Tropical Cyclone Tam developed over the South Pacific Ocean east of New Caledonia on Tuesday. At 5:00 a.m. EDT on Tuesday the center of Tropical Cyclone Tam was located at latitude 21.9°S and longitude 171.4°E which put the center about 335 miles (540 km) east of Noumea, New Caledonia. Tam was moving toward the southeast at 25 m.p.h. (40 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 988 mb.
A low pressure system over the South Pacific Ocean east of New Caledonia strengthened during Monday night and the Fiji Meteorological Service designated the system as Tropical Cyclone Tam.
The distribution of thunderstorms around Tropical Cyclone Tam was asymmetrical. Tam was located under the eastern side of an upper level trough that was east of Australia. The upper level trough was producing strong northwesterly winds that were blowing toward the top of Tam’s circulation. Those winds were causing strong vertical wind shear. The strong wind shear was causing the asymmetrical distribution of thunderstorms in Tropical Cyclone Tam. Thunderstorms were occurring in bands in the southern and eastern parts of Tam’s circulation. Bands in the northern and western parts of Tropical Cyclone Tam consisted primarily of showers and lower clouds.
The asymmetrical distribution of thunderstorms was also causing the distribution of wind speeds to be asymmetrical. Winds to tropical storm force extended out 250 miles (400 km) in the eastern side of Tropical Cyclone Tam. The winds in the western half of Tam’s circulation were blowing at less than tropical storm force.
Tropical Cyclone Tam will move into an environment that will be unfavorable for the intensification of a tropical cyclone during the next 24 hours. Tam will move over water where where the Sea Surface Temperatures are near 24°C. The upper level trough east of Australia will continue to cause strong vertical wind shear. The combination of cool Sea Surface Temperatures and strong vertical wind shear will cause Tropical Cyclone Tam to make a transition to a strong extratropical cyclone during the next 24 hours.
The upper level trough east of Australia will steer Tropical Cyclone Tam toward the south during the next 24 hours. On its anticipated track, Tam will move quickly away from New Caledonia. Tropical Cyclone Tam will move closer to northern New Zealand.