UAH to make detailed study of deadly April 27 tornadoes

• HUNTSVILLE, Ala. (July 11, 2011) -- Scientists at The University of Alabama in Huntsville are organizing a research program to better understand the deadly outbreak of tornadoes that killed more than 240 people in Alabama and other Southeastern states on April 27.
  
  Supported by a one-year, $150,000 grant from the National Science Foundation (NSF), the UAHuntsville team will analyze radar data from that day, then merge that information with detailed storm surveys and other data. They want to learn more about how the storms formed, what made that day's storms so
  unusually powerful, and what might be done to make tornado warnings more effective.
  
  In addition to studying the physics of the storm, the team will also look at
  the psychology and sociology of storm warnings. A graduate student from the
  University of Oklahoma, UAHuntsville student volunteers and faculty are
  interviewing survivors to learn more about how and when people reacted to
  that day's repeated tornado warnings.
  
  "One thing we're after is whether people are desensitized because the false
  alarm rate is so high, especially in counties where there are only
  countywide alerts," said Dr. Kevin Knupp, who leads UAHuntsville's severe
  weather research team.
  
  Data compiled by UAH post-doctoral student Tim Coleman shows that there has
  been about a ten-fold increase in warnings between Memphis, Atlanta and
  Tallahassee since the Weather Service installed the NEXRAD Doppler radar
  system, and that about 80 percent of all warnings are "false."
  
  The increase in warnings is due in large part to the NEXRAD radar's ability
  to spot "rotation" inside a storm system. Installed between 1993 and 1997,
  the five NEXRAD radar units in Alabama are also better at detecting small
  tornadoes than the previous system: In the years since NEXRAD was installed,
  the number of small tornadoes (EF-0 and EF-1) documented by the National
  Weather Service in Alabama has increased almost threefold, while the number
  of larger tornadoes has stayed roughly the same.
  
  "Before NEXRAD we didn't know these rotational elements along squall lines
  were so prevalent," Knupp said. "If a small tornado didn't cause property
  damage or wasn't reported, we might never know about it. Now we can see the
  rotation, pinpoint the location, then go out afterward and look for damage
  to confirm that there was or was not a tornado on the ground."
  
  The UAH survey team is trying to determine 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 or more 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."
  
  In their analysis of the storm data, Knupp and his team will use data from
  the NWS NEXRAD between Huntsville and Chattanooga, a dual-polarimetric
  Doppler radar at the Huntsville International Airport, and UAHuntsville's
  own mobile dual-polarimetric Doppler, which on April 27 was stationed
  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 that day," Knupp said.
  "We had a full spectrum of storms that day and it seemed that almost every
  storm was forming 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."
  
  NSF is funding this project through a Rapid Response Research (RAPID) grant,
  which enables support for fast-response research tied to events such as
  tornadoes.
  
  "Heavily forested rolling terrain and limited public awareness may present
  unique challenges to tornado detection in this area, as well as to
  widespread dissemination and effective public response to severe weather
  warnings," said Brad Smull, program director in NSF's Division of
  Atmospheric and Geospace Sciences, which funded the RAPID award.
  
  The dual polarimetric radars also picked signs of debris being thrown into
  the sky by tornadoes, Knupp said. "The Cullman 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 at Google Earth 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 was we saw in the radar
  with what was being churned up by the tornado."
  
  The detailed radar and surface data will also help the 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, including
  track of the tornado that went through Hackleburg and Phil Campbell.
  
  "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, I saw a heavy cast iron bathtub that was upside down and
  completely disconnected from its plumbing. That was obviously not
  survivable.
  
  "I 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."

• Radar impage from the National Weather Service Hytop (KHTX) radar at 6:34 a.m. CDT (1134 UTC), showing a large mesoscale cyclonic circulation and its associated banded structure. This circulation feature was associated with 15 EF-0 to EF-2 intensity tornadoes.

  Radar reflectivity from the UAH Advanced Radar for Meteorological and Operational Research (ARMOR) showing reflectivity curls associated with cyclonic circulations near the leading edge of a squall line at 1:23 p.m. CDT (1623 UTC). These circulations were directly associated with 7 EF-P to EF-2 tornadoes.

  ARMOR radar reflectivity showing the parent supercell storm at 3:33 p.m. CDT (2022 UTC).

  ARMOR radar reflectivity showing multiple tornado supercell storms at 4:30 p.m. (2130 UTC).

  Damage near Tanner, AL, from the EF-5 tornado that also hit Phil Campbell and Hackleburg, AL. The concrete slab of a small house, foreground, and the area surrounding the slab were wiped clean of most debris. (Photo by Kevin Knupp)

  Dr. Kevin Knupp monitors instruments launched aboard a helium balloon into violent storms on April 27. (UAH/ESSC photo)