Increased wind shear in an El Niño tends to rip apart embryonic storms in the Atlantic basin and Caribbean Sea. However, those winds are limited in a La Niña year, allowing storms to flourish. Consequently, the chances for the continental United States and the Caribbean Islands to experience hurricane activity increase substantially during La Niña summers and springs. Hurricane and tropical storm landfalls are also twice as common as illustrated by Atlantic hurricane seasons of 1999-2001. Hurricane Mitch devastated Honduras and Nicaragua in October 1998, killing at least 10,000 people.
On the Caribbean side of Central America, therefore La Niña is bad news for vulnerable islands such as Haiti, which is still recovering from the earthquake that struck it in January 2010. This immediately put the Haiti relief operations under the shadow of this threat, which should be a concern for humanitarian agencies.
In May, the National Oceanic and Atmospheric Administration (NOAA) in Miami predicted this Atlantic storm season could be the worst since the record-breaking 2005, when Hurricane Katrina ravaged New Orleans, Hurricane Wilma slammed into Florida's citrus groves, and Hurricane Rita hit hard the oilrigs in the Gulf and refineries along the Gulf Coast. Though we should be skeptical of such devastating forecasts, to err on the side of caution should characterize disaster preparedness planning. On a 70% confidence level, NOAA predicts there may be as much as 14 to 23 named storms, with wind speeds of more than 62km per hour, 8 to 14 are expected to be hurricanes and 3 to 7 major hurricanes. The first Atlantic 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. Whether Hurricane Alex is, a precursor of what can follow is difficult to predict, as much of the dynamics that characterize hurricane frequency or intensity is not fully understood yet.
The emergence of a La Niña is of particular concern to the oil industry in the Gulf of Mexico, already reeling from the massive oil spill caused by a leaking BP oil well. An increase in the number of hurricanes boosts the chances that at least one storm will slam into the Gulf, home to about 30 percent of U.S. oil and 12 percent of U.S. natural gas production.
Accordingly this hurricane season possess a huge risk of affecting US natural gas and oil production and therefore could send global prices soaring. BP Plc and Royal Dutch Shell Plc, the biggest oil producers in the Gulf, are already evacuating hundreds of workers from platforms in the western and central Gulf as a safety precaution. Median outcomes for production shut-ins in the Gulf because of hurricanes may be 26 billion barrels of oil and 166 billion cubic feet of natural gas, according to a June U.S. Energy Information Administration simulation. A cooler La Niña winter in the U.S. besides may drive heating oil and natural gas consumption that adds to price pressure. However, currently the U.S. has above-average inventories that act as a preventive cushion.
As for the cleanup of BP Gulf Oil Spill, La Niña can either equally aid or even worsen its already devastating impact. When a hurricane, like Alex, hits the Gulf, there is likely to be upwelling of water that would generally mix up the water and oil. According to Greg Holland of the National Centre for Atmospheric Research in Boulder, Colorado, who is on the panel of scientists briefing the US Congress and Senate on the BP Oil Spill, this is really good news because the dispersed oil would be easier for bacteria to break down and consume than the larger clumps.
Nevertheless, Holland also cautions that hurricanes also by their very nature move in a counter-clockwise direction and so tend to move water from east to west. This is in the opposite direction from the way the oil has generally been spreading so far. In such a scenario, the oil slick could well run into the delta of Louisiana, New Orleans and into its marshlands. However, the likelihood of it doing so is dim as these distances are too far. The net import of Holland's assessment suggests that the likelihood of Atlantic hurricanes worsening the BP oil spill cleanup is rather low. The chances are that nature will clean up man's messes of ecology.
La Niñas of the past have demonstrated that they have a wider affect on the weather than just hurricanes. If this region received higher precipitation and lower temperatures during El Niño, then during a La Niña year, we could see below-average precipitation over the central equatorial Pacific.
In the past, for the contiguous United States, potential La Niña impacts include above-average precipitation in the Northern Rockies, the Pacific Northwest, and the Ohio and Tennessee Valleys. Below-average precipitation can be expected across the South, particularly in the southeastern states. Severe weather is likely to be further north and west during La Niña than in the case of an El Niño year. The cooling patterns often bring dryer, warmer weather to the southern half of the U.S., increasing the wildfire threats in Florida and California. La Niña could affect corn, soybean and orange production. In Canada, La Niña generally causes a cooler, snowier winter, such as the near record-breaking amounts of snow recorded during the La Niña winter of 2007/2008 in Eastern Canada.
South America
La Niña affects different parts of the region and sometimes, within the same country, very differently. La Niña tends to provoke intense rains often accompanied with catastrophic floods in Northern Brazil, Colombia, and Ecuador, the high plains of Bolivia and Peru and northwestern Argentina. These rainy spells are often accompanied by outbreaks of cholera and leptospiris. During the last La Niña episode:
La Niña years for that reason make the task of food output forecasting very nightmarish because of this dual character impact of La Niña on South America. Output losses in the U.S., Argentina and Brazil, which make up 82 percent of global soybean output, may end a 13 percent slump in prices because of record crops. La Niña years are among the worst for grain and oilseed crops in Brazil. Aside from sugar cane, that may also affect coffee production in Brazil, the world's top producer. The Latin American country is the world's second biggest exporter of soybeans. Argentina is the biggest exporter of soymeal and soyoil.
Asia &Oceania
During La Niña years, the easterly winds from the Americas are stronger than usual. That drives more than the normal amount of warm sea-surface water westward, in turn causing larger than normal volumes of deep, chilly water to rise to the surface and producing a ‘cold tongue’ that extends 4,800 kilometres along the Equator from Ecuador to Samoa