“Serious fires are caused by Fire + Santa Ana winds. Santa Ana winds ALWAYS blow in a westerly direction. Maybe west by northwest or west by southwest or directly west but NEVER north, south, or east. This is a simple fact of the phenomena that creates the Santa Anas a high pressure zone over Las Vegas or Utah to the east.”
You may be correct that 4S is somewhat protected.
However, fires move out in a cone,primarily to the west, but this cone can approach as much as 180 degrees. An example is the witch fire. (see diagram below).
Also, Santa Ana winds always end with a reversal to the normal on-shore flow. Although this cooler and less velocity wind reduces the threat of fires, the change-over period can cause erratic movement of fires in various directions. AT that point the direction of the fire is influenced by the availability of fuel as much as the wind.
