Tropical Storm Bertha expected to dump rain on Gulf Coast

The big picture: The system is expected to reach Louisiana on Wednesday and Texas on Friday, the National Hurricane Center's latest forecast shows.

• Heavy rain, coastal flooding and gusty winds are possible, the National Weather Service in Slidell says.
• Tropical storm watches are in effect for the coasts of Louisiana, Mississippi and Alabama as of Monday afternoon.
• Additional watches and warnings will likely be needed over the next day or two, NHC says.

The latest: The center of the storm was about 105 miles south of Panama City, Florida, as of 4pm Monday. See the latest track.

• The slow-moving storm is drifting northwest and is forecast to move near or along the north Gulf coast for the next several days, NHC forecasters say.
• The depression had winds of 35mph and was becoming better organized Monday. It's expected to become Tropical Storm Bertha late Monday.
• It's forecast to continue gradually strengthening Tuesday before making landfall late Wednesday in southeast Louisiana.

Zoom in: Sandbags were in high demand Monday at city-run distribution sites in New Orleans.

• The Hollygrove site ran out of bags in less than an hour, prompting the city to bring in additional supplies.
• Other sites also had increased demand, City Council staffers said.
• The mayor's office advised residents to clean catch basins before the rain arrives and stay off flooded roads once it does.

What they're doing: The New Orleans Sewerage and Water Board is increasing staffing levels and cleaning catch basins, executive director Randy Hayman said Monday.

• Plus, the utility is lowering canal levels to increase stormwater storage capacity. Jefferson Parish says it is doing similar preparations.
• SWBNO has come under increased scrutiny this summer after power failures during Tropical Storm Arthur and human errors during a recent thunderstorm.
• Hayman and Kaitlin Tymrak, the new general superintendent, say they've made changes to fix power issues and retrained staff to prevent similar errors.

By the numbers: The drainage systems in New Orleans and Jefferson Parish are designed to handle one inch of rain in the first hour and a half-inch every hour after that.

• If three inches fall in an hour, it would take five hours to drain, Hayman says.
• See SWBNO's current pump status.

Storm threats

Rain: The system is expected to drop 2 to 4 inches of rain through Friday along the Gulf Coast. Some areas could get up to 8 inches.

• In New Orleans, 3 to 5 inches are likely, with areas south of Lake Pontchartrain getting more rain, NWS says.
• The rain could cause flash flooding. The heaviest rainfall — up to 16 inches — is currently expected to be over the Gulf. See the map.

Surge: A storm surge watch is in effect for part of Louisiana, meaning rising water could move inland from the coast.

• The surge from the Mississippi River to the Alabama/Florida border could be 2 to 4 feet, NHC says.
• Lake Pontchartrain and coastal areas west of the river could get 1 to 3 feet. See the map.

Rip currents: Swells from the storm are likely to cause life-threatening rip currents during peak beach season.

• They are already affecting portions of Florida's Gulf Coast and are expected to spread west this week, NHC says. See the map.

Wind: Strong wind gusts are possible in New Orleans and southeast Louisiana, NWS says.

• The winds could down trees and large limbs, which could lead to scattered power outages and some damage to porches and awnings.

Editor's note: This story was updated Monday afternoon with additional information.