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Santa Ana Index
The Santa Ana (SA) Index predicts the strength of a SA wind event, which is a downslope wind common to Southern California. The methodology was produced by a team from San Diego Gas & Electric Company, combining surface pressure gradient, 825-hPa wind speed, and 825-hPa cold air advection. The SA Index is calculated below using the West-WRF ensemble output along multiple transects over Southern California.
Top left: Map showing the transect locations. Red dots indicate their start and end locations, while blue circles show the location where 825-hPa wind speed is forecasted. Yellow highlights the chosen transect.
Bottom left: Seven-day forecast of the SA Index components: Surface pressure gradient (top row), 825-hPa wind speed along the transect (middle row), 825-hPa cold air advection along the transect (bottom row). Left Column: West-WRF ensemble forecasted maximum/minimum (blue lines), 10th/90th percentiles (red lines), and ensemble mean (black line) of each SA Index component. Right Column: Shading represents the probability of each SA Index component reaching above various thresholds (as defined by colorbars).
Top right: Seven-day forecast of the SA Index from the West-WRF ensemble with maximum/minimum (blue lines), 10th/90th percentiles (red lines), and ensemble mean (black line).
Bottom right: Shading represents the probability of the SA Index along the selected transect calculated by the number of ensemble members predicting a given SA Index value at each forecast lead time.
Bottom plot: Summary of the seven-day SA Index from the West-WRF ensemble. Each row represents a transect and each column represents a forecast day. Color shading indicates the maximum SA Index forecasted by the 90th percentile of the West-WRF ensemble on the given day for the given transect.
Select a coastal and inland location below to display the SA Index for that transect.
