Catalina eddy

The Catalina eddy leads to June Gloom, which is so much a part of the late spring and early summer weather in Southern California.

[2] Though the coastal marine layer can develop at any time of the year, predominantly these eddies occur between April and September with a peak in June.

When the flow is blocked by the mountains that ring the Los Angeles Basin to the east and north, a counterclockwise vortex is created.

As the heat over the deserts causes air to rise, the resulting pressure gradient and increase in the normal onshore winds causes the vortex to dissipate.

The result is the common local weather forecast calling for "late night and early morning low clouds and fog, followed by afternoon sunshine and sea breezes."