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La Nina shouldn’t affect Atlantic hurricanes: NASA

May 4, 2006

By Deborah Zabarenko

WASHINGTON (Reuters) – La Nina, a Pacific Ocean phenomenon
that can help form Atlantic hurricanes, is not expected to be a
factor this season, good news after last year’s disastrous
storm season.

La Nina, Spanish for “the girl,” refers to a pattern of
usually cold surface temperatures in the eastern tropical
Pacific. In North America, it has been known to contribute to
droughts in the West and to spur hurricanes in the East.

That happens because La Nina tends to push high-altitude
jet stream winds to the north, away from the customary
hurricane-forming areas, David Adamec, an oceanographer at
NASA’s Goddard Space Flight Center outside Washington, said on
Thursday.

Jet stream winds can rip the tops off developing
hurricanes, and without those winds, hurricanes can form
unimpeded, Adamec said by telephone.

“La Nina gives a little extra kick, keeping the jet streams
away,” he said.

There have not been strong La Nina patterns in the past two
years, Adamec said, but “it has not helped the situation.”

The 2005 hurricane season was the costliest and most
destructive on record, with 27 named storms, of which 15 became
hurricanes. Hurricane Katrina alone caused $80 billion in
damage, killed about 1,300 people and devastated New Orleans
and parts of the U.S. Gulf Coast.

A patch of colder-than-usual surface water in the eastern
Pacific looked very much like a La Nina pattern earlier this
year, Adamec said, but that had now warmed up to normal,
leading scientists to believe it will not have an impact on
this year’s Atlantic storms.

“The fact that the cold water has disappeared now … gives
you a lot more confidence it’s not going to come back,” he
said.

LA NINA AND EL NINO

La Nina is different from the El Nino weather pattern,
which starts as a patch of warmer-than-usual water in the
eastern tropical Pacific, said Bill Patzert of NASA’s Jet
Propulsion Laboratory in Pasadena, California.

El Nino, which means “the boy,” can bring unusually warm
weather and storms to the American West, but it pulls jet
stream winds into hurricane-forming areas, Patzert said in a
telephone interview.

“We cringe in California when somebody says El Nino,”
Patzert said. “El Nino is the blessing for hurricane country
and La Nina is the curse.”

No Atlantic hurricanes came ashore in 1997 and 1998, when
there were strong El Nino patterns, Adamec said.

A noted U.S. forecasting team projected this year’s storms
would not be as severe as last year’s, with 17 named storms
expected to form in the Atlantic basin during the six-month
season, which officially begins on June 1.

More information and images are available online at

http://www.nasa.gov/vision/earth/lookingatearth/lanina_effect.ht

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Source: reuters



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