La Nina stirs weather extremes.

The Pacific chill known as La Nina has contributed to the drought currently plaguing the Mid-Atlantic states and will whip up an unusually strong hurricane season in the Atlantic this year, according to the National Oceanic and Atmospheric Administration (NOAA).

Cold water appeared in the equatorial central Pacific in May of 1998 and has lingered there since then, upsetting weather patterns across the world. NOAA's Climate Prediction Center last month forecast that La Nina will persist for the next several months and possibly into early 2000.

In some ways the opposite of El Nino, the Pacific cooling helped set up atmospheric pressure patterns that kept rain away from the Mid-Atlantic this spring. La Nina could drag the drought out for several more months, says NOAA chief D. James Baker.

Repercussions of the Pacific cooling will reach clear around the world to West Africa, the birthing ground for Atlantic hurricanes. In May, NOAA's National Hurricane Center issued its first, ever preseason hurricane outlook, in which it forecast above-normal storm activity this year.

La Nina fosters hurricanes by influencing the winds blowing off West Africa toward America. In particular, it tends to reduce the shearing between high-altitude and low-altitude wind. Such shearing can lop the top off storms as they build.