Tropical Depression Twentyone formed over the southwest Caribbean Sea near Nicaragua on Monday afternoon. At 5:00 p.m. EDT on Monday the center of Tropical Depression Twentyone was located at latitude 11.6°N and longitude 83.5°W which put it about 35 miles (55 km) southeast of Bluefields, Nicaragua. The tropical depression was moving toward the west at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1007 mb.

A low pressure system over the southwest Caribbean Sea near Nicaragua strengthened on Monday afternoon and the U.S. National Hurricane Center designated the system as Tropical Depression Twentyone. More thunderstorms formed near the center of the tropical depression on Monday afternoon. Several short bands of showers and thunderstorms were revolving around the center of circulation. Storms near the center generated upper level divergence that pumped mass away from the tropical depression.

Tropical Depression Twentyone will move around the southern side of a high pressure system over the Gulf of Mexico. The high pressure system will steer the tropical depression toward the west during the next 24 hours. On its anticipated track, Tropical Depression Twentyone will move inland over southeast Nicaragua in a few hours. The tropical depression could drop heavy rain over parts of Nicaragua. Heavy rain could cause flash floods in some locations.

Elsewhere, Hurricane Tammy moved farther north of the Leeward Islands. At 5:00 p.m. EDT on Monday the center of Hurricane Tammy was located at latitude 22.3°N and longitude 63.8°W which put it about 695 miles (1115 km) south of Bermuda. Tammy was moving toward the north-northeast at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 75 m.p.h. (120 km/h) and there were wind gusts to 90 m.p.h. (145 km/h). The minimum surface pressure was 990 mb.