Tropical Storm Barry inched across the northern Gulf of Mexico on Thursday, ahead of what's expected to be a wide swoop to the northwest that would send it into the south-central Louisiana coast sometime Saturday and bring its worst rains and wind to the Baton Rouge and Lafayette areas.

Through the day Thursday, what had been an unorganized tropical cyclone took shape and strengthened into a named storm. By 4 p.m., forecasters with the National Hurricane Center aired some uncertainty about the storm’s ultimate path due to varying computer simulations, but still projected Barry would become a hurricane by landfall.

A hurricane warning is in effect from Intracoastal City to Grand Isle, with tropical storm and storm surge warnings extending across much of the Louisiana coast and in lakes Pontchartrain and Maurepas. Tropical systems also often produce tornadoes when they make landfall.

Meanwhile, East Baton Rouge Mayor-President Sharon Weston Broome declared a state of emergency Thursday, as authorities in Ascension and other parishes in southeast Louisiana have already.

"I want to ensure it is clear we have not reached that point, however. Filing that emergency declaration is continuing in our proactive approach in protecting our citizens," Broome told reporters. “There's still time to prepare. As you know, this weather event is not written in stone. I do not want our community to be fearful, but I do want our community to be prepared."

Broome announced that city-parish’s government offices will be closed on Friday. Only essential personnel will be working, she said.

The mayor stressed that city-parish maintenance and drainage crews will continue cleaning out ditches, supplying sandbags and checking levees in the anticipation of widespread flash flooding.

Officials at a few of the region's refineries and chemical plants also said they were monitoring and making preparations for the storm, but none contacted said they had slowed operations, including for ExxonMobil’s operations in Baton Rouge, for Shell at Norco, Convent and Geismar and for BASF in Geismar and Vidalia.

“ExxonMobil is proactively working to minimize the risk to personnel and equipment associated with large amounts of rainfall," said Stephanie Cargile, ExxonMobil spokeswoman. "Safety measures include arranging for standby staffing, identifying and tying down material and delaying discretionary work.”

Bringing dangerous storm surge, heavy rain and strong winds, Barry was moving west 5 mph about 90 miles south of the mouth of the Mississippi River and 175 mile southeast of Morgan City, the National Weather Service reported in its 4 p.m. update Thursday.

A reconnaissance team flew into the storm system and found sustained winds at 40 mph, strong enough to make Barry the second named storm of the 2019 hurricane season. Once Barry becomes a hurricane, winds would be 74 mph or higher.

Heavy rains are expected, with 10-20 inches possible across much of the area, with 20-25 inches possible in isolated areas of southeastern Louisiana and southwestern Mississippi, the forecasters said.

“The slow movement of Barry will result in a long duration heavy rainfall and flood threat along the central Gulf Coast and inland through the lower Mississippi Valley through the weekend into early next week,” a Hurricane Center report says.

The worst flooding is expected along the storm's direct path and to the east of it, putting Baton Rouge in harm’s way.

In reports Thursday from the National Hurricane Center, forecasters said the tropical storm was being steered by a ridge that was expected to develop a weakness in the next 24 to 48 hours and allow the storm to move to the northwest and then north.

The storm was expected to start making its turn to the northwest Friday, but computer models that forecast the storm's path had a wide range: from the storm moving due north across the southeastern corner of the state to the storm heading for the Texas coast. Other models were in-between those two points.

The track that forecasters have settled on has the tropical storm headed for the central Louisiana coast.

Nearly three years removed from the unnamed August 2016 rainstorm that caused some form of flood damage to more than 91,600 of households in Louisiana, the breadth and intensity suggested by the newest rainfall estimates are bringing Barry closer to that historic rain, though not exceeding it.


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State Climatologist Barry Keim said the August 2016 flood was notable both for the intense localized rainfall across a northern swath of East Baton Rouge and Livingston parishes but also the lesser but still heavy rain — 10 to 15 inches — across a far wider region.

"We had this heavy rain over this incredibly broad area, and it gave the water no place to go because every place downstream also got that same amount of water and it all just started backing up on each other," Keim said.

Nine locations across East Baton Rouge and Livingston parishes had rainfall totals between Aug. 11-14, 2016, that exceeded at 1,000-year rain, or rainfall that has a 0.1 percent chance of happening in a given year.

For instance, the Watson area received more than 31 inches during that period, over essentially a two-day period. Other areas surpassed 20 or 25 inches of rain.

At the same time, Keim warned the National Hurricane Center's potential rainfall estimates are rough ones, at best, because the technology isn't there yet to pinpoint rainfall intensities with fine precision.

"We're just not that good at doing that yet," Keim said. "And, of course, this also has everything to do with the track. I mean if this track goes off the rails a little bit and changes, you know this pattern could change dramatically."

In East Baton Rouge, parish officials are encouraging residents to stay off the roads once the storm moves in. But local law enforcement agencies and first responders are poised to deploy should residents need rescuing due to high water conditions, officials said.

The mayor said any evacuation order will be made in conjunction with the Governor’s Office as well as the parish’s unified command center.

“I can assure you we are prepared because of prior incidents and events that have taken place,” she said. “We’re also prepared at the right time to open shelters when necessary and get that information out in a timely manner.”


SEE MORE TROPICAL STORM BARRY COVERAGE BELOW:


Email David J. Mitchell at dmitchell@theadvocate.com

Follow David J. Mitchell on Twitter, @NewsieDave.