Shear Gets Credit for Short Atlantic Hurricanes Thus Far

When it comes to Atlantic hurricanes, brief and ugly is beautiful, at least to Phil Klotzbach, lead author of Colorado State University’s seasonal storm forecast.

That’s because a ragged-looking tropical system that only lasts a few days is an indication that conditions across the basin aren’t helping these storms form or thrive, he said.

That means fewer chances for Florida orange growers, Gulf of Mexico energy operations and homeowners along the East and Gulf coasts to be beaten up by high winds, flooding storm surge and heavy rains. That may also mean Klotzbach’s forecast, calling for a below-average 10-storm season, will stay on track.

“While we’ve had three hurricanes in the Atlantic, they have all been short-lived and rather ugly,” Klotzbach said in a telephone interview earlier this week. “Shear in the Caribbean has also been much stronger than normal so far this year. All in all, I’m pleased with the way the forecast is looking so far this year.”

Here is how it works: shear, when winds blow in different directions or speeds at varying altitudes, can tear at a storm, shredding its symmetry.

A good example of this is Cristobal, which was in such ragged shape a few days ago that it took a reconnaissance flight to discover it was even a hurricane, Weather Underground’s Jeff Masters wrote in his blog earlier this week.

“These missions proved the value of the hurricane hunter flights, since there is no way that we would have known Cristobal was a hurricane based on satellite data,” said Masters, who’s based in Ann Arbor, Michigan. Masters himself flew on those missions a few decades back.

There is another piece to all of this. The shear that kept hurricanes Arthur, Bertha and Cristobal short and ugly has almost certainly killed off a few other potential storms before they could even form in the steady string of African waves that drift across the Atlantic every summer.

To see evidence of this, look at what happened to some waves this year when they kept marching west until they crossed Central America and emerged in the eastern Pacific Ocean, where sea surface temperatures are warm and there’s much less shear than in the Atlantic.

The eastern Pacific has had 13 named storms since its season began on May 15. The average is 15, and the season doesn’t end until Nov. 30.

A couple of those storms have been real monsters, including Hurricane Marie, which exploded into a Category 5 system, the strongest there can be, on the five-step Saffir-Simpson scale. Luckily, it went out to sea.

The Atlantic season starts on June 1 and ends at the same time as the Pacific’s. There have to be nine more storms to match the basin’s 30-year average of 12.

“Obviously, we’ve still got a long way to go,” Klotzbach said.