As the spring sun reaches farther northward toward the first day of summer, extreme storm activity in the northern Pacific and the high-energy winter waves that they generate will fade to a memory. Wave action along the Central Coast is seasonal, responding to the storms that move over the northern and southern Pacific Ocean.
This wave climate has a profound effect on many of our treasured sandy beaches. These beaches provide homes to countless creatures, nearly endless recreation opportunities and a lift to our spirits. They are also an important financial asset for San Luis Obispo County, attracting millions of dollars a year in tourism.
Generally speaking, waves become wider and deeper during summer and narrower and shallower during winter as waves and currents move a river of sand back and forth from the sea. However, bulky Southern Hemisphere swell trains during summer can also produce beach erosion.
The dirty-blond beaches of the Central Coast are mostly made of erosion products of pebbles, rocks and boulders along with seashell fragments.
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Unfortunately, they can also include our junk, such as glass or plastic.
Overall, the flatter the beach, the less wave energy it normally receives. The material from which the beach is made is smaller, ranging from sand to fine silt. In general, beaches with high wave action are steeper in character and are composed of larger pebbles or cobbles, and even boulders in extreme situations.
When the high-energy waves hit our shoreline, the sediments stored in the dunes and berms of the beaches are transported out to sea, leaving behind narrower beaches, larger rocks and sometimes even exposing bedrock. During calmer wave conditions, this sediment is transported by currents toward the land and stored in the dunes and berms of the shoreline.
It’s amazing the amount of sand that is actually transferred back and forth from deeper water. One of my jobs at PG&E was to dive on the mooring system that holds the Diablo Canyon Waverider buoy in place. A 600-pound solid steel railroad wheel anchors this mooring and is in about 100 feet of water. On some dives, the top of the railroad wheel would be exposed to our eyes; on other dives, the wheel would be buried under several feet of sand.
Today’s weather report
A 1,022-millibar high will remain nearly stationary about 400 miles to the southwest of San Luis Obispo for an extended period.
High pressure in the upper levels of the atmosphere will build in from the west. This condition will bring slightly warmer temperatures today for the North County and coastal valleys. However, marine low clouds and weak onshore flow will keep the beaches mostly overcast through Monday morning.
Today’s maximum temperatures will range from the high 50s to low 60s along the beaches, mid-60s in the coastal valleys and the high 80s to the low 90s across the North County.
An upper-level low-pressure system will approach the Central Coast tonight and most likely bring extensive coastal low clouds, fog and areas of drizzle tonight into Monday morning.
This low-pressure system will be followed by a pattern of fresh to strong (19- to 31-mph) northwesterly winds during the afternoon hours along with marine low clouds and fog along the beaches and coastal valleys during the night and morning hours. The skies will remain clear in the North County and will clear from the coastal valleys and most of the beaches during the afternoon hours.
Temperatures will remain near normal through the week as northwesterly onshore winds persist. This typical late spring/summer weather pattern will continue through Friday, if not longer.
Today’s surf report
Today’s 2- to 3-foot northwesterly (315-degree deep-water) swell (with an 8- to 11-second period) will remain at this height and period through Monday morning.
Fresh to strong (19- to 31-mph) northwesterly winds will generate 2- to 3-foot northwesterly (320-degree shallow-water) seas Monday afternoon. These short-period northwesterly seas will continue through Friday.
Arriving from the Southern Hemisphere: A Southern Hemisphere swell with intervals of more than 22 seconds will arrive along our coast this afternoon at 1 to 3 feet, building to 2 to 4 feet (with a 17- to 19-second period) Monday and Tuesday.
This swell will remain at this level but its period will gradually decrease through Wednesday. Another low-height and long-period Southern Hemisphere swell is expected along our coastline Thursday through Friday.
Seawater temperatures will range between 53 and 56 degrees through Monday, decreasing to 52 to 54 degrees Tuesday, and will remain at this level through Friday.
An interesting blog that provides an in-depth look at the intersection of energy and the environment can be viewed at www.pge currents.com/next100/.
NEXT100 is written and edited by Jonathan Marshall, and it focuses on trends in clean technology and the Earth’s climate that will most impact the energy industry and PG&E customers over the next 100 years — PG&E’s second century in operation.
John Lindsey, meteorologist 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.