Catalina Eddy. It’s not an old fishing buddy of mine who like to hit the island every weekend. It’s a weather phenomenon that you’ve probably heard of…but what exactly is it?
A very typical late spring/early summer pattern along the west coast has a semi-permanent area of high pressure over the eastern Pacific…known simply as the “Pacific High.”
Wind circulating around a high pressure center in the northern hemisphere flow clockwise, producing a general, steady northwest wind along the California coast.
As that wind blows past the Central Coast, it encounters the Southern California “Bight.” That refers to an abrupt shift in the orientation of the coastline from North-South to more of a West-East alignment.
This curved stretch of coast extends from Point Conception south to San Diego and includes all of the Channel Islands.
When the wind interacts with the bight, a counter clockwise circulating low pressure area forms with its center in the vicinity of Catalina Island.
This formation is typically accompanied by a southerly shift in coastal winds, a rapid increase in the depth of the marine layer, and a thickening of the coastal stratus.
A bummer for beachgoers is our typical marine layer known as “May Gray” or “June Gloom.”
A Catalina eddy is rarely prolonged.
Heat over the deserts causes air to rise.
That results in an increase in the normal onshore winds causing the vortex to dissipate.
The end result is the common local weather forecast calling for “late night and early morning low clouds and fog, followed by hazy afternoon sunshine and sea breezes.”