Twin threats: Marco weakens as Laura gains strength

2020-08-24 16:01:03

Twin tropical storms Marco and Laura launched a week of tropical storm conditions on the Gulf Coast and the Florida Keys, with the former weakening and the latter gaining strength on Monday.

Even as Marco finishes up its tour along the Gulf Coast, authorities fear that Laura will pack the powerful punch that its predecessor didn’t.

“We’re only going to dodge the bullet so many times. And the current forecast for Laura has it focused intently on Louisiana,” Louisiana Gov. John Bel Edwards told reporters on Monday.

And just 260 miles west of New Orleans, the mayor of Port Arthur, Texas, announced the city will be issuing a mandatory evacuation, scheduled for Tuesday morning if conditions don’t improve.

Mayor Thurman Bartie asked his constituents to make plans early on Tuesday to go north, west or at least to seek higher ground.

“In the morning at 6 a.m., if the information does not change, then we will want you to leave Port Arthur,” Bartie told reporters on Monday.

As of an 11 a.m. advisory from the National Hurricane Center, the disorganized and lop-sided remains of Marco registered maximum sustained winds of 50 mph and was 55 miles southeast of the mouth of the Mississippi River. It was moving north-northwest at 8 mph. The heaviest rainfall was east of the center of Marco, across portions of the Florida Panhandle, where more than 8 inches fell overnight.

A storm surge warning remained in effect from Morgan City to Ocean Springs, Mississippi, where 2 to 4 feet of storm surge was possible. A tropical storm warning was still in effect from Morgan City, Louisiana, to the Alabama and Mississippi border, an area that includes New Orleans and Lake Pontchartrain.

Marco is expected to approach Louisiana by Monday afternoon and evening before turning northwest and parallel the coast for a time, though the exact timing and location of landfall remained uncertain. Regardless of exactly when landfall occurs, Marco was expected to produce an average of 3 to 5 inches of rain, and in some areas up to 10 inches, for portions of the Gulf Coast through Monday night. Isolated tornadoes were also possible.

Marco was forecast to finally weaken Monday night and dissipate by Tuesday.

With Marco exiting stage left, Tropical Storm Laura is entering stage right. And Laura is forecast to be bigger and stronger than Marco.

Throughout Monday, Tropical Storm Laura meets Cuba where the interaction with the land mass will keep any intensification at bay. It will produce tropical storm conditions for Cuba, Jamaica and portions of the Florida Keys.

As of the 2 p.m. ET advisory from the National Hurricane Center, Laura — with maximum sustained winds of 60 mph — was 15 miles south of Cayo Largo, Cuba, and moving west-northwest at 20 mph.

A tropical storm warning was in effect for the middle and lower Keys from Craig Key to Key West.

When Laura enters the Gulf of Mexico on Tuesday, the forecast gets interesting.

Right now landfall is projected to be late Wednesday or early Thursday as a strong 105 mph Category 2 storm, borderline Category 3, near the Texas and Louisiana border.

But no one knows just how strong Laura will get.

One possibility is rapid intensification, in which case maximum sustained winds would have to increase by 35 mph in 24 hours. It’s far from impossible: The elements are there to support the potential for explosive strengthening: warm Gulf of Mexico water in the mid-to-upper 80s, low wind shear and plenty of moisture in place.

Should this happen, the rapid intensification will occur from Tuesday afternoon to Wednesday afternoon.

This will be important to watch, as a stronger Laura would head more west toward Houston whereas a weaker storm would be steered more toward the Texas and Louisiana border.

As of Monday afternoon, there is an increasing risk of dangerous storm surge, tropical storm force winds and rainfall beginning Wednesday along portions of the Gulf Coast. From late Wednesday through Friday, Laura is expected to produce rainfall of 5 to 10 inches, locally up to 15 inches, near the Texas and Louisiana border north into portions of the lower Mississippi Valley.

Hurricane and storm surge watches will likely be required for portions of the Gulf Coast by Monday evening.

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