Update on the 2007 La Niña by Steph Ball
La Niña translates from Spanish as "the little girl" and has become meteorologically established as the opposite effect of the El Niño phenomenon. It is characterised by unusually low ocean surface temperatures in the equatorial Pacific, as compared to El Niño, which is characterized by unusually warm surface temperatures. Its influence on the weather is global.
Signs of a La Niña year in 2007 were well evident by mid-November with sea surface temperatures (SST’s) in the eastern and central equatorial Pacific showing well below average values. A La Niña “episode” has been known to last anything from a matter of months to as long as two years, and leaves its own signature on global weather patterns.
The effects of La Niña become more pronounced from December to March. Across India it normally gives rise to heavier monsoon rains with wetter than average conditions also affecting Australia, the Philippines and Indonesia, with those wetter conditions spreading as far west as southern Africa.
Across the US it normally gives rise to colder winters, especially in the Midwest and Northwest, while drought conditions are common in the Southwest. With the La Niña in effect one would also expect a more active hurricane season to ensue in the Atlantic, with the potential for more strikes across the US.
Evidence of the strengthening La Niña may already be showing its face. This week a severe winter storm has hit America’s Midwest hard, bringing heavy snowfalls and ice. A state of emergency was declared across four states, with the state of Oklahoma particularly hard hit. Meanwhile Australia, which has been in the grip of its worst drought for a century, has seen its east side lashed by storms and flash floods this week.
Given that the current La Niña is just in its early stages; its influence is likely to become more pronounced over the next few months.
|
|
