Missing: Sunshine in SoCal

An example of "May Grey" in Southern California (Source: Associated Press)

It's that time of year again in Arizona. The mercury rises, schools let out and Phoenicians head west.

We jokingly call San Diego "Phoenix West" in the summertime and if you take a walk down the boardwalk, it's easy to see why. You'll spot many ASU and U of A hats, and likely even run into several people you know from the Valley.

If you're familiar with California in the summertime, you've likely heard of May Grey and June Gloom.

Visitors seeking the sunshine on the beaches may be disappointed at the lack of rays during these two months.

Although it varies somewhat year to year, it’s a fairly reliable weather phenomenon that means there are typically fewer sunny days in late spring and early summer along the Southern California coast.

Mobile/App users: Click here to see the AP image of "May Grey"

A layer of marine stratus is the culprit. Sometimes this marine layer of low clouds sticks around all day, and sometimes it’s mainly a morning fog, giving way to an almost hazy afternoon sunshine. These coastal clouds also lead to cooler temperatures, which is why there can be such a big difference between temperatures sometimes a few miles inland and on the beach.

These low, coastal clouds can be seen on satellite imagery like on this day in June of 2004.

Mobile/App users: Click here to see the NWS satellite image of "June Gloom"The usual marine layer common to the West Coast plays a role in the May Grey and June Gloom formation, but so does something called the Catalina eddy. The eddy often forms near Santa Catalina island and can enhance the June Gloom by pushing a deep layer of stratus clouds inland.

Usually, this eddy weakens when the land heats up in July. As the air over the desert heats and rises, a stronger onshore flow develops and the eddy begins to dissipate. Occasionally, the gloomy conditions can last until July or August...which locals have dubbed "No Sky July" and "Fogust."

Again, the number of days of "gloomy" weather varies year to year. Some years there are just a few overcast days, and some years there are stretches of several weeks in May and June without sun along the coast.

Forecasters in that region often look at ocean temperatures leading up to those months to predict whether or not the year will be "gloomier" than normal. Cooler waters associated with La Nina conditions often lead to more cloudy days during May and June. Generally, more sunny days can be expected during El Nino years.

This year, recent months have brought near-average sea surface temperatures, with neither El Nino or La Nina conditions present. So that makes it tough to predict what June will look like if you’re headed west to San Diego.

But I can still guarantee you it will be a whole lot cooler than the Valley of the Sun.

See you there!--April

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