Hurricane Hunter: Laura Impacts Could be Severe

August 26, 2020


Above – Big Lightning is a sign of an intensifying storm.

Jeff Masters in Yale Climate Connections:

Hurricane Laura powered its way to major hurricane status overnight, putting on an impressive display of rapid intensification over the very warm waters of the Gulf of Mexico.

Laura is headed towards a landfall expected Wednesday night or early Thursday morning in northeastern Texas or western Louisiana as a major category 4 hurricane, and is expected to cause “catastrophic” wind and storm surge damage, according to the National Hurricane Center (NHC). Rain squalls from Laura’s outer spiral bands were already affecting the coasts of Texas and Louisiana on Wednesday morning, and they will increase in intensity throughout the day.

Laura rapidly intensified by an impressive 50 mph in the 24 hours ending at 11 a.m. EDT Wednesday, with the winds rising from 75 mph to 125 mph and the pressure falling from 990 mb to 956 mb. This far exceeds the definition of rapid intensification, which is a 24 mb drop in 24 hours. Buoy 42395, located just east of Laura’s eye on Wednesday morning, reported sustained winds of up to 76 mph, wind gusts as high as 107 mph, and a wave height of 37 feet (11 meters).

At 11 a.m. EDT Wednesday, Laura was already generating a storm surge of 1 – 3 feet along much of the Texas and Louisiana coasts; the largest surges, between 2.5 – 3 feet, were at Shell Beach, Louisiana, located to the southeast of New Orleans, and Freshwater Canal Locks, on the south-central coast of Louisiana. Laura’s storm surge can be tracked using the Trabus Technologies Storm Surge Live Tracker or the NOAA Tides and Currents page for Laura.

Laura continues to rapidly intensify

At 11 a.m. EDT Wednesday, Laura was located over the waters of the central Gulf of Mexico, about 235 miles southeast of Galveston, Texas. These waters were a very warm 30 degrees Celsius (86°F). Laura was headed northwest at 15 mph with top sustained winds of 125 mph and a central pressure of 956 mb, putting it just 5 mph below category 4 strength.

Satellite images and data from the Hurricane Hunters showed that Laura has closed off a large eye about 30 miles in diameter. Intense thunderstorms with very cold cloud tops surrounded the eye and extended high into the atmosphere. The eye had not yet fully cleared out, which likely will occur by Wednesday afternoon as the hurricane continues to intensify.

High-level cirrus clouds were streaming out to the east and south of Laura, indicating good upper-level outflow on that side. Upper-level outflow was steadily improving to the north and west, showing that Laura was establishing a second outflow channel that connected up with the trough of low pressure over the central U.S. This improved outflow structure will help Laura intensify further on Wednesday afternoon. Laura was embedded in a moderately dry region of the atmosphere, with a mid-level relative humidity of 60%, but this dry air was not hindering the hurricane anymore, as the moderate wind shear of 10 – 15 knots affecting the storm was not high enough to drive the dry air into the well-developed inner core.

Figure 2

There’s not much mystery on where Laura is going. The hurricane has made its expected turn to the northwest, and is headed toward a landfall near the Texas/Louisiana border around midnight Wednesday night. After landfall, Laura will turn to the north, following steering currents from a trough of low pressure over the central U.S. The rapidly weakening storm will then turn to the east on Friday, passing through the Tennessee Valley on its way to the mid-Atlantic coast, where it will move out to sea by Sunday.

Ocean temperatures are a very warm 30 degrees Celsius (86°F), and Laura will be passing over Gulf waters with very high heat content on Wednesday. Conditions for intensification will be very favorable until four to six hours before landfall, when strong upper-level winds from the trough of low-pressure steering Laura will bring a high 20 – 25 knots of wind shear and likely halt the intensification process. Interaction with land may also slow intensification at that time. Data from the Hurricane Hunters late Wednesday morning showed that Laura might be starting to develop concentric eyewalls, a process common in intense hurricanes, which leads to a temporary halt in intensification when the double eyewalls become fully developed. This process could slow down Laura’s intensification by Wednesday night. The top dynamical intensity models – the HWRF, HMON, and COAMPS -predicted in their 0Z and 6Z Wednesday runs that Laura would be a category 4 hurricane at landfall.

National Hurricane Center:

Unsurvivable storm surge with large and destructive waves will cause 
catastrophic damage from Sea Rim State Park, Texas, to Intracoastal 
City, Louisiana, including Calcasieu and Sabine Lakes. This storm 
surge could penetrate up to 30 miles inland from the immediate 
coastline in southwestern Louisiana and far southeastern Texas.

5 Responses to “Hurricane Hunter: Laura Impacts Could be Severe”

  1. dumboldguy Says:

    15 to 20 foot storm surge? It just keeps getting scarier—-is anyone here surprised?

  2. rhymeswithgoalie Says:

    This is a typical post-Rita house in Cameron Parish.

    • dumboldguy Says:

      A 20 foot storm surge will lift this off the pilings and destroy it. Will they then use government money to rebuild it on 25 foot pilings? Don’t discount it.

      • rhymeswithgoalie Says:

        It’s common for rebuilding after a flood event for the landowners and builders to try to convince the zoning authorities that they be allowed to build lower than the (often new) minimum height.

        At some point the storms come frequently enough that they’ll stop building. I’d be OK if they reverted to building ground-level cinderblock homes (as I’ve seen on the Florida coast) that just get flushed out, but can be re-roofed and furnished in fairly short order. This would work for people who otherwise live cheaply off the land, growing vegetables and fishing.

  3. redskylite Says:

    “Damage from whopper hurricanes rising for many reasons”

    Scientists agree that waters are warming, and that serves as hurricane fuel, said NOAA climate scientist Jim Kossin. A study by Kossin found that, once a storm formed, the chances of its attaining major storm status globally increased by 8% a decade since 1979. In the Atlantic, chances went up by 49% a decade.

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