Laura officially became a hurricane at 10 am this morning. It is now fully away from the mountains of Cuba that have been been keeping it from strengthening, and is now moving over the open, warm waters of the Gulf of Mexico. Water temperatures in the path of Laura are mainly between 85 and 88 F, with some apparent upwelling of cooler water over the north-central Gulf due to Marco.
Both NOAA and USAF aircraft are flying in Laura today. I peak flight-level wind of 77 knots was found this morning, and SFMR instrumentation that can estimate winds at the sea surface indicated 65 knots, the low end of hurricane intensity.
Laura is moving along quickly, toward the WNW at 16 mph. The upper-level ridge to the northeast of Laura has weakened some, and it will likely turn right, or more NW then NNW, over the next 24 hours. These hurricanes generally find the path of least resistance to the north, as redistributing heat from the tropics to the midlatitudes is one of their roles in nature.
The model guidance is fairly tightly packed today, showing a landfall between Lake Charles, LA and Beaumont, TX on Thursday morning. The National Hurricane Center is following the eastern edge of this envelope, with a landfall near Lake Charles, LA around sunrise on Thursday. Despite some northerly shear affecting the storm right now, the warm water and humid air over the northwest Gulf should allow Laura to intensify quite a bit before landfall. NHC expects it to reach major hurricane status (Category 3), with sustained winds of 115 mph and gusts to 140 mph.
This storm will be moving into the low-lying bayous of southwest Louisiana. Much of south Louisiana is less than 10 feet above sea level, so storm surge will inundate hundreds of square miles of land, up nearly to I-10 in some areas. Note, in map below, that some areas of south Louisiana will be under 9 feet or more of water, and water will even move into some parts of Beaumont, TX and Lake Charles, LA. Given that the storm is moving fairly quickly, will be strong at landfall, and will not weaken as quickly in southern Louisiana as it would, say, in NW Florida due to the low elevation/storm surge waters, hurricane force wind gusts could reach well inland, including eastern parts of Houston metro and also Alexandria, LA. Tropical storm force winds could reach much farther inland, probably north of I-20. This would include Shreveport, Monroe, and parts of south Mississippi and south Arkansas. This storm will down a lot of trees and power lines over a wide area.
Two other threats with this storm are flooding rainfall and tornadoes. It looks like the heaviest rainfall with the storm will stay near and just east of the center, with rainfall totals of 5 to 10″ from Lake Charles up through Shreveport and Little Rock. Some outer bands could develop and produce locally heavy rain in the very humid atmosphere moving inland from the Gulf over Mississippi and western Alabama, but the flood threat rapidly decreases as you go east of the Mississippi River. Similarly, the tornado threat will primarily be over Louisiana, but can’t be ruled out in the outer bands, primarily in Mississippi.
We are now in the prime part of hurricane season, the next 4 weeks. This will be a significant windstorm over a wide area, with the additional storm surge flooding in south Louisiana and potential flooding from rainfall in Louisiana, Arkansas, and even parts of NW Mississippi and western Tennessee.
Dr. Timothy A. Coleman
Coleman and Knupp, LLC