Alphabetical Anomaly

At the intersection of mythology and meteorology lies a South Texas weather pattern that has been observed for more than 50 years, earning it a Farmer’s Almanac-type authenticity in the collective imagination.

Since 1953, when the National Hurricane Center began naming storms, all hurricanes to strike the state’s southern Gulf Coast have had names that begin with A, B or C.

But the phenomenon is no mere coincidence, say weather experts who point to science and geography to explain the alphabetical anomaly.

“Climatology plays a role in it,” said Dennis Feltgen, a Florida-based spokesman for the National Hurricane Center. “The prevailing (storm) tracks in the first half of the season — when the first several names on the list would be used — carries the storms toward Texas.”

Feltgen explained the probability of hurricanes or tropical storms threatening the Rio Grande Valley depends largely on the region’s place in the world.

“(The Valley’s) geographic location plays a role in the number of storms the area will experience,” he said. “The return frequency of a hurricane in this region, of at least Category 1 intensity, is once every 14 to 15 years.”

“Major” storms, Category 3 or better, can happen “once every 44 to 46 years,” Feltgen said.

“The frequency is higher along the northern Texas coastline,” according to the NHC.

Nezette N. Rydell, head meteorologist at the National Weather Service in Brownsville, explained the pattern like this: “Part of that is circumstance and part of that has a reason.”

“Sometimes it’s just chance.”

The Valley has not seen a direct hit from a major storm since Hurricane Beulah, a Category 3, made landfall between Brownsville and the mouth of the Rio Grande this week in 1967.

Hurricane Allen, a Category 5, hit north of Brownsville in August 1980. Hurricane Bret came ashore in 1999 near South Padre Island as a Category 4.

“Where storms form depends on the time of the year,” Rydell said. “They can form anywhere, anytime, but on average (they form) early in the season.”

The Atlantic hurricane season — the period encompassing all but a small fraction of the Atlantic’s tropical storm activity — officially runs from June 1 to Nov. 30.

“(In) June more storms tend to form in the Gulf (of Mexico) than out in the open Atlantic,” Rydell said.

The Gulf’s warm, shallow water feeds hungry storms.

“The water warms up faster (in the Gulf),” she said. “You need warm water for a hurricane.”

Almost four months into the 2007 Atlantic hurricane season, the Valley so far has been spared any tropical storm activity:

— Tropical Storm Erin threatened the Valley in August but eventually drifted north and made landfall near Lamar, Texas.

— Later the same month, Hurricane Dean was projected to come ashore near Brownsville but turned toward the Yucatan Peninsula.

— Hurricane Felix showed little chance of threatening the Texas-Mexico border and instead hit Nicara

gua early this month.

— And just last week, early Thursday morning, Category 1 Hurricane Humberto struck the Texas coast, but the storm’s main impact was well north of the Valley, in Galveston, Jefferson and Orange counties.

Geographic location and time of the year aren’t the only predictors of the Valley’s likelihood of taking one on the chin.

“You also have some other things going on,” Rydell said.

“You’re still getting some weak cold fronts down (here) that provide a little surface focus — you know, things that help get those hurricanes started.”

It’s typical in June for the Valley to see, if not feel, weak cold fronts move through the area.

“A surface boundary or focus sometimes can play a part (in storm tracks),” she said.

But water temperature is still the most critical factor in the birth of a storm.

For a tropical depression to form, “water must be 28 degrees centigrade or 82.4 degrees Fahrenheit, or warmer,” Rydell said. “Out in the middle of the Atlantic in June, it’s still too cool.”

Those conditions exist in the Gulf early in the season, coinciding with the names at the top of the National Hurricane Center’s naming roster.

“By the time you get to August you are in the H’s,” Rydell said.

So can Valley residents rest easy once the storm list is in the D’s?

“That’s a myth” Rydell said. But “there are rules of thumb. Â… Once we get our first cold front through here, our chances of a hurricane, while not zero, are pretty small.”

When cold weather develops, “the weather patterns have shifted. And it’s very hard for the tropics to re-establish themselves.”

The first cold front usually makes its way through the Valley in the first or second week of October, cooling off the Gulf in the process.

“And then we are safe, usually, until next year,” Rydell said. “Usually.”

The A, B, C of it

Hurricanes that have made landfall along the Texas coastline, south of Corpus Christi, or have been a direct threat to the Rio Grande Valley since 1953 have had a name that starts with A, B or C. Before 1953, the National Hurricane Center did not name storms.

Aug. 9, 1980

ALLEN made landfall north of Brownsville as a Category 5 hurricane.

Sept. 20, 1967

BEULAH made landfall between Brownsville and the mouth of the Rio Grande as a Category 5 hurricane.

Aug. 23, 1999

BRET made landfall near South Padre Island as a Category 4 hurricane.

Sept. 11, 1961

CARLA made landfall between Port O’ Connor and Port Lavaca as a Category 5 hurricane.

Aug. 3, 1970

CELIA made landfall near Corpus Christi as a Category 5 hurricane.

Source: National Hurricane Center