Jun 3, 2016

The Arbitrary Definition of the Current Atlantic Major Hurricane Landfall Drought

by
Robert E. Hart, Daniel R. Chavas, and Mark P. Guishard
,
Bulletin of the American Meteorological Society (BAMS)
  • States that a major hurricane [96+ knots (kt; 1 kt = 0.51 m s–1) of 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-yr streak for this metric as 177 yr, suggesting extraordinary rarity, especially in the context of the length of the record (1851–2014)
  • Shows that the significance or even existence of the current 9-yr drought is highly dependent on the metric used
  • Examines the same record using landfall thresholds of 95–105 kt, acknowledging that wind intensity estimates are binned every 5 kt and have approximate 10-kt uncertainty
  • Using 105-kt landfall, 1993–2003 becomes a previously unreported yet more remarkable 11-yr drought and 1981–88 becomes an 8-yr drought
  • Finds that landfall minimum sea level pressure is more reliably estimated than maximum sustained wind speed
  • Finds that for landfall intensities stronger than 960 hPa (a climatological threshold for 100 kt), the current drought disappears because of Irene (2011) and Sandy (2012)
  • Tests a coastline-independent yet nearby proximity metric, which reveals a nonexistent drought
  • Accordingly, this study suggests the following:
    • 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, and potentially nonscientific contributions), regardless of intensity metric
    • 3) From a societal context, human and financial losses matter most, and Irene [2011; $8 billion (U.S. dollars)] and Sandy (2012; $88 billion) occurred during the current drought