Storm Surge Vulnerability

• One of the first things to consider for a potential evacuation in Siesta Key due to a hurricane is the vulnerability of its specific evacuation zone to storm surge, or rising tide levels. This is considered using a combination of forecasted landfall data, as well as historical precedents. Siesta Key is located within Sarasota County's "A" evacuation zone because of its position on the coast, which is vulnerable to an evacuation for as little as a tropical storm. Using factors such as hurricane track, forward speed, intensity and size, forecasters analyze the predicted amount of storm surge for evacuation zone A to determine if it meets the minimum for evacuation.
  
  

Wind Vulnerability

• Another factor for officials to consider in the possible evacuation of Siesta Key is the vulnerability of its structures to hurricane force winds of 74 miles per hour and over. Researchers look at the total number of mobile homes -- the most vulnerable structures -- then to the number of site-built residential and commercial buildings. According to 2009 data from Florida's Statewide Regional Evacuation Study Program, Sarasota County contains 80 mobile home and RV parks across its various evacuation zones. The call for evacuation on this basis is made by assessing both the storm track and wind speeds to determine the level of structural vulnerability.
  
  

Population At-Risk

• The number of at-risk population per evacuation zone -- those citizens directly in harm's way who must vacate the zone -- is used to determine both the time of evacuation, as well as response and recovery needs. According to the Statewide Regional Evacuation Study Program, Sarasota County's evacuation zone A, which includes Siesta Key, has a 2010 population at-risk of over 29,000 people. This number includes both those vulnerable to storm surge, as well as the mobile homes that could be affected by high winds.
  
  

Evacuation Population

• Explicit at-risk data for Siesta Key's evacuation zone are not the only numbers to consider when determining the need to evacuate. Attention must also be paid to the residents living outside the evacuation zone who abandon their homes, despite not being directly vulnerable to either storm surge or high winds. On the other hand, there are also those residents who stay behind, despite an evacuation warning. In order to plan the most efficient use of the state's evacuation routes, emergency management officials use behavioral analysis models to predict the evacuation population in what is called the "Operational Scenario."