99L is Set to Strengthen

Located about 500 miles southwest of the Cape Verde Islands, 99L is a large but disorganized tropical wave, with a broad zone of scattered convection. The wave is located close to 10°-15°N and 30°W and is heading westward. 99L’s low latitude, and the lack of northward component to its motion, means that it is well positioned to head toward the Caribbean. An upper-level ridge to the northwest of 99L should keep it on a low-latitude path for the next several days, and models are in strong agreement that 99L will continue on its general westward trek, which could put it in the vicinity of the Lesser Antilles by around the middle of next week. The track forecast becomes more uncertain by that point, and it’s too soon to tell which parts of the island chain might be affected.

Wind shear is expected to remain fairly light along 99L’s path (10-15 knots), and SSTs should remain in the 28-29°C range over the next several days. Both of these factors favor development of 99L. In its 8 am EDT tropical weather discussion, NHC gave 99L only a 10% chance of development by Sunday, but a 50% chance by Wednesday. The discussion noted another wave coming off Africa over the weekend that has a 30% chance of development by Wednesday