Pacific and Atlantic Hurricane Season

Pacific and Atlantic Hurricane Season



March 2007 - On the heels of 
El Niño, its opposite, the cooling weather pattern in the 
east-central equatorial Pacific known as La Niña is expected 
to arrive soon, according to government forecasters. La Niña 
conditions in the Pacific typically mean a greater than normal 
number of Atlantic hurricanes. 
In a weekly update, scientists at the NOAA Climate Prediction 
Center said that as the 2006-2007 El Niño has faded, surface 
and subsurface ocean temperatures have rapidly decreased. 
Recently, cooler than normal water temperatures have developed 
at the surface in the east-central equatorial Pacific, 
indicating a possible transition to La Niña conditions. 
La Niña conditions occur when ocean surface temperatures in 
the central and east-central equatorial Pacific become cooler 
than normal. 
Dolphins play in the eastern tropical Pacific Ocean. 
These changes affect tropical rainfall patterns and 
atmospheric winds over the Pacific Ocean, which influence the 
patterns of rainfall and temperatures in many areas worldwide. 

Typically, across the United States during the spring and 
summer months, La Niña conditions do not significantly impact 
overall inland temperature and precipitation patterns,but La 
Niña episodes often do have an effect on Atlantic and Pacific 
hurricane activity. 
"Although other scientific factors affect the frequency of 
hurricanes, there tends to be a greater than normal number of 
Atlantic hurricanes and fewer than normal number of eastern 
Pacific hurricanes during La Niña events," said NOAA 
Administrator Conrad Lautenbacher. 
"During the winter, usual La Niña impacts include drier and 
warmer than average conditions over the southern United 
States," he said. 
"NOAA's ability to detect and monitor the formation, duration 
and strength of El Niño and La Niña events is enhanced by 
continuous improvements in satellite and buoy observations in 
the equatorial Pacific," Lautenbacher explained. 
The observing systems currently at work include the TAO/TRITON 
moored and Argo drift buoys, as well as NOAA's polar orbiting 
satellites. 
"La Niña events sometimes follow on the heels of El Niño 
conditions," said Vernon Kousky, research meteorologist at the 
NOAA Climate Prediction Center. "It is a naturally occurring 
phenomenon that can last up to three years." 
"While the status of El Niño/La Niña is of vital importance to 
our seasonal forecasts, it is but one measure we use when 
making actual temperature and precipitation forecasts," said 
Kousky. 
La Niña episodes tend to develop during the four months from 
March through June, reach peak intensity during the December 
to February period, and then weaken during the following March 
to May period. 
"The last lengthy La Niña event was 1998-2001, which 
contributed to serious drought conditions in many sections of 
the western United States," said Douglas Lecomte, drought 
specialist at the NOAA Climate Prediction Center. 
Radar image of Hurricane Wilma making landfall in South 
Florida, October 2005. Wilma was the most intense hurricane 
recorded in the Atlantic basin and only the third Category 5 
ever to develop in the month of October. With the formation of 
Hurricane Wilma, the 2005 season became the most active on 
record. 
In addition, atmospheric scientists have uncovered fresh 
evidence to support the controversial theory that global 
warming has contributed to the emergence of stronger 
hurricanes in the Atlantic Ocean. 
Scientists at the University of Wisconsin-Madison and NOAA's 
National Climatic Data Center report that all the physical 
variables that converge to form hurricanes - wind speeds, wind 
directions and temperatures - feed off each other in ways that 
only make conditions more ripe for a storm. 
The unsettling trend is confined to the Atlantic and does not 
hold up in any of the world's other oceans, researchers have 
also found. 
James Kossin, a research scientist at UW-Madison's Cooperative 
Institute for Meteorological Satellite Studies, says the 
pattern emerged from a new dataset that correlates a variety 
of different satellite data over 22 years from 1983 to 2005. 
"While we can see a correlation between global warming and 
hurricane strength, we still need to understand exactly why 
the Atlantic is reacting to warmer temperatures in this way, 
and that is much more difficult to do," says Kossin. "We need 
to be creating models and simulations to understand what is 
really happening here." 
NOAA will issue the U.S. Spring Outlook on March 15, and its 
Atlantic Hurricane Season Outlook in May. Both outlooks will 
reflect the most current La Niña forecast. 





 

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