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For more than a year, El Niño has disturbed the weather around the world. Now, as the current El Niño cycle draws to a close, scientists are debating what its lingering effect will be on the 1998 hurricane season.
As late as 1970, weather textbooks did not even contain the phrase "El Niño." But at least since the big El Niño "event" of 1981-82 meteorologists everywhere have realized that weather around the world may be linked to the ocean temperature of the eastern Pacific. Normally the Pacific is cold off the west coast of South America; during an El Niño event it is abnormally warm.
The present El Niño cycle began early in 1997. It peaked as expected around the end of the year, but its effects will continue through much of 1998. In the temperate zone where we live, the effects of El Niño are somewhat delayed and indirect. Initially, the biggest effect was on the 1997 hurricane seasons. In the Pacific, where there is more warm water than usual off the coast of Mexico, the season was a bad one; Hurricanes Nora, Pauline, and Rick in particular caused great damage. In the Atlantic, El Niño caused abnormal strong westerly winds to blow at high altitudes across the tropical Atlantic, cutting off the tops of developing storms. After an active start, the Atlantic hurricane season simply stopped around the end of July 1997 and only one storm, Erica, was able to form later.
As long as the El Niño westerlies continue to blow, there probably won't be many Atlantic hurricanes. But if they stop, the hurricanes may break out with unusual intensity. Presently, the best authorities are split about 50:50 on whether the hurricane season just beginning will be more or less active than normal. William Gray, the Colorado State scientist famous for his hurricane season predictions, is predicting a year of strong storms: 10 named storms, including six hurricanes, two of them being severe.
To understand El Niño, we need to know a little about tropical weather. Generally speaking, easterly winds, the famous trade winds, blow fairly steadily across all the Earth's tropical oceans. The explorer Magellan learned in 1519 that in the South Pacific the trade winds blow for a huge distance, more than ten thousand miles from the coast of South America to Indonesia and the Philippines. In fact, the trade winds blow so steadily they blow the entire ocean westward, so sea level in the Philippines is normally half a meter higher than it is on the coast of Peru.
The trade winds blow the warm equatorial water west away from South America, forming the South Equatorial Current. This surface water is replaced by cold water from the Antarctic, brought northward along the coast of South America by the Peru Current. These cold waters are rich in marine life (like the waters off Newfoundland in the North Atlantic) and support thousands of fisherman.
But sometimes, every decade or so, the trade winds falter or even reverse. Then the warm water is not blown away from the coast, sea temperatures off South America rise dramatically, and the fishery fails. The worst of it usually falls around Christmas (summer in the Southern Hemisphere). Peruvian fishermen have long called this economic disaster El Niño, the Christ Child, because of its association with Christmas.
El Niño strengthens the subtropical jet stream across the southern part of the United States, bringing stronger storms eastward along the Gulf coast. NC State meteorologists predicted in November that as these storms turned northward along our coast, we were likely to see major nor'easters. And so we did: the Outer Banks were battered by nor'easters in January and February, and most of the state had a cool, rainy late winter and early spring.
Only time will tell whether El Niño will linger long enough to reduce the intensity of the new hurricane season. Weather watchers will be on the alert, and they will continue to be aided by a plethora of outstanding Internet sites. Some of these sites are listed below.
Internet Sources
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Copyright © 1998, Center for Mathematics and Science Education. Teachers have permission to duplicate this page for use in teaching their own classes. All other rights reserved. You are welcome to link to this page, but do not copy its contents.
Our El Niño page was first posted October 9, 1997. Updated November 12 and 19, 1997, with additional links and the NCSU forecasts. Further updated December 19, 1997, with current information, and January 6, 1998, with the NASA link. Updated again February 2, 1998, bringing the weather news up to date. This most recent update was posted June 2, 1998.
CMSE Online features remain online as long as they remain current; they may be updated if new information becomes available.
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