Tropical Storm Isaac is "getting better organized," as it moves northwest toward Haiti, forecasters with the National Hurricane Center said Friday night.

The Tampa Bay area still is within the cone of uncertainty, with Isaac projected to arrive Tuesday morning, as a Category 1 hurricane.

The storm could affect plans for the Republican National Convention, which begins Monday in downtown Tampa and runs through Thursday. 

The New York Times reported Friday that presidential candidate Mitt Romney's nomination has been moved up two days, from Wednesday to Monday. The change will enable the process to be completed before the storm is forecast to reach the Tampa Bay area.

Isaac was moving northwest at around 14 mph as of 11 p.m. Friday but is expected to pick up speed tonight through Sunday, forecasters said.

Isaac's center was expected to make landfall in Haiti Friday night and approach the Florida Keys by Sunday, according to the hurricane center's latest projections.

The Florida Keys and the southern Florida peninsula are under a tropical storm watch tonight, the National Weather Service reports.

Florida's tropical storm watch extends from the Keys to Palm Beach County and (inland) to Glades County, as the storm intensifies, with winds reaching 70 mph.

The following counties are under a tropical storm watch:

• Glades
• Hendry
• Palm Beach 
• Collier 
• Broward
• Miami Dade
• Monroe

A watch means that tropical storm conditions are possible within the next 48 hours.

Stay with Patch for updates as they become available.