Strong high pressure aloft off the California coast, and surface high pressure over the Great Basin, will keep dry and warm Santa Ana conditions over the southwest California through Monday with periods of gusty northeast winds near the coastal foothills.
Upper level low pressure over the Baja Peninsula will bring increasing moisture and slow cooling beginning Tuesday as it drifts northward bringing with clouds, and a small chance for sprinkles or scattered, light showers at times.
Onshore flow and seasonal temperatures return for the latter half of the week as a developing trough of low pressure moves inland across the West.
United States WX Overview...
Cooler temperatures with lower humidity for the northeastern states.
Heavy rain and thunderstorms expected across Texas.
“El Cordonazo” or “The Lash of St. Francis”, an actual tropical storm hit Southern California on this day and on 9/26 and caused the greatest September rainfall ever. The storm lost hurricane status shortly before moving onshore at San Pedro at tropical storm strength. Torrential rains hit LA with 5.42 inches in 24 hours. Mt. Wilson received 11.60 inches. Both of these amounts are also records for the entire month of September. Nearly seven inches fell in three hours at Indio from one thunderstorm. 9.65 inches fell at Raywood Flat and 1.51 inches fell in Palm Springs. 2.81 inches fell in Santa Ana, the greatest daily amount on record for September. 45 were killed in floods all over Southern California, and 48 more were killed at sea in estimated seas of 40 feet. $2 million damage occurred to structures along the coast and to crops. The eastern Coachella Valley was under two feet of water. Californians were generally unprepared and were alerted to their vulnerability to tropical storms. In response, the weather bureau established a forecast office for Southern California, which began operations in February of 1940.