Hurricane season blew over...
La Niña likely
to make it
a wash
Isles' top meteorologist
By Helen Altonn
expects wet months but not
a major La Niña
Star-BulletinHawaii escaped serious tropical storms during this year's hurricane season, which ends this month.
"We were very fortunate in that nothing really threatened the islands this year," said Jim Weyman, meteorologist-in-charge and area manager of the National Weather Service.
"It only takes one (hurricane) in the right location to cause devastation."
Only three tropical-storm systems occurred in July and August, compared with nine last year, he said.
Hurricane Darby was the only hurricane entering the region -- the first in four years -- and it weakened before passing by the islands in July.
The other two systems were a tropical storm and a tropical depression that didn't develop into a storm, Weyman said.
Looking at the months ahead, the meteorologist said more rain is predicted because of a shift from El Niño to La Niña conditions.
But he added, "It doesn't look like it will develop into a major La Niña."
Both events involve a large-scale change in sea-surface temperature across the central and eastern tropical Pacific.
South American fishermen were the first to notice such a change, which occurs around Christmastime, and named it El Niño, meaning "little boy," for the baby Jesus.
Scientists named the opposite phenomenon La Niña, or "little girl."
El Niños are usually stronger and associated with ocean warming, and weak or no tradewinds. La Niñas involve cooler-than-normal central and eastern tropical Pacific waters.
During El Niño years, water temperatures usually increase from the 60s and 70s to more than 80 degrees Fahrenheit, in a "warm pool" across the central and western Pacific and extending into the tropics.
Sea temperatures are expected to drop 1 to 4 degrees Fahrenheit in the equatorial area during La Niña, Weyman said.
Cooler episodes and stronger easterly winds also are forecast through May, he said.
Hawaii and many other areas experienced drought during the recent El Niño while parts of the nation had severe storms.
But above-normal rainfall drenched Hawaii during the last major La Niña in December, January and February of 1988-1989, Weyman said.
Honolulu had 15.26 inches of rain (normal is 9.56 inches) in that period; Hilo had 47.46 inches (normal is 32.21); Lihue had 25.30 inches (normal is 14.34); and Kahului had 17.16 inches (normal is 10.28).
During 11 La Niña periods since 1950, Weyman said, eight were wetter in Hilo and Lihue, seven were wetter in Honolulu and six in Kahului.
Except for a tendency for winter months to be wetter, he said, there isn't enough data to prove definite correlations between La Niña and climactic events.
Tropical cyclone activity in this area varied from none to five in La Niña years, he said.
But the University Corporation for Atmospheric Research reported that cooling of the tropical Pacific "may already have influenced this fall's string of powerful Atlantic hurricanes, from Bonnie to Mitch."
Weyman said there are a lot of theories about why El Niños evolve into La Niñas, "but we don't really know the basic cause.
"As we get more information, I think we will be able to find the root cause and forecast the onset of conditions," he said.
