Feature article

Southwest Pacific Tropical Cyclones Summary for 2003/2004 Season

Stuart Burgess, NIWA

The 2003/04 tropical cyclone season had only three occurrences, being equal lowest in the last 30 years (see Figure 1). About nine tropical cyclones can normally be expected in an average season. Two of the three 2003/04 tropical cyclones reached major hurricane strength, with sustained wind speeds of at least 168 km/h. Two of the 2003/04 tropical cyclones originated west of the date line (the tracks of which are shown in Figure 2), and all occurred in the December through March period.

The most devastating tropical cyclone of the 2003/04 season was ‘Heta’, which originated north of Fiji on 28 December, developing into a tropical cyclone on 2 January. Heta passed west of Samoa on 5 January where high winds (145-160 km/h gusts) and heavy rainfall resulted in damage to property, crops, roads and bridges. Heta intensified further to become very destructive as its centre passed just west of Niue on 6 January, with estimated wind gusts of 275 km/h there. One person died, with several others injured, and many people were left homeless. A national disaster resulted, with considerable property destroyed, roads closed, telecommunications and electricity outages, and crops severely damaged. ‘Ivy’ formed west of Fiji on 22 February, bringing damaging winds (up to 130 km/h) and high rainfall to parts of Vanuatu on 25-26 February. ‘Grace’, originated in the Coral Sea west of New Caledonia on 19 March, but winds only reached gale force and it was rather short-lived. Strong winds and high, but not excessive rainfall affected parts of New Caledonia.

Sea surface temperatures were above average along with MJO enhanced convection in western equatorial regions during the season. These would normally assist tropical cyclones. However, most of the low level depressions that did occur during the season did not have the upper-level atmospheric support to develop into tropical cyclones.

Figure 1. The number of Southwest Pacific tropical cyclones for the 2003/04 season (solid red bar) compared to frequencies during the past 30 years. The horizontal green line indicates the 30-year average.

Figure 2. Southwest Pacific tropical cyclone tracks: for the 2003/04 season.

Table 1. Estimates of maximum sustained wind speeds for named tropical cyclones in the 2003/04 season.