The La Niña phenomenon has officially arrived and disaster response teams around the world might need to brace themselves for heavier monsoons, bigger and more frequent hurricanes, and angrier cyclones.
“There is global consensus that we are at the beginning of a La Niña, but we cannot pronounce the intensity of the event yet – we have to wait for it to evolve,” said Rupa Kumar Kolli, Chief of the World Climate Applications and Services Division at the World Meteorological Organization (WMO).
La Niña is characterised by unusually cold ocean temperatures in the eastern equatorial Pacific Ocean; El Niño is characterised by high temperatures, the US government’s National Aeronautics and Space Administration says on its website.
The colder-than-normal ocean temperatures prevent rain-producing clouds from forming over the eastern equatorial Pacific region, including the open ocean south of Mexico and Central America, but enhance rainfall over the western equatorial Pacific region of Indonesia, Malaysia and northern Australia.
This in turn affects the jet streams, or strong wind-flows, in the upper levels of the atmosphere and the behaviour of storms outside of the tropics in both the northern and southern hemispheres. In short, La Niña is a global phenomenon.
The National Hurricane Centre at the US government’s National Oceanic and Atmospheric Administration (NOAA) has been expecting a La Niña to occur, and by May 2010 predicted a 70 percent chance that there would be 14 to 23 named storms, with wind speeds of more than 62km per hour. This is far more than the average of 11 named storms during the hurricane season in the Atlantic region, which began in June.
The first hurricane of the season, Alex, hit Mexico on 30 June. NOAA said it was the first hurricane to be recorded in June in the Atlantic Basin since 1995, and the strongest in that month since 1966.
On the Caribbean side of Central America, La Niña is bad news for vulnerable islands such as Haiti, which is still recovering from the earthquake that struck it in January 2010.
Source: JOHANNESBURG, 8 July (IRIN)
La Nina is:
* Snow and rain on the west coast
* Unusually cold weather in Alaska
* Unusually warm weather in the rest of the USA
* Drought in the southwest
* Higher than normal number of hurricanes in the Atlantic
Source: Relaxed Politics
Another useful site, from NASA: here