Recent numerical experiments on three-months extended and seasonal weatherprediction with a thermodynamic model

The Adem thermodynamic climate model (ATCM) has been adapted to carry out t hree-month extended and seasonal numerical weather predictions. The model u ses the Northern Hemisphere NMC polar stereographic grid with 1977 points a nd a grid distance of 408.5 km. The performance of the model has been evalu ated for the period February 1981 to November 1983, which includes the "El Nino" 1982-83, and more recently in a real time basis for the "El Nino" per iod from June 1997 to August 1998 for Mexico. The results show good skill i n predicting seasonally temperature and precipitation anomalies during this "El Nino" period, which also confirms the results for the "El Nino" 1982-8 3. During the whole period June 1997 to August 1998, the model predicted ab ove normal air-temperature and below normal precipitation, in agreement wit h the observations, which corresponded to a severe persistent drought in Me xico that existed during that period. The results show that the ocean tempe ratures play an important role in the predictions, and it may be suggested that the above normal ocean temperatures in the Pacific Ocean regions conti guous to Mexico associated with "El Nino" produced the above normal surface air-temperature and the below normal precipitation possibly favoring the d rought situation in Mexico.