree on this with further intensification.

FORECAST:
12hrs valid at 130600 UTC near 20.3S 177.1W mov S at 06kt with 65 kt close to the centre.
24hrs valid at 131800 UTC near 21.4S 177.1W mov S at 06kt with 65 kt close to the centre.

OUTLOOK:
36hrs valid at 140600 UTC near 22.4S 177.3W mov S at 06kt with 60kt close to the centre.
48hrs valid at 141800 UTC near 23.5S 176.9W mov S at 05kt with 60kt close to the centre.

The next Tropical Disturbance Advisory on Tropical Cyclone VAIANU will be issued around 130200 UTC.
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The TONGA FORESCAST from RSMC-Nadi Tropical Cyclone Centre

Special Weather Bulletin Number SIXTEEN for Tonga on TROPICAL CYCLONE VAIANU issued from RSMC NADI
Feb 12/2122 UTC 2006 UTC.

TROPICAL CYCLONE WARNING.

A GALE WARNING REMAINS IN FORCE FOR NOMUKA GROUP, HA'APAI GROUP, TONGATAPU GROUP AND NEARBY SMALLER ISLANDS.
A STRONG WIND WARNING REMAINS IN FORCE FOR NIUAS AND VAVAU GROUP.

Tropical Cyclone VAIANU [975hPa] centre was located near 19.5 South 176.9 West at 122100 UTC. Position fairr and based on MTSAT/EIR with animation and peripheral surface reports. Repeat position 19.0S 177.0W at 121700 UTC. Cyclone moving southwest at about 05 knots but is expected to turn south in the next 6 to 12 hours. Maximum 10-minute average winds estimated at 60 knots close to the centre. Expect winds over 47 knots within 30 miles of centre and winds over 33 knots within 100 miles of centre in the eastern semicircle and within 80 miles elsewhere.

On its current track, the cyclone is expected to lie 125 miles west of Nomuka or 115 miles west-northwest of Nukualofa at 130600 UTC and 110 miles west of Nukualofa or 140 miles west-southwest of Nomuka at 131800 UTC.

FOR NOMUKA GROUP, HA"APAI GROUP, TONGATAPU GROUP AND NEARBY SMALLER ISLANDS:
Expect damaging gale force winds with average speeds of 35 knots and momentary gusts of 55 knots. Periods of heavy rain and squally thunderstorms. Flooding including sea flooding of low-lying coastal areas expected. Very rough to high seas. Damaging heavy swells.

FOR VAVAU GROUP, NIUAFO'OU AND NIUATOPUTAPU:
North to northwest winds 25 to 30 knots, gusting to 45 knots. Periods of rain, heavy at times, with squally thunderstorms. Flooding including sea flooding of coastal areas expected particularly over the Vavau group. Very rough seas. Damaging heavy swells gradually easing over the Niuas.

THE FOLLOWING INFORMATION IS PROVIDED ESPECIALLY FOR MARINERS:
Expect sustained winds of 60 knots close to the centre with phenomenal seas. Expect winds over 47 knots within 30 miles of centre with very high seas and winds over 33 knots within 100 miles of centre in the eastern semicircle and within 80 miles elsewhere with high seas.

The next Special Weather Bulletin for Tonga on Tropical Cyclone Vaianu will be issued around 130000 UTC. TONGA PSE ACKNOWLEDGE THE RECEIPT OF THIS BULLETIN. NOTE THAT THIS BULLETIN IS NUMBER 16. 121800Z ISSUE SHOULD HAVE BEEN NO 15.
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APCEDI will continue to monitor the progress of this system.

Kevin Vang
APCEDI Coordinator
http://www.afap.org/apcedi/

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