Hurricane Delta was intensifying over the warm waters of the Gulf of Mexico early Thursday afternoon. It is expected to turn north on Thursday night and make landfall in western Louisiana on Friday afternoon or evening as a category 2 hurricane. A hurricane warning and storm surge warning are in effect from High Island, Texas, to Morgan City, Louisiana, with the storm surge warning extending to Ocean Springs, Mississippi.
On Wednesday night, Delta moved over Scorpion Island, a Mexican national park off the north coast of the Yucatan Peninsula. The island reported sustained winds of 65 mph, gusting to 90 mph, before the station stopped transmitting data at 7 p.m. EDT.
Hurricane hunter aircraft from both NOAA and the Air Force were in Delta on Thursday morning, and reported that the hurricane was steadily intensifying. The central pressure dropped from 973 mb at 2 a.m. EDT to 968 mb at 11 a.m. EDT, and the surface winds increased from 100 to 105 mph. They reported that the large eye of Delta was 40 miles in diameter, and open on the south side. This gap in its eyewall was allowing only slow intensification to occur.
Air Force hurricane hunters based at Keesler Air Force Base in Mississippi evacuated all their planes to Texas because of the threat Delta poses to that state.
The NOAA Hurricane Hunters this season have started delivering significant real-time wave height data to the National Hurricane Center from a Ka-band Interferometric Altimeter (KaIA); the data is being posted here. On Thursday morning, a NOAA hurricane hunter aircraft measured significant wave heights (the mean wave height of the highest third of the waves) of up to 30 feet inside Delta.
Modest damage and no deaths in Mexico from Delta’s landfall
Hurricane Delta made landfall at 6:30 a.m. EDT Wednesday, October 7, near Puerto Morelos, Mexico – 20 miles south of Cancun – as a category 2 storm with 110 mph winds. Delta caused widespread tree damage, power outages, and street flooding in Cancun and the surrounding area. As of Wednesday evening, no deaths or injuries were reported, and property damage appeared to be modest. About 32,000 tourists were relocated to shelters, according to local news site La Palabra Del Caribe.
Track forecast for Delta
There isn’t much mystery about where Delta will make landfall, with western Louisiana squarely in the crosshairs of the storm. Steering of Delta is being controlled by a ridge of high pressure to the storm’s northeast and a trough of low pressure to its northwest.
As Delta heads northwest on Thursday toward the trough, southwesterly upper-level winds will turn the hurricane sharply to the north and then north-northeast, bringing Delta ashore over western Louisiana late Friday afternoon or early Friday evening. The computer models are tightly clustered, giving confidence in this forecast. Delta’s landfall location is likely to be within 50 miles of where devastating category 4 Hurricane Laura made landfall on August 27.
Intensity forecast for Delta
Delta has favorable conditions for intensification through Friday morning. The hurricane will be over warm, deep waters with high heat content, easily capable of sustaining intensification. Ocean temperatures at that point will decrease from 29 degrees Celsius (84°F) on Thursday to 28 degrees Celsius (82°F) on Friday morning, temperatures warm enough to support a category 3 hurricane. Wind shear is predicted to be moderate, 10 – 15 knots, and Delta will be embedded in a moist atmosphere.
Rapid intensification, defined by NHC as a 35-mph increase in winds in 24 hours, is a possibility: The 12Z Thursday runs of the SHIPS-RII and DTOPS rapid intensification models were giving a 12% and 20% chance, respectively, of this occurring. Delta will also expand in size before landfall, with NHC predicting over a 25% expansion in the area experiencing tropical storm-force winds. The expected increase in Delta’s size likely will lead a large section of the U.S. Gulf Coast to experience damaging storm surge at landfall, with NHC predicting a peak storm surge of between seven and eleven feet.
The live storm surge tracker at Trabus Technologies showed that Delta had not yet begun to generate a significant storm surge along the U.S. Gulf Coast early Thursday afternoon, with most tide gauges in Louisiana reporting a storm surge of 0.5 – 1.5 feet.
On Friday afternoon, conditions for intensification will grow more hostile. Ocean temperatures beneath Delta at that point will be 26 degrees Celsius (79°F), the atmosphere will dry to a mid-level relative humidity of 50%, and high wind shear of 20 to 30 knots will affect the hurricane. This high wind shear may be able to inject dry air to Delta’s west into its core, significantly weakening the storm. However, a strong band of upper-level winds to the north of Delta will provide a more efficient upper-level outflow channel as the storm approaches the coast, helping counteract the increased shear. In addition, Delta will be a larger storm better able to resist high wind shear and dry air.
The top intensity models generally predicted with their Thursday morning runs that Delta would be a category 2 hurricane at the time of landfall in Louisiana. Delta will be a highly destructive storm, with significant threats from wind damage, heavy rains, and storm surge. Damages will be limited because Delta will be hitting a relatively sparsely populated portion of the coast.
Louisiana still recovering from Hurricane Laura
Hurricane Laura on August 27 roared ashore in western Louisiana as a mighty category 4 storm with 150 mph winds – the strongest landfalling hurricane in Louisiana history, and the fifth-strongest hurricane on record to make a continental U.S. landfall. Laura brought a storm surge as high as 17.2 feet above dry ground (20 feet above sea level) to Rutherford Beach, Louisiana, ranking as the ninth-highest storm surge on record for the Gulf Coast. In its wake, Laura left 33 people dead in the U.S. and over $10 billion in damage, with Lake Charles, Louisiana, suffering some of the most severe impacts.
An aerial photograph taken on Tuesday, October 6, 2020, by Erik Stratton from Moss Bluff, Louisiana (see Tweet by Lora Perkins) shows a sea of blue roof tarps as far as the eye can see, helping to put into perspective the vulnerability of the city to Hurricane Delta after the devastation wrought by Hurricane Laura. With Delta predicted to make landfall within 50 miles of where Laura did, Lake Charles is at risk that numerous debris piles from Laura heaped up by many road sides could lead to dangerous projectiles. However, Lake Charles is likely to be on the weaker (west) side of Delta’s core, and therefore should experience much lower winds than it did during Laura.
The city of Lafayette, Louisiana, on the stronger right side of Delta’s center, is likely to see much stronger winds than occurred there during Laura. Lafayette Parish, which includes the city Lafayette, has grown rapidly in recent decades. It had an estimated 250,000 people in 2019, compared with just 150,000 in 1980 and 57,000 in 1950.
Flooding on the Vermillion River that flows through the city is a significant concern. A 2020 paper by Civil Engineer Dr. Michael Waldon of the University of Louisiana, Lafayette, found “growing public awareness of the rise in both rainfall-driven and storm surge-caused flood risks within the Vermilion Watershed. These growing risks are the result of a combination of causes including land development, hydrologic changes, rising frequency of intense storms, and coastal land loss.”
What if the name Delta needs to be retired?
According to the World Meteorological Organization, if the name Delta needs to be retired from the list of hurricane names as a result of its impact on Mexico and Louisiana, it would be retired as “Delta 2020” and Delta would continue to be used when the Greek alphabet is needed again.
Bob Henson contributed to this post.
Posted on October 8, 2020 (1:35pm EDT).