This season’s rain total looking great

We are approaching the end of the 2018-’19 water-year, and rainfall patterns in the Concord/Clayton area this winter can easily be described as pretty wacky.

The beginning months of the current rain season were nearly bone dry. Barely a drop fell through the first three weeks of November, bringing fears of another drought.

The storm door flew open on Thanksgiving weekend, and the rainy weather began. During the first three months of 2019, dry days became scarce as soggy atmospheric river storms repeatedly pelted the state.

I like to use records from Concord’s Buchanan Airport to evaluate local rainfall data. The National Weather Service recommends using a 30-year period (1981-2010) for developing comparative statistics, and the Concord Airport is one of few stations in Contra Costa County with data records covering that period.

For Concord, the average annual rainfall is 18.10 inches. As of April 10, 18.73 inches has been reported – meaning that if not another drop fell by the end of June, we’ll have 103 percent of normal annual precipitation this water-year.
Most of this winter season’s rainfall occurred since the first of the year. The local airport reported measurable precipitation on 49 of the first 100 days of 2019.

In January, a series of mild storms produced more than 120 percent of normal monthly rainfall. The monthly average temperature was more than 5 degrees above normal.

These atmospheric river storms originate in temperate waters of the Central Pacific. For the majority of my meteorology career, we called this a Pineapple Express.

February was chilly and wet, with rain recorded on 17 of 28 days. The monthly total of 6.34 inches represents more than a third of our expected annual average precipitation. Normal rainfall for the second month of the year is 3.34 inches.

Jet stream winds directed more wet weather systems toward the West Coast in March. We recorded nearly 3½ inches of rain, more than an inch above the monthly normal.

All this recent wet weather has affected the Sierra Nevada watersheds in a positive way. The California Department of Water Resources conducted a snow survey during the first week of April. The agency reports that statewide, the Sierra snowpack reached 162 percent of normal.

Water managers use snow-water equivalent measurements to estimate spring runoff. On average, the Sierra snowpack supplies about 30 percent of California’s agricultural, industrial and residential water needs. The recent DWR measurements show that water content is about twice the normal value.

All this recent rainfall is beneficial for our water supply and local spring wildflowers. It took a long time for the rains to show up this winter season. But once the storms came, they stayed for a long while and delivered drought-busting precipitation amounts to the Bay Area and entire state.

Woody Whitlatch is a meteorologist retired from PG&E. Email your questions or comments to
clayton_909@yahoo.com