El Nino to bring A mild to moderate El Nino is forecast this year in the Pacific, bringing increased tropical storm and hurricane activity and dry winter conditions.
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El Nino will bring a dry winterBy Helen Altonn
haltonn@starbulletin.com"El Nino is developing as we speak," Roger Lukas, University of Hawaii oceanographer, said today.
He said the eastern equatorial Pacific is unusually warm -- about 6 degrees Fahrenheit above normal off Peru. "It has already caused some unusual rains."
El Nino, meaning "boy child" in Spanish, is a phenomenon associated with abnormal warming of eastern Pacific waters that upsets wind and rainfall patterns and causes storms, droughts and crop failures around the world.
Lukas said he believes the rainier winter and lack of trade winds the past few months could be attributed to the early development of El Nino. "It's something we really haven't noticed well before."
He said the El Nino should last until next April, with dry conditions November through February. "We were lucky to have some rain this year."
Generally, more tropical cyclones, including tropical depressions, storms and hurricanes, occur during an El Nino.
Tom Schroeder, Joint institute for Marine & Atmospheric research (JIMAR) director and Tom Heffner, National Weather Service warning coordinator meteorologist, delivered the same message:
Residents should prepare every season for storms.
"When all is said and done, it only takes one," Heffner said.
Both meteorologists pointed to 1992 when the central Pacific had an El Nino with an active tropical cyclone season.
The weather service reported 11 Pacific tropical cyclones in 1992, of which three were tropical storms, five tropical depressions and three hurricanes. One was Iniki, which hit Kauai and part of Oahu.
The same number of tropical cyclones occurred in 1994, also an El Nino year, with five hurricanes, three tropical storms and three tropical depressions.
In 1997, the first part of an El Nino, there were nine tropical cyclones.
Meteorologists are just as concerned about tropical storms and depressions as they are hurricanes, Heffner said. "Tropical storms certainly can produce damage and tropical depressions heavy rainfall and flash flooding."
He said last year was pretty much a normal season, with four tropical cyclones, none close to Hawaii. The long-term average for the central Pacific is 4.5 cyclones, he said.
Another major concern for Hawaii from an El Nino is the likelihood of far less rainfall and extended dry periods, Heffner said. The rainfall last winter was close to normal after a 1997-98 El Nino with a three-year period of below-normal rainfall, he said.
A La Nina, associated with very cold conditions, occurred from 1998 until about spring of last year, when it began to shift to El Nino onset conditions, Lukas said.
Scientists at the UH and the International Pacific research Center are studying El Nino-La Nina patterns over 10-year periods -- the Pacific Decadal Variability -- to increase understanding of the events.
"Our understanding of El Nino phenomenon is based on observations that have been biased in one way or another by this decadal variability," Lukas said.
"Until now, we haven't properly appreciated that, so now we're trying to separate out that effect."
"In addition to our observations being biased by that, our prediction models have been tuned to certain conditions which don't always hold."
Lukas said waters of the east equatorial Pacific could get warmer. During the 1997-98 El Nino, the increase was almost 10 degrees Fahrenheit above normal.
One thing the scientists have learned, he added, is there is no direct correspondence between the magnitude of the sea surface anomaly and global impacts.
"But we are improving our understanding and, with a breakthrough recognizing decadal variability, predictions will improve markedly in the next few years."
Central Pacific Hurricane Center
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