Post by Bennett D. Ebberly on Oct 26, 2003 15:49:56 GMT -5
El Nino Update
8AM EDT, October 25, 2003
By WeatherBug Meteorologist, Justin Consor
As Canadian air masses begin to win the battle and the first snow falls in many northern areas, attention is turning to the outlook for the upcoming winter.
One factor that typically has a large impact is El Nino and its sister, La Nina. El Nino is defined as a periodic warming in the eastern and central Pacific near the equator. El Nino conditions usually favor a warm and dry winter in the northern U.S. with cool and wet conditions in the south and especially in California.
La Nina is a cooling in the eastern and central Pacific near the equator. Its effects are typically opposite, cool and wet in the northern and western U.S. with warm and dry conditions in the southeast.
As the image in the upper right corner shows, water temperatures in the equatorial Pacific have crept above normal.
Climate scientists say the Pacific has reached El Nino when water temperatures in the equatorial Pacific from the South American coast to the international dateline average at least 0.5 degrees Celsius (about 1 degree Fahrenheit) above normal for at least three consecutive months.
When there is a weak El Nino or neutral conditions, other climate factors play a larger role, for instance, water temperatures in the north Pacific and north Atlantic, the amount of snow cover, and how wet the soil is.
The persistent drought and very dry soil in the West would encourage warmer than normal conditions unless other factors cause a reversal of the drought.
Another important factor may be the large pool of cool water developing in the north Pacific from Japan to the Pacific Northwest. This pool of cold water, combined with warm water further south, has helped to invigorate Pacific storms that recently dumped record rainfall in the Pacific northwest.
Last winter, other factors also played a large role. A moderate El Nino was present during fall 2002, but it became weaker as winter 2002-03 progressed. The El Nino helped to increase precipitation from the Deep South through the Mid-Atlantic.
Early snow cover over eastern Canada and the northeast U.S. as well as very warm water temperatures between Greenland and eastern Canada forced cold air masses into the heart of the eastern U.S.
While the Atlantic water temperatures are similar to last fall`s pattern so far, snow cover is running behind last year`s pace over Canada and Alaska.
This pattern would favor cold air and snow covering a wider area than last year with bone-chilling air masses most often plunging into the Plains and Great Lakes. Meanwhile, the probable weak El Nino conditions and the warm water off the northeast coast favors another wet winter for the eastern seaboard.
Look for WeatherBug El Nino updates every weekend through the fall, and then a full winter outlook on November 20.
8AM EDT, October 25, 2003
By WeatherBug Meteorologist, Justin Consor
As Canadian air masses begin to win the battle and the first snow falls in many northern areas, attention is turning to the outlook for the upcoming winter.
One factor that typically has a large impact is El Nino and its sister, La Nina. El Nino is defined as a periodic warming in the eastern and central Pacific near the equator. El Nino conditions usually favor a warm and dry winter in the northern U.S. with cool and wet conditions in the south and especially in California.
La Nina is a cooling in the eastern and central Pacific near the equator. Its effects are typically opposite, cool and wet in the northern and western U.S. with warm and dry conditions in the southeast.
As the image in the upper right corner shows, water temperatures in the equatorial Pacific have crept above normal.
Climate scientists say the Pacific has reached El Nino when water temperatures in the equatorial Pacific from the South American coast to the international dateline average at least 0.5 degrees Celsius (about 1 degree Fahrenheit) above normal for at least three consecutive months.
When there is a weak El Nino or neutral conditions, other climate factors play a larger role, for instance, water temperatures in the north Pacific and north Atlantic, the amount of snow cover, and how wet the soil is.
The persistent drought and very dry soil in the West would encourage warmer than normal conditions unless other factors cause a reversal of the drought.
Another important factor may be the large pool of cool water developing in the north Pacific from Japan to the Pacific Northwest. This pool of cold water, combined with warm water further south, has helped to invigorate Pacific storms that recently dumped record rainfall in the Pacific northwest.
Last winter, other factors also played a large role. A moderate El Nino was present during fall 2002, but it became weaker as winter 2002-03 progressed. The El Nino helped to increase precipitation from the Deep South through the Mid-Atlantic.
Early snow cover over eastern Canada and the northeast U.S. as well as very warm water temperatures between Greenland and eastern Canada forced cold air masses into the heart of the eastern U.S.
While the Atlantic water temperatures are similar to last fall`s pattern so far, snow cover is running behind last year`s pace over Canada and Alaska.
This pattern would favor cold air and snow covering a wider area than last year with bone-chilling air masses most often plunging into the Plains and Great Lakes. Meanwhile, the probable weak El Nino conditions and the warm water off the northeast coast favors another wet winter for the eastern seaboard.
Look for WeatherBug El Nino updates every weekend through the fall, and then a full winter outlook on November 20.