Like any aspect of the weather, El Niños are notoriously difficult to pin down, especially when considered from a long way off. The current predicted chance of a coming El Niño — which rises from 71 percent in October/November/December to 78 percent in March/April/May, according to Columbia University’s International Research Institute for Climate and Society — doesn’t actually mean it will rain hard.
In Santa Barbara County, individual El Niños have historically delivered between 6 and 46 inches of rain. The current “weak to moderate” prognosis, however, has showered “above normal precipitation” about half the time since 1950, when the National Weather Service began keeping stats on El Niño events, said the service’s Eric Boldt. At Santa Barbara County climatology, a part of Public Works, a chart documenting El Niño/La Niña events demonstrates that even “strong” El Niños have delivered a deluge only four times out of six. The herald of an El Niño — defined as a certain degree of sea-surface warming along the Pacific equator — has led to what can only be called highly inconsistent rain results in Santa Barbara, said Shawn Johnson, a county hydrologist.
Whether a debris flow could result from the coming El Niño depends on the intensity, not the quantity, of rain, Kevin Cooper with the U.S. Forest Service pointed out. Additionally, the greenery on the hills burned by the Thomas Fire is growing back better than expected — about 35-40 percent in places, he said. Rainfall intensity isn’t necessarily an automatic trip switch for such a natural disaster, said Cooper. Other factors, such as duration and frequency of storms, could also play a part.
Boldt agreed that the vegetation recovery could mean that more rain may have to fall than did on January 9 to send mud and boulders down the mountain front. The number of weak to moderate El Niños — 18 — since 1950 is a small sample to work from, Boldt added. It’s roughly 50/50 now for rainfall over the county’s average 18.5 inches, and if it comes, it would likely hit during Santa Barbara’s usual rainy months, January through March.