La Nia

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La Niña

• By Wesley Synnott

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What is La Niña?

• La Niña is characterized by unusually cold ocean
  temperatures in the Equatorial Pacific, compared
  to El Niño, which is characterized by unusually
  warm ocean temperatures in the Equatorial
  Pacific. Both of these Naturally occurring events
  change the sea-surface temperature dramatically.
  La Niña is often referred to the sister event of
  El Niño. Where El Niño left drought, la Niña
  caused floods, massive cyclones and endless rain.

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Drought Forecast
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How La Niña Forms

• La Niña is a naturally occurring phenomena that
  is caused from the interactions between the ocean
  surface and the atmosphere over the tropical
  Pacific.

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Disaster from an Arkansas Tornado
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The Time of the Year it Occurs In

• La Niña occurs throughout the year from month to
  month in various locations. Through December to
  February, northern South America and southern
  Africa experience wetter than normal conditions.
  The same happens for south-eastern Australia
  during June to August.

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Continued

• The opposite, which is drier than usual
  conditions, occur in north-western Peru, the
  coasts of Ecuador, and the equatorial eastern
  Africa during December to February. As well as in
  southern Brazil and Central Argentina from June
  to August. All of these involve the rainfall
  conditions that La Niña brings.

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Continued

• Through December to February, south-eastern
  Africa, Japan, southern Alaska, western and
  central Canada, and southeastern Brazil all get
  abnormally cool conditions. From June to August,
  there are also very abnormally cool conditions in
  India, south-eastern Asia, the west cost of South
  America, the Gulf of Guinea region, and across
  northern South America, and portions of central
  America.

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Continued

• Warmer than normal conditions occur through
  December to February along the Gulf coast of the
  United States. All of these involve the weather
  conditions that La Niña brings.

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Disaster from a Drought
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Most and Least Common Places for la Niña to Occur

• La Niña is not most likely to occur in just one
  place specifically. It occurs in many places
  depending on the time of the year, stated in the
  previous few screens shown. This is the same with
  where it is least likely to occur. It is not in
  just one place, it depends on the time of the
  month. A few places where there arent many noted
  effects are in extremely cold places like the
  north and South Poles.

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Disaster from a Tennessee Tornado
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Latest Events in Our Area

• There have not been any noticeable effects in
  our area lately. The closest areas where we
  experience the effects of La Niña are in
  Western/Central Canada, Alaska, and the rest of
  the united States. Canada experienced
  below-normal temperatures through December to
  February when La Niña is around. This is the same
  with Alaska. Warmer than normal conditions are
  experienced through the United States during the
  same times.

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Disaster from a Drought
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Recent Examples and Occurrences

• The most recent occurrence of La Niña was in
  1997. Some of the effects of it went on up until
  1999. In 1997, Sea Surface Temperature anomalies
  were the warmest observed in the past hundred
  years. The climate crystal ball was sufficiently
  clear in 1997 to motivate disaster preparedness,
  mitigation efforts, and other worldwide responses
  to developing La Niña conditions on an
  unprecedented scale.

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Disaster from an Oklahoma Tornado
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Destruction from La Niña

• In 1999, on May 3rd, a monster F-5 Tornado hit
  Oklahoma City. It was one of the most powerful
  twisters ever recorded. The path of destruction
  covered 19 long miles and nearly one mile wide.
  The Tornado stayed on the ground for a full hour,
  which is unheard of for normal tornadoes. The
  winds approached 300 miles per hour. Scientists
  have said that this is the work of la Niña.

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Continued

• La Niña caused the massive tornado because it
  creates a colder than normal jet storm over the
  Continental United States, which mixes with warm
  moist air coming up from the Gulf of Mexico which
  produces the ideal conditions for such Tornadoes.

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How Tornadoes Form from La Niña
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How Often It Takes Place

• La Niña occurs on an average of three to five
  years apart from each other. Some of the
  previously known occurrences are
• 1903, 1906, 1909, 1916, 1924, 1928, 1938, 1950,
  1954, 1964, 1970, 1973, 1975, 1988, and 1997.
• These events typically continue into the
  following Spring. La niñas, since 1975, have been
  only half as frequent as El Niños.

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Weather Factors that Bring Forth La Niña

• Scientists are still not sure of what exactly
  triggers the La Niña phenomenon. However, every
  three to seven years or so, all of the effects La
  Niña brings start to occur once again. Scientists
  are still dazzled by some of the strange things
  that happen. The easiest ways to tell when La
  Niña has arrived is by listening in to the news
  of cyclones and temperature changes.

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La Niña and the Future

• Science is only just beginning to unravel the
  mystery of La Niña . People are still trying to
  predict her arrival so we can benefit and prevent
  the disaster is causes. There has been an
  increase in the number of El Niños and a decrease
  in the number of La Niñas in the Last few
  decades. No one knows If this is part of a
  naturally long cycle, or if the cycles are being
  altered by the arrival of new factors. Only time
  will tell.