El Niño and La Niña occur on average every 3 to 5 years. However, in the historical record the interval between events has varied from 2 to 7 years. According to the National Centers for Environmental Prediction, this century's previous La Niñas began in 1903, 1906, 1909, 1916, 1924, 1928, 1938, 1950, 1954, 1964, 1970, 1973, 1975, 1988, and 1995. These events typically continued into the following spring.

El Niño and La Niña result from interaction between the surface of the ocean and the atmosphere in the tropical Pacific. Changes in the ocean impact the atmosphere and climate patterns around the globe. In turn, changes in the atmosphere impact the ocean temperatures and currents. The system oscillates between warm (El Niño) to neutral (or cold La Niña) conditions with an on average every 3-4 years. See similar questions...

La Niña conditions typically last approximately 9-12 months. Some episodes may persist for as long as two years. See similar questions...

El Niño and La Niña are extreme phases of a naturally occurring climate cycle referred to as El Niño/Southern Oscillation. Both terms refer to large-scale changes in sea-surface temperature across the eastern tropical Pacific. Usually, sea-surface readings off South America's west coast range from the 60s to 70s F, while they exceed 80 degrees F in the "warm pool" located in the central and western Pacific. See similar questions...

Both El Niño and La Niña impact global and U.S. climate patterns. In many locations, especially in the tropics, La Niña (or cold episodes) produces the opposite climate variations from El Niño. For instance, parts of Australia and Indonesia are prone to drought during El Niño, but are typically wetter than normal during La Niña. See similar questions...

La Niña often features drier than normal conditions in the Southwest in late summer through the subsequent winter. Drier than normal conditions also typically occur in the Central Plains in the fall and in the Southeast in the winter. In contrast, the Pacific Northwest is more likely to be wetter than normal in the late fall and early winter with the presence of a well-established La Niña. See similar questions...

The jury is still out on this. Are we likely to see more El Niños because of global warming? Will they be more intense? These are the main research questions facing the science community today. Research will help us separate the natural climate variability from any trends due to man's activities. We cannot figure out the "fingerprint" of global warming if we cannot sort out what the natural variability does. See similar questions...

This question does not have a simple or straightforward answer, since this is not a settled issue. Fundamentally we are not exactly sure why the Pacific should have an El Niño/La Niña cycle and the Atlantic not. We observe that this is the case and can think of reasons why this makes sense, but if we had no observations to tell us the answer in advance I don't think we would deduce it from theory. See similar questions...

Scientists from NOAA and other agencies use a variety of tools and techniques to monitor and forecast changes in the Pacific Ocean and the impact of those changes on global weather patterns. In the tropical Pacific Ocean, El Niño is detected by many methods, including satellites, moored buoys, drifting buoys, sea level analysis, and expendable buoys. See similar questions...

Since a strong jet stream is an important ingredient for severe weather, the position of the jet stream determines the regions more likely to experience tornadoes. Contrasting El Niño and La Niña winters, the jet stream over the United States is considerably different. During El Niño the jet stream is oriented from west to east over the northern Gulf of Mexico and northern Florida. Thus this region is most susceptible to severe weather. See similar questions...

Dr. William Gray at the Colorado State University has pioneered research efforts leading to the discovery of La Niña impacts on Atlantic hurricane activity, and to the first and, presently only, operational long-range forecasts of Atlantic basin hurricane activity. According to this research, the chances for the continental U.S. and the Caribbean Islands to experience hurricane activity increases substantially during La Niña. See similar questions...

It is inaccurate to label individual storms or events as a La Niña or El Niño event. Rather, these climate extremes affect the position and intensity of the jet streams, which in turn affect the intensity and track of storms. During La Niña, the normal climate patterns are enhanced. For example, in areas that would normally experience a wet winter, conditions would likely be wetter than normal. See similar questions...

Most children with autism never receive the quality, intensive services that research shows could give them their best chance to overcome the debilitating impact autism will have on their lives. Many parents in Southern California have never heard of ABA. Or they may have been told that their school or regional center agency "does ABA." But parents often don't have any way to evaluate the quality or effectiveness of school and regional center autism programs. That's why LA FEAT is here. See similar questions...

There have only been two strong La Niña events. Although scientists have looked for a correlation between La Niña and tornadoes, there just isn't enough data to make any conclusions. See similar questions...

BSE was first observed in Great Britain in April 1985 and was officially diagnosed in 1986. By June 1990, some 14,000 cases were confirmed (out of an estimated population of 10 million cattle) in Great Britain. Since 1986, more than 185,000 cases of BSE have been confirmed in Great Britain. The epidemic peaked in 1992-93 at almost 1,000 new cases per week. Control measures have since reduced incidence of the disease, and currently fewer than 100 new cases are reported per week. See similar questions...

Fistula occurs when emergency obstetric care is not available to women who develop complications during childbirth. This is why women living in remote rural areas with little access to medical care are at risk. Before the medical advances of the 20th Century, fistula was quite common in Europe and the United States. Today, fistula is almost unheard of in high-income countries, or in countries where obstetric care is widely available. See similar questions...

In 2007, there are approximately 2 million people with limb loss in the United States (excluding fingers and toes). There are more than 185,000 new amputations preformed each year in this country. The prevalence rate in 1996 was 4.9 per 1,000 persons. The incidence rate was 46.2 per 100,000 persons with dysvascular disease, 5.86 per 100,000 persons secondary to trauma, 0.35 per 100,000 secondary to malignancy of a bone or joint. The birth prevalence of congenital limb deficiency in 1996 was 25. See similar questions...

Sound enters your ears in sound waves. These sound waves hit your eardrum and are converted to pressure changes in the inner ear. This causes special nerves to impulse, which are read by your brain as sound. When these nerves are exposed to a surplus of pressure changes, they may become damaged. You may have noticed that if you listen to loud music for several hours that your ears "ring." This is a Temporary Threshold Shift, or a temporary reduction in hearing. See similar questions...

Conception, or fertilization, occurs when the male's sperm meets with the woman's ovum (egg) and successfully penetrates it. This typically takes place in one of the woman's fallopian tubes and the fertilized egg then travels to the uterus and implants in the uterine lining. For pregnancy to take place, fertilization of the egg must be followed by a successful implantation. Only one egg is released for fertilization in each menstrual cycle. See similar questions...