Tropical Storm Isaias: what to know about its Gulf Coast path

Where are watches in effect, and what hazards are forecast?

The NHC issued a hurricane watch from Bay St. Louis, Mississippi, to Indian Pass, Florida, and a tropical-storm watch for adjacent areas. A storm-surge watch covers the coast from the mouth of the Mississippi River to Yankeetown, Florida. A watch means hazardous conditions are possible, not certain. (NHC advisory)

Rain could affect areas well beyond the coast. The NHC forecast 3 to 6 inches across the central Gulf Coast, from far southeastern Louisiana to the Florida Panhandle, with localized totals up to 10 inches. Across parts of the Southeast as far north as the Tennessee Valley and the Carolinas, the forecast calls for 1 to 3 inches, with localized totals up to 5 inches. The NHC warned of possible flash, urban and isolated river flooding.

Joe Maniscalco, a National Weather Service meteorologist in Mobile, told Courthouse News Service: “There is becoming an increased concern for significant impacts to the local area, including tornadoes to the east of the eye.” The NHC also forecast swells to spread north toward the Gulf Coast later in the week, with life-threatening surf and rip currents possible. (Courthouse News Service)

What does Isaias’ forecast cone show?

The cone depicts the probable path of the storm’s center, with its width reflecting uncertainty based on historical forecast errors. It does not show the storm’s size or the full reach of dangerous weather. Rain, wind and other hazards can affect places outside the cone. (NHC explanation of the cone)

That difference matters for people looking at maps to judge their risk. In the NHC’s 10 a.m. advisory, tropical-storm-force winds extended as far as 45 miles from Isaias’ center—a separate measure from the center-track cone. Inland rain forecasts also extend across the Southeast, including the Carolinas.

What should people in the forecast area monitor?

Florida Gov. Ron DeSantis declared a state of emergency Tuesday for 25 counties in the Panhandle and Big Bend. The declaration activates the state emergency-management plan and allows preparation measures such as deploying personnel and equipment. (CBS News)

Residents and visitors in watch areas should follow updates from the NHC and their local National Weather Service offices, which can provide area-specific alerts. The forecast points to possible hazards across a broad stretch of the Gulf Coast and Southeast; the cone’s edge is not a boundary between danger and safety.