Friday, March 16, 2012

How strong was Charlotte's tornado?

The tornado that touched down two weeks ago Saturday morning in the Reedy Creek area of northeast Charlotte has triggered a lot of conversation, behind the scenes, by meteorologists not only locally but across the nation.

While the somewhat unusual conditions that accompanied the tornado likely will spur some research papers, a more interesting question has surfaced:

How strong was the tornado? Or more specifically, was it really stronger than an EF2.

Larry Gabric, chief meteorologist at the National Weather Service's office in Greer, S.C., and the office's warning coordinator, Tony Sturey, visited the tornado site -- a 3.8-mile stretch from near Reedy Creek Elementary School to the Steeple Chase subdivision along the Mecklenburg-Cabarrus line -- several hours after the storm hit.

Gabric and Sturey surveyed the damage and decided it was an EF2, with top winds of a bit more than 130 mph. That rating is on the Enhanced Fujita scale, than runs from EF0 (the weakest) to EF5.

Some of the TV meteorologists in the Charlotte area, and their counterparts elsewhere, asked if the storm might have been an EF3. They pointed to some of the damage -- specifically, a house blown off its foundation; and a house losing its second story -- and said it was more typical of what you'd see in an EF3 storm.

Even Greg Forbes, the severe weather specialist at the Weather Channel, weighed in. Forbes didn't visit the area and certainly wasn't second-guessing Gabric and Sturey, but he said (based on what he was told) that it sounded like EF3 damage from winds of 145 to 150 mph.

Gabric and Sturey are sticking with their guns, however, saying the overall damage in the area is more consistent with the 130 mph winds.

Granted, to the people who lost their homes or had them heavily damaged, it seems trifling to quibble over the strength of the tornado. This is a scientific issue, but an EF3 rating would have been interesting, because since 1950 -- the start of the data base kept by NOAA -- there has not been a tornado stronger than an EF2 recorded in Mecklenburg County.

Mike Dross, a former Duke Energy meteorologist who operates the Wright-Weather website, notes that the scenario could have been much worse.

"Had this cell developed the tornado about 10 minutes earlier, it would have touched down near uptown Charlotte," he said. The amount of damage, Dross said, would have multiplied several times.

The March 3 tornado remains an interesting topic to meteorologists.

It formed from a thunderstorm with cloud tops of about 35,000 feet -- relatively shallow, compared to the 55,000-foot storm tops in the supercells that produced killer tornadoes March 2 in the Midwest and South. And the tornado developed in an area that had been locked in a cool and relatively stable air mass for much of the preceding 24 hours.

The March 3 tornado in Mecklenburg and Cabarrus counties will provide research material for the meteorologists who have studied this storm -- Dross, WCNC's Brad Panovich, WBTV's Eric Thomas and Al Conklin, and News 14's Jeff Crum, among others.