San Luis Obispo County finished the rain year Wednesday with precipitation levels near normal, breaking three years of dry conditions.
An El Niño weather event caused the wetter conditions this year. El Niño events feature warmer than normal ocean temperatures in the mid-Pacific, which drive storms farther south into the Central Coast.
“Overall, rainfall amounts were near to above normal in most locations throughout the county,” said John Lindsey, weather forecaster and communication specialist with Pacific Gas and Electric Co.
Ironically, rainfall totals near the historic average actually mean the year was unusual, Lindsey said. Most years, rainfall totals are quite a bit above or below the average.
San Luis Obispo’s wetter conditions followed a statewide pattern, said Stuart Seto, weather specialist with the National Weather Service in Oxnard. The state received rainfall totals 10 percent above normal.
The strength of the El Niño event varied throughout the year but was strongest during the first three months of the year, which is when most of the rain falls.
These El Niño conditions could also be at least partially responsible for the cooler than normal conditions so far this summer, Lindsey said.
A drop in ocean temperatures of even a degree or two can significantly influence air temperatures. Strong northwesterly winds also contributed to upwelling and lower ocean temperatures.
Conditions, however, are changing. The El Niño is giving way to a La Niña, which features colder than normal sea temperatures. La Niñas often produce warmer summers and dryer winters.
However, these long-term forecasts are subject to lots of variability and should be taken with a grain of salt, Lindsey said. “It just takes one winter storm to stall over the area, and we suddenly have a wet winter,” he said.
The rain year begins annually on July 1, running through June 30 of the following calendar year.