A Doppler weather radar was taken off-line by the storms of April 27, 2011, making accurate reporting for Chattanooga and the surrounding area more difficult.
Power outages earlier in the day hindered communications and warnings in some counties.
The April 27 storms didn't just cause unprecedented chaos and destruction, they also helped to change National Weather Service procedures - including the wording used in warnings and backup plans for weather service offices affected by storms.
Those changes came after a multiagency team evaluated the storm forecasts and investigated why so many people were killed in the storms. In December, the team issued 24 recommendations to improve weather service performance, improve safety and build outreach programs.
One key finding was the warnings used by the Weather Service were too generic and did not emphasize how catastrophic the approaching storms could be.
"People were not aware that the forecasts for this event were different from others," the report says.
Gary Woodall, meteorologist in charge at the Phoenix National Weather Service office and one of the team leaders assessing the storms, said information from the April 27 storms and the Joplin, Mo., tornado on May 22 had very similar findings about the warnings.
Using wording such as "Doppler radar indicated" when spotters already reported there were large destructive tornadoes on the ground diluted the impact of the warnings, the report noted.
"There are limits to the science, but we are adjusting the language to make it more specific," Woodall said.
Five National Weather Service offices in Kansas and Missouri will use the new wording this year - phrases that include "catastrophic damage" and "a severe threat to human life" for the worst storms.
Woodall said the service will evaluate the warnings to see if they then will be implemented nationwide, possibly as early as next year.
One of the most significant events that impacted the tri-state forecasts on April 27 was when the Doppler radar near Hytop, Ala., failed due to infrastructure damage, going off-line soon after 6 p.m. EDT, just as the worst storms first hit.
The radar would have provided the best low-level information, which hampered predictions from the weather service office in Morristown, Tenn.
"The Morristown office still did a really great job with the warnings, but it did prevent them from knowing what was going at the very low levels of the storm," Woodall said.
The report recommends putting in place a back-up fiber-optics link between the radar and the prediction office.
The report also praises the Peachtree City, Ga., office for monitoring reports coming from 911 centers, giving them real-time notifications of emergency dispatches.
More offices have begun to implement that practice, Woodall said.
The report notes that people were more likely to take shelter when they received warnings from several sources, such as television, the weather service and family or friends.
Some National Weather Service offices are telling people to "phone a friend, save a life" as part of awareness campaigns, Woodall said.
DeKalb County, Ala., was one of the areas most affected by earlier power outages, a fact that officials there believe may have contributed to the deaths of 35 people in the county.
Rainsville City Councilman Bejan Taheri has been one of the more vocal proponents of the county having better backup systems in place, saying he thinks many of those killed had no warning.
Jason Heard, Ider Rescue Squad captain, agreed that a lack of warning because of power outages may have played a role.
"They didn't have a clue [the tornadoes were coming]," Heard said. "Nobody had battery-powered radios."
Woodall said the assessment underscores the need for multiple warning systems such as battery-powered weather radios and even battery-powered TVs.
"You need to have a variety of sources," he said. "We will always be trying to out-guess Mother Nature, but we try to make changes to improve."