QuikSCAT, a NASA satellite instrument that measures winds, observed a strong typhoon
threatening the Philippines on March 4, 2002, (top) unusual in the winter season, and a
similar tropical cyclone passing along the Australian coast towards Nuomea.
These unusual phenomena are results of the westerly winds (blowing from
Indonesia towards the American coast) along the equator which started back in
February 25, (lower) as QuikSCAT revealed. Color in these images relates to wind speed, arrows
The reversal of the usual Trade Winds (which blow from the American coast
towards Asia) generally triggers Kelvin waves (warm surface water that moves
along the equator from Indonesia to the coast of Peru) and twin cyclones, which are
early indicators of El Niño. The equatorial westerly winds generate a counter-clockwise vortex in the Northern Hemisphere and a clockwise vortex in the
Southern Hemisphere. The Trade Winds push warm water from east to west
across the Pacific, reaching the American coast in one to two months.
The increase in frequency and strength of the Kelvin Waves may lead to
El Niño. Strong westerly winds and twin cyclones were
also observed by QuikSCAT during last Christmas season (2001) and the Kelvin wave
triggered at that time reached South America in Early March 2002.