“I have been amazed at the strong offshore winds that can occur in and around Morro Bay during this time of year. I’ve noticed the weather station on top of the hang glider hill in Cayucos sometimes hits gusts of 50+ mph during these offshore events. What is so remarkable is how localized these winds appear to be.” — Karl Schoettler, Visalia
This January, I have received other emails commenting on the variance in the speed of these Santa Lucia (northeasterly) winds from one location to another.
Last Friday, a low-pressure system moved southward along the spine of the Sierra Nevada mountains, followed by an area of strong high pressure that produced a steep pressure gradient that in turn created gusty northeasterly winds in many parts of California, including the Central Coast.
Diablo Canyon reported sustained northeasterly winds of 31 mph with gusts of 61 mph at 8:45 p.m. on Friday. The PG&E Mt. Lowe weather station on the Cuesta Grade saw northeasterly wind gusts of 59 mph, while Whale Rock Reserve reported gusts to 50 mph.
In fact, gusty Santa Lucia winds were felt in the Estero Bay area, especially along Highway 41 from Morro Bay High School heading toward Atascadero about halfway up the grade, as well as the coastal canyons and gaps, and parts of eastern San Luis Obispo, including Cal Poly, San Luis Obispo High School and French Hospital Medical Center. However, many other San Luis Obispo County locations only reported gentle winds.
It is much easier to predict the wind speed coming off the ocean with no obstructions than from the land. Due to the Santa Lucia, Caliente, La Panza mountain ranges in San Luis Obispo County and the Sierra Madre, San Rafael and Santa Ynez mountains in Santa Barbara County, wind speed can be radically different over a short distance, and here’s why.
To begin with, the direction of the wind is reported by the direction from which it originates.
Westerly winds blow out of the west toward the east and are called “onshore.” In other words, the air blows from the ocean to the shore. Easterly winds blow from the east to the west and are called “offshore” winds, the air that blows from the land to the sea.
Over the decades, I have often been told that the terms “onshore” and “offshore” as applied to winds are confusing in two ways: The terms are vague and fuzzy in themselves — offshore sounds like it could be inland — and especially so since those terms don’t define the perspective from which the winds are considered.
Due to the topography of the Central Coast, offshore winds are typically downslope winds, which are technically called “katabatic wind,” from the Greek word katabatikos, which means “going downhill.”
Traditionally, according to wind data recorded at Diablo Canyon Power Plant’s meteorological tower, the winds blow about 60 percent of the time out of the northwest quadrant along the Pecho Coast. The winds blow approximately 12 percent of the time out of the northeast quadrant and about 23 percent out of the southeast quadrant. The other 5 percent of the time, the winds are spread evenly across the rest of the cardinal headings. Northeasterly Santa Lucia winds are more common during dry years, while wet years will see more prefrontal southeasterly winds.
This January, transitory high-pressure systems over the Great Basin have been common, perhaps due to the current La Niña condition, which tends to push the jetstream/upper-level winds further northward into the Pacific Northwest. Historically, this tends to lead to below-average rainfall for the Central Coast.
These gusty Santa Lucia (northeasterly) winds are often low-level winds associated with canyons, passes and gaps in the coastal mountain ranges.
If the canyon is orientated toward the northeast, the Santa Lucia winds are funnel and accelerated down the canyons like a venturi and become turbulent and gusty in nature. This condition is similar to a river flowing through a narrower channel over boulders and creating rapids.
If the winds shift out of the north or east, even by a few degrees, the winds can rapidly decrease from one area to another. Naturally, if the pass is orientated in a northerly direction, winds out of the north can be accelerated, while easterly winds can be blocked. This is one of the main reasons the wind speed can be radically different from one location to another over a short distance in the coastal regions of the Central Coast.
PG&E has completed its long-term goal of installing more than 1,300 weather stations in high fire-threat areas. These weather stations are used year-round and will help to further improve weather forecasting capabilities. The station observations are available to state and local agencies and the public through such online sources as pge.com/weather, at the National Weather Service, and MesoWest at mesowest.utah.edu/.