Longer-Term Weather Forecasts May Be Possible

December 9, 1999

USDA believes longer-term weather forecasts may be possible in the future based on El Nino and La Nina patterns. Other possibly predictable climate mechanisms lead some to believe interseasonal climate prediction may be possible under certain circumstances.

After analyzing 103 years of climate data, Agricultural Research Service scientists found evidence of higher winter wheat yields during El Nino's cool, wet winters and lower yields during La Nina's warm, dry winters. The current La Nina that began in the spring of 1998 suggests an increased probability of warm and dry conditions over the winter wheat belt in coming months.

This and other persistent and possibly predictable climate mechanisms lead some to believe that interseasonal climate prediction may be possible under circumstances. ARS atmospheric scientist Steven A. Mauget and soil physicist Dan R. Upchurch are studying if, where and how such predictions might be used by farmers.

They plan to search ocean temperature and air pressure records over the past century for clues to 12 and 20 year rainfall cycles observed in the Midwest. They want to see if they can isolate the source and test to see if the cycles are predictable.

Also, they will test how farmers might best use the forecasts, using computer simulations to track a farming career with and without seasonal forecasts.