Growing up as a kid in California, I always assumed that the rest of the world’s kelp beds and tide pools were filled with as much life as the ones we enjoy in San Luis Obispo County. Traveling throughout the world with the Navy, I quickly realized that’s certainly was not the case. The majority of coastlines that I visited did not have kelp beds and their intertidal zones were seemingly barren.
As we head into fall, you can see the kelp beds of our county growing in size before the first large swells of winter rip them apart.
If you ever have a chance to dive on these kelp beds on a day with good seawater visibility, please do it. Rays of sunlight often beam through this underwater forest illuminating fish, invertebrates and the occasional marine mammal. It has been rightfully compared to flying near the ground through a redwood forest in Big Sur.
If the boundary conditions between the atmosphere and hydrosphere are just right, California giant kelp can grow up to 24 inches in just one day! At that growth rate, you could almost see this type of algae grow in front of your eyes.
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The ingredients required to achieve this type of growth rate are plenty of sunshine and lots of upwelling. Both can be caused by the northwesterly winds that blow along much of California’s coastline. If the winds are strong enough, they can mix out the temperature inversion layer that helps to create the coastal stratus, allowing abundant sunlight to reach the water. More importantly, these winds also create upwelling.
As the northwesterly winds blow parallel to our coastline, the friction of the wind causes ocean surface water to move. Combined with the rotation of the earth, theses winds push the surface waters to the right of the wind direction, thus pushing these waters out to sea which creates a void. Cold and nutrient-rich water is drawn from below to fill this void.
The upward movement of this colder water is called upwelling. During periods of strong to gale force northwesterly winds, I’ve seen seawater temperatures along the immediate coastline drop nearly 7 degrees in just one day.
Upwelling is the primary reason why our seawater temperatures are chilly, but it also prevents the development of hurricanes.
As the nutrient-rich water reaches the surface, phytoplankton blooms often develop and form the foundation of the food web. The zooplankton population can explode as they eat phytoplankton and other zooplankton, creating abundant food for small baitfish such as anchovies.
Over the last few weeks, the waters off Port San Luis have come alive with hundreds of pelicans and shearwaters diving and swimming into the sea at fierce speeds in search of these fish.
Not only have the marine birds taken advantage of this bounty, but also larger fish and marine mammals such as humpback whales have adventured surprisingly close to Harford Pier at Port San Luis.
Because of upwelling, the waters along with the kelp beds and tide pools along San Luis Obispo County are some of the most biologically productive anywhere in the world.
This morning’s marine layer is blanketing the coastal valleys and beaches of San Luis Obispo County. However, the North County is mostly clear and sunny. Marine low clouds will burn off from the coastal valleys later this morning and from the southwesterly facing beaches by this afternoon.
The northwesterly facing beaches will remain mostly overcast with a few periods of sunshine.
The northwesterly-facing beaches (Cambria, Morro Bay, Los Osos Montaña de Oro and Nipomo) will range from the high 50s to mid-60s, while the southwesterly-facing beaches (Cayucos and Avila Beach) will range from the low to mid-70s.
The coastal valleys (San Luis Obispo) will range between the mid- to high 70s, while the North County (Paso Robles) will hit the high 90s to low 100s. Subtropical moisture will continue to stream north across the the southern and central Sierra with the threat of thundershowers, while the Central Coast will see periods of variable mid- to high-level clouds toward the eastern sky. Slightly stronger northwesterly (onshore) winds this afternoon will mark the beginning of a cooling trend, with a deeper marine layer and cooler temperatures by Monday across all locations. This cooling trend will continue each day through Wednesday.
It continues to look like a warm high pressure ridge in combination with gentle to moderate (8- to 18-mph) northerly (offshore) winds will develop Thursday. These winds should push the coastal low cloud deck offshore and to the south, with very pleasant to warm weather Thursday through about Saturday of the Labor Day Weekend, including the northwesterly-facing beaches.
Today’s Surf Report:
Today’s 3- to 4-foot northwesterly (310-degree deepwater) sea and swell (with a 5- to 10-second period) will remain at this height and period through Monday.
Increasing northwesterly winds off Cape Mendocino will produce a 4- to 6-foot northwesterly (300-degree deepwater) sea and swell (with a 5- to 9-second period) along the Central Coast on Tuesday.
The northwesterly winds off the Northern California coast are forecast to increase further to moderate gale to fresh gale force (32- to 46-mph) levels later Tuesday, generating a 5- to 7-foot northwesterly (300-degree deepwater) swell (with an 8- to 12-second period) along our coastline Wednesday through Thursday.
A 3- to 5-foot northwesterly (300-degree deepwater) swell (with an 8- to 11-second period) is forecast for our coastline on Friday through next Saturday.
Note: Swell from Typhoon Talas, currently south of Japan, is not expected to affect our area.
Arriving from the Southern Hemisphere:
An intense storm with hurricane force winds developed 700 miles southeast of New Zealand earlier this week and produced southwesterly seas of over 50 feet in height.
A long-period Southern Hemisphere (210-degree deepwater) swell from this storm will arrive along the Central Coast on Wednesday and will continue through next Sunday.
This swell is expected to reach the NOAA SE Hawaii marine buoy Xstationed about 185 nautical miles southeast of Hilo on Monday and peak on Tuesday at 5- to 7-feet (with an 18- to 20-second period).
This swell will reach the Central Coast on Wednesday at 2- to 3-feet (with a 22+ second period), gradually building to 3- to 4-feet (with an 18- to 20-second period) on Thursday.
This swell will peak at 4- to 5-feet (with a 16- to 18-second period) on Friday through next Saturday, gradually decreasing next Sunday and Monday.
Note: A few beaches in Southern California (The Wedge in Newport Beach) may see wave faces reaching over 12 feet in height.
Another southern hemisphere swell could arrive along our coastline on Sept. 19 and 20. However, it will not be as nearly energetic as this week’s event.
An increasing amount of upwelling along the coastline has produced cooler seawater temperatures.
Seawater temperatures will range between 54 and 56 degrees through Wednesday, increasing on Thursday through next Saturday.
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John Lindsey, media relations representative for PG&E and local weather expert has lived along the Central Coast for more than 25 years. To subscribe to his daily weather forecast or ask him a question, email him at firstname.lastname@example.org.