Above-average rain season could be coming

I had the pleasure recently to speak with John Neil of the Atascadero Mutual Water Co. The company has collected rainfall data since 1914 at a rain gauge at the confluence of the Salinas River and Atascadero Creek.

As you can imagine, rainfall plays a critical role in company decisions and policies on water use and supply.

After he carefully reviewed the historical data from this rain gauge, Neil discovered that when this station received more than 2 inches of rain during October, the rest of the rain season, which runs through June 30 of the following year, was higher than normal.

I reviewed the rainfall data from the Diablo Canyon Power Plant Ocean Lab rain gauge and noticed the same trend of a wet October leading to near or above-normal precipitation for the rain season.

This year, the company’s rain gauge recorded more than 5 inches of rain during October, the second highest — 2005 had 5.89 inches of rain in October versus 5.14 for October this year — of any October on the company’s records.

This year’s soggy October was because of one of the stronger weather systems that I’ve seen over the past 19 years of forecasting weather along the Central Coast. The extraordinary wet storm of Oct. 13 and 14 produced many records for a 48-hour period of rainfall during October throughout San Luis Obispo County.

The latest long-range forecast from the National Oceanic and Atmospheric Administration’s Climate Protection Center seems to support this trend.

The center is forecasting above-normal rainfall for most of California, including the Central Coast, because of continued strengthening of El Niño.

The warmer ocean water in the equatorial Pacific is forecast to shift the position of the jet stream further south, thereby directing more Pacific storms toward the Central Coast this winter.

So far, SLOweather.com in San Luis Obispo is reporting more than 10 inches of rainfall this season — twice the normal amount of precipitation for this time of the year. After three seasons of lower than normal rainfall, this is welcome news.

This week’s forecast

A fast-moving frontal boundary pushed through San Luis Obispo County on Saturday with periods of heavy rain, a few lightning strikes and very gusty southerly winds.

In fact, southerly winds at the Diablo Canyon Power Plant reached 32 mph sustained, with gusts to 55 mph late Saturday afternoon.

An upper-level trough will pass our area this morning with rain and moderate to fresh (13-24 mph) southerly winds.

As the upper-level trough passes the Central Coast, the winds will shift out of the northwest and decrease to gentle to moderate (8-18 mph) levels and this morning’s rain will turn to scattered showers by this afternoon.

Today’s high temperatures are forecast to reach the mid to high 50s.

Partly cloudy weather with gentle to moderate northwesterly winds is forecast tonight for the Morro Heights Luminaries.

Another mild night is expected for all locations tonight with overnight lows mostly in the mid 40s to the low 50s.

Mostly clear and dry weather is forecast for Monday, except for patchy night and morning fog developing in the valleys.

Clouds are expected to increase Tuesday afternoon, leading to a few scattered rain showers on Tuesday night and Wednesday morning as the end of a cold front passes over San Luis Obispo County.

High pressure will build over California on Wednesday afternoon through Friday bringing fair and dry weather, although widespread valley fog will likely be an issue in the fog-prone areas.

Surf and sea report

A 5- to 7-foot westerly (280-degree deep-water) swell (with an 8- to 12-second period) will arrive along our coastline this morning.

This swell will increase to 8- to 10-feet (with an 11- to 18-second period) and will shift out of the west-northwest (280-degree deep-water) this afternoon and tonight.

This west-northwesterly swell will decrease to 6- to 8-feet (with a 10- to 18-second period) on Monday, further lowering to 3- to 5-feet (with a 13- to 15-second period) on Tuesday.

A 967 millibar storm system covering a large chunk of the eastern Pacific is forecast to develop about 2,600 miles northwest of Diablo Canyon later today.

A 4- to 6-foot west-northwesterly (285-degree deep-water) swell (with a 17- to 19-second period) from this storm will arrive along our coastline on Wednesday morning, increasing to 7- to 9-feet (with a 16- to 18-second period) by Wednesday night.

This swell will continue to build to 9- to 11-feet (with a 15- to 17-second period) on Thursday and will remain at this height and period through Friday, decreasing on Saturday.

Conservation tip

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John Lindsey is a media relations representative for Pacific Gas and Electric Company. He is also a local weather expert and has lived along the Central Coast for more than 22 years. If you have a question, send him an e-mail at pgeweather@pge.com.