Hurricane Nate Slams the U.S. Gulf Coast, Spawns Southeast Tornadoes After Flooding Parts of Central America (RECAP)

Hurricane Nate became the fourth hurricane to landfall in the U.S. in a frenetic 45-day stretch of the 2017 Atlantic hurricane season, producing storm-surge flooding and damaging winds along the northern Gulf Coast after triggering deadly flooding in Central America, and then spawning tornadoes in the Carolinas as it raced inland.

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Nate made a pair of Gulf Coast landfalls, both as a Category 1 hurricane, first near the mouth of the Mississippi River in southeast Louisiana on Oct. 7, then near Biloxi, Mississippi, just after midnight on Oct. 8.

Storm-surge flooding swamped parts of the surge-prone northern Gulf Coast, from southeast Louisiana to Mississippi, Alabama and the Florida Panhandle.

Particularly hard-hit was the Mississippi Gulf Coast, where a storm surge of 6.3 feet was recorded at Pascagoula, Mississippi, the highest measured anywhere along the Gulf Coast. 

Surge flooding pushed over Dauphin Island, Alabama, and piled into Mobile Bay, with water levels reaching roughly 5.5 feet above normal high tide at Mobile, Alabama (Coast Guard station), and 5.8 feet above normal high tide at Bayou La Batre, Alabama.

Water levels also topped out just over 4.5 feet above normal high-tide levels at Shell Beach, Louisiana.

Tropical-storm-force wind gusts were observed over parts of the Gulf Coast from Mississippi and Alabama to the Florida Panhandle on Oct. 8, then pushed well inland over the Southeast.

Here are some peak wind gust reports from Nate:

• Calvert, Alabama: 75 mph
• Pascagoula, Mississippi: 70 mph
• Mobile, Alabama: 66 mph
• Destin, Florida: 58 mph
• Gulfport, Mississippi: 52 mph

Among some of the notable wind damage or power outage reports included:

• Clay County, Alabama: Numerous trees down blocking roads, numerous power outages in northern and western parts of the county
• Highlands, North Carolina: Numerous power outages
• Tallapoosa, Georgia: One injured from a large tree downed on a building

Nate spawned 10 confirmed tornadoes from Alabama to North Carolina, including at least one waterspout near Gulf Shores, Alabama, in the hours prior to landfall on Oct. 7.

Four tornadoes were confirmed in upstate South Carolina from Oct. 8 – an EF0, an EF1 and two EF2 tornadoes. Twenty homes were damaged in Pickens County, South Carolina.

Near Valdese, North Carolina, multiple homes were damaged with people trapped in structures. Several roofs of houses were lost in Liberty, South Carolina, and significant damage to houses was also reported near Laurens, South Carolina.

In addition to the Gulf Shores waterspout, another four tornadoes were confirmed in central Alabama, all EF0 or EF1.

Here are the highest rainfall totals from Nate:

• 11.62 inches in Great Falls, North Carolina
• 11.17 inches in Bear Creek, North Carolina
• 10.48 inches in Hogback, North Carolina
• 9.37 inches in Highlands, North Carolina
• 8.32 inches in Crestview, Florida
• 6.99 inches in Milton, Florida
• 6.95 inches in Slidell, Louisiana
• 6.94 inches in Dixon, Alabama
• 6.54 inches in Foley, Alabama
• 6.12 inches near Greenville, Kentucky
• 5.48 inches at Anna Ruby Falls, Georgia

Nate's Early History

Hurricane Nate originated on the eastern end of a larger feature, called a Central American gyre (more on that below).

The tropical depression was then upgraded to Tropical Storm Nate on Oct. 5 based on radar data from San Andrés, an island east of Nicaragua, indicating a partial eyewall, and a surface pressure measurement over Nicaragua found to be lower than previous advisories. Nate moved ashore over northeastern Nicaragua and eastern Honduras later that day. 

On Oct. 6, Nate accelerated through the northwestern Caribbean and through the Yucatan Channel while organizing and intensifying. A wind gust of 52 mph was reported in Isabel Rubio in western Cuba as Nate shot the goal posts between the Yucatan and Cuba. A hurricane hunter mission reported a building eyewall in Nate's eastern semicircle. 

According to The Weather Channel senior meteorologist Stu Ostro, Nate then met the criteria for rapid intensification by the morning of Oct. 7, as Nate moved through the Gulf of Mexico.

Nate appeared to reach its maximum Category 1 intensity with 90-mph sustained winds and a central pressure of 981 millibars just hours before its first southeast Louisiana landfall, according to the National Hurricane Center, then lost a bit of intensity as it was moving into the Gulf Coast. 

One thing notable was Nate's impressive forward speed, a record for a Gulf of Mexico hurricane, according to the National Weather Service.

Prior to its U.S. impact, the overall Central American gyre that Nate was embedded in triggered deadly flooding in parts of Nicaragua and Costa Rica.

What Spawned This? More on Central American Gyres

This "gyre" is a large, broad area of low pressure over the Central American isthmus and western Caribbean Sea. This feature can lead to the development of a tropical cyclone in the Caribbean Sea and/or in the eastern Pacific Ocean.

These gyres most often form in the late spring and early fall, when cold fronts become uncommon in this region of the world. They're most common in September, but can be a source of tropical storms and hurricanes into November, and as early as May.

We typically see up to two gyres like this one set up each year, and they can spawn tropical storms in both the Atlantic and eastern Pacific basins, sometimes in each basin at the same time. Not all gyres produce tropical cyclones, but they all produce heavy rainfall.

Roughly 50 percent of Central American gyres have a tropical cyclone associated with them, according to Philippe Papin, Ph.D. candidate at the University of Albany. "When a tropical cyclone does occur, it tends to form on the eastern side of the [gyre] and rotates counterclockwise around the larger circulation." 

Gyre-like tropical systems are much more common in the western Pacific closer to southeast Asia, where the monsoon plays a larger role in the weather.

A notable example of gyre-induced tropical cyclone formation occurred in 2010 when Tropical Storm Nicole formed just south of Cuba from the gyre in late September.

Nicole was a short-lived and ill-formed tropical storm that tried to cross Cuba. It brought heavy rain to the Cayman Islands, Jamaica, Cuba and portions of South Florida.

Hurricane Stan in 2005 is another good example of a hurricane's interaction with a Central American Gyre, according to Papin.

Following Stan's dissipation over the mountains of central Mexico, its remnant spin became part of a larger gyre that caused heavy rainfall over Central America. While Stan's direct circulation resulted in around 80 deaths, according to the National Hurricane Center, heavy rainfall resulting from the gyre took more than 1,000 lives across Central America. 

Other examples include Tropical Storm Andrea (2013), Hurricane Ida (2009 – assist from the gyre) and Hurricane Patricia (2015 – assist from the gyre, not a direct result).

PHOTOS: Hurricane Nate