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With the recent announcement that 2009-2010 will be an official El Niño year, I decided to compile a list of things to know about the El Niño weather system.

1. El Niño events occur when the see-saw effect of the water movement in the western and eastern tropical Pacific Ocean reverse. When this happens, the tradewinds weaken and the surface water temperature in the eastern tropical Pacific rises.

2. The name, El Niño, comes from the Spanish for "the boy." It alludes to the birth of Jesus because the weather pattern is first noticed off the coast of South America in the month of December.

3. There are written records of El Niño’s effects in Peru at least as far back as 1525, and researchers have found geologic evidence of El Niños in Peruvian coastal communities from at least 13,000 years ago.

4. El Niño is known to have had an effect on the Incas. They often sacrificed people during El Niño events based on their belief that the excessive rain from El Niño was a punishment from the gods. To appease the gods and stop the rain, they sacrificed more people.


5. An El Niño event typically occurs every 3 to 5 years and lasts for 1 to 2 years. The most recent El Niño system occurred in 2006, and the worst in recent history occurred in 1997 when abnormally high rainfall triggered flooding and mudslides in the western portion of the United States and Mexico as well as Eastern Europe. While these places were flooding, a severe drought was going on in Australia and Indonesia.

6. El Niños have produced devastating storminess in California and Central and South America and disrupt marine life on the West Coast. In 1997, California experienced some of the heaviest flooding and mudslides that I ever remember. The photo below was taken in Laguna Beach during the 1997 El Niño system.


7. When El Niño is in effect, California receives the most rain from March to May.



8. El Niño reduces the number of hurricanes in the Gulf of Mexico. Just because the number of hurricanes is reduced, though, doesn't mean that the Gulf States are out of the woods because El Niño likes to drop lots of rain there.

9. Hawaii's most powerful hurricanes hit during El Niño years. Another danger is the lack of rainfall during El Niño years.

10. El Niño's effect on weather has a profound impact on health. Heavy rainfall creates puddles that become the perfect breeding grounds for mosquitoes. Incidents of malaria, dengue, and Rift Valley fever increase in El Niño years, as do cases of cholera. Hantavirus pulmonary syndrome (HPS) - a lung infection which causes eye pain, haemorrhaging in the lungs and other side effects - first appeared in the USA in 1993 after the 1991/2 El Niño; 14 cases were reported between January and August 1998 which scientists at the University of New Mexico think are linked to the El Niño of 1997/98.


11. The 1997-98 El Niño marked the first time in human history that climate scientists were able to predict abnormal flooding and droughts months in advance, allowing time for threatened populations to prepare.

12. The development of the TAO (tropical atmosphere/ocean) array of 70 moored buoys that span the equatorial Pacific help scientists to predict an El Niño year. Completed in 1994, the TAO buoys are now the world’s premier early-warning system for change in the tropical ocean. They monitor water temperature from the surface down to 1,600 feet [500 meters], as well as winds, air temperature, and relative humidity.

13. El Niño/Southern Oscillation involves only one-fifth of the circumference of the planet, but it transforms weather around the globe.