Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS

NOVA Online (click here for NOVA home)
Tracking El Niño Site Map
Questions and Responses
Posted February 15, 1998 | previous set

I'm interested in information on El Niño in the South Pacific, and how long it will last. We're planning a trip there (Cook Islands) next September, and are wondering if the weather will still be impacted by El Niño.

(name witheld by request)
The Cook islands are between New Zealand and Samoa, in the southwest Pacific. By September, El Niño will have faded away, but its alter ego La Niña may be active, possibly influencing weather there. Let me explain a little. El Niño's fancy scientific name is ENSO, and that stands for El Niño-Southern Oscillation. The "Southern" refers to the south Pacific, and some part of the mysterious cyclic coming and going of El Niño is intimately tied to the south Pacific and the atmosphere above it. Weather records show that throughout the ENSO cycle of several years, conditions on one side of the Pacific tend to be the mirror opposite from the other side; this past year, for example, we saw drought in the west and excessive rains in the east. However, the farther you get from the equator, the less direct the correlation.

There may be some La Niña-ish effects next fall in the Cooks, but most scientists would tell you at this point that it's only an educated guess. If you'll accept that warning, then I can guess that perhaps it will be rainier than normal there in September. But probably not enough to change your plans.

Just wondering, haven't seen a mention of it, is there a crack in the crust under the ocean that is warming the waters? The heat runs up against S. America and has no where to go, so it builds up? I can't exactly think of an example but the closest I can come is the lava escaping at the edge of one of the Hawaiian volcanoes. If you have an address that can answer this question it would be much appreciated. Thanx.

(name witheld by request)
You'd be surprised at how many people are interested in that question. In fact, I've asked Billy Kessler, the oceanographer whose wisdom we present in our Frequently Asked Questions section, to respond, and you will find a detailed answer there.

In the meantime, I can tell you there is a crack in the crust under the ocean. In the middle of the Atlantic and the Pacific, cracks called mid-ocean spreading zones create ridges thousands of miles long that look almost like the seams on a baseball, wrapping right around the Earth, if you look at a map of the ocean bottoms. At these cracks, the Earth spews up fresh lava from the mantle below, and this hardens into new seafloor rock, pushing the existing rock west and east as it shoves its way in. This rock moves (at about the speed your fingernails grow) for hundreds of millions of years, travelling thousands of miles, until it finally is pushed into trenches near the coasts of the continents, to descend back into the Earth, and be heated all over again. In the Pacific these trenches form the so-called "Rim of Fire" because volcanoes and earthquakes frequently occur near them. Scientists call the study of these phenomena "plate tectonics." For more on this subject, try "The Restless Earth," by Nigel Calder.

Scientists have calculated how much heat is transferred to the oceans from volcanoes, and it is considerable—enough to make changes in the ocean's circulation and also in its chemistry. But because the heat is released under miles of water, into the thick cold layer at the bottom, the effects are diffuse, and do not produce sharp changes. The ocean, so to speak, only notices the volcanic heat slowly.

El Niño, on the other hand, is driven by solar energy, and the amount of energy involved is almost beyond imagination. See Global Weather Machine for an idea of how much energy we're talking about. Also, this heat is concentrated in a thin top layer (a couple of hundred feet deep) on the ocean's surface. Here, the energy can be quickly transferred to the atmosphere. This high reactivity is intimately involved in the mechanics of El Niño.

My husband and I will be taking a cruise leaving March 1 going to Western Caribbean (Grand Cayman, Cuzumel, Mexico). Can you please give me your opinion on how the weather will be in these places during that week? Will the ocean over there be rough and rocky or will I never know the difference? Help me if you can.

Thank you, Rosemarie

Henderson, NC
Someone else asked recently about Aruba, and the answer given there will likely suffice for you as well. In short, ocean roughness (or storminess) will not be much of an issue; you may see more variability than normal (it might be cloudier or rain more than usual), but you should get plenty of sunny days as well. If you were going to the other side of Mexico, say Cabo San Lucas, then you might have some problems because of the southerly trend in the jet stream lately, the same culprit behind the current drenching of southern California.

Your coverage of El Niño is quite extensive and very interesting. One area I am finding difficult researching is the progress of El Niño and how it has compared with earlier forecasts. I have read that its impact should begin weakening mid 1998, but have not seen any confirmation on this. I am most interested as to the effect El Niño will have on the northeast United States during the summer months. Any information regarding the above would be appreciated. Thanks for providing such a great site on this exciting topic.

Rich DelMonte
Weymounth, MA
First, thanks for your enthusiasm. Second, good news: there's a lot of info available on how this El Niño stacks up compared to others. Briefly, this is a record breaker in almost every way.

Take a look at this chart in Mapping El Niño; it's an animation of the intensity of four different El Niños, including this year's, and you can see for yourself how they compare. In short, this El Niño started earlier, peaked earlier, sustained its peak longer, and developed a total energy content higher than any other measured El Niño. Most El Niños start weakening in the last two months of the year; this one kept growing right up until the end of December. Although it is weakening right now, and will stop making most of its mischief within another couple of months, this El Niño has demonstrated remarkable staying power. Some people mistakenly thought it was washed up when it didn't produce drastic effects in California during January; that thinking has now changed with February's onslaught of storms. Peru has also been devastated recently, with catastrophic flooding having killed dozens of people.

Although this has been a record-breaker, remember, human records of El Niño don't go very far back; reliable and widespread weather records have only been kept since the beginning of the 19th century. Other records from nature herself suggest that every 500 years or so we get a "Super El Niño." See El Niño's Reach through Time for more on the natural record.

As far as what El Niño portends for the US this summer, others have asked similar questions, and it will be worthwhile to read some of the earlier mail here on that subject. In short, some scientists feel we may have a hot, dry summer in the middle and eastern parts of the US, although the evidence for such a prediction is far from conclusive.

I would like to know what predictions were made worldwide based on this 1997/98 El Niño, and what has actually happened. I am doing this for a science project, and any information you can give me or guidance to other sites would be appreciated. Thank you in advance for your assistance.

Michael Williamson
Franklin, VA
There was no shortage of predictions about El Niño's effects this past year, ranging from the thought provoking to the ludicrous. The science of prediction is improving at breakneck speed, but it still has a long way to go; it relies on models and theories that take into account what has happened in the past, and then tries to integrate them with current conditions. This is a HUGE computing task, and even the most powerful supercomputers have trouble working in enough detail to make the predictions better. That much said, predictions of the major effects this year have been remarkably accurate. When you are dealing with probabilities, such as "an 80 percent chance of decreased rainfall in southern Africa," it's tough to know how the prediction will play out on a smaller, local scale. Maybe part of southern Africa is dry as a bone, while other parts are only a little drier than usual—predictions may be way off for some places, and right on the money for others. But when you look at the big picture, then the probabilities are pretty useful. In general, predictions for dryness in the western Pacific, greatly increased rainfall in the eastern Pacific, and abnormalities elsewhere, such as in North America and Africa, have been borne out. Check out the interactive map in the El Niño's Reach section of this Web site for an overview. And if you need more info, several of the NOAA Web sites listed in our resources section will have what you need.

(previous set of questions & responses)

Anatomy of El Niño | Chasing El Niño | El Niño's Reach
Dispatches | Resources | Mail | Site Map | El Niño Home

Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule
About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print
PBS Online | NOVA Online | WGBH

© | Updated November 2000

Support provided by

For new content
visit the redesigned
NOVA site