Why does the Southern California FOG Bank always seem to move?

Question

*farther inland* than the Bay Area FOG Bank??

The Bay Area is a much cooler area than Southern California, right?
So the FOG should move farther inland in the Bay Area and not......Southern Calif.

What gives?? :)

http://www.nrlmry.navy.mil/sat-bin/display10.cgi?SIZE=full&PHOT=yes&AREA=pacific/eastern/sierra&PROD=vis&TYPE=ssmi&NAV=epac_westcoast&DISPLAY=Latest&ARCHIVE=Latest&CGI=epac_westcoast.cgi&CURRENT=20071103.2130.goes11.vis.x.sierra.x.jpg&MOSAIC_SCALE=15

(Yes. I live here in the Bay Area :)

Answer 1

In additon to what "Big kat" said, i think part of the reason too is that the fog is not as low to the ground. The fog along coastal Southern CA is not as thick or dense usually as the fog that tends to blanket the Northern CA coast. The fog in Northern CA is cooler and produces more wind when moving in than in SoCal. The fog is not as low to the ground and the ceiling is higher so it can move farther inland over the mountains and hills along coastal SoCal.

They really don't call it "fog" down in SoCal that much either, it's usually just referred to as the "marine layer" b/c it's not that close to the ground and produces more overcast like conditions than thicker, heavier fog found in the bay area. It is cooler in the Bay Area and colder air is heavier so that could be part of the reason the fog is closer to the ground that in SoCal and why it does't move as far inland. Both the ocean and air temperatures are warmer in SoCal so that is probably part of the reason why the marine layer isn't as cold and dense as it is in NorCal.

Answer 2

Hi,
There are a couple of obstructions in the San Francisco Bay Area that helps to keep the "FOG" from flowing inland. First is the coastal hills or Mt range. This stops or slows down the marine layer. You can watch this take place as the fog rolls over the coastal hills and down into the Bay Area. The next would be the inner hills or Mt range that run from the North Bay above Napa, Vallejo, all the way down the bay to way south of Holister.
Next is the prevailing North-Westerly winds. These winds are constant and blow the fog down the bay toward San Jose. This is the funnel effect as the fog moves and comes in contact with the warmer conditions in the South Bay the fog burns off.
The fog will come in through the Golden Gate and make it all the way to Antioch and even inland form there.
The Southern California "FOG" moves inland because of the lack of coastal hills and the way the state is located south of Pt Conception. The south-land turns and runs West to East more than North to South
The Los Angles area is like the south bay the fog funnels in with no restrictions. Hence the "FOG" flows inland along. way.
Hope this helps....

Answer 3

you actually have two different types of fog that you are referring to. southern california and most inland valleys like the central valley gets what is called Tule fog. which sort of isn't really fog at all. it is forms in the late fall and into the winter most of the time when cold mountain air down into the valleys during the night, and fills them to the brim so to speak. there isn't a lot of wind, and thus the fog bank can't move resulting in very thick fog.

normal fog on the other hand technically a cloud that touches the ground. Point Reyes is one of the foggiest places in the world...just north of San Francisco, in Norcal.

And just because the bay area is cooler than so cal, that isn't really the answer...not all fog happens because it is cold. A lot of it has to do with wind movement and osbstructions. if you have a frontal system that moves fog inland from the ocean, and it meets say the mountains of santa cruz, san jose may not get foggy. but the marine layer in san diego could go a long ways inland due to lack of mountains keeping the fog at the coast.

Answer 4

Ahhh... that my friend is the dreaded "tule" fog. The stuff that causes all those horrible pile-ups on Southern California highways. There was one last weekend where 108 cars were involved and two people died. Most people will tell you that it only occurs in the central valley but if you've ever been in the farmland along the So. Cal. coast you know different. I remember driving with my family through Oxnard one time as a kid and I could barely see the brake lights of the semi in front of us. Scary as hell.