Tropical Cyclone Delilah

1 - 4 January 1989


Towards the end of December 1988, the SPCZ was very active and the westerlies to its north extended to 160°W. Two depressions formed in this zone; one in the Coral Sea near Australia developed into Delilah and the other, close to with gusts near its centre to 135 km/h. Samoa, developed into Gina .

During Delilah 's formation, pressure falls around the depression were very localised. At about 1800 UTC 30 December, an intensifying anti-cyclone in the Tasman Sea caused significant pressure rises along the eastern Australian coast. This intensification appears to have increased the cyclonic. shear on the southwest flank of the depression and, within the next six hours, the winds near its centre increased to about 55 km/h. Satellite pictures revealed enhanced convection and two very prominent spiral cloud bands feeding into the low-level centre.

The cyclone slowly intensified and moved east-southeast at 20 to 35 km/h. The wind distribution was asymmetric with average winds of 75 km/h near the centre with gales extending 320 km in the southern semicircle and 240 km elsewhere. Despite the replacement of the upper-level anticyclone over Delilah by increasing westerly winds, further intensification occurred.

After 1200 UTC 1 January, Delilah curved towards the southeast moving at 30 to 35 km/h. Winds near the centre had increased to 110 km/h with gusts around 145 km/h by 1200 UTC 2 January; satellite imagery revealed 'banding' characteristics (Dvorak 1977).

The intensifying upper-level westerlies grad- ually increased the vertical shear and, after 1800 2 January, east of Noumea, the cloud pattern started to become disorganised. At this time, winds around the centre were about 100 km/h. This intensity was maintained but the cyclone decelerated to 15 km/h. Twelve hours later the system became extratropical and moved south-wards, passing close to the north of New Zealand, before merging with a cold front on 8 January.

Track and intensity

Best Track of Tropical Cyclone Delilah