Dry lake bed as a result of the start of La Niña phenomenon. (Photo: NOAA)
NOAA upgrades La Niña Watch to Advisory
Friday, September 09, 2011, 23:40 (GMT + 9)
La Niña, which contributed to extreme weather around the globe during the first half of 2011, has re-emerged in the tropical Pacific Ocean and is forecast to gradually strengthen and continue into winter. This week, forecasters with the National Oceanic and Atmospheric Administration’s (NOAA) Climate Prediction Centre upgraded last month’s La Niña Watch to La Niña Advisory.
NOAA will issue its official winter outlook in mid-October, but La Niña winters often see drier than normal conditions across the southern tier of the US and wetter than normal conditions in the Pacific Northwest and Ohio Valley.
“This means drought is likely to continue in the drought-stricken states of Texas, Oklahoma and New Mexico,” said Mike Halpert, deputy director of the Climate Prediction Centre. “La Niña also often brings colder winters to the Pacific Northwest and the northern Plains, and warmer temperatures to the southern states.”
Climate forecasts from NOAA’s National Weather Service give American communities advance notice of what to expect in the coming months so they can prepare for potential impacts. This service is helping the country to become a Weather Ready Nation at a time when extreme weather is on the rise.
Seasonal hurricane forecasters factored the potential return of La Niña into NOAA’s updated 2011 Atlantic hurricane season outlook, issued in August, which called for an active hurricane season. With the development of tropical storm Nate this week, the number of tropical cyclones entered the predicted range of 14-19 named storms.
The strong 2010-11 La Niña contributed to record winter snowfall, spring flooding and drought across the US, as well as other extreme weather events throughout the world, such as heavy rain in Australia and an extremely dry equatorial eastern Africa.
La Niña is a naturally occurring climate phenomenon located over the tropical Pacific Ocean and results from interactions between the ocean surface and the atmosphere. During La Niña, cooler-than-average Pacific Ocean temperatures influence global weather patterns.
La Niña typically occurs every three-to-five years, and back-to-back episodes occur about 50 per cent of the time. Current conditions reflect a re-development of the June 2010-May 2011 La Niña episode.
Photo Courtesy of FIS Member National Oceanic and Atmospheric Administration NOAA/NMFS