Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2017-272
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Brief communication
24 Jul 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Natural Hazards and Earth System Sciences (NHESS).
Brief Communication: 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 1Division of Atmospheric Science, Desert Research Institute, Reno, Nevada, 89512, USA
2Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma, 73019, USA
3NOAA/NWS/NCEP Storm Prediction Center, Norman, Oklahoma, 73072, USA
Abstract. Strong afternoon downslope Sundowner winds in southern California's Santa Ynez Mountains favor wildfire growth. To determine whether Sundowners are different from Santa Ana winds (SAW), we use surface observations from 1979–2014 to develop a climatology of extreme Sundowner days. The climatology was compared against an existing SAW index from 1979–2012. Sundowner occurrence peaks in late spring whereas SAWs peak during winter. SAWs demonstrate amplified 500 hPa geopotential heights over western North America and strong anomalously positive inland mean sea level pressures. In contrast, Sundowner-only conditions occur during zonal 500 hPa flow and moderate negative inland sea level pressure anomalies.

Citation: Hatchett, B. J., Smith, C. M., Nauslar, N. J., and Kaplan, M. L.: Brief Communication: Differences between Sundowner and Santa Ana wind regimes in the Santa Ynez Mountains, California, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-272, in review, 2017.
Benjamin J. Hatchett et al.
Benjamin J. Hatchett et al.
Benjamin J. Hatchett et al.

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Short summary
Severe wind events in southern California create extreme fire hazard. Sundowner winds are a local downslope wind 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 hazard. Sundowner winds are a...
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