How NWS Impact Statements Were Used to Communicate Imminent Danger from Severe Hurricanes

In 1999, a project was initiated by the National Weather Service (NWS) Weather Forecast Offices (WFO) covering central and south Florida, to explain the physical effects that wind and freshwater flooding would have on communities impacted by tropical cyclones. Impact statements were created for incremental threat levels for each parameter, and made available to all WFO with tropical cyclone responsibility prior to the 2002 Atlantic hurricane season. Wind and freshwater flood impacts were available for the Hurricane Local Statement (HLS); wind impacts were also available for inland wind watches and warnings.

The 2004 and 2005 Atlantic Hurricane seasons featured two United States landfalling Category 4 hurricanes (Charley and Katrina). For each cyclone, strongly worded wind impact statements were included in WFO products issued by NWS Tampa Bay, FL (Charley) and NWS Slidell, LA (Katrina), well in advance of the event. The enhanced response by users of these products will be discussed, in relation to the NWS primary mission of protecting American lives and property. Future application of these impacts, as well as those for storm surge, will also be addressed.