Active Systems: The National Hurricane Center is issuing advisories on Hurricane Fiona, located less than 200 miles west of Bermuda, and on Tropical Storm Gaston, located less than 200 miles northwest of the central Azores. 1. Central Caribbean Sea: Satellite imagery indicates that showers and thunderstorms have increased and are showing signs of organization tonight with a well-defined low pressure system located over the central Caribbean Sea about 100 miles north-northeast of Curacao. Even though the upper-level wind environment is currently only marginally favorable, only a small additional increase in organization would result in the formation of a tropical depression later today. The system is expected to continue moving west-northwestward at 10 to 15 mph across the central and western Caribbean Sea. Locally heavy rainfall and gusty winds are likely to affect northwestern Venezuela, the ABC island chain, and northeastern Colombia through Friday. Interests in Jamaica, the Cayman Islands, and western Cuba should closely monitor the progress of this system. * Formation chance through 48 hours...high...90 percent. * Formation chance through 5 days...high...90 percent. 2. Eastern Tropical Atlantic: A broad area of low pressure, located roughly in between the Cabo Verde islands to the east and the west coast of Africa, is producing a large area of showers and thunderstorms. While this activity is gradually becoming better organized, earlier satellite wind data indicated the circulation remained fairly broad. Environmental conditions are forecast to be generally conducive for some development over the next day or so, and a tropical depression is likely to form by this weekend while the system moves northward at about 10 mph, parallel to the coast of west Africa. * Formation chance through 48 hours...high...70 percent. * Formation chance through 5 days...high...70 percent. 3. Central Tropical Atlantic: Shower and thunderstorm activity remains disorganized association with a broad area of low pressure located several hundred miles west-southwest of the Cabo Verde Islands. Despite marginal environmental conditions, some slow development of this system remains possible over the next several days while it drifts northwestward or northward over the central tropical Atlantic. * Formation chance through 48 hours...low...20 percent. * Formation chance through 5 days...low...30 percent.