Next week's storms

In the last post, I talked about the active weather pattern predicted by computer models for the first week of October, but there was considerable uncertainty in that forecast. Well, as the event(s) draw closer, we have a better idea of what will happen.

Storm #1: The first storm is already impacting the West Coast, with a weak cold front moving into Washington, Oregon, and northern California. This is evident on the visible satellite image below. This will bring some light rain to those areas, but the precipitation will stay well north of San Francisco. This front is, however, helping to disturb and breakup the marine layer. That's why we're not seeing much fog around the Bay today. Also of note is the big swirl west of Mexico. Those are the remains of Hurricane Hilary. A few days ago, Hilary was a very strong hurricane, but has since moved north over cooler waters and weakened (hurricanes get their energy from warm ocean waters, usually mid-80'sºF or warmer).

Storm #2: The second storm is still well offshore but is stronger and will move further south than the first storm. The computer models are still a little uncertain on timing, but it looks like light rain will spread over our area Monday afternoon, starting in the North Bay. We won't get a lot of rain out of this system (maybe a quarter-inch), but this will be the first widespread rain event of the season.

Storm #3: We'll have a break on Tuesday with partly sunny skies. The final and strongest system will move in Tuesday night into Wednesday. This system will bring several hours of rain, which will be moderate to heavy at times - rainfall totals may be over one inch. Let's keep in mind that the average rainfall at SFO for the entire month of October is 1.04 inches. This storm also may bring a period of gusty winds as the cold front itself moves through. And, colder air associated with this front will result in snow in the high Sierras - mostly above 7000 feet.