The Arbitrary Definition of the Current Atlantic Major Hurricane Landfall Drought

A major hurricane (96+ kt maximum sustained wind) has not made landfall in the United States since Wilma (2005). Recent elegant stochastic-statistical modeling estimates the return period of a 9-year streak for this metric as 177 years, suggesting extraordinary rarity, especially in context of the record length (1851-2014). Current awareness of the drought is increased given the 2015 hurricane season is expected to be suppressed from El Niño, and the recent anniversaries of several noteworthy landfalls.

Yet, here we show that the significance or even existence of the current 9-year drought is highly dependent on metric used. Acknowledging that wind intensity estimates are binned every 5kt and have approximate 10kt uncertainty, we examine the same record using landfall thresholds of 95 to 105kt. Using 105kt landfall, 1993-2003 becomes a previously unreported yet more remarkable 11 year drought and 1981-1988 becomes an 8 year drought. Further, landfall minimum sea-level pressure is more reliably estimated than maximum sustained wind speed. For landfall intensities stronger than 960hPa (a climatological threshold for 100kt), the current drought disappears due to Irene (2011) and Sandy (2012). A coastline-independent yet nearby proximity metric is tested and reveals a nonexistent drought.

Accordingly, this study suggests: 1) Caution is advised when identifying a hurricane drought and its historical significance; 2) Using hurricane landfall statistics to infer a climate signal is fraught with issues (threshold, coastline, potentially non-scientific contributions), regardless of intensity metric; 3) From a societal context, human and financial losses matter most, and Irene (2011; $8 48 billion) and Sandy (2012; $88 billion) occurred during the current drought.

Hart, R., D. Chavas, and M. Guishard, 2015: The arbitrary definition of the current Atlantic major hurricane landfall drought. Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-15-00185.1, in press.