Eastern Tropical Atlantic:A tropical wave is forecast to emerge off the west coast of Africa by this weekend to the south of the Cabo Verde Islands. Thereafter, environmental conditions appear favorable for some slow development of this system as it moves westward to west-northwestward at 15 to 20 mph, moving across the eastern into central Tropical Atlantic through the middle of next week.* Formation chance through 48 hours...low...near 0 percent.* Formation chance through 7 days...low...20 per