Strengthening La Nina could mean more hurricanes

September 9, 2010 By RANDOLPH E. SCHMID , AP Science Writer
Visitors to Salado, Texas snap photos of a submerged truck under the main street bridge on Wednesday morning, Sept. 8, 2010 as waters begin to receed from excessive rainfall caused by Tropical Storm Hermine. (AP Photo/Temple Daily Telegram, Rusty Schramm) MANDATORY CREDIT; TV OUT

(AP) -- The La Nina climate phenomenon is strengthening, increasing the likelihood an active hurricane season could get even busier.

The update from the National Oceanic and Atmospheric Administration on Thursday comes as residents of Texas are cleaning up from the deluge of Tropical Storm Hermine, and Tropical Storm Igor is drifting in the Atlantic.

La Nina is marked by a cooling of the tropical Pacific Ocean and was reported to be developing a month ago. It strengthened throughout August and appears likely to last at least through early 2011, NOAA's Climate Prediction Service said.

"La Nina can contribute to increased Atlantic hurricane activity by decreasing the vertical wind shear over the Caribbean Sea and tropical ," the center noted.

Wind shear is a sharp difference in wind speed at different levels in the atmosphere. A strong wind shear reduces hurricanes by breaking up their ability to rise into the air, while less shear means they can climb and strengthen.

NOAA has been calling for an above-normal . The forecast issued in August anticipates 14 to 20 named tropical storms. The started June 1 and ends Nov. 30, but the peak period runs from August through October.

La Nina's cooling of the tropical Pacific is the opposite phase of the El Nino event, which is marked by unusually warm tropical water in that region. Each can take place every few years, usually with neutral conditions in between.

Both can impact climate worldwide by changing the direction and strength of winds and altering air pressure and rainfall patterns.

In addition to hurricanes in the Atlantic and Gulf of Mexico, the impact of La Nina can include above-average rain or snowfall in the Pacific Northwest and below-average precipitation in the Southwest and in portions of the middle and lower Mississippi Valley and Tennessee Valley.

In other regions, La Nina tends to suppress hurricane activity across the central and eastern tropical North Pacific and increases rainfall in Indonesia.

NOAA said its computer climate models disagree on how strong this will be, but all concur it will last at least through early 2011.

Explore further: Another busy hurricane season possible

More information: Online:


Related Stories

Another busy hurricane season possible

February 22, 2006

A La Nina was being watched closely by the U.S. National Weather Service for the possibility it might help produce another busy Atlantic hurricane season.

Forecasters say El Nino may be developing

June 8, 2009

(AP) -- A new El Nino could be approaching. Sea-surface temperatures have been warming in the tropical Pacific Ocean, suggesting the potential for the development of the El Nino climate phenomenon this summer, according ...

New type of El Nino could mean more hurricanes make landfall

July 2, 2009

El Niño years typically result in fewer hurricanes forming in the Atlantic Ocean. But a new study suggests that the form of El Niño may be changing potentially causing not only a greater number of hurricanes than in average ...

Recommended for you

Can Paris pledges avert severe climate change?

November 26, 2015

More than 190 countries are meeting in Paris next week to create a durable framework for addressing climate change and to implement a process to reduce greenhouse gases over time. A key part of this agreement would be the ...

Amazon deforestation leaps 16 percent in 2015

November 28, 2015

Illegal logging and clearing of Brazil's Amazon rainforest increased 16 percent in the last year, the government said, in a setback to the aim of stopping destruction of the world's greatest forest by 2030.


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Sep 10, 2010
Global cooling!??
buy i've be told global warming would cause more hurricanes? or is el nina caused by global warming?
not rated yet Sep 10, 2010
Cooling chills the poles much faster than the tropics, increasing the difference. That means more forceful heat transport and overall stronger storms. Warming does the opposite, producing calmer weather overall.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.