Weather Watch

You may want to keep your umbrella handy

This year, the rainy season has been quite unpredictable and has delivered mixed results, from an overabundance of rain during December to a nearly dry January as La Niña continues to strengthen.

The Central Coast is just about at its halfway point of the rainfall season, and things could be changing again.

La Niña, which generates cooler-than-normal sea surface temperatures in the central and eastern equatorial Pacific, usually produces below-normal rainfall along the Central Coast.

An El Niño condition —warmer-than-normal ocean water in the equatorial and eastern Pacific — usually produces above-normal rainfall.

Both of these oceanographic phases are considered to be a standing pattern. In other words, they stay fixed in the same geographic area. These phases usually last for about a year or so.

Unlike El Niño and La Niña, the Madden-Julian Oscillation is a large traveling pattern of increased rainfall and thunderstorm activity that propagates eastward at approximately 8 to 18 mph across the tropical parts of the Indian and Pacific oceans.

This cycle usually lasts between 30 and 60 days.

In 1971, Roland Madden and Paul Julian stumbled upon this pattern when analyzing wind anomalies in the tropical Pacific.

But little attention was paid to the oscillation until the strong 1982-83 El Niño event, which led researchers to believe that this pattern may have enhanced the amount of rain in California.

The Madden-Julian Oscillation is also called the “30 to 60 day oscillation” and the “30 to 60 day wave.”

The latest Madden-Julian Oscillation forecast from the Climate Prediction Center in Silver Spring, Md., indicates an oscillation is present in the western Pacific and is strengthening.

There is growing evidence that what happens in the tropics can influence our weather along the Central Coast.

Models suggest that the oscillation will travel eastward. Historically, especially during La Niña phases, as the Madden-Julian Oscillation moves across the Pacific Ocean, a split in the polar jet can develop.

The southern branch of the polar jet can extend far out over the Pacific toward the coast of California. This river of air in the upper-atmosphere can steer moist, subtropical air toward California and can bring several days of rain.

If this scenario develops, rain may be in the forecast by early to mid-February.

However, when trying to predict the weather, there are no guarantees.

That being said, you may want to keep your umbrella close for the time being.

This week’s forecast

A 1,027-millibar Eastern Pacific High parked about 500 miles west-northwest of San Luis Obispo combined with an area of strong high pressure over the Great Basin will produce gentle to moderate (8 to 18 mph) and at times gusty northeasterly (offshore) winds.

This condition is expected to produce strong Santa Ana winds in Southern California this morning.

These offshore winds will bring clear skies and warm afternoon temperatures to the Central Coast today.

The exception will be the San Joaquin Valley, where tule fog will persist through this week.

High temperatures will range between the high 60s to low 70s in the North County (Paso Robles) and along the northwesterly facing beaches (Morro Bay and Los Osos).

High temperatures in the coastal valleys (San Luis Obispo) and along the southwesterly facing beaches (Avila Beach and Cayucos) will reach the mid- to high 70s.

The winds will shift out of the northwest (onshore) Monday, allowing marine low clouds to develop along the northwesterly facing beaches of Montaña de Oro, Los Osos and Morro Bay by Monday afternoon and night.

Another round of northeasterly (offshore) winds will bring clear skies along with warm afternoon highs and cool morning lows Tuesday through Friday.

Overall, January is shaping up to be a below-average rainfall month after a very wet December — the second wettest since 1996.

Surf and sea report

Today’s 7- to 9-foot west-northwesterly (290-degree deep-water) swell (with a 16- to 18-second period) will decrease to 6 to 8 feet (with a 14- to 16-second period) on Monday.

This west-northwesterly (290-degree deep-water) swell will further lower to 5 to 7 feet (with a 13- to 15-second period) on Tuesday.

A 5- to 7-foot west-northwesterly (285-degree deep-water) swell (with a 14- to 18-second period) will arrive along our coastline Wednesday, increasing to 6 to 8 feet (with a 13- to 15-second period) on Thursday and remaining at this height and period through Friday.

Seawater temperatures will range between 53 and 55 degrees through Monday, increasing to 54 and 56 degrees Tuesday and remaining at this range through Friday.

Conservation tip

You can apply for a monthly discount on your energy bill through the California Alternate Rates for Energy Program — CARE. To lean more, please visit www.pge.com.

John Lindsey is a media relations representative for PG&E. He’s a local weather expert and has lived along the Central Coast for more than 23 years. To subscribe to his daily weather forecast or ask him a question, e-mail pgeweather@pge.com.

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