US: Hurricane Sally strengthens to Category 2 hurricane September 14 /update 2

Event

Hurricane Sally has strengthened to a Category 2 hurricane Monday, September 14, as it moves northwest near the coast of Louisiana and Alabama. According to the National Hurricane Center (NHC)'s 16:00 (CDT) advisory, Sally is located 218km (135mi) southeast of Mobile (Alabama) and is sustaining winds of up to 161kph (100mph). Forecasters have warned that Sally may strengthen to a Category 3 hurricane prior to making landfall between Tuesday, September 15, and Wednesday, September 16, potentially to the west of Mobile.

The NHC has warned that Sally will produce up to 406mm (16in) of rainfall over the central Gulf Coast from the Florida Panhandle to southeast Louisiana. Rainfall may reach up to 610mm (24in) in some areas and produce life-threatening flash flooding. Minor to moderate river flooding is also likely across Alabama and Mississippi. The NHC has also warned that a life-threatening storm surge is expected in some areas, and flooding resulting from the surge has already been reported in Alabama, Florida, Mississippi, and Louisiana.

The NHC has issued the following watches and warnings:  

• A hurricane warning between Morgan City (Louisiana) and Navarre (Florida), and Lake Pontchartrain and Lake Maurepas, including metropolitan New Orleans
• A tropical storm warning east of Navarre (Florida) and Indian Pass (Florida)
• A storm surge warning between Port Fourchon (Louisiana) to Okaloosa/Walton county (Florida), and for Lake Pontchartrain, Lake Maurepas, Lake Borgne, and Mobile Bay

The governors of Alabama and Mississippi have declared states of emergency. In Mississippi, authorities assembled sandbag stations, ordered boat owners to move their vessels out of city marinas and harbors, and closed islands and areas of national parks along the coastline. Campers at the Davis Bayou campground were told to evacuate by 09:00 on Sunday, September 13. Authorities in Alabama have recommended that coastline areas of the state be evacuated, particularly in Baldwin and Mobile counties. Mandatory evacuation orders are in place in both Mississippi and Louisiana.

The following areas are under mandatory evacuation orders in Mississippi:

• In Hancock county, for all residents in living low lying areas, on rivers, bayous, and in travel trailers or mobile homes
• In Harrison county, for areas south of the Harrison County Sand Beach sea wall, including Harrison County Sand Beach in addition to low-lying areas
  

The following areas are under mandatory evacuation orders in Louisiana:

•  In Lafourche Parish, south of Leon Theriot Lock in Golden Meadow and all low lying areas of Lafourche
• In New Orleans, all residents living outside of the Orleans Parish levee protection system including Venetian Isle, Irish Bayou, and Lake Catherine
• In Jefferson Parish, the town of Grand Isle and Jeanne Lafitte including Barataria, Crown Point, and Lower Lafitte
• In Plaquemines Parish, the entire East Bank and the West Bank between Phillips 66 Alliance Refinery to Venice. A voluntary evacuation order has been issued between Oakville and the Phillips 66 Alliance Refinery.
• All of St. Charles Parish 
• In St John the Baptist Parish, Pleasure Bend and low-lying areas north of Interstate 10 in LaPlace, including the areas of Frenier, Peavine, and Manchac. A voluntary evacuation order is in place for the rest of the parish
  

Wind damage, coastal flooding, and dangerous sea conditions are expected during the passing of the storm, and significant disruptions to transportation, business, and utilities are likely in the coming days.

Context

The Atlantic hurricane season runs from late May through to the end of November, with activity typically peaking in late August and early September. Numerous tropical storms form in the Atlantic Ocean during this period, with most affecting the Caribbean, the Gulf of Mexico, and the east coast of the United States. Although communities in the region are generally well prepared for adverse weather conditions during the hurricane season, severe storms bring a significant risk of flooding and infrastructural damage.

Organized tropical activity tends to peak in August and September. Storms tend to flood sections of highways and cause dirt-based roads to become temporarily impassable. More organized systems, depending on intensity, can prove catastrophic in terms of tidal surge, wind damage, flooding, and mudslides.

Advice

Those in the above areas are advised to monitor local weather reports, avoid areas directly affected by flooding, confirm road conditions before setting out, and adhere to instructions issued by local authorities.