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Climatological, meteorological, and societal implications for the large number of fatalities from central Florida Dry Season tornadoes during El Niño

Bartlett C. Hagemeyer, NOAA/NWS, Melbourne, FL; and L. A. Jordan, A. L. Moses, S. M. Spratt, and D. F. Van Dyke III

Since 1980 there have been 78 tornado fatalities in the Florida dry season(November through following April) during just seven El Niño years, while only nine fatalities were reported in the 23 other dry seasons. In February 1998, 42 people died in mobile homes and campers from violent tornadoes that formed around midnight; in February 2007, 21 people died under almost identical circumstances. These deaths occurred despite long tornado warning lead times and attempts throughout the preceding day to highlight the overnight tornado threat and to emphasize the value of NOAA All Hazard Weather Radios to alert people even if they were asleep.

Comprehensive studies of Florida weather hazards for the past 20 years have demonstrated that variability in Florida dry season storminess is closely linked with the El Niño/Southern Oscillation. Skillful seasonal forecasts of Florida dry season storminess have been made at NWS Melbourne since 2000. During El Niño years a strong and persistent jet stream extends over the Gulf of Mexico and Florida, accompanied by an increase in strong extratropical cyclones and attendant severe weather, including strong and violent tornadoes. The number of deaths and injuries from tornadoes in east Central Florida during recent El Niños has been astounding. The increased risk of strong tornadoes is known well before the dry season begins, and the extratropical cyclones that spawn the tornadoes are often forecast five to seven days before they strike. In addition, timely watches and warnings are almost always issued prior to the occurrence of the strong tornadoes, and this information is typically well-communicated by the media.

The likelihood of multiple tornado deaths in central Florida during the dry season is highly correlated with El Niño. However, can the deaths be directly attributed to El Niño? The concept of attribution is key in this case, and cases like it. The attribution in the aftermath of these devastating events to El Niño or an “Act of God or Nature” does not address the root cause of the carnage which the authors have seen firsthand. There are relatively simple and inexpensive mitigation methods to better secure homes, and preparedness concepts that can be implemented to provide safe havens, given the knowledge we have of the likelihood of violent tornados during El Niño's. The relatively small area of central Florida happens to be the focus for so many tornado fatalities because its unique physical geography and cultural housing practices directly intersect with a planetary scale shift in the winter storm track.

This presentation will update the climatology of Florida Dry Season storminess from the author's previous work through the 2008-2009 dry season, and present the meteorological settings of the most recent extreme events. The bulk of the presentation will be an in-depth philosophical discussion of the root cause of the high number of tornado fatalities in El Niño dry seasons and what can be done to reduce them in light of the climatological, meteorological and sociological issues at play.

extended abstract  Extended Abstract (2.0M)

Supplementary URL: http://www.srh.noaa.gov/media/mlb/pdfs/Florida_El_Nino_Impact_Tornado.pdf

Joint Session 4, Research on extreme weather and climate events and inter-relationships
Tuesday, 19 January 2010, 3:30 PM-5:30 PM, B216

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