Summary of Forecasts

 For ENSO and Other SST

Dynamic Models: Almost all the dynamic models (NCEP, COLA anomaly coupled, BMRC, LDEO1, LDEO3, UCLA, SIO) agree in predicting that La Niña conditions will continue and even amplify over the next two to three seasons. These models also generally agree that the SSTA will rapidly return to normal during the spring of 2000. The most notable exception is the unflux corrected COLA coupled model, which, in the ensemble mean, predicts the decay of the cold anomalies during the next one to two seasons with slightly warm conditions developing in the tropical Pacific during boreal winter 1999-2000.

Statistical Models: The statistical models (linear inverse model, neural network model, CLIPER model, constructed analogue model, Markov model) are predicting that the current La Niña will evolve similar to the forecasts produced by most of the dynamic models. The La Niña conditions are forecasted to persist and amplify through the winter 1999-2000 and decay rapidly during the following spring season. The linear inverse model is predicting the development of cold SSTA in the Caribbean and the north tropical Atlantic.

For Land Surface Temperature and Precipitation

Dynamic Models: With persisted SSTA, the regional spectral model forecasts decreasing fire potential associated with enhanced precipitation for the western U.S. over the next 1-2 months. The NCEP AGCM forecast using predicted SSTA in the tropical Pacific calls for a tendency toward wetness in the eastern U.S. through late summer 1999, while the U.S. west coast is predicted to be on the dry side straight through to winter. Going into winter 1999-2000 a dry area develops in the eastern and southern U.S.

Statistical Models: The linear regression forecast for U.S. surface temperature during JAS 1999 calls for above normal temperatures over the much of the southern U.S., the Pacific Northwest, and in the Ohio River Valley. The temperature forecast for SON 1999 indicates above normal temperatures continuing from late summer into fall in Florida and the Southwest. The CCA forecast for JAS 1999 over Canada calls for warm conditions throughout most of the country. The CCA forecast for Sahel rainfall during JAS 1999 calls slightly higher than climatological probabilities for above normal rainfall over the eastern and western edges of the domain, and over parts of central Sahel, including Burkina Faso, southeastern Chad, and western Sudan are expected. However, slightly higher than climatological probabilities for below normal rainfall are expected across much of central Sahel. The linear regression forecast for east-central China call for calls for both an early onset and a later ending of the Meiyu in 1999.