| Day | Date | High/Low | Forecast |
| Mon | 5th | 99/74 | Sunny day. Mostly clear evening. |
| Tue | 6th | 96/72 | Sunny day. Mostly clear evening. |
| Wed | 7th | 89/68 | Sunny day. Mostly clear evening. |
| Thu | 8th | 86/66 | Sunny day. Clear evening. |
| Fri | 9th | 83/66 | Mostly sunny day with variable mid/high clouds. Scattered evening mid/high clouds. |
Synopsis
For the second time this month, the UCLA temperature reached 100 degrees (previous a couple days ago). Such high temperatures don’t occur every year on campus (prior year occurrence in September, 2024). Today’s high edged out the record maximum for the date by one degrees (99 degrees in 1953). The balmy, overnight low temperature of 79 degrees set a new record high minimum for the date (previous record 71 in 1987).
I have to admit that I hadn’t expected the latest heat wave to reach such heights near the coast (102 degrees at Santa Monica airport a couple days ago; 91 degrees at the Santa Monica pier yesterday and day before). The off-shore flow had more kick to it than the computer models forecast last week (regulated ocean breezes more than anticipated). Today’s model forecast are showing weakening high pressure aloft this week, but it may be a slow process. For today’s campus forecast, I went with a steady, slow cooling trend. However, there are some model forecasts showing tomorrow may be virtually the same as today.
Should the predicted on-shore flow increase at a faster pace than most models show, the cooling trend should pick up the pace, especially for areas near the coast (UCLA included). However, I still wouldn’t expect the coastal plain will return to seasonable temperatures before Saturday. That’s when the models forecast an upper level trough setting up somewhere on the West Coast. The models disagree on how strong this trough will be as well as where the axis of the trough will lie. The strength question has bearing on how fast cooling will occur this weekend (stronger trough favors more rapid cooling…cooler than normal as early as Sunday).
The various models have also have had difficulties on possible, future interactions of the aforementioned trough with a subtropical trough (currently way out at sea to the northeast of the Hawaiian Islands) and current hurricane Rachel (about 500 miles west-southwest of the southern tip of Baja California this afternoon). The three way interaction, in some scenarios, result in wet weather in southern California (sometime in the Sunday-Monday window). A few solutions favor widespread, significant, wet weather (inch plus rains). A lot has to occur in the right places at the right time for this scenario to work (least likely outcome, for the time being). The other scenarios limit areal coverage of wet weather (some to the south and east of L.A. County). As of now, I’m leaning on the limited coverage scenario (at worst, up to a quarter inch rains in the L.A. County lowlands).
Whichever scenario verifies, a return to sunny weather is anticipated by the middle of next week. Most show a warming trend, but they disagree on whether a warm, off-shore flow pattern will develop. It’s too early to gauge the strength of the potential off-shore flow, but it probably won’t get as hot as the current event.
No issued forecast/synopsis will be available later this week through next week. So, the next forecast/synopsis should be on Monday, 19 October.