MIAMI – Odds of a tropical wave forming into a storm were raised to 70 percent by National Hurricane Center forecasters in a 2 a.m. July 31 advisory, possibly becoming a cyclone by midweek when the wave reaches the western Caribbean Sea.

A fast-moving tropical wave is nearing the Lesser Antilles. Although showers and thunderstorms are fairly well-organized, there are currently no signs a closed surface circulation.

However, this system has the potential for some slow development during the next couple of days, but the best chance for tropical cyclone formation is likely to be by the early to middle part of next week.

A second wave to the east of this potential storm showed signs of weakening overnight and its chances at development plunged to low status.

The first system is expected to bring locally heavy rains and gusty winds to portions of the Lesser Antilles, Virgin Islands, and Puerto Rico today. Shower and thunderstorm activity should spread westward across the eastern Caribbean Sea and Hispaniola by tonight and on Monday. Interests in these areas should monitor the progress of this disturbance.

Formation chance through 48 hours is thought to be medium at 40 percent, however, but formation chance through five days has been listed as high at 70 percent.

Shower and thunderstorm activity associated with the second tropical wave and a low pressure system centered about 650 miles west-southwest of the Cabo Verde islands has changed little in organization. This system is moving westward at 10 to 15 mph, and development, if any, should be slow to occur due to unfavorable upper-level winds.

Formation chance through 48 hours and for the next five days was listed as low at 10 percent.