Coastal California "May Gray" Continues
May 05, 2012; 5:50 AM
Weather folks call it a marine layer. Most other Southern California natives call it "May gray" or "June gloom." At any rate, it's here.
Moisture will continue to stream in off the Pacific Ocean in the low levels of the atmosphere.
Coastal areas and a portion of the inland empire are in for the morning low clouds and areas of drizzle into the weekend and beyond.
The marine flow will vary from day to day and along with it the extent and duration of the cloud cover.
The deck of clouds will tend to lift and, in some cases, break up during the midday and afternoon. However, some coastal areas will merely switch from low overcast with drizzle to mid-level overcast and no drizzle.
For non-natives and recent residents, the onshore flow of moisture and the clouds it brings can be caused by several features which can take turns or combine forces.
The most simple explanation has to do with the action of the interior being heated by the sun. The rising air over the interior is replaced by a flow from the west, grabbing cool, moist air from the Pacific along the way. This is most common during the late spring and early summer.
According to Meteorologist Mark Mancuso, "A dip in the jet stream (trough) in the West can also scoop up moisture from the Pacific, dumping low clouds along the coast."
"If this is intense enough it can contribute to pockets of rain," Mancuso added.
The trough can occur at just about any time of the year, but is most common during the late fall, winter and early spring.
Finally, the infamous Catalina Eddy, or circulation created in part by the topography and shape of the Southern California coast, can pump low level clouds across part of the region, mainly from Point Conception on south to northern Baja California, Mexico.
This archive satellite image and stream flow overlay appears courtesy of the National Oceanic and Atmospheric Administration (NOAA).
During intense cases, clouds can reach into the inland valleys. This counterclockwise flow of air is most common in the spring and summer.
The pattern will bring near to slightly below-normal temperatures along the coast. Across the interior valleys and over the deserts, temperatures will average near to slightly above normal.