Daniel SwainThe following is an excerpt with permission from the
By Daniel Swain of Weather West
The last month: steadily elevated anomalous heat, especially inland
August 2022 was a substantially hotter than average month all up and down the West Coast, although there were no extreme heatwaves in California. Image via climatetoolbox.org.
The past month has been warmer than August averages across nearly the entire state. There have not really been any extreme heatwaves, but these steadily elevated temperatures have yielded what will ultimately be another much warmer than average month in California. Although wildfire activity has been relative modest in recent weeks, vegetation drying has continued at a near-record pace for the date due to these much warmer than average temperatures and the legacy of long-term severe drought nearly everywhere. This sustained, but modest, antecedent warmth will amplify the impacts of what now appears likely to become quite a severe heatwave in the coming days (discussed in detail below).
Dangerous, prolonged, and likely record-breaking heatwave peaks Labor Day
Extremely hot temperatures–with 850mb anomalies exceeding +20F–will be widespread across California and Nevada at the peak of the upcoming heat event.
An extreme, and in some cases possibly historic, heatwave will unfold over nearly all of California over the next 7 days (or longer). This heat event will be remarkable in at least three distinct ways:
1) Daytime high temperatures will be extremely high across inland areas, particularly the Sacramento Valley and the inland valleys of southern California (but also elsewhere).
2) Overnight minimum temperatures will be greatly elevated in many areas, even relative to more ordinary heatwaves. This will be especially true in the middle elevation thermal belts.
3) The duration of this event will be very long. In parts of SoCal, the heat is already building and will not relent for at least 7-8 days. In many areas, 7-10 consecutive days of 100+ degree days are likely, with some days peaking above 110F.
A ~600dm ridge will slowly build directly over northern and central California between Wednesday and Saturday, with temperature becoming progressively hotter each day from Wed through at least Sunday (and perhaps Monday). Peak temperatures are expected in most areas either on Sunday or Monday, at which time numerous locations across interior California are likely to set new all-time September monthly high temperature records. A few places, especially in the southern Sacramento Valley and in the San Fernando Valley, could even approach all-time, any-month temperature records.
Just how hot will it get? Temperatures in the Sacramento Valley and San Fernando Valleys will likely exceed 110F on multiple days, locally getting as high as 115F or even a bit hotter than that locally (!). For perspective, Sacramento’s all-time record high temperature is 114F (or 115F, depending on observing site). While the upcoming heatwave may ultimately fall just short of that historic benchmark, it will be a close call.
In the far eastern SF Bay Area, temperatures could approach or locally exceed 110F. Hot to very hot temperatures will be likely (especially Sunday and Monday) even in the near coastal areas; most of the Bay Area and the Westside of Los Angeles will probably be at or above 100F by that point. The extremely anomalous heat may not make it all the way to the beaches–there is still some uncertainty there. But recent historical experience with autumn heatwaves suggests that the models may be underestimating the extent of coastal heat, since it would only take a very weak offshore breeze to send beach temperatures skyrocketing in this kind of extreme “heat dome” pattern. Personally, I’d err on the bullish side there.
An extremely anomalous ridge (around ~598-600dm in magnitude)–2.5 to 3 standard deviations from the average–will set up shop directly over California during this severe heat event.
So, to summarize: there is high confidence in extremely hot inland temperatures that may break monthly records. There is lower confidence in how close to the coast the heat may ultimately reach, but there’s a good chance that near-coastal areas will get quite hot and even a chance that the beaches will as well.
This type of heatwave will be quite dangerous from a human health perspective–which is why there has been very strong language and messaging coming from local National Weather Service offices (including a slew of Excessive Heat watches and warnings that cover over 90% of California population). The prolonged nature of this heatwave, as well as limited overnight relief (especially in urban areas and topographical thermal belts) will be a major challenge. There are also some concerns regarding power grid stability amid a prolonged and severe event, especially in a year when hydropower is limited due to the severe drought. Any power outages or brownouts that do occur would have elevated impacts since they would disrupt mechanical cooling (air conditioning and fans)–so folks should be prepared for that possibility. Additionally, although winds are not expected to be strong with this event (fortunately), a long stretch of extremely hot temperatures and progressively lowering humidity will pose much higher wildfire risks that have been seen recently (especially given extremely dry landscapes amid the severe drought).
It is worth noting that the above numbers are actually a bit lower than the high-resolution models are currently spitting out for the Sacramento and San Fernando valley regions (with some values in the 116-118F range). Both the ECMWF and GFS have recently exhibited some positive biases in surface temperatures (i.e., the are running too hot) during extreme heatwaves in dry regions, so human forecasters are trying to take that bias into account (hence why some automated websites are suggesting even higher temperatures than expert-adjusted ones). My best guess is that these models are still running a bit too hot given the strength of the ridge, and I am currently shaving several degrees off of peak predicted surface temperatures from the raw ECMWF and GFS data. But there is a slight chance that actual observed temperatures could be a couple of degrees hotter than even the record-breaking values already noted above–hence at least the *potential* for all-time records in some places.
Expect a significant escalation in wildfire activity in early Sep
There have been some deadly (McKinney) and destructive (McKinney and Oak) fires already this season in California, so I hesitate to call it a “mild” fire season to date. But it is certainly true that the overall number of large/destructive fires has been significantly below the (decidedly hyperactive) benchmark of recent summers. Part of this is due to simple luck: despite record-dry vegetation conditions, we simply haven’t seen that many extreme fire weather patterns yet (i.e., extremely low humidity and/or strong winds), and we also had a mercifully mild and damp spring in NorCal. Another factor is likely the increasingly aggressive initial attack and heavy air support that have been used to respond to virtually all fires this year in the wake of recent disasters. We’ve also gotten lucky that potentially significant fire starts have thus far occurred more of less sequentially–rather than all at once–essentially allowing firefighting resources to focus on one at a time.
Unfortunately, I doubt this luck will persist past this week. The upcoming prolonged and extreme heatwave will likely mark the beginning of a significant uptick in fire frequency and intensity in the coming days/weeks, with increasingly many escaping initial attack as vegetation continues to be at or near record dry levels. This is especially true as autumn “wind season” approaches in both northern (and, later,) southern California. My fingers are crossed that luck remains on our side–especially when it comes to strong wind events in the coming weeks–but the reality is that any major heat, wind, or lightning event between now and the onset of the rainy season is going to pose a major fire weather threat given the state of the vegetation. And as the upcoming heatwave will likely affect a broad and already drought-afflicted region, including Oregon, Nevada, and parts of Idaho, it is very possible that Western U.S. fire activity will broadly increase in the coming days, resulting in resource drawdown as multiple fires compete for firefighting capacity. In other words: this fire season isn’t over yet, and will likely has a much higher peak than we’ve seen so far.
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It won’t be record breaking for Santa Barbara.
A-1661924120: I stand corrected. Your chart says it must be 102 degrees over Labor Day weekend to be a record and the forecast is 88 degrees. So it will be 14 degrees too low not 20.
why would this get a DV? by people who no little of the history of SB! SB had the record for the hottest day on earth, the Sahara beat it in the 1930s i believe by just a few points. SB record high 133 degrees. No joke, here is the link. Surprised so many of you down voting know it alls didn’t know this…then again, you guys run here for info instead of using the rest of the internet…
https://www.noozhawk.com/article/santa_barbaras_hottest_day_and_a_record_high_of_133_degrees_20200617
Is this the cost if MCGA? Make coal great again the numbskulls said
“We can’t change the weather”
Climate, and we can and have.
General, the Aztecs thought human sacrifices would bring an end to the drought which led to the decline of their civilization. Today, many people support a different form of sacrifice. They believe that by dismantling the infrastructure necessary to provide reliable low cost energy we will somehow put a stop to heatwaves and make temperatures cooler in the future. As we shut down our coal and nuclear power production, other countries like China build back that capacity several times over. We can’t change the weather, but we can definitely reduce our standard of living. Here is an example of what we have to look forward to if we continue down this path. Not long ago, the UK had the capacity to produce enough coal to meet all of its energy needs. Then the leaders of the UK decided they could improve the weather by dismantling the infrastructure they needed to produce their own energy. Now, energy costs are soaring and the people will suffer this winter as the standard of living declines. There is also a major risk of civil unrest.
https://www.bloomberg.com/news/articles/2022-08-31/uk-energy-crisis-households-take-extreme-measures-to-cut-back-on-surging-bills
CHIP The Vatican is posing as Snow White, but the Bible says that she is a prostitute, “the great whore,” a cult (Rev. 19:2). She uses government agency branches in every country, including the United States, as her vicious little dwarfs. The more power and control she gets in government, the more she will fade away into the background in her “Snow White” disguise so that government will be used and blamed for all her evil deeds.
REASON: To enforce laws that harass, malign, destroy, and censor everyone and every idea that is not Roman Catholic so she can sit as the satanic queen (the big whore).
Because of her age-old desire to control the world government and church, the serpent-like Vatican has infested the world and the U.S. government with so many of her zealous, highly-trained and dedicated Jesuit devotees, that she now controls the United Nations (which she created), the White House, Congress, every state, federal, civic, and social government agency, including the U.S. Department of Labor, the IRS, the FBI, the Supreme Court, judicial systems, the armed forces, state, federal, and other police, also the international banking and federal reserve systems (called the Illuminati and Agentur), labor unions, the Mafia, and most of the heavyweight news media. With all of that being said – you don’t seem very knowledgeable about the environment.
“We can’t change the weather” but Sleestak can. They use the shiny crystals in those caves – there is always a T-Rex outside the cave 🙂
But yeah Chip – the UK should friend up with Russia and continue buying their oil. Everything will be alright – right? Don’t look to the future only look at the nickels you have in your sausage fingers. Helped in ’37 right? Well actually it didn’t help in ’37 so there is that.
I do remember back in the early to mid 80’s when I resided and worked over on the Eastside, during those summer months the temps were in the low upper 90’s to low 100’s . It will be very hot till this coming Labor Day weekend. But not that hot. Still hot enough. I lived in Phoenix, AZ. for over 8 years and that is “HOT” during the summer months, and the humidity is just God awful during monsoon season which ends around mid September. One year I had my A/C going on till mid November.
“I do remember”
People misremember. The record tells a different story, and of climbing average global temperature and more than 3 times as many heat records being broken as cold records.
We’ll see if they can keep the lights on, especially on Monday. CAISO is already expressing concern.
trumpy news sites from the midwest are like that. Anything to try to deflect.
Here it is from Newsweek, I always thought they leaned left, but maybe they’re “trumpy ” too.
https://www.newsweek.com/californians-told-not-charge-electric-cars-gas-car-sales-ban-1738398
None of that changes the fact that the trumpy site was trying to deflect and conflate two actions that reduce CO2 emissions and help stall the warming that is causing all the problems in the first place.
“I always thought they leaned left”
You were wrong.
“but maybe they’re “trumpy ” too.”
Quite a bit these days. (That’s right Chip, things *change*.)
It will be very interesting to see how it plays out Shasta. Here is some irony.
https://www.mystateline.com/news/national/california-asks-residents-not-to-charge-electric-vehicles-days-after-announcing-gas-car-ban/
I can’t think of a time in the last 30 + years where we were asked not to use electricity on hot days or during certain hours during the summer. But you do your agenda.