Weather

Rain season ends with some SLO County spots at double their normal totals

A woman watches the elephant seals at Piedras Blancas under the protection of a umbrella. Coastal areas in San Luis Obispo County received considerably more precipitation this year than inland.
A woman watches the elephant seals at Piedras Blancas under the protection of a umbrella. Coastal areas in San Luis Obispo County received considerably more precipitation this year than inland. jjohnston@thetribunenews.com

San Luis Obispo County wrapped up a welcome above-average rain season Friday with totals that saw some coastal locations reaching double their normal amounts.

From San Simeon to Nipomo, every weather station monitored by the county’s Public Works Department either roughly met or exceeded rainfall averages for the rain season ending June 30. But local communities along the coast exceeded their averages by much higher amounts than those inland.

The county’s largest recorded total for the year fell at Rocky Butte near San Simeon where 87.11 inches of rain was recorded, more than double its average of 40 inches, according to the county Public Works’ rainfall data.

Camp San Luis tallied 33.33 inches compared to a normal year of 20; Arroyo Grande saw 27.96 inches vs. its average of 18; and Hog Canyon Road in Paso Robles nearly met its annual average of 16 inches, with a total of 15.96.

“The nature of this year’s rainfall season was that we didn’t see a lot of convective storms (or thunderstorms), which are more in the mid to upper levels of atmosphere and tend to drop more rain inland,” said PG&E meteorologist John Lindsey.

Instead, Lindsey said, the county had more low level atmosphere, subtropical systems that dropped more rainfall along the coast.

Lindsey recalled that on one day Rocky Butte was soaked by up to 12 inches of rain while over the hills to the east, Paso Robles only saw a trickle, half an inch.

Atascadero tallied 22.18 inches this season, compared with its average rainfall of 18. Rain in Shandon totaled 12.68 inches, just over it’s annual average of 12.

The rainiest months were January and February, which together accounted for more than 60 percent of the rainfall at Cal Poly’s station. The weather station at the university tallied more than 13 inches in January, 11 inches in February, and nearly 39 inches for the year.

To put that in perspective, the highest rain total in the past five years at the Cal Poly station was 19.4 inches in 2015, and the lowest was nearly 10.6 recorded in 2010.

A scant amount of rainfall dropped during the summer months last year, but none fell in June.

Lindsey said this year was a weak La Niña, similar to 1964, 1994, and 2004. A split in the jet stream caused a shift farther southward and steered significant surges of subtropical moisture from the Pacific Ocean toward California, he said.

The phenomena is also referred to as the “pineapple express” and produces higher amounts of rainfall.

With a wet season, local lakes and reservoirs that were well below capacity last summer have significantly increased their volumes.

According to the latest county figures, Lake Nacimiento is now at 74 percent capacity, Santa Margarita Lake, or Salinas Reservoir, is at 100.2 percent, Whale Rock Reservoir is at 78 percent, and Lopez Lake is at 60 percent.

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