Weather Watch

It's been really windy in SLO this spring. Why that's bad for fire — but good for giant kelp

Marine biologist Jim Kelly holding California Giant kelp in the Diablo Canyon Marina.
Marine biologist Jim Kelly holding California Giant kelp in the Diablo Canyon Marina. Special to The Tribune

A late-season upper-level trough parked over the Central Coast will create gentle southerly winds, mostly cloudy skies and areas of heavy drizzle with a few light rain showers on Father’s Day along the coastal regions of San Luis Obispo and Santa Barbara counties.

This late spring tempest will give us a break from the relentless northwesterly winds we’ve seen this spring.

I have received numerous emails commenting on the stronger-than-normal spring winds. Bob Huttle wrote: “I’ve lived in San Luis Obispo County for almost 40 years and I never recall having such strong winds for so many weeks. What’s up?”

The meteorological towers at Diablo Canyon Power Plant have recorded some of the most persistent and robust northwesterly winds during June in decades. Numerous days this month have seen afternoon northwesterly wind gust to 50 mph; on June 9, wind gust reached 56 mph.

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This condition has produced vast amounts of upwelling.

As the northwesterly winds blow parallel to our coastline, the friction of the wind causes the ocean surface water to move offshore, causing upwelling as cold and nutrient-rich subsurface water rises along the immediate shoreline. On June 12, the seawater temperatures at Diablo Canyon dropped to 48 degrees.

These winds also tend to mix out the marine/temperature inversion layer, leaving behind mostly clear skies with plenty of sunshine. This condition has created optimum growing conditions for kelp this spring. You see, kelp loves nutrient-rich, cold and clear water with lots of sun, all of which can become abundant during heavy upwelling events.

Giant kelp (Macrocystis) can grow at the unbelievable rate of 1 to 2 feet per day under the right conditions along the Central Coast, ultimately reaching well over 150 feet in length. Giant kelp is one type of marine algae or seaweed among thousands that exist in the oceans. Seaweed is divided into three color varieties: green, red and brown.

Marine biologist along the Pecho Coast reported exceptional amounts of kelp and other marine algae growth. In fact, a diver with 30 years of experience at Diablo Canyon claimed the algae growth is unprecedented for this time of year.

Which leads to the question, what can coastal California expect with a warming climate? One possible scenario could be more persistent northwesterly winds and a more considerable amount of upwelling.

Let me explain: As the Central Valley warms, it could produce a deeper thermal trough, which is often a predominant weather feature during the spring, summer and fall. A deeper trough would create a stronger pressure gradient between the waters off our coast and the interior, producing a higher frequency of occurrence of northwesterly (onshore) winds and cooler air temperatures at the lower levels of the atmosphere.

Over the past few decades, this hypothesis seems to be verifying. The stronger northwesterly winds have reduced the amount of low coastal clouds and the fog and mist they bring. Cloud cover measurements collected from the San Luis Obispo County Airport shows a downward trend.

This situation is leading to problematic conditions for our treasured firefighters. These winds not only help to dry vegetation through evaporation but also provide plenty of oxygen to combust.

Overall, warmer air temperatures, cumulative winds and abundant fuel have fed into a dreadful feedback loop. Average yearly temperatures are forecast to rise by 6 degrees by the end of this century. According to Cal Fire, a 300 percent increase in wildfire risk in non-urban areas of California is predicted by 2050 due to climate change.

None of this is comforting considering the enormous amount of uncertainty about our climate.

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With each passing year, I’m more and more convinced that climate change is caused by human activity, but others feel it’s just a natural cycle. Regardless, we can all agree that having clean air to breathe is a fundamental human right. In 2017, nearly 80 percent of the electricity that PG&E provided to our customers came from sources that are renewable and/or emit no greenhouse gases.

John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at or follow him on Twitter: @PGE_John.