Learning From Past Tornadoes

In Cleveland, OH it is planned for new and improved tornado warnings to be implemented this April so more people will know when to react to storm warnings and potentially save their lives.  Effective warning systems are great ways to prepare communities for the potential disasters tornadoes often bring with them.

New tornado warning system could reduce your risk and save your life

By Mark Johnson, newsnet5.com

CLEVELAND – New enhanced tornado warnings are slated to begin in April to help provide more specific information during severe weather.

The year 2011 proved to be a very deadly one for tornadoes. Last year, in April alone, more than 300 people lost their lives when swarms of tornadoes tore through Alabama, Missouri, Tennessee, Georgia and North Carolina.

But the carnage didn’t stop there. On May 22, one of the deadliest tornadoes in U.S. history struck Joplin, Missouri, killing 159 people and injuring more than 1,000. This was the single deadliest tornado to hit the United States since 1953, when a twister killed 116 people in Flint, Michigan. The tornado was rated an EF-5 on the Enhanced Fujita Scale, with winds more than 200 mph. Residents of this southwest Missouri town had several minutes of advanced warning that the twister was coming. Warning sirens blared through out the town. But, as later studies showed, many did not react immediately to the warnings issued by the National Weather Service.

A National Weather Service (NWS) investigation found that a large majority of Joplin residents did not immediately head for safety when the warning was first issued. They didn’t heed the warnings. Investigators, instead, found that most chose to look for further information or confirmation before assessing the storm risk. In other words, most Joplin residents had to confirm through additional information if there was indeed a tornado heading their way.

So, what caused this hesitancy? It’s all about human nature. If you’ve lived through many false alarms, then you are less likely to respond immediately to the latest severe weather warning.

“Responding to warnings is not a simple act of stimulus-response,” said the report. “Rather it is a non-linear, multi-step, complex process. Relationships between false alarms, public complacency and warning credibility are highly complex as well.”

The assessment team interviewed dozens of survivors, as well as media members, emergency managers, and city officials. There were many different reasons for not heading the tornado warning that day, but most boiled down to that person’s previous experiences with severe weather. For Joplin residents, they had heard the warnings sirens so often, they stopped taking it seriously.

“This suggests that initial siren activations in Joplin (and severe weather warnings in general) have lost a degree of credibility for most residents — one of the most valued characteristics for successful risk communication,” said the report.

Instead, the majority of Joplin residents waited for confirmation of the tornado from a different source. Some of them saw the twister and ran for cover. Others, needed confirmation from radio or television reports.

Now, the National Weather Service is taking action to improve severe weather warnings by providing better information in the initial issuance. This new experimental tornado warning system will be “impact-based.” That means, especially during extreme tornado events, it will provide more specific information, so local residents will better understand the threat that is coming.

Here are the goals:

– Provide a non-routine warning mechanism that prompts people to take immediate life-saving action in extreme events like strong and violent tornadoes.
– Be impact-based more than phenomenon-based for clarity on risk assessment.
– Be compatible with NWS technological, scientific and operational capabilities.
– Be compatible with external local warning systems and emerging mobile communications technology.
– Be easily understood and calibrated by the public to facilitate decision making.
– Maintain existing “probability of detection” for severe weather events.
– Diminish the perception of false alarms and their impacts on credibility.

So, here’s a look at the new system that will be launched in several regions this April:

1) Standard Tornado Warning: These warnings are the basic ones issued by the National Weather Service when radial velocities on radar indicate a possible tornado. Most of the time, these are the basic warnings issued by all offices across the United States.

2) Potentially Dangerous Situation (PDS) Tornado Warning: If a PDS Tornado Warning is issued, then it means that the storm has a tornado on the ground that was spotted by a storm chaser or the public. These warnings are the second highest level that the NWS will issue.

3) Tornado Emergency: In a tornado emergency, a large tornado is on the ground producing a lot of damage and is headed towards a populated city. Tornado emergencies were issued back on April 27, 2011 when a supercell thunderstorm was pushing into Tuscaloosa, Alabama. A tornado emergency is the highest level of emergency on this scale.

The warnings above will now include more specific tags to communicate the seriousness of the threat. For instance, the warning will now include an indication whether the tornado is radar-indicated or observed on the ground. An additional line will expand

on the tornado threat. The tornado threat will be significant if there is credible evidence that a tornado, capable of producing significant damage, is confirmed on the ground. The tornado threat will be catastrophic if there is a severe threat to human life and when catastrophic damage from a tornado is occurring. This type of statement will only be used when credible sources confirm a violent tornado in progress.

NWS Officials hope this more-specific information provided initially will motivate residents to act immediately, instead of waiting and risking injury or death.

This new warning system will be launched on an experimental basis in St. Louis, Kansas City, Topeka, Wichita, and Springfield, Mo. If the system proves effective, it will be expanded nation-wide in the coming years.


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