Colombian coffee exporters revised a forecast.

Colombia’s coffee output for the 1986-87 coffee year will be at least 15% less than officially forecast, according to Gilberto Arango, president of the Assn. of Private Exporters. Arango said that output from Colombia, a major coffee producer, will be less than 10.3 million 132-pound bags, compared to the official projection of 12 million. He said that heavy rainfall and other problems will reduce the crop. Colombian coffee production for the year ended Sept. 30 was 11.9 million bags.