Weather Synopsis – July 8, 2024

James Murakami

Mon8th77/63Low clouds clearing late morning; Sunny afternoon. Chance of evening low clouds.
Tue9th78/64Good chance of early morning low clouds; Otherwise, mostly sunny day. Clear evening.
Wed10th80/65Chance of some early morning low clouds; Otherwise, mostly sunny day with some afternoon high clouds possible. Some high clouds in the evening.
Thu11th79/65Chance of some early morning low clouds; Otherwise, mostly sunny day with some high clouds. Variable mid/high clouds in the evening.
Fri12th78/64Chance of some early morning low clouds; Otherwise, mostly sunny day with variable mid/high clouds. Variable mid/high clouds in the evening.


I am confidant that no wet weather nor excess heat (i.e. 90 degrees or higher) will befall UCLA this week. Other than that, confidence in this week’s forecast is shakey. Last week, a shallow but effective marine layer was more influential on campus weather for most of the week than I forecast. High pressure aloft did warm the Southland, but it applied mainly for well inland locales. Unfortunately for me, on-shore flow stayed mostly stronger than forecast by the numerical models. Only on Friday and Saturday did the campus reach 80 degrees. Last Thursday (4th) was unusually cool (maximum of just 72 degrees…my forecast was for 79).

High pressure aloft was centered over the Southland this morning (north of Lancaster). It’s center is forecast to meander for another day or so followed by eastward migration to eastern Utah (possibly as far east as western Colorado). A weak, upper low pressure is also forecast to develop west of southern California tomorrow. It too should meander for a day or two before it migrates northward. The predicted gyrations of the high and low pressures should have relatively minor effects on the low level, on-shore flow (main weather influencer in the coastal plain lately). Based on today’s model consensus, on-shore flow should weaken some tomorrow (already started today compared with yesterday). The marine layer should be the most shallow for this week on Wednesday. It should re-deepen a little thereafter lasting till Saturday afternoon.

If all goes according to plan (???), there should be less marine layer clouds/fog for the next couple of days. An increase in areal coverage should return later in the week (peaking Friday). Besides marine layer clouds, the predicted low pressure aloft to the west should start drawing upper level moisture northward from the sub-tropics (“monsoon” moisture). Some high clouds could show up as early as tomorrow afternoon, but such clouds shouldn’t be widespread before Thursday. There is some chance that the atmospheric motions associated with the sub-tropical clouds will disrupt the local, low cloud field. That could have some affect on temperature near the coast (more on that in a bit).

Since the various models show some warming for the next couple of days, I followed suit in this forecast. However, like last week, a shallow but effective marine layer could wreak havoc with the campus forecast (so far , it’s cooler than I forecast for today!). If the marine layer should get disrupted late this week, it may actually wind up warmer than I show in this forecast (probably not more than a few degrees though). At this time, no big temperature trends are forecast for next week (some renewed warming for the interior after a modest “cool down” this weekend). As long as the marine layer remains in place, areas near the coast should be within a few degrees of normal for this time of year.

The only other predicted weather to speak of is a chance of mountain/desert showers and thunderstorms this weekend (mainly mid/late afternoon hours). Most of the models show sufficient import of “monsoon” moisture to promote atmospheric instability over the southern mountains and low deserts. However, as I’ve stated in previous synopses, a small error in predicted wind flow can have noticeable effects on what weather actually transpires. Insufficient moisture import may result in just afternoon cloud build ups but no shower clouds. In any case, most of the models show a decrease in upper level moisture in the Southland early next week.

Next issued forecast/synopsis should be on Monday, 15 July.