Weather Watch

2011 made a splash into June, but 2012 starts dry and may stay that way

Cumulonimbus clouds that towered over Estero Bay on April 8 produced snow flurries, thunder and hail throughout San Luis Obispo County.
Cumulonimbus clouds that towered over Estero Bay on April 8 produced snow flurries, thunder and hail throughout San Luis Obispo County. Photo by John Lindsey

East of the Rocky Mountains, 2011 was an awful weather year. Severe weather events started New Year’s Eve as tornadoes ripped through Arkansas and Missouri and continued through a fall marked by a series of wild weather episodes.

Record snow and rains rocked many parts of the Midwest and East Coast. The Northeastern Seaboard, its ground already saturated by heavy rains earlier in the year, experienced record floods as tropical storm Irene dumped copious amounts of precipitation on New England.

Floods not seen in decades also developed along the Mississippi, Missouri and Ohio rivers.

In other parts of the country, heat waves allowed wildfires to spread across drought-stricken landscapes. The worst hit was Texas. Overnight highest minimum temperatures in the Dallas/Fort Worth area averaged 82.5 degrees in August. The next warmest August on record occurred last year, which averaged 79 degrees. To make matters worse, monster swarms of tornados killed hundreds and laid waste entire towns, making 2011 one for the record books.

Thank goodness, the weather along the Central Coast was relatively mild in comparison.

The first few days of 2011 were wet and cold as a storm moved southeastward along the California coastline. Afterward, a strong Eastern Pacific high-pressure ridge took up a position west of San Luis Obispo and deflected the storm track to the north. This kept the Central Coast mostly dry from Jan. 4 all the way through Valentine’s Day. In fact, both January and February, historically our wettest months, had only about half normal rainfall.

By March, the Eastern Pacific high moved westward to a position north of Hawaii and opened the door to a series of Pacific weather systems. On the morning of March 20, a well-defined cold front passed Diablo Canyon with heavy rain and winds. During frontal passage, southeasterly winds hit 49 mph with gusts clocked at 64 mph. There was also a report of a wind gust of 99 mph at Vandenberg Air Force Base at an elevation of 1,450 feet.

On April 8, a cold upper-level low-pressure system moved over the county and created some interesting weather. The atmosphere became cold and unstable, featuring snow flurries as low as 1,000 feet along the Santa Lucia Mountains and stretching from Hearst Castle southward toward Morro Bay. A clap of thunder was heard throughout the Central Coast. Chris Arndt of SLOweather.com reported hail the size of garbanzo beans at his home in western San Luis Obispo. Otherwise, the month was mostly dry.

A late-season cold front produced rain in May. This front was followed by an even later season system in June. This slow-moving and tightly wound 1,006- millibar storm produced record-breaking June rains throughout San Luis Obispo County. More than 1 inch of rain was recorded at Cal Poly, breaking the previous record set back in 1991. During that 72-hour period, Cambria recorded nearly 2 inches and Rocky Butte near San Simeon had 4 inches of precipitation.

By summer, the jet stream buckled over the West Coast, producing a series of upper-level, low-pressure troughs along the California shoreline. The troughs decreased the amount of subsidence, or sinking of the air mass, that normally occurs during the summer. That, in turn, allowed a deeper marine layer to develop and produced below-normal temperatures, especially along the beaches.

Despite below-average temperatures, surfers were rewarded when an intense storm with hurricane-force winds developed off New Zealand. Southern Hemisphere swell from this storm traveled across the Pacific Ocean and arrived along the Central Coast on Aug. 31 at 8 feet with a 22-second period at the Diablo Canyon wave-rider buoy.

Wonderful surfing conditions continued through the first of September.

On Nov. 30, a steep pressure gradient developed along the entire length of California and produced one of the fiercest wind events in Southern California in many years. A wind gust of 97 mph was recorded at 4,120-foot Whitaker Peak in Los Angeles.

Closer to home, the weather station atop the condor lookout facility on Hi Mountain, about 15 miles east of San Luis Obispo, reported sustained winds of 55 mph with gusts to 63 mph. State Parks officials decided to cancel tours at Hearst Castle because they were worried about visitors being struck by falling tree debris. Falling trees and debris produced widespread power outages in Cambria.

October and November had near or above-normal rainfall amounts, but December went nearly dry. Only 0.18 inches of rain was recorded at Cal Poly, the city’s home of record for climatology.

So what does 2012 hold for San Luis Obispo? The Climate Prediction Center in Camp Springs, Md., recently predicted that the current La Niña will continue through this winter and should produce below-normal rainfall. Except for July, monthly average seawater temperatures at Diablo Canyon have been below normal and continue to confirm La Niña conditions along our coastline. La Niña periods usually produce below-normal rainfall on the Central Coast. We have never had above-normal precipitation from back-to-back years with a La Niña cycle. However, only time will tell.

Today’s forecast

The Eastern Pacific high about 400 miles to the west of San Luis Obispo will continue to force Pacific storms toward the Pacific Northwest in a classic La Niña pattern. Dry and mild weather will be the weather scenario for the first week of the new year.

Today’s gentle southerly winds and shallow marine temperature inversion layer should allow areas of coastal low clouds to develop. Otherwise, variable high-level clouds will continue to stream over the Central Coast through this week. These high-level clouds have produced spectacular sunsets.

Temperatures will be quite mild, especially in the coastal valleys, with readings approaching the high 70s and the low 70s elsewhere. Overnight lows will range from the 40s along the beaches and coastal valleys down to the 30s in the North County.

A strong 1,045-millibar area of high pressure is expected to develop over the Great Basin. If this happens, fresh to strong (25- to 31-mph) northeasterly (offshore) winds may develop Tuesday night into Wednesday morning. These offshore winds will be especially gusty in the coastal canyons and passes, eastern San Luis Obispo near Cal Poly, Sierra Vista and French hospitals and Morro Bay High School.

A pattern of gusty northeasterly (offshore) winds developing during the night and morning hours, then shifting out of the northwest (onshore) during the afternoon hours is expected to continue through next weekend.At this time, dry weather is forecast across the Central Coast through mid-January — a long, dry spell indeed.

Surf report

This morning’s 6- to 8-foot northwesterly (305-degree deep-water) swell (with an 11- to 13-second period) will decrease to 4 to 6 feet by tonight.

A 3- to 5-foot northwesterly (300-degree deep-water) swell (with an 11- to 14-second period) is forecast Monday.

An 8- to 10-foot west-northwesterly (285-degree deep-water) swell (with a 15- to 17-second period) is expected along the coast Tuesday, decreasing to 6 to 8 feet (with an 11- to 13-second period) Wednesday.A 968-millibar storm with 55-knot westerly winds is forecast to develop in the Gulf of Alaska. If this storm develops as advertised, an 11- to 13-foot northwesterly (305-degree deep-water) swell (with a 16- to 18-second period) will arrive along the Pecho Coast on Thursday into Friday.

Combined with this northwesterly swell will be 3- to 5-foot northwesterly (320-degree shallow-water) seas Thursday and Friday.

Seawater temperatures

Intake seawater temperatures will range between 54 and 56 degrees

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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 pge weather@pge.com.

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