Barry to unleash severe flooding across Gulf states
Hurricane watches have been issued, a state of emergency has been declared in Louisiana and mandatory evacuations have been ordered in some places as Tropical Storm Barry formed over the Gulf of Mexico on Thursday morning.
The National Hurricane Center (NHC) declared Barry the second named storm of the Atlantic hurricane season with maximum sustained winds of 40 mph and moving west at 5 mph.
Barry is forecast to make landfall along the Louisiana coast Friday night or Saturday.
"There is a fairly high chance that Tropical Storm Barry will become a Category 1 hurricane on the Saffir-Simpson scale before making landfall," according to AccuWeather Hurricane Expert Dan Kottlowski.
If so, Barry will become the first hurricane of the 2019 Atlantic season.
"The key to whether Barry becomes a hurricane before landfall or not will depend on the amount of time it is able to spend over the warm water of the Gulf of Mexico," Kottlowski said.
If Barry turns northward quickly and makes landfall Friday night, then it may not have time to strengthen to a hurricane. If Barry tracks to the northwest for a longer period, it may not make landfall until later Saturday and would have more time to strengthen.
Barry's flooding rainfall to have much more impact than a typical Category 1 hurricane or tropical storm
In terms of impact, AccuWeather is initially designating this a level 2 storm on its RealImpact™ Scale for Hurricanes. The scale ranges from "Less than 1" to a 5 with 5 having the most severe impact.
The greatest storm surge will impact most of the central and southeast coastal areas of Louisiana.
There is concern the levee system may be topped along the Mississippi River due primarily to Gulf of Mexico water backing up the channel. On top of that, heavy rain will pour down on the immediate area from Friday night to Saturday, adding volume to runoff.
Water levels on the lower Mississippi River remain high from spring flooding that was still flowing downstream from the middle and upper part of the basin.
In comparison, the level on the Mississippi River prior to the arrival of Hurricane Katrina was 2 feet. On Thursday morning, the river level was just above 16 feet. Flooding in New Orleans occurred primarily as levees failed as a storm surge caused waters to rise in Lake Pontchartrain.
At New Orleans, the Mississippi River is estimated to surge to near 19 feet, according to National Weather Service (NWS) hydrologists. This was revised downward from 20 feet from original estimates earlier this week.
However, near the 20-foot level, some overtopping of the Mississippi River levee can occur in low spots should this scenario unfold.
The storm will arrive after 6-10 inches of rain deluged New Orleans, which is below sea level, causing a flash flood emergency Wednesday. The drainage system could not keep up with rainfall of 2-3 inches per hour that fell at times, resulting in serious street flooding and numerous high-water rescues.
Damaging winds, tornadoes and waterspouts possible with Barry
While the Barry is forecast to peak no higher than Category 1 hurricane strength, sustained hurricane-force winds of 74 mph or greater are only likely in a small area near and northeast of the eye.
However, with this particular tropical feature being rather larger, bands of severe thunderstorms with wind gusts to tropical storm force can occur well away from the center and especially so on the eastern side of the storm.
There is the ongoing potential for spin-up tornadoes and waterspouts up through a day or two after landfall in the region. Some of these may be wrapped in rain and difficult to see until they are already in the neighborhood.
Some of the oil and gas rigs in the Gulf of Mexico have been evacuated as a precaution, according to CNBC.