High impact weather events (HIWE) are defined as hurricanes, tornadoes, hail, damaging winds, droughts, flash floods, river floods, and severe winter storms; often occurring concurrently in a 24-hour period. These concurrent HIWEs overwhelm emergency response systems and tend to have lasting impacts on populations, transportation systems, and infrastructure. Much of the time, communities impacted by these weather events are simply overwhelmed by the immense destruction.

Recent examples of high impact weather events include: 

• May 22, 2011–Deadly tornado/flash flooding in Joplin, Missouri. 
• April 27, 2011–Super tornado outbreak in Mississippi, Alabama, Georgia, and Ohio River Valley states.
• March 2011–Flood wave that spread down the Mississippi River from Minnesota to New Orleans.
• Winter 2011–Snowstorms that hit much of the U.S. including Chicago and Washington D.C.
• May Day 2010–Severe flash flooding and tornado assault on Memphis.

Rescue efforts during the previously mentioned tornado and flooding events have been hindered by heavy rains, flooding, and repeated passage of severe thunderstorms. Evidence indicates that many impacted communities are faced with the following immediate and concurrent losses:

• Critical infrastructure damage to fire stations, hospitals, and commercial food and building supply stores, 
• Communications capabilities with land-line telephones, cell phones, radio, and television, and
• Diminished community services (transportation, fire, and public works).

Although HIWEs may feature several concurrent storm events in a 24-hour period, hazard mitigation and flood response plans tend to deal with significant weather events as a singular occurrence. Presently, guidelines for these plans do not identify the need to consider concurrent or multiple severe events. While creating hazard mitigation and response plans, we can develop guidelines for the inclusion of these more infrequent but dangerous concurrent HIWEs that can quickly overwhelm cities, counties, states, or regions.