Weather Watch

Looks like a wet winter despite La Niña

Just like last year, the above-average rains this fall seem to point to a wet winter despite the La Niña conditions in the equatorial and eastern Pacific.

This month alone, Cal Poly — the home of climatology for San Luis Obispo — has recorded 3.19 inches of rain. Normally, Cal Poly receives about 2.5 inches during the month of November.

So far this rain season, Diablo Canyon Power Plant has seen 4.01 inches, or 122 percent of normal. SLOweather.com in western San Luis Obispo has recorded 6.63 inches or about 203 percent of normal.

Among the key influences on our weather are El Niño and La Niña, which are triggered by changing atmospheric conditions over the Pacific Ocean. El Niño events produce above-normal seawater temperatures and La Niña gives below-normal temperatures. The federal Climate Prediction Center in Camp Springs, Md., recently predicted that the current La Niña will continue into this winter.

Except for July, monthly average seawater temperatures at Diablo Canyon have been below normal and continue to confirm La Niña conditions along our coastline. Jan Null, a former National Weather Service lead forecaster and PG&E meteorologist, is recognized as an expert on La Niñas and El Niños and their relationship to California’s weather.

According to Null’s studies (see his Web page at http://ggweather.com/

enso.htm), weak, moderate or strong La Niña periods usually produce below-normal rainfall — typically about 87 percent of normal on the Central Coast and even less in Southern California. Cooler-than-normal sea surface temperatures tend to shift the storm track northward towards the Pacific Northwest.

However, last year’s La Niña serves as a reminder that not all such events are created equal. Last year, I predicted below-average rainfall for the Central Coast due to La Niña. The heavy rains of mid-December busted my forecast wide open. Careful measurements by PG&E hydrographers in the Sierra last year indicated that the snowpack was the deepest in years. In fact, there was so much rain and snow last year, Gov. Jerry Brown declared an end to the three-year drought.

Despite the above-average rain last season, the strongest storms with their destructive winds remained mostly north of San Luis Obispo County in a classic La Niña fashion.

Even though this year seems to be following last year’s lead, I still predict we will have below-average rainfall. We have never had above-normal precipitation from back-to-back La Niña cycles.

The most important months for rain are December, January, February and March. January alone averages above 5 inches. If we go into an extended dry spell during this time frame, which a few of the long-range models are indicating, we could quickly fall below normal.

If we do have above-normal rainfall this year and La Niña conditions persist, it may signal a fundamental change in our climate due to global warming. Only time will tell for sure.

Today’s forecast

A 1,034 millibar surface high off the California coast combined with another area of high pressure over the Great Basin will continue to produce night and morning northeasterly (offshore) winds. These offshore winds will give clear, dry and warmer conditions in the coastal valleys and along the beaches of San Luis Obispo County. Valley fog in the San Joaquin Valley will be slow to dissipate and temperatures will stay relatively cool throughout the day in the affected areas.

Today’s temperatures will range from the low-70s in the North County to the high-70s and maybe even the low-80s in the coastal valleys (San Luis Obispo). The beaches will mostly be in the-70s.

A 6.4 foot high tide will occur at 10:26 a.m. and combined with sunny and warm weather will produce ideal kayak and paddle board conditions in Morro Bay before the ebb tide.

Little change is expected on Monday with slightly cooler temperatures on Tuesday and Wednesday.

The northeasterly (offshore) winds may be especially strong with gust to 45 mph Wednesday night into Thursday morning in the coastal canyons and passes, eastern San Luis Obispo near Cal Poly and French Medical Center and areas surrounding Morro Bay High School.

In the extended time frame, the Navy Operational Model is advertising a cutoff low developing off the Central Coast later on Thursday with unsettled weather on Friday. However, most of the other models are not indicating this condition at this time. Regardless, dry and mild weather is forecast next weekend.

Today’s surf report

This morning’s 4- to 6-foot northwesterly (310-degree deep-water) swell (with an 11- to 13-second period) will decrease to 3- to 5-feet by this afternoon and will remain at this height and period through Monday morning.

A 5- to 7-foot west-northwesterly (280-degree deep-water) swell (with a 13- to 16-second period) is forecast along our coastline on Monday afternoon, increasing to 6- to 8-feet (with a 12- to 14-second period) on Tuesday.

Increasing northwesterly winds on Monday afternoon will produce 2-to 3-foot northwesterly seas.

A 5- to 7-foot northwesterly (305-degree deep-water) swell (with an 11- to 13-second is expected on Wednesday, decreasing to 5- to 7-feet (with an 8- to 15-second period) on Thursday through Friday.

Seawater temperatures

Seawater temperatures will range between 56- and 58-degrees through Wednesday.

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John Lindsey is a media relations representative for PG&E. He is also a local weather expert and has lived along the Central Coast for nearly 25 years. To subscribe to his daily weather forecast or ask him a question, email pgeweather@pge.com.

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