Enhanced tornado warnings to begin Monday in Decorah and throughout Iowa

The National Weather Service starting Monday will have three possible levels of tornado warnings for Decorah and the rest of Iowa.

The agency is expanding a program it experimented with last year. 

"All tornado warnings indicate a serious situation, but we realize that the strongest storms and those that stay on the ground longer pose a greater risk to life," said a NWS official in explaining the new system.

The project gives forecasters three-tiered tornado warning options:

• When a tornado is possible based on radar data, the warning will include a bulleted list that clearly communicates hazards and impacts. This is the most common type of warning.

• When there is substantial evidence of a large and dangerous tornado, the warning will include the phrase, "This is a particularly dangerous situation," to identify a high threat level, describe expected damage and promote urgency to seek immediate shelter. A damage threat tag of "considerable" will be embedded in the warning.

• When a known, potentially violent tornado is likely to produce devastating damage, the warning will announce a "Tornado Emergency" and direct the public to seek shelter immediately. A damage threat tag of "catastrophic" will be embedded in the warning. This is the highest level of tornado warning and will be reserved for rare cases like the deadly EF-5 that struck Joplin in 2011.