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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 2 | Copyright
Nat. Hazards Earth Syst. Sci., 18, 419-427, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Brief communication 06 Feb 2018

Brief communication | 06 Feb 2018

Brief Communication: Synoptic-scale differences between Sundowner and Santa Ana wind regimes in the Santa Ynez Mountains, California

Benjamin J. Hatchett1, Craig M. Smith1, Nicholas J. Nauslar2,3, and Michael L. Kaplan1 Benjamin J. Hatchett et al.
  • 1Division of Atmospheric Science, Desert Research Institute, Reno, Nevada, 89512, USA
  • 2Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma, 73072, USA
  • 3NOAA/NWS/NCEP Storm Prediction Center, Norman, Oklahoma, 73072, USA

Abstract. Downslope Sundowner winds in southern California's Santa Ynez Mountains favor wildfire growth. To explore differences between Sundowners and Santa Ana winds (SAWs), we use surface observations from 1979 to 2014 to develop a climatology of extreme Sundowner days. The climatology was compared to an existing SAW index from 1979 to 2012. Sundowner (SAW) occurrence peaks in late spring (winter). SAWs demonstrate amplified 500hPa geopotential heights over western North America and anomalous positive inland mean sea-level pressures. Sundowner-only conditions display zonal 500hPa flow and negative inland sea-level pressure anomalies. A low-level northerly coastal jet is present during Sundowners but not SAWs.

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Short summary
Severe wind events in southern California create extreme fire hazards. Sundowner winds are local downslope winds in the Santa Ynez Mountains near Santa Barbara that often coincide with damaging fires. Here we produce a climatology of Sundowner winds and compare their seasonal occurrence and large-scale atmospheric patterns to the well-studied Santa Ana wind regime. We find that Sundowner winds are distinctly different from Santa Ana winds in terms of peak seasonality and synoptic structure.
Severe wind events in southern California create extreme fire hazards. Sundowner winds are local...