This week’s announcement by national forecasters that an El Niño weather pattern is gaining strength, and could increase the odds that this winter will be a wet one, came as temperatures dropped and a few raindrops fell across the Sacramento region during the normally hot, dry summer.
The weather patterns aren’t related, and whether the longed-for winter rains will fall and relieve California’s epic drought remains deeply uncertain, forecasters said.
“With weather there is no guarantee. El Niño is only one of many things that could impact California’s rainy season,” said Tom Di Liberto, meteorologist for the federal Climate Prediction Center.
Cloud cover and rain this week were largely a product of “monsoon moisture” carried to Northern California by a weather system from the desert Southwest, said Courtney Obergfell, a meterologist with the National Weather Service in Sacramento.
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In addition, a strong Delta breeze brought cool, coastal air to the capital region and helped push temperatures far below normal, she said. Thursday’s high in Sacramento was 77; the average temperature for the day is 93.
Temperatures should climb back into the mid-90s by Wednesday.
No measurable rainfall fell in Sacramento this week, but the Sierra Nevada and parts of the Coast Ranges saw thunderstorms and heavy downpours that produced an inch or two of rain, Obergfell said.
“We do get this kind of weather sometimes in the summer,” but El Niño effects aren’t felt this time of year, she said.
We won’t know until at least late fall whether El Niño will bring rains to California, Obergfell said. Even if it does, Southern California is more likely to feel its effects than Northern California, she said.
El Niño is a large-scale ocean-atmosphere phenomenon linked to the warming of the sea surface in the central and eastern equatorial Pacific Ocean. An El Niño effect is detected by satellites and buoys. It can cause torrential downpours in California, and drought in Australia.
A strong El Niño such as the one developing this year is usually associated with powerful winter storms, much like the very wet winter of 1997-98 when flooding and landslides occurred across broad stretches of Northern California.
In March, forecasters declared a weak El Niño had developed. On Thursday, the National Oceanic and Atmospheric Administration announced El Niño is strengthening.
Specifically, forecasters believe that there is a greater than 90 percent chance that El Niño will continue through next winter in the Northern Hemisphere, and around an 80 percent chance it will last into the early spring of 2016.
“We will have to see what happens as we go forward, but what we see now in the Pacific Ocean and the way the (computer) models are predicting it, we are expecting a strong (El Niño) event as we get into the late fall and winter,” Di Liberto said.