Hot and Dry Weekend and then ... More Rain?

On Tuesday Los Angeles picked up 2.39" inches of rain which was the second-highest 24-hour total in September ever. This also was about 1/6 of the average rainfall that LA receives in an entire year! But in California it was feast and famine. Much of Northern California received no (or very little) rain at all - especially in the Sierra Nevada where hungry reservoirs need it the most. A weak frontal system did move through far northern California yesterday and today bringing higher-than-expected rain to the Valley Fire and other areas of the northern third of the state. Even the northern portions of the Bay Area got some water. But we're gonna need a LOT more. 

Here in the Southland, we have now transitioned into a warmer and drier spell. An unusual high pressure will build in to the area, with heights reaching a maximum this weekend before yet another surge of tropical moisture from the south brings us...  another chance of rain! (??)

500mb heights will peak on Sunday possibly near 580 with a weak offshore flow both at the surface and aloft. This means dew points should be relatively low (less humidity!) and nights should be a little cooler than last week. There is very little upper-air support for a proper Santa Ana event, but temperatures should warm into the 90s (yet again, ugh!) on Saturday and Sunday.

But the warm/dry spell will be broken by yet another surge of humid tropical air from the south. I've attached a gif of precipitable water looping from 4pm on Sunday through 10am on Wednesday. You can see the surge of purples and yellows moving up west of Baja from the south - this indicates warm tropical air on the move. 


It is still too early to say with any sort of accuracy that we will get rainfall. But, the models have all been trending in this direction for a few simulations now and it is looking increasingly likely that we will at least have some scattered thunderstorms and light rain. Could be much more. I want to stress that the frequency of these tropical surges is truly unreal and unprecedented. 

As usual, stay tuned :) 

Mika ToscaComment