This was a wacky winter. Warmer than usual during the day, extra chilly at night, which put the well-known microclimates of San Luis Obispo County in sharp focus. Causing all the wackiness was an unusually high amount of northeasterly offshore winds coupled with many days of clear and dry winter skies.
I’ll give you a few examples.
Since 1948, Paso Robles has averaged a minimum overnight temperature of 34.9 degrees. This winter it averaged a bone-chilling 31.4 degrees, or about 3.5 degrees colder than normal. The city’s average maximum temperature is 60.8 degrees, while this winter it was 64.4 degrees. As you might expect, the overall average temperature was a normal 47.8 degrees, with the cold nights canceling out the warm days.
At Cal Poly, the average minimum temperature since 1928 is 42.1 degrees; this winter it was 39.8 degrees. The average maximum temperature on campus is 63.1 degrees, while this winter’s average was 65.7 degrees. The overall average temperature, meanwhile, was slightly above the normal 52.6 degrees.
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An abnormally high number of nights saw temperatures below the freezing level, especially in the valleys that were protected from the northeasterly winds. Without the winds, the denser cold air flowed downward along the mountain slopes and accumulated on the valley floors. On the other hand, the persistent offshore winds produced warmer conditions in the passes, canyons and gaps in the coastal mountains. During these wind events, morning temperatures varied widely, even among locations just a few miles apart.
Former county Supervisor Bill Coy, who grows avocados on his Cottontail Ranch near Cayucos, told me this was one of the coldest winters he can remember, with plenty of nights in the high 20s and low 30s. However, he didn’t experience any hard freezes like those in the winters of 1987, 1990 or as recently as 2007, which produced extensive frost damage throughout the Central Coast.
“When the winds were blowing, our overnight temperatures were mostly in the low 40s, while just a short distance away, our neighbors reported high 20s or low 30s,” Coy said.
When temperatures did drop below freezing, Coy would activate the wind machines on his ranch. These machines mix the cold air at the surface with the warmer air above, which can prevent frost from developing. He used his wind machines only about seven or eight times this winter. Some fellow avocado growers in the coastal valleys near Cambria have run their machines between 12 and 16 nights per month, which becomes quite expensive.
Most of these machines use propane, which goes for about $4 a gallon, and when they are running, they consume about 10 to 14 gallons per hour!
John Salisbury of Salisbury Vineyards in Avila Valley said the great number of nights that dropped below the freezing temperature this year delayed the wine grape bud break. Consequently, most of San Luis Obispo County’s vineyards escaped the ravages of frost this spring, unlike last year. Early indications, especially from the pinot noir vines, indicate a good crop of grapes this year.
Today’s weather report:
Yesterday’s high temperature reached 96 degrees in Paso Robles, while San Luis Obispo only was able to peak at 74 degrees as the marine layer deepened along the coastline.
A 1,007-millibar low-pressure system will develop about 100 miles west of San Luis Obispo today and will be nearly stationary through Monday. This system will produce gentle to moderate (8- to 18-mph) southerly winds, extensive marine clouds and fog with significantly lower temperatures today through Monday. The marine layer will burn off from the coastal valleys by the afternoon hours, but will persist along the beaches today.
Today’s maximum temperatures will reach the low 80s in the North County and the low to mid-70s in the coastal valleys. The beaches will only reach the 60s.
The southerly winds will increase Monday, producing more sunshine and higher temperatures along the northwesterly facing beaches (Morro Bay, Los Osos, Montaña de Oro State Park and the Nipomo Mesa), while the rest of the coastline should remain mostly overcast through the day.
A vigorous late-season upper-level low will approach our coastline Tuesday with moderate to fresh (13- to 24-mph) southerly winds and increasing mid- to high-level clouds. As this storm approaches the Central Coast, moderate to heavy rain will develop Wednesday with a chance of thunderstorms. Rain will turn to scattered showers and a chance of additional thunderstorms Thursday.
Strong to gale-force (25- to 38-mph) northwesterly winds and mostly fair weather should develop Friday and continue through next weekend. Today’s surf report:
Today’s 3- to 5-foot northwesterly (295-degree deep-water) swell (with an 8- to 11-second period) will lower to 2 to 4 feet (with a 9- to 12-second period) and will remain at this height and period through Friday.
Combined with this northwesterly swell will be 1- to 2-foot southerly (190-degree shallow-water) seas Monday, building to 3 to 4 feet Tuesday through Thursday.
A 6- to 8-foot northwesterly sea and swell (with a 5- to 12- second period) is forecast along our coastline Friday through next Sunday. Seawater temperatures:
Seawater temperatures will range from 51 to 53 degrees through Monday, increasing to 52 to 54 degrees Tuesday through Thursday.
Congratulations Oceano Elementary School teacher Jim DeCecco is PG&E’s 2012 Solar Schools Inspirational Educator of the Year Award winner.
DeCecco was presented the award in a surprise presentation in the classroom Friday.
DeCecco and his class will receive a trip to the San Francisco Giants game on Sunday, July 15. They will go on a behind-the-scenes tour of the ballpark and see the stadium’s sustainability actions. Students will also have an opportunity to go onto the field to shout, “play ball,” and DeCecco will get to throw the ceremonial first pitch of the game.
John Lindsey is a media relations representative for PG&E. He is a local weather expert and has lived along the Central Coast for more than 25 years. If you would like to subscribe to his daily weather forecast or ask him a question, send him an email at firstname.lastname@example.org.