A Comparative Climatological Analysis of Santa Ana Wind Occurrences for Two Nearby Coastal and Mountain Stations in Southern California

     This study performs an in-depth climatological analysis of Santa Ana wind events for two proximate coastal and mountain stations in the Oxnard plain area of Southern California.  Historical records of the Point Mugu Naval air base, located a mile east of the Pacific Coast (altitude 13 ft), and Laguna Peak, a 1450 foot mountain station several miles east of Point Mugu, are examined for days in the historical record classified as “Santa Ana Day” episodes, defined using both Point Mugu and Laguna Peak criteria.

    As described at a UCLA Department of Meteorology Internet site, “the Santa Ana is a blustery, dry and warm (often hot) wind that blows out of the desert”. It develops most commonly during the months of October through March. High pressure builds over the Great Basin and the cold air there begins to sink. However, the air is forced downslope towards the Pacific Coast in which it is compressed and warmed during its descent. As its temperature rises, the relative humidity drops precipitously, the air also picking up speed as it is channeled through passes and canyons.  Santa Anas can cause a great deal of damage. The fast, hot winds cause vegetation to dry out, increasing the danger of wildfire. Once the fires start, the winds fan the flames and hasten their spread. They also tend to make for choppy surf conditions in the Southern California Bight, and often batter the north coast of Santa Catalina Island, including Avalon cove and the island's airport. In addition, the winds create turbulence and establish vertical wind shear (in which they exhibit substantial change in speed and/or direction with height), both posing aviation hazards. 

    From a forecasting standpoint, the fact that Santa Ana winds originate at higher altitudes to the east and northeast from the coast makes wind information collected from these higher elevation points, either near the coast itself or more remotely inland (an example of the latter being the Sandberg station – elevation 4163 ft, about 50 miles NE from Pt. Mugu), useful in providing early signs as to the possible onsets of Santa Anas at the lower, near sea-level elevations.  The Laguna Peak station was established in the 1960’s for this reason by request of the Los Angeles National Weather Service Office. Over the years, climatological analyses on Santa Ana wind episodes have been produced for the Point Mugu station, but Laguna Peak observations have been utilized almost exclusively anecdotally, with few “formal” analyses, either on a standalone basis or concurrently with Pt. Mugu’s.  This study seeks to fill in the analytical gap relative to the two, and in the process providing a sample case study.    

     A variety of climatological and graphical analyses are presented, including (for each station): 1.) monthly relative frequencies of Santa Ana day events  2.) yearly event totals, 3.) comparisons of individual hourly tendencies for Santa Ana winds during  episodes, 4.) relative frequency distributions of Santa Ana hours’ tallies, and 5). frequency distributions of multi-day runs .  In addition, utilizing a Data Mining Clustering methodology, idealized hourly midnight-to-midnight wind patterns or “modes” will be created  for Santa Ana Day events, both on an individual and paired Point Mugu and Laguna Peak basis, making use of midnight-to-midnight decomposed u and v individual hourly wind calculations as input. The resulting clusters’ centroid mean u’s and v’s are then recombined into hourly mean vector wind statistics that serve as a method of discriminating and interpreting the different idealized patterns/modes of Santa Anas. This statistical technique has been employed previously on Southern California coastal stations’ hourly wind data (Fisk 2012, 2016), with useful results, especially for those stations that exhibit naturally pronounced midnight-to-midnight diurnal wind variation.