Different patterns for tropical cyclones in the Pacific
The chances of a tropical cyclone affecting the Melanesian countries from southern Papua New Guinea to New Caledonia are higher than usual this cyclone season, according to climate scientist Dr Jim Renwick of the New Zealand National Institute of Water and Atmospheric Research (NIWA).
However, the Polynesian countries in the north (Tuvalu) and east from Samoa to French Polynesia are likely to experience fewer than average tropical cyclones this season. This pattern of risk is expected because El Niño/Southern Oscillation (ENSO) conditions that are affecting the tropical Pacific region, which are in a weak La Niña state, are expected to be near neutral over the season as a whole.
[The table below lists the chances of tropical cyclone for different island groups.]
Dr Renwick said tropical cyclones develop in the South Pacific over the wet season, usually from November through April. Peak cyclone occurrence is usually during January, February and March.
“On average, the highest numbers occur in the region around Vanuatu, New Caledonia, Fiji and the adjacent Coral Sea. In seasons similar to the current one, between two and four tropical cyclones usually occur in that region. Taken over the whole of the South Pacific, as many as 16 tropical cyclones can occur in a season, or as few as six,” Dr Renwick said.
“Tropical cyclones require huge amounts of energy to survive, and will form only over specific regions of the globe’s tropical oceans, where conditions are right for their formation and development. The La Niña and El Niño phenomena alter the patterns of climate, altering the risk of a cyclone in different parts of the South Pacific.”
Major tropical cyclones bring extremes of wind, rainfall and sea surges, resulting in river and coastal flooding, landslides, and extensive damage to crops, trees, houses, power lines, ports and roads. Many lives can be lost. For a small South Pacific island country the whole economy can be severely affected. Individual tropical cyclones are, however, rather unpredictable; so most South Pacific islands are exposed to some degree of risk every year and must be always prepared.
Table: Average number of tropical cyclones occurring within 100 km square
for the main island groups of the South Pacific
(Based on 20 years of data, and for tropical cyclones having winds over 34 knots)
|Area||Average over all years||Average over Neutral ENSO years||Comment|
|Southern Papua-New Guinea||1.3||1.8||Increased risk|
|Solomon Islands||1.0||1.5||Increased risk.|
|New Caledonia||2.7||3.7||Increased risk.|
|Northern Cook Islands||1.1||1.0||Average risk|
|Southern Cook Islands||1.3||1.0||Average risk|
|Wallis and Futuna||1.5||1.0||Reduced risk|
|Society Islands/Tahiti||0.7||0.3||Reduced risk|
|Austral Islands||0.7||0.2||Reduced risk|
For further information:
In Pacific islands – contact your local Meteorological Service.