San Diego has convened an El Niño working group as Super El Niño snowfall predictions point to a very strong season this winter. Assistant Fire Chief Robert Rezende is leading the planning, and the city has put every department into the effort to prepare for flooding, fire risk and coastal damage.
Tyler Rodenbaugh said scientists report an El Niño event when sea surface temperatures rise one-half degree Celsius above normal. At 1.5 degrees above normal, he said, scientists declare a very strong El Niño. The current conditions are what Rodenbaugh described as a very strong El Niño.
Robert Rezende on San Diego
Rezende said the city has to watch a wide stretch of ground as it prepares. “From San Ysidro all the way up to Sorrento Valley and Lake Hodges, anywhere there are creeks and rivers and lakes, you have to keep a close eye on those areas to ensure we’re prepared for an extreme weather event,” he said.
San Diego has aging stormwater systems and century-old dams, so the city’s planning is focused on where water moves first: creeks, rivers, lakes and other low-lying channels. That makes the working group more than a general briefing. It is a citywide check on the places most likely to be tested if winter storms line up.
Dan Cayan and Lindbergh Field
Dan Cayan said large El Niños tend to tilt the odds toward more winter north Pacific storms and larger ones. “Large El Niños tend to tilt the odds toward more winter north Pacific storms and also larger ones, because of the energy imparted to the atmosphere from the ocean,” he said.
The numbers from Lindbergh Field show why San Diego is planning early. The El Niño events of 1982-83 and 1997-98 each produced nearly 20 inches of rain, while a typical year brings about 10 inches. San Diego had 70 wet days in 1982-83, compared with 40 to 45 wet days in a normal year.
Alexander Gershunov and atmospheric rivers
The pattern is not fixed, though. The 2015-16 Godzilla El Niño brought slightly dryer conditions, with 8 inches recorded at Lindbergh Field. Gershunov said the outcome depends on specific storms called atmospheric rivers. “What actually will happen depends on specific storms called atmospheric rivers, which do not dance to the tune of El Niño,” he said.
Atmospheric rivers transport water vapor from the tropics and produce extreme rainfall, which is why the same El Niño setup can lead to very different results in San Diego and the Sierra Nevada. For residents, the practical takeaway is that the city is already preparing around the places most exposed to runoff, while the winter total still hinges on which storms arrive and track inland.
