Hot Time in the Summer: SouthPac Cyclones

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It’s almost impossible for a meteorologist to write about the tropics without mentioning El Niño and its worldwide effects. Here in the States we’re more conditioned to understand that an active El Niño this time of year brings enhanced rains and cooler temperatures to the southern United States. But what about elsewhere?

“For every action there is an equal and opposite reaction.” Newton’s Third Law of Motion. So if the eastern Pacific is undergoing an active El Niño season (enhanced thunderstorms, warmer ocean water temperatures, increased upward vertical motions) it would stand to reason that the other side of the Pacific would be experiencing fewer thunderstorms, cooler water temperatures and air with a tendency to sink rather than rise. Given this, one might think fewer topical cyclones in the South Pacific would result.

One would be wrong.

Remember that in the Atlantic, tropical storms get their best footing under the relaxed atmosphere of high pressure. The same is true in the Pacific where, in the Southern Hemisphere, summer temperatures are now at their peak and widespread high pressure dominates. And just because South Pacific water temperatures are cooler that doesn’t mean they are cool; they are not. So actually, El Niño years can bring about slightly higher numbers of tropical cyclones in Pacific waters.

Interestingly, South Pacific surface water temperatures have been even warmer than a typical El Niño might suggest. Waters of the Coral Sea and along the north coast of Australia are warmer than normal and just in the past four weeks there have been four cyclones in this area including Tropical Cyclone Olga right now.

The seasonal forecast from Australia’s Bureau of Meteorology:

Western regions (142.5E to 165E): 4-5 cyclones (5 is average). The chance of a higher number: 29%.
Eastern regions (165E to 120W): 7-8 cyclones (7 is average). The chance of a higher number: 61%.

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