Effects of "the Little Girl" on Alaska

Last fall, the prediction for Alaska's winter wasn't a warm one. La Nina, the cold-hearted sister of El Nino, was supposed to bring cold snaps and plenty of snow. Now that winter 98-99 in almost over, it's time to see what, if anything, La Nina has done to the north.

Ants Leetmaa is director of the National Weather Service's Climate Prediction Center in Washington D.C. He was in Fairbanks recently to spread the word about the climate prediction center, which issues season-long forecasts based on weather events that tend to be somewhat predictable, such as El Nino and La Nina.

La Nina, Spanish for "little girl," occurs when the waters of the Pacific Ocean at the equator are unusually cool. During the last La Nina in 1988, surface temperatures of the Pacific Ocean near the equator dropped as low as 68 degrees Fahrenheit from a normal temperature of about 80 degrees. Even though the cooling happens thousands of miles away, the interactions of ocean and atmosphere carry La Nina's effects to Alaska and all over the globe.

Leetmaa said the 1998-1999 version of La Nina should have three noticeable effects on Alaska: it should be cooler than normal, more snow should fall, and Alaska thermometers should read below zero more often than in a non-La Nina year. As much of Alaska recovers from a cold snap that held temperatures well below normal for much of January and February, it would seem La Nina has done her job. Leetmaa pointed out that the last time Alaska made national news for an extended cold period (the winter of 1988-1989) was a La Nina year.

Though cold snaps fit the pattern of a year affected by La Nina, Leetmaa said a few weeks of cold weather can't be tied to any one source. He said the real test of La Nina's intrusion on Alaska will be the overall average winter temperatures, snowfall, and the number of cold days.

Jan Curtis of the Alaska Climate Research Center at the Geophysical Institute checked on Alaska's winter to date and saw a few features that might be the result of La Nina. In December and January, Southeast Alaska had more snow than normal fall, especially in Juneau and surrounding areas. Thanks to a 19-day cold snap, January temperatures were about three degrees colder in Anchorage, five degrees colder in Barrow, eight degrees colder in Nome and almost seven degrees colder than average in Fairbanks.

Curtis tallied the days of temperatures of 40 below or colder in Fairbanks from 1948 to the present and found there was some correlation to La Nina years. This winter, for example, there have been 15 days in which it was colder than 40 below. Last winter, an El Nino year, there were only four days of 40 below. Other years show excellent correlation between cold days and La Nina.

The winter of 1964-1965 was a La Nina year that featured 38 days of temperatures colder than 40 below. And then there's the renegade years, like the El Nino winter of 1965 to 1966 that featured 25 days of 40 below, and the La Nina winter of 1995 to 1996 that wasn't especially cold. Curtis said if he could figure out a fail-safe method of predicting the effects of La Nina and El Nino, he would win the Nobel Prize. But, of course, weather is not simple.

Strong El Ninos, such as the one experienced last year, make it somewhat easy for forecasters to predict lots of rain in California, but more subtle events, such as this year's La Nina, don't express themselves as dramatically. That's why predictions are among the most challenging tasks of scientific research.