APCEDI Alert SP/FJ Cyclone Vaianu (TD12F) #3-2006: Cyclone Vaianu Slowly Strengthens between Central Tonga and Fiji's Southern Lau Group

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

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

Cyclone Vaianu is located equidistant between the Central Tonga Groups and the Southern Lau Group of Fiji over 200 km from either area. This is good news because 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 06 knots (11 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 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 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, Fiji 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 VAVAU GROUP, HAAPAI GROUP AND NOMUKA GROUP AND IS NOW IN FORCE FOR SOUTHERN TONGA.
A STRONG WIND WARNING REMAINS IN FORCE FOR NIUAS.

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 IS NOW IN FORCE OVER LAND AREAS OF THE LAU GROUP.
A DAMAGING SWELL WARNING IS NOW IN FORCE FOR FIJI
A STRONG WIND WARNING IS NOW IN FORCE FOR LAU WATERS, KORO SEA, KADAVU AND VATU-I-RA PASSAGES, SOUTHWEST VITI LEVU AND MAMANUCA 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 A9 issued from RSMC NADI
Feb 12/0818 UTC 2006 UTC.

Tropical Cyclone VAIANU [975hPa] centre was located near 18.3 South 176.4 West at 120600 UTC. Position fair and based on MTSAT/EIR with animation and peripheral surface reports. Repeat position 18.3S 176.4W at 120600 UTC. Cyclone moving southwest at about 06 knots but is expected to turn south in the next 24 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 the eastern semicircle and within 80
miles elsewhere.

System organisation has improved after initial supression due to diurnal influence around 0300 UTC. Convection wraps closer and tighter to llcc and Vaianu still struggles to form a banding eye. The system remains embedded in the 250hPa subtropical ridge in a diffluent region. Outflow remains good in all quadrants. CIMMS indicates mininal shear over the cyclone and its forecast track southwards. Vaianu is expected to further intensify as it moves southwards tonight, aided by diurnal changes and low environment shear. SST in the area is about 29-30C. Dvorak analysis based on 1.05 wrap on log10 spiral gives DT=PT=4.0 while MET=3.5, yielding T4.0/4.0/D1.5/24hrs. The system is steered southwest by a mid-level ridge located to the east for the next 12 hours and it is expected to curve southwards beyond 12 hours in response to an approaching broad upper trough from the west. Global models agree on an initial southwest track with further intensification.

FORECAST:
12hrs valid at 121800 UTC near 19.3S 177.0W mov SSW at 05kt with 65 kt close to the centre.
24hrs valid at 130600 UTC near 20.7S 177.2W mov SSW at 05kt with 70 kt close to the centre.

OUTLOOK:
36hrs valid at 131800 UTC near 21.9S 177.3W mov SSW at 05kt with 70kt close to the centre.
48hrs valid at 140600 UTC near 22.5S 176.8W mov S at 05kt with 70kt close to the centre.

The next Tropical Disturbance Advisory on Tropical Cyclone VAIANU will be issued around 121400 UTC.
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The TONGA FORESCAST from RSMC-Nadi Tropical Cyclone Centre

Special Weather Bulletin Number TWELVE for Tonga on TROPICAL CYCLONE VAIANU issued from RSMC NADI
Feb 12/0848 UTC 2006 UTC.

TROPICAL CYCLONE WARNING.

A GALE WARNING REMAINS IN FORCE FOR VAVAU GROUP, HAAPAI GROUP AND NOMUKA GROUP AND IS NOW IN FORCE FOR SOUTHERN TONGA.
A STRONG WIND WARNING REMAINS IN FORCE FOR NIUAS.

Tropical Cyclone VAIANU [975hPa] centre was located near 18.3 South 176.4 West at 120600 UTC. Position fair and based on MTSAT/EIR with animation and peripheral surface reports. Repeat position 18.3S 176.4W at 120600 UTC. Cyclone moving southwest at about 06 knots but is expected to turn south in the next 24 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 the eastern semicircle and within 80 miles elsewhere.

On its current track, the cyclone is expected to lie 130 miles westnorthwest of Ha'afeva at 121200 UTC and 130 miles westnorthwest of Nomuka at 121800 UTC.

FOR VAVA'U GROUP, HA'APAI GROUP, NOMUKA GROUP, KOTU GROUP:
Expect damaging gale force winds with average speeds 30 to 35 knots and momentary gusts of 55 to 60 knots about Vava'u Group, easing later tonight. North to northeast winds 25 to 30 knots gusting to 45 knots about Ha'apai Group, Nomuka group, Kotu group, increasing to damaging gale force with average speeds of 30 to 35 knots and momentary gusts of 55 knots overnight. 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 SOUTHERN TONGA:
Easterly winds 20 to 25 knots with gusts to 35 knots. Winds gradually turning northeast and possibly increasing to damaging gale force with average speeds of 35 to 40 knots and momentary gusts of 50 to 60 knots within the next 12 to 24 hours. Rain, heavy at times with squally thunderstorms. Flooding including sea flooding of low-lying coastal areas expected. Very rough to high seas. Damaging heavy swells developing.

FOR NIUAFO'OU AND NIUATOPUTAPU:
West to northwest winds 25 to 30 knots, gusting 45 knots. Rain, heavy at times with squally thunderstorms. Sea flooding of coastal areas. Rough to very rough seas. Heavy northwest swells.

THE FOLLOWING INFORMATION IS PROVIDED ESPECIALLY FOR MARINERS:
Expect sustained winds of 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 the eastern semicircle and within 80 miles elsewhere.

The next Special Weather Bulletin for Tonga on Tropical Cyclone Vaianu will be issued at 121200 UTC. TONGA PSE ACKNOWLEDGE THE RECEIPT OF THIS BULLETIN.
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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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