“A great sea fog is not homogenous – its density varies; it is honeycombed with streets, it has its caves of clear air, its cliffs of solid vapour, all shifting and changing place with the subtlety of legerdemain.” ~ Henry de Vere Stacpoole, “The Blue Lagoon”
It’s that time of year again, albeit a little early. More associated with June’s weather, the marine layer is slowly creeping inland this May. Leaving the cold Pacific Ocean waters behind, it drifts into the inland valleys. Temperatures drop and the sun disappears, obscured by heavy fog. Days go by without much of a break as sometimes it remains overcast until noon if not the entire day. In years past, it managed to linger beyond the Fourth of July. Usually the gloomy weather is just an annoyance as we anticipate clear summer days. Sadly, last Sunday a pilot lost his life due to the lack of visibility; a heavy blanket of fog shrouded the San Gabriel Mountains below Mt. Wilson. Once known only as “June Gloom” the term expanded to include “May Gray” as well. The weather may be a little dull and ho-hum for our liking, but atmospherically speaking it is considered a unique climatic condition. Besides Southern California, only a few places in the world have the right combination of factors making for an annual fog. Those include Namibia in South Africa, the Canary Islands and Peru. So what exactly happens in our part of the world? According to the National Weather Service, the marine layer is not the stratus or the fog; it refers to a layer of cool moist air over the cold ocean waters off the U.S. west coast. As summer approaches, the upper atmosphere warms and creates a ceiling, trapping the cooler layer beneath. Within a 2,000-3,000 foot space, the marine layer transforms becoming low clouds, fog and mist. With an assist from the Catalina Eddy (a wind pattern), the marine layer often reaches into the desert. Thus the short story of “May Gray and June Gloom.” We’ve enjoyed a couple of warm clear days as an offshore flow pushed the marine layer out to sea. Come Friday a cooling trend, compliments of a good dose of “May Gray,” settles in. These typical springtime conditions are expected to stay with us into early next week. As summer draws nearer, we’ll look back longingly at these cool foggy days. Sue Kilpatrick is a Crescenta Valley resident and Official Skywarn Spotter for the National Weather Service. Reach her at firstname.lastname@example.org.