As you may have suspected, 2013 was the driest calendar year on record from San Francisco to Los Angeles and for most areas in between.
The numbers are also bleak when looking at totals for the current rainfall season — which started July 1 — rather than at the calendar year.
Cal Poly, home of climatology for San Luis Obispo, has recorded 11.1 inches of rain or about 50 percent of normal for this far into the rain season. In the North County, Paso Robles has recorded only 4.9 inches of precipitation. Normally, it should be near 12 inches. Along the beaches, Diablo Canyon power plant has recorded 5.6 inches of rain, which is on track to be the driest rainfall season on record.
For most of 2013, the southern branch of the polar jet stream remained north of our latitude out over the eastern Pacific Ocean due to a persistent ridge of high pressure along the west coast. This condition kept the storm door steadfastly closed.
This year started out dry with only 0.03 inches of rain reported in January at Cal Poly. Then in February, the ridge of high pressure finally moved eastward so the jet stream could move southward over the Central Coast. This condition allowed the storm door to swung wide open for a series of Pacific storms that brought much-needed rain to California.
Normally, Cal Poly receives about 4.6 inches of rain February. This February 5.8 inches of precipitation was recorded. In late February, a 968-millibar storm that resembled a gigantic pinwheel rotated toward the Central Coast. This was one of the most powerful Pacific storms that I've seen off the San Luis Obispo County coastline in my meteorological career. Not only did this tempest bring precious rain, but it also produced high southwesterly swell and seas.
This southwesterly wave event peaked at 21 feet with a 14-second period at the Diablo Canyon Waverider Buoy, the highest wave height since 2008.
Unfortunately, the pattern of above normal rainfall didn’t last through March. In fact, just about 2.6 inches of rain fell in March, or about 76 percent of normal. Sadly, 2014 didn’t see a March miracle. So far in April, 1.4 inches of rain has fallen, which is about average for the month. In early April, 1-inch diameter hail struck Cayucos from intense thunderstorms.
This recent precipitation has turned the coastal hills with their rock formations of apple-green serpentine to emerald green as grazing grasses sprouted. The rains have also temporarily decreased wildfire risk and produced very modest flows into our lakes and reservoirs.
However, California’s rainy season is winding down as we head toward our dry season. After three consecutive years of well below normal precipitation, drought conditions still persist.
Nevertheless, this record-breaking drought may come to an end by next winter. The current conditions in the equatorial eastern Pacific strongly resemble those observed in the lead-up to the powerful 1997-1998 El Nino event. That event produced well above normal rainfall amounts throughout the Central Coast.
The numerical models have been increasing the chances for a moderate to strong El Niño event developing; but keep in mind, historical rainfall data indicates that the there are no guarantees of drought breaking rainfall events in California during an El Nino events.
But one can certainly say this; next winter has the potential to be very different than the last three we’ve experienced.
In honor of National Volunteer Month this month, PG&E has announced an unprecedented employee volunteerism goal for the company of 50,000 employee volunteer hours this year. This goal is supported by the company’s Month of Service program, which will feature more than 100 employee volunteer projects throughout Northern and Central California.