NEW ORLEANS | Potential Tropical Cyclone One was moving northeast along the middle Texas coast Wednesday morning and was expected to bring dangerous, potentially life-threatening flash flooding from the northwestern Gulf Coast into the lower Mississippi Valley and Deep South. At 7 a.m. Central Time, the National Hurricane Center placed the disturbance near 28.3 degrees north and 96.2 degrees west, about 15 miles east-southeast of Port O'Connor, Texas, with maximum sustained winds near 30 mph. A Tropical Storm Warning was in effect from Sabine Pass to Morgan City, Louisiana, and a Tropical Storm Watch extended from Sargent to Sabine Pass. The center was forecast to move inland over southwestern Louisiana by Wednesday night. Rain, not the storm's eventual name or maximum wind, was the primary threat.
Flooding is the greatest danger
The National Hurricane Center forecast widespread rainfall totals of 5 to 10 inches, with isolated amounts near 20 inches through Thursday in parts of the affected region. Rainfall of that magnitude can overwhelm drainage, flood roads and rapidly raise small streams.
A forecast maximum is not expected everywhere. Local bands can produce extreme totals over a short distance. Residents should follow local National Weather Service warnings because flash-flood conditions can develop away from the forecast center.
Warnings cover the Louisiana coast
The Tropical Storm Warning from Sabine Pass to Morgan City means tropical-storm conditions were expected within 12 to 24 hours. The watch westward to Sargent indicated that those conditions were possible.
Warnings can change as the system moves. Coastal residents should use official NHC and local weather-service products rather than maps or posts that are no longer current.
The system could briefly become Tropical Storm Arthur
The disturbance had a 60% chance of becoming a tropical storm before moving inland, according to the morning advisory. If it develops enough organization and wind, it would receive the name Arthur.
Impacts do not depend on classification. A poorly organized system can cause catastrophic flooding because rain extends far from the center. People should not wait for a name before acting.
Strong shear kept thunderstorms displaced
The NHC said strong westerly wind shear placed the deepest thunderstorms well east and southeast of the low-level center. That structure limited organization but directed heavy rain toward areas away from the center.
Track cones focus on the center and do not represent the full hazard. Rain, gusts, surf and tornado risk can occur outside the cone.
The track leads inland toward Louisiana
The low was moving northeast near 7 mph and was expected to accelerate. The forecast brought it along the Texas coast and inland over southwestern Louisiana by night, with weakening after landfall.
Even as the circulation weakens, tropical moisture can continue producing heavy rain inland. Flood risk can persist after coastal wind warnings are discontinued.
Dangerous surf and rip currents are expected
The system was producing rough seas and was expected to create large surf and life-threatening rip currents along portions of the northwestern and north-central Gulf Coast.
Beachgoers should stay out of the water where warnings are posted. Rip-current danger can continue after weather appears calmer on shore.
Flood watches extend inland
Local National Weather Service offices issued flood watches and warnings across parts of Louisiana and Mississippi. Some locations were already dealing with saturated ground and high water.
A watch means conditions are favorable; a warning means flooding is occurring or imminent. People should know which product applies to their location and be prepared to move to higher ground.
Do not drive through floodwater
Most flood deaths occur in vehicles. Water can be deeper or faster than it appears, and roads may be washed out beneath the surface.
Turn around and use another route. Never move barricades. At night, the depth and edge of flooded roads are especially difficult to judge.
Prepare for power and communication interruptions
Gusty winds and saturated soil can bring down trees or lines. Charge phones, keep flashlights available and secure medication and documents in waterproof containers.
Generators must operate outdoors and away from doors and windows because carbon monoxide can accumulate rapidly. Follow manufacturer and local safety instructions.
Know where to receive official alerts
Enable Wireless Emergency Alerts and monitor the National Hurricane Center, local National Weather Service office and local emergency management. Weather radio can provide updates if internet service fails.
Do not rely on one social-media account. Forecast graphics can be reposted after they expire. Check the timestamp and advisory number.
What to watch through Thursday
Watch for changes in the tropical-storm warnings, flash-flood warnings and the corridor of heaviest rain. The system was expected to weaken inland, but moisture could spread toward Mississippi, Alabama, western Georgia and the Florida Panhandle.
The safest plan is based on local flooding and evacuation information, not whether the system reaches tropical-storm strength. Residents in low-lying areas should be ready to act before roads become impassable.
Additional Reporting By: National Hurricane Center; National Hurricane Center forecast discussion; NOAA; National Weather Service Lake Charles; WDSU.