During the early morning hours of Sunday, Aug. 16, a radical weather event covered the Bay Area. Record-breaking temperatures mixed with tropical conditions to produce a dry lightning event that led many to marvel and wonder at what caused the dramatic storm — and what to expect in the coming days and weeks.
Berkeleyside’s sister site, The Oaklandside, reached out to local meteorologists and agencies to find answers.
What was behind this weekend’s “un-California-like” weather?
Bay Area meteorologist Steve Anderson points to Tropical Storm Fausto off of Baja California. “We have some juicy atmosphere thanks to Fausto throwing moisture and instability our way,” said Anderson, who works with National Weather Service, a federal government agency that provides weather forecasts and monitors dangerous storms.
Basically, a very large ridge of high, hot, and dry pressure sitting over the desert Southwest brought us hot temperatures over the past several days. As we moved into Saturday night, a disturbance moving around this ridge tapped into Tropical Storm Fausto’s tropical moisture, causing thunderstorms to develop.
Anderson and other meteorologists at NWS Bay Area watched the disturbance as it approached Southern California and moved up the coast around Point Conception, through the Monterey Bay area, and up into the Bay Area.
KGO-TV meteorologist Drew Tuma tweeted his astonishment in the early hours of Sunday morning. “This is an INCREDIBLE amount of lightning moving into the Bay Area right now. Nearly 200 lightning strikes in the past 15 minutes!” he wrote.
In a tweet, NWS shared a striking number — 212 cloud-to-ground lightning strikes had been reported since 5 a.m. Sunday. The entire weather event totaled roughly 2,300 cloud-to-ground lightning strikes from Monterey to Napa. NWS’s chart shows that far more lightning strikes were recorded in Oakland than in other Bay Area locations.
“The last time we’ve seen this level of lightning activity is back in 2008,” said Anderson. The 2008 lightning siege in Northern California saw more than 6,000 lightning strikes over two days that June. That storm followed a very dry spring, and more than 600 wildfires were tied to it.
Some community members recall only seeing lightning this weekend, but not hearing thunder, which can be explained by the distance that you’re standing from the storm. It’s simply not possible to have lightning without thunder, but it’s more common to see lightning and not hear thunder during heat lightning events.
The rule of thumb is that thunder can be heard when you’re standing 10 miles away from the source. Since it takes about five seconds for the sound of thunder to travel a mile, count the number of seconds between a flash of lightning and the sound of thunder, and divide that by 5.
“This activity typically occurs for a few hours at most and then moves out of the area,” said Anderson. “But [it] was ongoing for over 12 hours, with another round Sunday and Monday morning. So that is almost unprecedented.”
Dry lightning? Sounds like an oxymoron—what does it mean?
Dry lightning is a storm event where lightning and thunder are accompanied by little to no rainfall.
“We characterize lightning as dry if rain falls, but it doesn’t wet the ground,” said Anderson. For dry lightning to occur, storm clouds are typically high enough that rainfall will mostly evaporate before it hits the ground. Anderson characterized most of the Saturday evening’s weather as dry lightning.
On top of that, the thunderstorms moved so quickly that lightning was striking in areas where it wasn’t raining, which is why also we’re seeing wildfires start.
Was the Bay Area also dealing with big fires this weekend?
On Monday, the NWS wrote a follow up to the weekend’s events, including the alarming news that there were eight relatively large fires — including the Marsh Fire in Sunol and the Deer Zone Fires in Contra Costa County — burning across the Bay Area, along with some and smaller ones, with more likely to appear on the radar. Since Sunday, 13 new fires, many in Santa Cruz County, were ignited.
“This 20 year forecaster can’t recall such a widespread convective event on the heels of such a heat wave,” the author wrote. “June 2008 would be a good proxy, but don’t recall the Bay Area getting nearly as much convection.”
Sunol’s Marsh Fire has already burnt 1,775 acres with zero percent containment. Mandatory evacuations for the area were recently announced.
Many in the community were surprised to see lightning events paired with extreme heat in the Bay Area. On Friday, Oakland saw record-breaking temperatures of 100 degrees Fahrenheit, shattering its previous all-time high temperature of 90 degrees in 2019. As California makes its way through its annual fire season, the NWS forecasted on Monday the possibility of wildfire ignition as a result of widespread heatwaves in the triple digits and dry vegetation.
In extreme wind-driven weather events, the NWS will often issue a 72-hour “red flag advisory” about high-risk fire conditions, which may or may not turn into a “red flag warning.”
The Oakland Fire Department was alerted to the NWS’ red-flag warning on Saturday, said OFD chief of staff Michael Hunt. The warning predicted dry lightning strikes, record temperatures, and overnight extreme dryness early Sunday morning. “The East Bay hills experienced a very high probability of ignition for any ground strikes,” said Hunt.
How do last night’s events fit in the history of past weather events? Is climate change playing a role?
It’s actually not uncommon to see lightning events like the one we saw early Sunday morning. It happens periodically, said NWS Bay Area meteorologist Cindy Palmer. Anderson said usually every several years. Southern California tends to be a little more prone to it than we are here in Northern California.
Palmer is hesitant to call the weekend’s storm event unprecedented. To her, it’s all about what’s been happening in the desert Southwest, and the fact that the region got a late start to its monsoon season.“The fact that the storm got all the way up here [to the Bay Area] doesn’t surprise me, given the position of the high-pressure ridge,” said Palmer.
Meteorologists and climate scientists don’t like to link individual storms to climate change, as climate change and its symptoms must be studied over a longer period of time. But Anderson said climate change is behind the fact that we’ve generally been seeing more widespread extreme weather, more occurrences of intense hurricanes, more Category 5 hurricanes, and longer, more intense wildfires.
“If we continue to see episodes of this kind of lightning activity year after a year, and increasing throughout the year for 10, 20 years, then we can start looking at the possible links to climate change,” said Anderson.
UCLA climate scientist Daniel Swain, who studies extreme weather and climate events, tweeted on Sunday that the weekend’s storm “is probably the most widespread and violent summer thunderstorm event in memory for Bay Area.” In his weather blog, Swain foreshadows tropical and subtropical weather events combined with extreme heat in California over the next week or so. What this could mean is more thunderstorms—as well as further wildfire risk.
PG&E marine meteorologist and media relations spokesperson John Lindsey said Sunday in a tweet that he hasn’t seen a subtropical system expand and make its way north like tropical storm Fausto did — and Lindsey has been forecasting weather for almost 30 years.
Is there anything I can do to stay prepared and safe in a similar event?
For all you storm chasers out there (this means you with the smartphone, recording on rooftops!), the NWS advises staying under roofed shelters (so yes, you can still record storm activity from your car), sheltering for at least 30 minutes after hearing thunder, and be careful around outlets.
To conserve energy and support the California Independent System Operator’s efforts to stabilize the electrical grid, PG&E’s Lindsey suggests cooling down with a fan instead of air conditioning, using appliances like laundry machines in the evening, and setting thermostats at 78 degrees or higher. Keep your devices charged as much as possible and have charged battery packs ready. If you have an electric vehicle, avoid charging that during heatwaves.
PG&E is prepared to do rotating outages if power demand overwhelms the supply, at the direction of CAISO, the grid operator. While customers in San Francisco, San Mateo and Contra Costa counties were notified of potential power shutoffs, Alameda County was not at risk of losing power.
Finally, as the heatwave drudges on for the rest of the week, the NWS recommends staying hydrated, rescheduling strenuous activities to early morning or evening, wearing lightweight and loose-fitting clothing, and scheduling frequent rest breaks if you’re working or spending time outdoors.
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What was behind this weekend's weather, and what can you expect next? - Berkeleyside
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