Posted on 11/25/2008 6:14:48 AM PST by JohnJeykis
SOUTHERN CALIFORNIA - November 25, 2008 (OWSweather.com) Severe thunderstorm threat possible.
It's been months since Southern California has seen a good storm system move through. Lots have tried and many have failed. However one storm system managed to escape the grasp of the arctic jet stream and will make friends with the tropical moisture plume to the South to give us much needed rain.
The rain will start this morning, increasing over the day and into the evening. The Ventura areas will likely see the rain overnight tonight into Wednesday morning as a plume of tropical moisture reaches the area. The rainfall will cause mudslides in the area, especially where the burn areas have been. The rain will exit the Ventura zones Wednesday morning in terms of heavy downpours. Left over hit and miss showers or thunderstorms will be possible as the center of the storm and cold air aloft moves in Wednesday afternoon and evening.
The National Weather Service in Oxnard and San Diego issued flood watches yesterday. The system will bring the rain and verify the flood watches.
OWSweather.com Meteorologist Kevin Martin sees a different scenario for parts of the Southland. "Dynamics are quickly coming together offshore, and we may be in for one heck of a ride East and South of Los Angeles overnight tonight into Wednesday morning. "Martin explained. "Everyone is so focused on the flooding potential that we may actually be having a rare 30 year severe thunderstorm and embedded tornado event in the Southland. This threat is centered around Eastern Los Angeles County, The Inland Empire, All of Orange County, and Northern San Diego County."
The snow levels will start off above 10,000 feet today and lower to 9,000 feet by late tonight into Wednesday morning. The tropical nature of this system has a lot of moisture in tropical form which does raise snow levels. The mountains will easily see over four inches of rain in spots with 1 to 2 in the valleys, and 1 inch around the coast.
Martin called the National Weather Service in San Diego to talk about the storm and get another insight on it. "Thunderstorms and waterspouts are possible on Wednesday afternoon and evening. "Stan Wasowski from the National Weather Service said. "Rain is the most likely scenario with less chances of a thunderstorms tonight into Wednesday morning with the main band of moisture."
It is evident the National Weather Service is not going to go with thunderstorms with the main band but Martin will see how things go. Martin says he respects the position and will help get the latest data to the National Weather Service tonight into Wednesday from his team. Reporters will be live on the field to update on the storm's progression into their areas. The target for the severe thunderstorm chances will be East and South of Los Angeles.
Both Martin and the National Weather Service agree on thunderstorms on Wednesday.
The system should depart sometime Thanksgiving with left over light showers possible.
OWSweather.com staff
More information: www.OWSweather.com
How much rain is needed for a mudslide?
I think since the area has not seen much it is in for it. I’m more interested on these predicted thunderstorms.
Is it raining on your parade yet?
Mudslides happen where there is a lot of rain quickly and the soil cannot absorb it as fast as it comes — if it rains really hard for an hour, let’s say. We get flashfloods out in the desert this way.
Well, my Mudslide recipe is 1 oz vodka, 1 oz Kahlua, 1 oz Bailey’s, 1 oz cream, crushed ice. I think the question really is: How many Mudslides are needed for a rainstorm?
High desert?
Everywhere. It’s really coming in.
Mudslides are only partly caused by the amount of water. The type and structure of the soil are a bigger determinant, and then we have the unique (and appropriately silly) manner of hillside construction that seems so popular in SoCal that contributed unsupported land masses to the mix - the cliffside homes, the new buildings on top of eroding bases, etc. Anything to make a buck.
http://www.structuremag.org/Archives/2006-3/California-Mud-Slides-March-06.pdf
See Figure 1, Laurel Canyon Blvd in Studio City? I saw those structures (and many others) 20 years prior to the event and was asking people in Studio City “Uhhhh... was this construction designed by a CivEng PE?” and the answer invariably came back “No, but we had licensed contractors!” Many of these properties were built quite some time back and were priced (even then) into the stratosphere of prices.
OK, licensed contractors are great, but building right up to the edge (and in Studio City, *over* the edge) of a vertical landform isn’t such a hot idea with the best of materials and money, and it is foolhardy if any shortcuts were/are taken. I was thinking as I walked around Studio City (esp up the canyons, or on Ventura Blvd looking up and west) “Man, someday, there’s gonna be a whole lotta folks who have permanent next-door visitors in their bedrooms...”
One of the questions I was asking back then that was never answered was this:
Let’s say you have such a house that is built in a slide area. Let’s further say you have a deed to this piece of property.
Does your homeowners insurance insure against the land simply... going away? ie, what happens when (not if) there is a slide/quake/etc, and your lot joins thousands of other former potential building sites at the bottom of the hill as Mom Nature continues what has obviously been going on for eons, and the property to which you have a deed ceases to exist at all?
People looked at me like “You silly man. Why, no one would dare do that to *us* — we have taste and style!”
So Calif gets storms:
I remember the forecasters telling us we would get about /12 an inch of rain in early 1980. 10 days later and over 10 inches of rain...It was a mess.
It rarely gets big Thunder and Lightning storms.
That’s why I’m interested to see if the “severe thunderstorms” come in as one forecaster is seeing from a place called OWSweather.com or Ontario Weather Service.
I can’t find it elsewhere. It is interesting though we could have severe storms.
I made a documentary for the Red Cross and since 1862 —every twelve years—there has been a killer storm for southern California. Last killer storm was exactly 12 years ago. So get ready for a whole lot of water out in South California. Mudslides, flooding, rivers full of water, fools caught in the fast moving water etc... The worst time will be January and February. Thats the historical profile. Time to clean out your rain gutters (I did mine yesterday). Get your kit ready as well. Flashlight that work. Battery powered radio. Food you don’t need to cook. First aid kit. bottles of water.
We are in the foothills north of Los Angeles/ Sierra Madre, near Pasadena. Forest starts about 1/2 miles from here. The canyons are steep, the mountains rise sharply. With chaparral burned off, the soil cannot hold the water.
We do not get soft rain as they get out east, but rather thunderstorms/ torrential downpours that don’t last too long, etc. When it rains it pours. I have been on our main road coming up the hill from the freeway — ie, civilization is not far from here — where I thought my car would be washed off the road. We had mudslides down the canyon close to here last winter.
It’s the West, you know? Wild and wooly.
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