Cold Bay Area Weather Creates ‘May Gray’ and ‘June Gloom’

RIP Springtime (April 27, 2023 – April 27, 2023).

After a historically harsh winter and then a momentary heat wave, summer fog is already blanketing the Bay Coast region, a dismal pattern that is expected to persist into next week. And beyond.

“It’s covering the bay every morning, and some of it has entered the delta,” said meteorologist Jan Null of Golden Gate Weather Services at Half Moon Bay, which experienced only one fogless sunset while the month.

“It’s a year where that summer pattern sets in early,” he said.

Sure, Memorial Day weekend is always a melancholy holiday, honoring the tragic loss of young lives alongside picnics and barbecues. Thus, our time strikes an appropriate tone.

Beachgoers at Point Reyes National Seashore sat bundled up in jackets and sheltered between the dunes. Only a few people braved swimsuits, and all of them were children.

Monday forecast: foggy with a high risk of frustration.

The best weather drama of the holidays occurs in the Sierra Nevada, where towering cumulus clouds produce thunderstorms and lightning.

Because of all the snow, there’s a tremendous amount of water vapor, according to National Weather Services meteorologist Rick Canepa. When heated by the sun, this water and warm air pockets begin to rise – updrafts propelled by mountain ridges and peaks. All this atmospheric instability creates storms.

The meteorological summer begins in two days, and not on the date of June 21 associated with the vernal equinox, called astronomical summer.

But the lingering low white clouds have already worn out their welcome.

This spring was 2.3 degrees cooler than average in San Jose during the months of March, April and May, Canepa said. The city’s temperature averaged 57 degrees, down from a historic average of 59.3 degrees.

If March was cold, it wasn’t your imagination. That month was 4.2 degrees below normal.

Oakland’s spring was even colder. The city’s average temperature was 55.5 degrees, more than three degrees lower than the historical average of 58.7 degrees. This is the third coolest spring on record since 1970.

It was the coldest spring in Half Moon Bay since 1999, Canepa said.

Do you remember those days when it was hot and sunny? Me neither.

But records show it happened a month ago, when temperatures hit 88 degrees in San Jose and 80 degrees in Oakland on April 26. There was another brief spike on May 13, when it reached 87 degrees in San Jose and 81 degrees in Oakland.

Anonymous Twitter personality @KarlTheFog commemorated our brief spring in a poem: “Roses are red. The fog is gray. Yesterday was summer. But it’s winter today.

As usual, the fog was most persistent at lower coastal elevations, thinning out at midday and in inland and high locations.

Driving under cool, cloudy skies, Matthew Dodder of the Audubon Society of Santa Clara County reached the top of the Santa Cruz Mountains this weekend to find sunshine and warmth — plus an exuberant springtime chorus of martins purple flycatchers, olive-sided flycatchers, western woodland peewees, blue-grey gnatcatchers and other special birds.

To the east, one of the earliest springs in recent memory has turned nature’s calendar upside down, with leaves appearing 23 days earlier in Baltimore and 11 days earlier in Atlanta, according to the USA National Phenology Network, which tracks seasonal changes. But the leaves germinated three days late in San Francisco and six days late in Los Angeles.

North of us is hot, with record high temperatures recorded in the Pacific Northwest and western Canada. Memorial Day will be mild in Portland, where temperatures could reach 79 degrees. In Seattle, it is expected to reach 70 on Memorial Day.

Here in the Bay Coast region, we are off to a great start on June Gloom.

Certainly, the fog has its fans. Sales of souvenir sweatshirts to chill tourists helps put money back into our local economy. Moisture is mopped up by thirsty redwoods and lichens. Without fog, film noir classics like The Maltese Falcon and Vertigo would lack mystery and dread.

What is going on?

May is usually a month of transition — fog free at first, then more and more gray, Null said.

Fog is caused by differences in seawater temperature and air temperature. Called the “marine layer”, it forms when warm, moist air passes over a body of cold water.

In late spring, the ocean water temperature remains quite cold and cools the lowest layer of the atmosphere, creating a stark contrast between it and the warmer layer above. This creates a temperature inversion, trapping cold air which eventually cools to its saturation point to form clouds.

Recently, the ocean has been exceptionally cool. A few days ago, temperatures of 49 degrees were measured on a buoy off the Sonoma County coast near Bodega Bay. .

And areas of low pressure in the upper atmosphere, called “troughs,” deepen this marine layer. Deeper sea layers can create fog far inland.

Normally, a pattern of low and high pressure systems dance around the mid-latitudes of the globe. Everything keeps moving.

“But we’ve had these dips on us all month… Not much is moving,” Null said.

Eventually the troughs will say goodbye and an anticyclone will arrive, brightening our days. As the air temperature warms, the cloud droplets evaporate until the sun shines, scorching the marine layer. The ocean will warm up. The National Weather Service’s Climate Prediction Center predicts a 33 to 40 percent chance of above-normal temperatures across most of California this summer.

But Fogust is just around the corner. To be followed later by Fogtober.