Why summer thunderstorms never hit southern California but very rare?

Question

Why summer thunderstorms never hit southern California but rare? I sometimes see thunderstorms develop over the mountains and desert but not over the coast of southern California during monsoon. I think is Marine Layer prevent thunderstorms develop over the coast? Pacific ocean is too cool water that cannot allow thunderstorms develop right? Atlantic Ocean and Gulf of Mexico both are very warm water that can allow thunderstorms develop. Florida has lot of thunderstorms during summertime because between Atlantic Ocean and Gulf of Mexico. I want to know some answer and learn about more.

Answer 1

Warning...long answer. There are three main types of systems that can bring bring active weather to southern California (SoCal) during the summer and early fall period...a weak troughs/closed upper lows, the remains of an old tropical systems, and a late summer/fall monsoonal type event. Read on for the bloody details.

1. A system may come from the westerlies, mainly during the early summer period. However, this is very rare because by this time of year the northern branch of the jet is usually weak and well north of SoCal. Sometimes this weak jet does split over the Eastern Pacific resulting in a weak trough or closed low developing of the coast of SoCal. If this system makes it inland, it usually results in a strong marine intrusion push inland in the low to mid levels. This will result in a stable airmass over the low elevations, but may fire off a few thunderstorms in the mountains.

2. Another type are the remains of an old tropical system that is now caught up in the southern stream (subtropical jet) and is now approaching from the southwest. Or one that is caught up in the flow around the four-corners high and is approaching from the southeast. These systems can be very unstable and can be very deep in moisture. If one holds together, frequent lightning, heavy rain, and flash flooding are usually a big threat in SoCal day and/or night. But you must get a direct hit when the are still strong and compact. Otherwise, with time, it will weaken or split and will likely lose its low to mid level moisture as it continues its transition to a cold core system. So these rare systems must hit SoCal directly before it weakens rapidly.

3. The relatively more common threat for thunderstorms are from the monsoonal moisture flow coming around the four corners upper high. Because the moisture usually moves over northern Mexico before reaching before reaching SoCal, the moutains in Mexico...through the process of orographic lifting..would have already strip the low to mid level moisture. This will only leave only with high level moisture available in most cases. This will result in mainly isolated high level mountain showers or thunderstorms with day time heating. In rare cases, if there is mid level moisture also available due usually to the merging of the southeast and southwest flow, a few high based thunderstorms may form over the rest of Socal resulting in high based isolated thunderstorms. This will mean a higher chance of virga or dry lightning over the lower elevations in the late afternoon and evening. This is when you usually get the Red Flag Warnings for SoCal for a monsoonal event.

In the coastal regions of the gulf coast and for Florida, the marine air is very warm due tothe warm gulf waters and the warmer Atlantic Ocean. So an onshore flow will not stabilize the lower airmass. There are also no significant orographic lifting from tall mountains that can strip the low to mid level moisture away or having a down slope flow that will dry the lower airmass. With the warm water, strong deep instability and better organized and larger tropical system and waves are possible. And with warmer waters at night, nocturnal coastal thunderstorms are possible near the coast with very weak systems too.

Answer 2

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RE:
Why summer thunderstorms never hit southern California but very rare?
Why summer thunderstorms never hit southern California but rare? I sometimes see thunderstorms develop over the mountains and desert but not over the coast of southern California during monsoon. I think is Marine Layer prevent thunderstorms develop over the coast? Pacific ocean is too cool water...

Answer 3

Thunderstorms require 2 things: * Moisture * Rapidly rising warm air While Southern California does have a source of moisture (the Pacific Ocean), it does not have the rapidly rising warm air (or unstable air) necessary for a thunderstorm. The air over SoCal is generally stable. It lifts when it gets to the mountains, which is one place where thunderstorms do occur.

Answer 4

The air in Southern California is hardly if ever moist and you need high level of humidity for a storm to form