I keep hearing the media (and everyday people) talk about El Niño — El Niño is here, it’s 8th (pick a number) the strongest since 19__, we keep getting El Niño storms, and so on. Last week I was on a plane flying to Arizona (to a meeting, not a vacation, unfortunately), and an elderly lady sitting next to me said “Now that El Niño is here we’re hoping that the rains will come.” Hmmmm. It made me realize that there are plenty of El Niño-related myths that keep popping up, and that perhaps I should address some of them. My friend Jan Null did a similar “myth buster” for California not long ago, and that inspired me.
Myth 1: El Niño is here or will come this year. No — El Niño never “comes” here. El Niño is a phenomenon that involves changes in the ocean temperatures in the tropical Pacific. Normally the ocean off South America is quite cool due to steady “trade winds” along the equator; the warmest waters are found in the western portions of the Pacific, near Indonesia. But about every three to five years this “normal” pattern changes, often due to reduction in trade winds, the water off South America warms up. Usually the very warm waters in the western Pacific cool off as well. The Pacific is big enough, and important enough, to affect weather pattern throughout the world, and El Niño represents a big change in the Pacific – and, therefore, in extreme weather worldwide. The weather changes “come” to us, but El Niño stays right where it started – in the tropical Pacific.
Myth 2: All El Niños are the same. Awhile ago I heard a scientist say, “we’re going to have to stop calling them ‘El Niño events,’ because each one is different.” How true. El Niños (gramatically I should probably say “Los Niños”) occur at different times of the year, in different parts of the Pacific, cover different areas, and have different ocean temperature patterns. In general, the larger the area and the greater the warming of the eastern Pacific’s equatorial waters, the greater the impact on other regions. Since 1950 there have been nine years with weak-to-moderate El Niños (1951, 1957, 1963, 1969, 1976, 1977, 1991, 1992 and 1993) and six years with strong El Niños (1965, 1972, 1982, 1987, 1994, and 1997). The current El Niño may not even be a bona fide El Niño because the waters off South America have remained rather cool, with the warmer water in mid-Pacific – certainly not “typical.”
Myth 3: There are El Niño-spawned storms. El Niño does not actually create any storms. It seems to shift the path of the “jet stream,” the zone of strongest winds in the upper atmosphere that delineates the path of the mid-latitude storms. This winter the jet stream has spent much of its time over northern California and southern Oregon, so those areas have gotten hit hardest. Several Oregon locations (including Cave Junction, Brookings, and Gold Beach) and more than 20 inches of rain in December. One remote mountaintop station in California had over 20 inches in 5 days!
Myth 4: We will see the impacts from El Niño any day now. So far this has not looked like a “typical” El Niño winter (if indeed such a winter exists). The long-range climate forecasts from NOAA have suggested a dry, mild winter, but we’ve actually had near-normal temperature and precipitation overall. More often than not, in an El Niño we have warmer than normal temperatures and lower than normal precipitation (in keeping with NOAA’s forecasts), but since this winter’s El Niño may not even BE an El Niño, one should not expect “typical” conditions.
Myth 5: When there is an El Niño, there is lots of rain in California and very little in the Northwest. Not necessarily. Historical records for the past five decades in central California show that during strong El Niño events the rainfall has been above normal four of the six seasons, but it has been below normal for five of the nine weak El Niños. Over the same span, Northern California had three wet years and three dry years during strong events, with five above-normal seasons during the nine weak-to-moderate El Niños. Southern California showed more of a wet bias during strong El Niños with above-normal rain in five of the six seasons and above-normal rain during five of the nine weak-to-moderate events. The bottom line is that California can get wet during El Niño, but not always. It is important to keep in mind that El Niño is not the only thing happening in the atmosphere and that other patterns can either enhance or detract from its overall impact.
In the Northwest, the driest winters usually happen during El Niño conditions (although the truly dry winter we had 2 years ago was not an El Niño year, and the last big El Niño, in 1997-98, produced average precipitation). Temperatures are more consistent, usually favoring mild winters and warm springs during El Niño.
Myth 6: El Niño means disastrous flooding for California. Occasionally, but it is just as likely that California will have significant flooding in a non-El Niño year. Of the 10 costliest flood years in California since 1950, only four happened during a time when there was an El Niño. Two others occurred during seasons with La Niña, when temperatures off South America are even cooler than normal (in essence, the opposite of El Niño). The final four were when the temperature of the tropical Pacific was near normal.