June Gloom! How is forms and why (Los Angeles, San Diego, San Francisco)

Discussion started by robweather 4 years ago

June Gloom is a southern California term for a weather pattern that results in cloudy, overcast skies with cool temperatures during the late spring and early summer, most commonly in the month of June. Low-altitude stratus clouds are formed over the ocean, then transported over the coastal regions by the wind. The overcast skies often are accompanied by fog and drizzle, though usually not rain. I've been to Southern California many times and yes it can be depressing when you look for all that typical California sunshine.

june gloom surf

June Gloom in southern California is caused by the marine layer effect common to the West Coast, and is enhanced by the Catalina eddy local to southern California. May and June together are usually the cloudiest months in coastal Southern California.

June Gloom has other colloquial names if the same weather pattern occurs in May, July, or August. June Gloom is stronger in years associated with a La Niña, and weaker or nonexistent in years with an El Niño. This weather pattern occurs in other parts of the world where climates and conditions are similar.

Scientists study the cloud fields that make up June Gloom to increase understanding of cloud behavior at the onset of drizzle and precipitation.

june gloom

A typical June Gloom morning consists of marine stratus clouds covering the coast of southern California, extending a varying distance inland depending on the strength of the June Gloom effect that day. The clouds, which are formed by the marine layer, move in at night, usually after midnight, and typically dissipate in the late morning, giving way to clear, sunny skies.

During a heavy June Gloom season, the condition may persist into the afternoon, or even all day during an exceptionally strong event. Often, the air is saturated with moisture, and fog also develops, along with frequent light mist and occasional drizzle. Fog and drizzle normally are found near the furthest inland extent of the gloom, where the cloud deck is closest to the ground. By late morning to early afternoon, solar heating usually is sufficient to evaporate the clouds, and the sun emerges. The phenomenon forms earliest and lasts longest at the coast, with weaker effects as it moves further inland. When the marine layer is strong and deep, clouds can fill the Los Angeles Basin and spill over into the San Fernando Valley and San Gabriel Valley, even extending into the Santa Clarita Valley on exceptionally strong June Gloom mornings.

june gloom2

 

If the condition is not as strong, the Basin may be filled while the valleys may be clear. It is not uncommon for motorists to drive over the Sepulveda Pass from the clear, sunny San Fernando Valley and plunge into a cloudy, fog-filled Los Angeles. On a weak June Gloom morning, the clouds and fog may only be present within a mile or two of the coastline, affecting only the beach cities.

The months of May and June are typically the cloudiest months of the year in coastal southern California, having only 59% and 58% sunny days, respectively, on average. The number of days in May and June that are "gloomy" vary from year to year. Anomalies in sea surface temperature can be used to forecast the number and intensity of June Gloom days.Years with warmer ocean temperatures, referred to as El Niño, may result in fewer gray days in May and June. Cooler ocean temperatures, associated with La Niña, usually foretell a more gray period.

June Gloom has been reported by some Californians to bring on symptoms consistent with seasonal affective disorder, although this is not well-supported by evidence. However, the normally-very-sunny Los Angeles climate also is home to people who thrive during the brief seasonal respite the gloom provides from the unending sunshine and clear skies.

marine layer

June Gloom has other names in southern California if it occurs in other months. These include May Gray if it begins early, and No-sky July or Fogust if it continues past June. In the early 20th century, this phenomenon was sometimes known as the high fog. A long June Gloom season, extending late into the summer, is known as Summer Bummer. The negative effects of a long June Gloom on the coastal California tourism industry is often reported in the local news media. The phenomenon can be especially disorienting to visitors from inland areas who, coming from the summer heat, would not expect cool temperatures and clouds and fog at the beach.

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