A hyperactive tropical East Pacific slings hurricanes toward Hawaii and Baja California, with indirect effects (modest moisture & potentially damaging ocean waves) in SoCal

It has already been a remarkable, and arguably historic, East Pacific hurricane season. Three hurricanes (Lala, Lowell, Nolo) have now directly impacted the Hawaiian Islands (though none made formal landfall), with significant flooding and associated water/wind damage occurring on both Kauai and the Big Island). 2026 thus marks the first time in recorded history in which 2 or more hurricanes have each passed within 50 miles of Hawaii, and joined only a handful of other years when 3 storms came within 100 miles. And recent activity in the east and central Pacific basin has upped the ante even further: Hurricane Polo exploded from a modest swirl of tropical thunderstorms into a top-end Category 5 storm in less than 24 hours (eventually achieving peak sustained winds of 180 mph), becoming either the fastest, or second fastest, intensifying hurricane ever observed in the Central or Eastern Pacific basins (the only other possible contender was Hurricane Patricia in 2015). And total Accumulated Cyclone Energy (ACE)–a measure of the total tropical storm and hurricane activity over a season–across the entire basin is now around 230% of average (a record for the calendar date).

And this is exactly as had been predicted: A rapidly strengthening El Niño event has, as anticipated, dramatically weakened storm-decapitating vertical wind shear in the Pacific and warmed tropical and subtropical ocean temperatures atop the already considerable global warming trend. And the tropical Atlantic, by contrast, is experiencing one of its quietest seasons on record due in large part to El Niño-induced strengthening of that same storm-decapitating wind shear in this other basin. All in all, this represents a fairly dramatic validation of rather bold seasonal outlooks made as far back as the spring as soon as our big El Niño event began to come into focus.

California has seen some tropical remnant moisture from other East Pacific hurricanes this summer and fall, and could yet see some more in weeks to come as activity remains greatly elevated. And far SoCal, including San Diego and Orange counties, may even see some brief local showers into Monday due to the remnants of yet another East Pacific hurricane (Odalys), but otherwise hurricane remnants should mostly stay away from California over the next 7 days or so (at least). With the big ridge pattern building (see below), there is about a 5-10% chance that the next round of hurricane development could send more moisture California’s way later in October; for now, that’s a low-but-not-zero possibility to keep an eye on.

Hurricane Polo, meanwhile, will make landfall early Monday on the south-central Baja California peninsula. This will be a significant Category 2/3 storm when it does so, and widespread heavy rainfall is expected across most of the peninsula (where rain is often sparse, and where flash flooding is almost guaranteed). Despite the storm’s strength, it will fortunately be making landfall in a rather sparsely populated area (though local impacts will still be substantial).

As is sometimes the case, the most concerning effects of Polo may not actually be in Mexico at all–but instead across the interior Southwest and Southern Plains of the United States, which will experience a high-impact heavy rain event and a potentially serious flood event as Polo’s remnants make a beeline northeastward. This very heavy rainfall will be a mixed blessing in the midst of a severe drought–while water is much needed here, it will probably be too much of a good thing in many places and will bring considerable dry-to-wet hydroclimate whiplash-related impacts. California, though, is not in the path this time; had the large-scale flow pattern been even moderately different, we might be having a very different conversation this week.

There will be, however, one notable impact from these various East Pacific hurricanes in SoCal: Large, battering, and potentially damaging southerly swell will once again affect the south-facing coastlines and harbors this week. Tides are already running a foot or more above average thanks to the extreme marine heatwave, and additional sea level elevation may begin soon as the largest coastally-trapped Kelvin wave of the El Niño-generated sequence thus far arrives in October. As a result, significant coastal erosion and local bluff collapses, plus shoreline inundation, are once again likely (perhaps comparable to, or slightly less severe than, that associated with Hurricane Marie earlier this year). Unfortunately, major coastal erosion and flooding concerns will persist and perhaps even worsen in the coming weeks as El Niño continues to intensify and as winter storm season approaches–so this is unlikely to be the last time such problems emerge this year.

A big autumn heatwave is coming to the Western U.S., including California, and could last for quite a while

California is no stranger to autumn heatwaves–along the immediate coast, early October is often the hottest period of the entire calendar year as the marine layer fades and as onshore breezes slacken. It appears 2026 will be no exception to that pattern, but with a couple of twists: The upcoming heatwave will be prominent not only along the immediate California coast, but also inland across the rest of the state–and indeed across most of the western U.S. It will also, unusually, be quite persistent with heat building for days and possibly persisting at least in some areas well into mid-October. In fact, right now it looks like a broad ridge and elevated autumn warmth will persist, once established in 24-48 hours, for the presently foreseeable future.

What’s driving this late-season heat? Well, the usual suspect would be a big, lumbering ridge of mid-tropospheric high pressure–and that’s exactly what’s in the cards. This one will actually be centered over the northern interior of the western U.S. extending northward into Canada and southward into the Desert Southwest, so will bring a broad region of generally elevated temperatures and below average precipitation during early-mid October. And some model members suggest that this heat could be pretty intense by October standards in some places (though not everywhere). Exactly how hot it’ll get depends on the details of how this ridge builds and develops, but I do expect multiple “pulses” of more notable heat embedded within a broader 10-14 day long period of above-average temperatures. And along the immediate California coast, this heatwave will be augmented by anomalously warm (and, in some cases, still near-record or record-warm) ocean surface temperatures (SST)–diminishing what remnant “coastal chill” might be present at this late date as the ridge persists.

Some record warmth does, in fact, appear possible at times during this event–but it might not be in the places you’d expect. The CA coast has pretty high records at this time of year thanks to offshore flow that tends to occur at about this time of year, so the likelihood of record-breaking heat may actually end up being higher inland and across mountain/desert parts of the interior west, as well as the Pacific Northwest and British Columbia, where records get “softer” heading into October due to the earlier seasonal cooling there.

In Southern California, humidity has once again been on the rise in recent days, and it might stay elevated during this coming heat event–amplifying its potential health-related impacts. While I don’t think things will get quite as hot, or as humid, as during the absolutely miserable events of August and September, southeasterly flow will likely entrain at least some late monsoonal and/or tropical moisture during this period, and that will combine with effects of extremely warm near-shore ocean waters to amp up humidity to uncomfortable levels once again in some areas.

Finally, while wildfire activity has (for the most part) quieted quite substantially in recent days compared to the summer peak (which, just to remind folks, was quite serious or even record-breaking in some parts of the U.S. West outside of California), we might well see a resurgence across parts of the West that haven’t yet seen multiple episodes of soaking season-ending rainfall. That does include most of California, the Great Basin, interior Pacific Northwest, and much of the Rockies. However, it probably will not include New Mexico or Arizona, which will see flooding rainfall from the remnants of Hurricane Polo in the next few days.

No signs of early seasonal rainfall in California–but this is not surprising, even with extreme El Niño maturing (just give it a minute!)

There has been quite a bit of early discussion regarding California’s 2026-2027 rainy season, and for good reason–with a record-breaking El Niño event likely to become the dominant influence on prevailing weather patterns this winter across the North Pacific, the odds of a wetter-than-average winter are very high nearly statewide, and the possibility of an exceptionally wet season are considerably elevated above baseline levels. But interestingly, the relationship between strong El Niño events and California precipitation events does not really emerge in the data–either in observations or in process-based model studies–until November at the earliest, and more likely December. In fact: the strongest connection actually does arise until the new year, from January through March. In other words: the expected relationship is very “back-weighted,” with the strongest links not occurring until the second half of the rainy season.

This means that what happens with California precipitation between September and November has no bearing–none whatsoever!–on what might happen later this winter, especially from mid-December onward into March. It might be dry, it might be wet, and neither will portend much of anything regarding what’s to come during the more consequential rainy season months.

And just to reiterate: El Niño is now reaching, by at least some key metrics, record-breaking intensity already. I’ll have another full update during the first half of October, once the next model update cycle is available, but I honestly expect few changes to the big picture. An extremely strong El Niño, and its potential coastal flooding and heavy rain-related impacts later this season, remain full steam ahead according to every available piece of data I can ascertain.

Weather West website announcement: Advertising is gone for good, and all you’ve got to do is click a button on a banner!

You may have noticed some changes afoot on this website! And I’ll start with the positive one first: weatherwest.com is now, for the first time in over 15 years, fully ad-free! The website has long been supported by display advertising that was necessary to defray the considerable, and rapidly rising, costs of operation. But I’ve finally made the move I wanted to for years and removed ads for good. This has been made possible by the growing level of grassroots community support–including via “memberships.” These memberships are, in effect, voluntary contributions to help subsidize Weather West for all. Said membership will, of course, no longer feature “ad-free” benefits (as no one will see ads moving forward!) but will now instead include invitations to occasional “thank you” livestreams on YouTube, the inaugural iteration of which I hosted last week!).

The other change is a bit less exciting, but was necessary–and will help ensure Weather West doesn’t disappear suddenly due to misdirected legal action. Some readers will already be aware that recent privacy laws in California, other U.S. states, and the European Union have forced major changes in the way websites and the entities that operate them handle personal information. This includes not only the obvious and sensitive stuff, but also everything up to and including the persistent but anonymous web-tracking tools known as “cookies”–including those needed to operate a comments section, embed YouTube and other social media content, track vital website statistics, and more. While the details are very complicated, and certainly frustrating from my own perspective as the operator of this modest website (and keep in mind–I have no legal or IT team! It is just me.), the most important thing to understand is that nothing fundamental about the operation of this website has changed. The content is all still here, the comments section is still here, and everything that has changed is on the technical, behind-the-scenes side.

What is the practical TL’DR version? Well, you’ll now see a banner at the bottom of your screen that will pop up when you visit Weather West, with blue buttons to either “Accept” or “Deny” permission to use cookies. If you accept, the banner will disappear and the site will be 100% back to normal, including the comments section! If you deny, you can still read all current and historical content–but the comments section will be blocked, as will any embedded content (like YouTube videos). If you initially declined, but later change you mind (or vice versa), you can always click the small “Manage Consent” button in the lower right of your screen to amend your selection. Additionally, if you want to accept cookie usage only to access the comments section, you can do so by clicking “leave a comment,” then the “load comments” button (which accepts the terms just for that part of the website). And if you’re still having issues, consider clearing your browser cache and reloading the page.

Thanks for your understanding and patience as I worked out the kinks in this new setup!

Check out my long-form interview on Disasterproof!

In this hour-long video podcast, part of a the recently-launched Disasterproof series (developed by Convective), I offer my thoughts on a range of topics near and dear to the Weather West audience. The conversation is wide-ranging, and includes discussion of: extreme weather and climate change, the worsening wildfire crisis (and what we can do about it), the promise of and limits on weather prediction, the fundamental and enduring importance of public investment in science for the betterment of society, and my honest appraisal regarding the role of tech (big and small) in addressing climate and disaster-related challenges. Notably, this segment was filmed on location at the NSF National Center for Atmospheric Research‘s Mesa Lab at the height of what has been a very challenging year for the institution and for American weather and climate science more broadly–so I’d like to thank both the NCAR communications folks as well as the Disasterproof team for making this possible! (There’s also a shorter accompanying Sunstack article, if that’s more your style.)

YouTube livestream on East Pacific hurricanes, upcoming CA heatwave, and more: Mon, Sep 28, at 3pm PT

You know the drill! In this Monday livestream, I’ll discuss the contents of this blog post in more detail–with a focus on both the hyperactive East Pacific hurricane season as well as the upcoming, and potentially quite significant, western U.S. California autumn heatwave.