Hurricane Dolly, Busy July Suggest Stormy Months Ahead

Willie Drye
for National Geographic News

July 23, 2008

As a strengthening Hurricane Dolly heads for landfall today near the Texas-Mexico border, some meteorologists see indications that the rest of this year's hurricane season could be very active.

As of noon eastern time today, the center of Hurricane Dolly was about 35 miles (48 kilometers) northeast of Brownsville, Texas.

The storm's strongest winds were blowing at about 96 to 110 miles (154 to 177 kilometers). That makes Dolly a Category 2 storm on the Saffir-Simpson scale, which rates hurricanes from 1 to 5 based on the damage they are likely to cause.

Dolly's winds could increase before the storm comes ashore around 1 p.m. eastern time, said Christopher Juckins, a meteorologist at the National Hurricane Center in Miami, Florida.

The storm is over warm water in the Gulf of Mexico—which could allow it to intensify—and there are no upper-level winds that would inhibit its development.

(Create your own interactive hurricane.)

Busy Month

Experts believe Hurricane Dolly's impact will be minimal, because it likely will go ashore in an area that is not heavily populated. Other July hurricanes in past years have been much more powerful than Dolly.

Still, the formation of Hurricane Dolly—as well as Hurricane Bertha and tropical storm Cristobal earlier this month—make July 2008 unusual, meteorologists say.

On July 19, Bertha, Cristobal, and Dolly were all active tropical weather systems, noted meteorologist Jeff Masters of Ann Arbor, Michigan, founder of the commercial forecasting Web site Weather Underground.

That's the first time three named systems have been active on the same day since the practice of naming hurricanes began in 1950, he said.

(Related: "Hurricane Forecasters Stick to 'Busy' 2008 Prediction" [June 3, 2008].)

Meteorologists also use a system called the Accumulated Cyclone Energy Index (ACEI) to calculate the energy produced by tropical-weather systems.

The measurement is based on a storm's wind speed, the duration of those winds, and the duration of the storm. The index can be applied to individual hurricanes, to all hurricanes during a particular month, and to an entire hurricane season.

Although there is more than a week left in July, this month already ranks as the third-most active on record, based on the ACEI, Masters said.

The three seasons with comparable July activity—1916, 1933, and 2005—ended up being three of the most active hurricane seasons on record.
This season's July activity also surpassed that of 1916, which had ranked third until this year.

A storm is considered a major hurricane when it reaches Category 3. Such hurricanes have winds exceeding 110 miles (177 kilometers).

"That does not bode well for the coming season," Masters said.

"All three years—1916, 1933, and 2005—had five major hurricanes. I'd say the odds of more than one major hurricane hitting us are enhanced this year."

Phil Klotzbach, a meteorologist at Colorado State University in Fort Collins, said early-season activity usually isn't an indicator of how the rest of the season will develop—unless storms are already forming in the so-called deep tropics east of Puerto Rico.

And that's what is happening this year, he said.

"When you have storms like Hurricane Bertha—which formed in the deep tropics—that tells you that things are trying to go very early," Klotzbach said. "That tells you that prior to the first of August, things are ripe for formation."

Masters of Weather Underground also noted that Hurricane Bertha was a bizarre storm. It was named on July 3, became a Category 1 hurricane on July 7, and retained its status as a named system until July 20.

Bertha also surprised meteorologists by suddenly intensifying to a Category 3 only a few hours after it reached hurricane status.

In addition, Bertha also developed near the Atlantic Ocean's Cape Verde Islands, the birthplace of some of the most severe storms on record.

These so-called Cape Verde hurricanes don't usually develop until later in the season—making Bertha the earliest Cape Verde storm on record, Masters said.

Anybody's Guess

Not all meteorologists agree that July hurricane data can predict that the rest of the season will be busy.

"A high ACEI may not tell the story of what follows," said Lian Xie, a meteorologist at North Carolina State University in Raleigh. "You can't look at half the season and make a prediction."

Still, Xie acknowledges that this July has been an active month.

He also predicted an active 2008 hurricane season in April and sees no reason to alter his preseason forecast, which says that six to eight hurricanes will form before the season ends November 30.

"We're looking at an active season," Xie said. "How much more active is anybody's guess."