I'm not sure of the exact number, but if LAX is 90% west (24/25) and 10% east (6/7), then among those east days, 90% is because of wet factors (winter storm/Catalina eddy) and 10% is because of dry factor (Santa Ana). Santa Ana winds rarely get strong enough to go all the way to LAX in significant speeds. First it's got to be east, not NE, then it will have to be very strong (e.g. 40-60 knots at ONT) to make it all the way down. Also, it takes less east winds to turn LAX around when the runways are wet.