May 24th, 2011 by Joshua S Hill
The World Meteorological Organisation, the weather agency of the United Nations, has announced that the current La Niña episode looks to be coming to an end.
The current La Niña episode developed in mid-July of 2010 and peaked in January 2011, and was responsible for devastating flooding and rainfalls across northern and eastern Australia, Indonesia, Southeast Asia, and portions of northern South America.
The La Niña episode is also believed to be responsible for below average rainfall in eastern equatorial Africa, and below average rainfall in central southwest Asia and south-eastern South America.
“The La Nina episode, which caused disastrously wet conditions in certain regions and drought in others, is coming to an end,” the World Meteorological Organization said in a statement.
Predictions for what happens next, however, are cloudy, as “this time of year is known to be particularly marked by low forecast skill.”
Nevertheless, the WMO does believe that near neutral conditions are likely for mid-year 2011, and that development of El Niño or re-development of La Niña is an unlikely outcome for the following months.
- A La Niña event of moderately strong intensity continued through the first quarter of 2011 in the oceans, and very strong intensity in the atmosphere.
- The La Niña event has been weakening in the oceans since about February, but is only now in the process of ending in mid-May. The atmospheric aspects of the event remained very strong through the end of April, and only now are finally weakening.
- Near-neutral conditions are considered the most likely outcome for mid-year 2011.
- In considering expected climate over coming months, it is important to recognize that atmospheric patterns typical of La Niña may in some regions continue for a couple of months after the decay of the cool waters in the tropical Pacific. Detailed seasonal forecasts should be consulted with these possible residual climate effects in mind.
- Looking ahead beyond mid-year 2011, there are currently no clear indications for enhanced risk of El Niño or La Niña in the second half of 2011. The ocean-atmosphere system is quite sensitive and flexible at this time of year. Monitoring for another 1 to 2 months is required to more firmly establish the direction of evolution of the system. Accordingly, near-neutral conditions are currently considered the most likely outcome for the second half of 2011.
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