Earlier today, I mentioned Jeff Master’s WunderBlog guest post from Dr. Michael Ventrice with a detailed explanation on the signs indicating a significant El Niño event for late 2014. What I found interesting was the pulse of westerly winds that can lead to the El Niño.
The trade winds near the equator typically blow from the east to the west (due to earth’s rotation). This pushes warm surface water where it pools near Indonesia and Australia. Cool deep water then upwells near Chile providing good fishing grounds. To counteract the easterlies, a westerly burst of winds weakens the trade winds. The warm surface waters then stay near Chile and the cool water stays in the ocean’s depths, i.e., an El Niño.
What can cause that westerly pulse? Basically, a pair of cyclones. North of the equator cyclones (or hurricanes in the Atlantic Ocean) rotate counter-clockwise; south of the equator, clockwise. If you have a near simultaneous occurrence of two cyclones bracketing the equator, the rotation will squeeze a burst of wind from west to east. It reminds me of the antique washing machine wringers used to dry clothes.