Rainy September also opens door for tropical systems

HARLINGEN — The annual weather pattern in the Rio Grande Valley which makes September our wettest month comes with a catch.

The rise of the Bermuda high and the fading of the summertime high pressure ridge over West Texas called La Canicula create a friendly path for what meteorologists call “peak tropical moisture” to flow from the Gulf of Mexico and into South Texas.

In the Valley, September rains account for about one-fifth of our annual precipitation total, with Brownsville averaging 5.91 inches, Harlingen 5.28 inches and McAllen 4.49 inches.

But like the doggie door off the kitchen, sometimes you’re never quite sure what’s going to come through the flap.

The ‘puzzle pieces’

Since 1950, 36 hurricanes or tropical systems bulls-eyed the Texas gulf coast in September, which is more than one-third of the total number of storms which have made landfall in that time.

August is second with 21 storms making landfall in that period, and October is third with 14 storms.

The usual atmospheric conditions which allow so much precipitation to reach the Valley each September also create favorable conditions for tropical systems to punch northward and hit the Texas gulf coast.

“The predominant atmospheric steering would come around the Bermuda high, deep into the tropics such as the Caribbean and the southern Gulf of Mexico, and bring what’s called deep tropical moisture high into the atmosphere across not only South Texas but also into much of northeastern Mexico,” Barry Goldsmith, warning coordination meteorologist with the National Weather Service in Brownsville, said in a recent interview.

“Our daily rainfall gets as high as two-tenths of an inch a day when we get into the peak of the hurricane season which is Sept. 10,” he continued. “That’s because we re-orient these atmospheric players, or puzzle pieces, or ridges and troughs of high and low pressure, to a place that allows that door to open up for that deep tropical moisture to come on into the Rio Grande Valley.”

La Canicula and ‘Veracruisers’

La Canicula’s impact on South Texas goes far beyond keeping our summers hot and dry.

When it comes to tropical cyclones, the high pressure ridge which squats on its haunches over West Texas, New Mexico and northern Mexico and refuses to budge, tends to prevent tropical storms and hurricanes from reaching the Valley in June, July and August.

Since hurricanes and tropical storms are very low pressure areas which have no steering mechanism, they’re in effect pushed around by high pressure areas like La Canicula. In the Valley, that means tropical systems driving westward typically make landfall to the south, in the vicinity of Veracruz, Mexico.

Meteorologists even have a name for hurricanes which occur in this pattern — “Veracruisers.”

An example of this classic tropical cyclone pattern occurred this year with Hurricane Franklin, a Category 1 storm.

Franklin came out of the Caribbean, sputtered over the Yucatan Peninsula, and was resurrected in the Bay of Campeche.

Instead of drifting toward Texas, the prevailing high pressure in the region, La Canicula, was still in full force in the first week of August, and this helped suppress Franklin from making a turn northward. Instead, the storm made landfall 500 miles south of Brownsville near Lechuguillas in Veracruz state on Aug. 10.

Harvey threads needle

By the time Hurricane Harvey was skirting South Padre Island to the east, La Canicula had retreated in West Texas, which created an atmospheric opening the storm could exploit.

“What Harvey was, we call serendipity,” Goldsmith said. “I call it the threading of the needle.”

“I like to use a hockey analogy, I’m a big hockey fan,” Goldsmith said, “and goalies have their five hole (between the legs), which is one of the holes in their armor where the pucks can somehow find their way through.

“Well, Harvey found that five hole,” he added. “He was able to squeeze between the ridge that was extending westward from Florida and there was another ridge that was the Canicula ridge, that had kind of retrograded back a little farther west, and in between was a gap.

“It went right into that little thin gap,” Goldsmith said.

Latest on rain, tropics

The September rains on Labor Day were hit and miss across the Valley, with Brownsville recording an official airport reading of .12 inches yesterday, Harlingen had .06 inches and McAllen was left with just a trace.

Some areas of Brownsville and Harlingen received far greater rainfall totals than the official totals as thunderstorms punched quickly and moved on from neighborhood to neighborhood.

In the Bay of Campeche, a disorganized trough of low pressure continues to persist as of late yesterday afternoon.

Erin Billings, a meteorologist at the National Weather Service in Brownsville, said the so far unnamed cluster of rain in a low-pressure system has a 40 percent to 50 percent of becoming better organized by the end of the week.

“Basically, what’s out there is a trough of low pressure over the southwest Gulf of Mexico,” she said yesterday. “It isn’t a very organized system at all, and the conditions are marginally conducive for some slow development and it’s expected to drift west-northwest over the southwestern Gulf of Mexico over the next few days.

“We’re keeping an eye on it, as always,” she added.

Late yesterday afternoon, Billings said Hurricane Irma was upgraded to a Category 4 hurricane and was strengthening as it approached the Leeward Islands in the Caribbean.

“The hurricane center is really keeping a close eye on that, and basically through the next five days the way this tracks it kind of moves it just north of Cuba,” Billings said.

Forecast models, called spaghetti models due to their appearance, almost unanimously indicate Irma will turn northward toward Florida later in the week. The hurricane poses no threat to the Texas gulf coast.

Rest of the season

The National Hurricane Center revised its initial Atlantic hurricane prediction for 2017 to a final forecast of 14 to 19 named storms, with five to nine being hurricanes, and between two and five of those becoming major hurricanes of Category 3 and higher.

As of Sept. 1, nine named storms, four hurricanes and two major hurricanes have occurred, which puts the actual season pretty close to the hurricane center’s revised forecast issued June 30.

“And while the Accumulated Cyclone Energy Index was rising steadily thanks to Harvey and especially Irma, the steering pattern will ultimately determine what, if any, impacts are experienced in the Rio Grande Valley into early October, when the season effectively closes down here,” meteorologists at the NWS in Brownsville wrote on their website.

“Another ‘Veracruiser’ is quite possible – and as always, the ability of pockets of wind shear and dry air to disrupt cyclones can be an issue as we get deeper into autumn,” they added.

South Texas-Northern Mexico storms 1950 to present

• June 15, 1958 – Tropical Storm Alma makes landfall on northeastern Mexico 70 miles south of Brownsville. At South Padre Island tides reach 2.9 feet. Rainfall peaks in McNeely Ranch in South Texas at 9.50 inches. Flooding causes substantial crop and structural damage. One person drowns near Galveston.
• Sept. 6, 1958 – Hurricane Ella makes landfall in southern Texas near Corpus Christi with winds of 45 mph.
• June 23, 1960 – Tropical Storm One of 1960 hits 30 miles south of Corpus Christi, Texas as a 45-mph storm. The storm loops over South Texas, dumping heavy rain. It moves slowly northward, and eventually dissipates over Illinois. Though weak, the storm causes $3.6 million in damages and 15 deaths.
• Sept. 20, 1967 – Hurricane Beulah makes landfall just north of the mouth of the Rio Grande as a Category 3 storm. Highest sustained wind is reported as 136 mph, recorded on South Padre Island, about 20 miles north of Port Isabel. The Lower Rio Grande Valley is inundated with torrential rains and strong winds. Gusts of over 100 mph are recorded as far inland as McAllen, Edinburg, Mission and Pharr. Beulah is a record tornado-producer (a record that would stand until 2004) that destroys homes, commercial property and inflicts serious damage on the region’s agricultural industry. South Padre Island suffers significant devastation. Within a 36-hour period it drops almost 30 inches of rain. Beulah causes an estimated $1.1 billion (in 2000 dollars) in damage. Sources report 58 or 59 deaths from the storm.
• Aug. 3, 1970 – Hurricane Celia of 1970 makes landfall in Texas. Celia kills 20 people due to extreme gusts, and causes hundreds of millions of dollars in damage. The storm produces microbursts, which are rare in a tropical cyclone. One person in Corpus Christi is killed and 460 injured.
• Aug. 31, 1975 – Hurricane Caroline of 1975 makes landfall 100 miles south of Brownsville.
• Sept. 2, 1977 – Powerful Hurricane Anita attains peak winds of 175 mph and makes landfall in eastern Tamaulipas as a Category 5 hurricane. It quickly weakens as it crosses Mexico, and after briefly redeveloping into a tropical depression in the eastern Pacific Ocean, Anita dissipates two days later.
• Aug. 10, 1980 – Hurricane Allen makes landfall near Brownsville as a Category 3 hurricane. A wind gust of 140 mph is reported in Port Mansfield. Heavy rainfall is reported across South Texas, with a peak of 20.2 inches in Kingsville. Nearly all structures on South Padre Island are destroyed.
• Aug. 28, 1983 – Hurricane Barry, a Category 1, makes landfall just south of Brownsville and forces the evacuation of 4,000 people, but causes only minor damage.
• Sept. 17, 1988 – Hurricane Gilbert makes landfall in northern Mexico with winds of 135 mph and causes tides to rise up to 5 feet above normal. As a result, beach erosion is reported on South Padre Island.
• June 20, 1993 – Tropical Storm Arlene makes landfall near South Padre Island. Heavy beach erosion occurs as a result of the storm. Arlene causes $55 million in damage and its flooding rains kill one person.
• Aug. 12, 1995 – Tropical Storm Gabrielle makes landfall just south of the Texas–Mexico border as a strong tropical storm, producing rainfall in southern Texas and peaking at 6.26 in Weslaco.
• Aug. 23, 1996 – Hurricane Dolly makes landfall near Tampico, Mexico. The storm causes beneficial rainfall in southern Texas, peaking at 5.53 in Corpus Christi, providing drought relief to the area.
• Aug. 23, 1999 – Hurricane Bret makes landfall as a Category 3 hurricane on South Padre Island, becoming the first major hurricane to hit Texas since Hurricane Alicia in 1983. Heavy rainfall occurs across South Texas, reaching 13.18 inches Sarita.
• Aug. 16, 2003 – Hurricane Erika makes landfall in the Mexican state of Tamaulipas as a minor Category 1 hurricane, causing minor coastal damage and beach erosion in parts of South Texas.
• July 20, 2005 – Hurricane Emily makes landfall in Tamaulipas, Mexico, providing rainfall to drought-affected areas of South Texas. Rainfall peaks at 5.2 inches in Mercedes.
• July 23, 2008 – Hurricane Dolly makes landfall at South Padre Island with winds near 100 mph. A storm surge of 4 feet is observed across much of the Texas coast. Dolly’s remnants cause coastal and inland flooding and over 12 inches of rain in some locations, peaking at 15 inches in Harlingen. On South Padre Island, moderate structural damage, mostly to roofs, is reported. Tree and utility pole damage is widespread across Cameron County. Widespread power outages are reported across South Texas.
• June 30, 2010 – Hurricane Alex makes landfall at Soto la Marina, Tamaulipas in Mexico as a large Category 2 hurricane, bringing heavy rains, wind and tornadoes to South Texas.
• July 8, 2010 – Tropical Depression Two makes landfall on South Padre Island, dropping 1 to 3 inches of rain in South Texas.

Note: Wikipedia list consists of major storms to hit from Corpus Christi south into northern Mexico.