Weather Watch

Dry spell nearing a record but winter rains look more promising

A view of Cuesta Ridge looking toward San Luis Obispo on Saturday. About the only moisture the region has received since late April has been the mist brought by marine low clouds from the Pacific Ocean.
A view of Cuesta Ridge looking toward San Luis Obispo on Saturday. About the only moisture the region has received since late April has been the mist brought by marine low clouds from the Pacific Ocean.

The last two months have seen record amounts of rainfall recorded north and south of San Luis Obispo County.

Just last week, Olympia, Washington set a record for Oct. 22 of 1.33 inches, edging out the old mark of 1.32 inches from 1951. South of us, Phoenix Arizona, saw 5.05 inches of rain pour from the heavens in September, nearly breaking the record of 5.41 inches set in 1939.

The remnants of Hurricane Norbert produced 3.3 inches of precipitation in one single day in late September at Sky Harbor Airport. The Phoenix area usually receives about 2.7 inches annually.

Closer to home, Northern California has seen a series of low pressure systems and associated cold fronts that produced much needed rain in Northern California.

“However, the state will need significantly more precipitation this rain season to start to relieve the current drought,” said Scott Strenfel, PG&E meteorologist.

Unfortunately, it hasn’t rained since late April in San Luis Obispo.

On April 26 a cold front moved eastward over the Central Coast and produced about a third of an inch of rain at Cal Poly. As of Saturday, 183 straight days have passed without any measurable rain at the Diablo Canyon power plant, just mist and drizzle. A hundredth of an inch was recorded at Cal Poly on Oct. 15.

This dry spell sparked my curiosity: What was the longest period of consecutive days without rain in coastal San Luis Obispo County?

I decided to filter out periods of coastal drizzle that can produce up to a few hundredths of an inch of precipitation. This gave a truer representation of actual rainfall across a greater portion of the county, because the inland areas received considerably less coastal drizzle.

After I reviewed 23 years of rain data and weather forecasts from the power plant, it was obvious that this year was one of the longer phases of dry weather on record at 183 days and counting. So far, the longest dry spell occurred in 2004 when it didn’t rain for 206 days (March 27 through Oct. 18). The other long phases occurred in 2012 with 169 days without rain, followed by 2013 which went 175 days without the wet stuff.

So what will winter bring for the drought-plagued Central Coast? The Climate Prediction Center is now indicating that “El Niño is favored to begin in the next 1-2 months and last into the Northern Hemisphere until spring 2015.” They’ve also increased the likelihood of normal or above rainfall for San Luis Obispo County this winter.

The other large-scale seawater temperature cycle that can affect our rainfall is the Pacific Decadal Oscillation (PDO). The PDO is still in a strong positive or warm phase. This condition is characterized by higher-than-normal sea-surface temperatures in the north and eastern Pacific and tends to enhance El Niño conditions.

Of course, these are long-range forecasts and there are no guarantees. Only time will tell the story. Nevertheless, I feel more confident in a prediction of normal to above-normal precipitation this rain season.

By the way, if you’re an educator in our public schools, you can apply for a PG&E Bright Ideas Grant to purchase a weather station for your school. These grants also fund innovative classroom projects about energy, conservation, environment, climate and weather. They are designed to inspire the bright ideas of the future and create exciting ways for the next generation to learn and succeed in science, technology, engineering, and mathematics (STEM).

The Bright Ideas Grants program provides $1,000, $2,500, $5,000, and $10,000 grants for K-12 public schools and community colleges to support solar projects, environmental programs, energy or science-related field trips, green your school projects, or professional development programs.

Applications are due Nov. 1, 2014. For information and to apply online, visit