Hoping changing conditions bring June gloom to the Central Coast

Over the last four years, a persistent ridge of high pressure over the eastern Pacific has kept the vast majority of Pacific storms to the north of San Luis Obispo County.

Not only has this condition dramatically reduced the amount of rain we usually receive; but to make matters worse, this ridge helped produce sustained Santa Lucia (northeasterly) winds that compressed and heated the air mass as it flowed down the Santa Lucia Mountains.

This ill-fated condition caused the warmest January through March on record this year and kept the marine layer far out to sea. This lack of coastal low clouds added insult to injury because there was much less moisture for plants in the coastal regions of our county.

When fog and mist rolls in from the Pacific at night, small water droplets suspended in the stratus clouds accumulate on tree limbs, leaves or needles and fall as rain. A single Monterey pine, redwood or eucalyptus tree can soak the ground beneath it. In fact, recent studies indicate that some coastal ecosystems acquire nearly half of their yearly water from fog drip each year.

Some long-time residents of the Central Coast complain about the reduced amount of fog; it turns out their observations are valid. Cloud cover data from the San Luis Obispo Regional County Airport indicates about a 33 percent reduction in cloud cover during the summer months, the prime season for fog drip, over the last four years. In other words, Morro Gray hasn’t lived up to its reputation over the last few years.

Thankfully, there are indications that we may be shifting back to a more normal weather pattern as the persistent ridge has been replaced by a trough of low pressure off the coastline. This has given rise to stronger northwesterly (onshore) winds. These winds have increased the amount of upwelling along the coast, which brings cold, subsurface water to the surface along the immediate shoreline.

The onshore winds transport the relatively warm air from farther out to sea across the much colder water along our immediate coastline. The overlying air then becomes chilled and drops its dew point temperature, which results in the wall of gray lovingly referred to as the “fog monster” by my 10-year-old son, Sean.

This month has seen the triumphant return of the marine layer and the cooler temperatures it brings along the shoreline. In fact, several rain gauges in the Los Osos area reported about one-hundredth of an inch of moisture early Saturday morning from heavy drizzle. In the Sierra Nevada, above normal amounts of precipitation has fallen this month.

More importantly, some climatologists believe that this change in the weather pattern may be caused by the current El Niño condition. The latest guidance from the Climate Prediction Center and other long-range forecast centers indicate the current El Niño condition could strengthen to a moderate or even a strong event by late fall or winter. Of course, this is no guarantee of plentiful rainfall later this year, but it certainly looks more promising.

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In 2014, more than 300 power outages were caused by metallic balloons that drifted into PG&E power lines, affecting electric service to more than 155,000 homes and businesses throughout Northern and Central California. So if you’re celebrating graduation with metallic helium balloons, make sure they are secured with a weight to prevent them from floating away.

This story was originally published May 30, 2015 at 7:19 PM with the headline "Hoping changing conditions bring June gloom to the Central Coast."