Understanding deadly tornadoes

might never know about it. Now we can see the rotation, pinpoint the location, then go out afterward and look for damage to confirm whether there was or was not a tornado on the ground.”

The UAH survey team is learning more about how the public judges the threat of dangerous weather.

“Did people perceive these tornadoes as dangerous?” Knupp asked. “There were tornado watches posted hours before the storms hit, and some of the tornado warnings went out 15 or 20 minutes in advance.

“Did people dawdle because they thought there was no need to rush to take shelter? It apparently takes visual images to make some people react. Of course, if we need pictures of an approaching tornado to make people take shelter, then we’ve got a problem.”

The release notes that in their analysis of the storm data, Knupp and his team are using data from the NWS NEXRAD between Huntsville and Chattanooga, Tenn.; a dual-polarimetric Doppler radar at the Huntsville International Airport and UAH’s own mobile dual-polarimetric Doppler that on 2 April was between the two stationary radars.

“Since we have three radars, we can reconstruct the wind field in detail for each of the cells and squall lines that moved through,” Knupp said. “We had a full spectrum of storms, and it seemed that almost every storm formed a tornado.”

The radar data will be compared to detailed aerial reconnaissance of the tornado tracks.

“The damage path is really the fingerprint of the tornado,” Knupp said. “That is why it was so urgent to do this reconnaissance quickly, before the cleanup or re-growth could erase the clear tracks.”

The dual polarimetric radars also picked signs of debris being thrown into the sky by tornadoes, Knupp said. “The Cullman [Alabama] storm had very high reflectivity up to 20,000 feet. That was debris being lofted to 20,000 feet. These storms were very efficient at that.

“We will look to see what was in those areas before the storms hit. Was it metal buildings, a residential area, forest or fields?” he asked. “We can use that information to relate what we saw in the radar to what was being churned up by the tornado.”

The detailed radar and surface data will also help scientists determine whether other factors, such as surface roughness, topography or gravity waves, played a role in forming or strengthening tornadoes.

Knupp assisted with the NWS surveys of the April storm tracks.

“I talked to one woman who took shelter in her bathtub,” he recalled. “Her house went one way and her tub went another. There was a post that pierced the tub, but she walked away from it.

“In Hackleburg [Alabama], I saw a heavy cast iron bathtub that was upside down and completely disconnected from its plumbing. That was not survivable.”

Knupp was surprised at the relatively large number of storm shelters in the area, even those that were just storm pits — “a mound of dirt with a door facing north or south,” he said. “There have been reports that some people were fearful of getting into their storm shelters due to a fear of snakes or spiders.

“Let me tell you, I have a near-phobia of spiders, but I would get into a storm pit if there was a tornado warning.”