SoCal Forecast
Updated most Sundays, Tuesdays, and Thursdays

Sunday 9/20/26 5:50 AM
By Nathan Cool

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At a glance:
Today (Sunday the 20th) there are a lot of swells to cover as the tropics have become quite active. Currently we have minor southern hemi ground swell that will build each day through Wednesday the 23rd. NW ground swell is due Wednesday as well. Tropical swell from Odalys is likely Thursday the 24th. Swell from Dujuan is likely Monday the 28th into Tuesday the 29th. And there is potential for very significantly sized surf by the 29th from what should soon be Hurricane Polo. I'll also address the Kelvin Wave that's been in the news lately and what that actually means right now and for this year's El Niño. Condition-wise: tropical rain reenters the forecast; winds trend onshore; tide levels are fair for now; and water temps are above normal.

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Current Conditions:
Early this morning, periods were primarily running 18 seconds from 210° and 8 seconds from 320°.

Most south facing breaks were running waist high with occasional chest high pluses at standouts. Direct west facing spots were mostly waist high.

Buoys in the outer waters were running 4-6'. Nearshore buoys were averaging 2'.

Tide levels barely budge today as we shift from a 3.8' high around 8:00 AM to a 3.3' low around 12:30 PM. We'll then see a 4.7' high around 6:00 PM.

Water temps were running 73-75° around most of SD and OC. LA was hovering around 72° in most spots. In VC, Channel Islands Harbor reported 72° yesterday. SB Harbor reported 71° this morning.

Surf Forecast:
Today (Sunday the 20th) is one of the smallest days in the forecast as southern hemi is slowly filling in from this activity that was near New Zealand about ten days ago (model generated by XyGrib from NCEP data):

This will increase a bit more Monday the 21st. But size will increase further Tuesday the 22nd into Wednesday the 23rd as that system reformed a couple days later and moved north on a better course for SoCal surf (model generated by XyGrib from NCEP data):

The result is initially waist high waves at south facing breaks today and Monday the 21st, increasing to waist to chest Tuesday the 22nd, and then chest high Wednesday the 23rd. Swell should be angled from 215-220° with periods 16-17 seconds.

Wednesday the 23rd should also see light to moderate NW ground swell in the mix from this system in the Gulf of Alaska (model from NOAA OPC):

Although housing 25' seas, this stayed at very high latitudes, angling swell from a difficult 320-325° (page 45). This should produce waist to at times chest high waves at west facing breaks Wednesday the 23rd with periods 14 seconds. Southern hemi should do better with chest high waves at south facing breaks Wednesday.

Thursday the 24th, along with lingering southern hemi and NW ground swell, we'll likely see SW ground swell from Odalys, shown here on the 2-day projection (model generated by XyGrib from NCEP data):

Odalys should gain hurricane status tomorrow before taking a turn to the east with seas 25-30'. This storm is expected to weaken shortly after when it travels north. Running the numbers on the 2-day models, south facing breaks would see chest+ sets Thursday the 24th with top spots head high, angled from 200° and periods 16 seconds. Southern hemi should be in the mix at chest high Thursday as well and the light to moderate NW ground swell should run about waist to chest at west facing breaks. Odalys's swell would likely continue at chest+ Friday the 25th.

Saturday the 26th and Sunday the 27th look like temporarily smaller days in the SoCal surf zone — so far. NW wind swell for the weekend has been downgraded so south facing breaks will likely run waist to chest Saturday and waist high Sunday the 27th. But that should change quickly.

Monday the 28th into Tuesday the 29th we're looking at two swells hitting SoCal. The first and more significant swell would be from what will likely become Hurricane Polo, shown here on the 7-day outlook (model generated by XyGrib from NCEP data):

That purple core represents 40-45' seas, which would be very impressive. Being that close to SoCal (about 1100 nautical miles) this would bring very sizable surf to SoCal. Bear in mind, this is on the 7-day outlook and this storm has yet to be named, let alone given an official course. Running the preliminary numbers this morning, south facing breaks could see face heights running 12-18' (DOH-TOH). The initial angle would be steep from 160° Monday the 28th, but become better focused on SoCal Tuesday the 29th and Wednesday the 30th from around 170°. Periods would run as fast as 19 seconds but its proximity means we'd see a variety of periods in the mix (page 161). Once again, we're in the very early stages of this storm and it's too early to call it right now.

The second swell for the 28th-29th is from Dujuan in the Western Pacific, which should take a retrograding course back out to sea, sending us NW ground swell (model generated by XyGrib from NCEP data):

That 2-day model shows 40' seas, but being distant from SoCal on a northeasterly course means the energy reaching SoCal would have a good deal of distance decay (page 51) and angular spread (page 52). Running the numbers this morning, this works out to spotty, inconsistent sets running upwards of head high at west facing breaks by Tuesday the 29th (building Monday the 28th). Swell from Dujuan should be angled from 300-305° with periods 19 seconds. Swell from Polo looks much more significant so far, which could provide enough diffraction into west facing spots to possibly outdo Dujuan's size (page 77).

There is another swell in the mix for the 29th, although I'll likely drop it from the forecast as it would be imperceptible now that Polo has entered the forecast. It's just a minor southern hemi (see model here) that would run waist high at south facing breaks, angled from 225° and periods 18 seconds. If Polo develops as models project, then I'll drop this minor southern hemi from the report.

One last swell to note before talking about the recently publicized Kelvin Wave affecting this year's El Niño is moderate SW ground swell from this system on the 4-day models east of New Zealand (model generated by XyGrib from NCEP data):

With 25' seas on that ideal northerly course, SoCal's south facing breaks would run chest high. Swell would be angled from 205-210° and periods 15 seconds.

El Niño and the Kelvin Wave: I wanted to wrap up the surf section in today's report to clarify something recently sensationalized and often misinterpreted in the media: Warnings of a Kelvin Wave heading to SoCal.

While the name sounds ominous, much of the media has misconstrued Kelvin Waves as giant surface swells or destructive tsunami-like waves. But that's not the case. Instead, oceanic Kelvin Waves are a common, foundational ingredient of every El Niño. Kelvin Waves don't ride at the surface of the ocean; instead, they are subsurface masses of warm water that drive El Niño's climate engine. Without Kelvin Waves we wouldn't have El Niño. But there are things to be aware of this year, so I'd like to separate the facts from media hype.

Westerly Wind Bursts (WWBs) are the trigger for Kelvin Waves and for the most part, El Niño itself. As you may know, under normal conditions, strong trade winds blow east to west, piling up warm water in the Western Pacific. But when those trade winds weaken, then that warm water moves to the Eastern Pacific, creating an El Niño. But if those winds don't just weaken but actually reverse, then we call that a Westerly Wind Burst, which drives more warm water at a faster rate to the Eastern Pacific, resulting in more warmth in the El Niño zones extending off Peru. That's a Kelvin Wave.

Once a Kelvin Wave reaches South America, the warm water essentially splits with a significant portion traveling north, morphing into what's known as a "Coastal Kelvin Wave". But once again, it's not a breaking wave — it's a mass of warm water. And this is where things get interesting.

Kelvin Waves are part of all El Niños and they played a role in the 1997 El Niño when Kelvin Waves started in December 1996 and lasted through mid 1997. The 2015 El Niño had Kelvin Waves too, which started in the spring of that year. For our current El Niño, Kelvin Waves started as early as January 2026 and we had strong Kelvin Waves in the spring. In June, after a strong Kelvin Wave made it to South America, it split and formed a Coastal Kelvin Wave that reached SoCal. Of all the Kelvin Waves so far this year, a fourth one occurred this summer, which is the one that the media has homed in on. Yet it, and the Kelvin Waves before it, are leading up to the same result.

Kelvin Waves bring warm water. Since warm water expands, sea levels rise, and that's what happened from this year's developing El Niño (known as thermal expansion). This year's event is similar in regards to past El Niños in that warm water has increased sea levels near SoCal. This happens with each El Niño. In 1997, sea levels rose 8-12" above normal. In 2015 they rose 6-10". And right now, sea levels are about 6-12" above normal. This year though, a compounding factor is the lack of sand at many beaches that were heavily eroded from this summer's swells — Marie in particular, adding a wrench in the works.

When Marie slammed SoCal, a tidal swing was underway with high tides in the 6' range. Add another 12" to that from thermal expansion and you essentially have a 7' high tide. Such an extreme high tide, combined with exceptionally heavy surf from Marie, added to the beach erosion. Even without the extra foot in sea level rise, the combo of very high tides and Marie's powerful surf would no doubt have caused some erosion. Adding the extra foot (or so) from thermal expansion worsened the erosion. Either way, we now have something to contend with, and prepare for.

Having less sand barrier now from this summer's beach erosion, combined with higher sea levels from warmer waters brought on by El Niño and the Kelvin Waves driving it, there is a higher risk of coastal flooding and further erosion during upcoming swells — not just for the short term like from Polo, but more so during the winter from El Niño-influenced NW swells. But the Kelvin Waves are just one aspect of this year's El Niño.

This year's El Niño is on track to reach a record "signal" strength, but we need to put that into perspective (image from NOAA CPC):

Over the next couple months (OND for October, November, December), this year's El Niño should have a strength of about 2.6°C. By comparison, the El Niño of 2015-16 measured 2.6°C, and the 1997-98 Niño was 2.4°C. But that's measuring warm water in the El Niño zones. If we take a look at the bigger picture, water temperatures are warmer across the entire Pacific, and our planet as well.

For instance, here's what water temps looked like leading up to the 1997-98 El Niño (model from NOAA Coral Reef Watch):

In that older model the Pacific wraps from the left to right side of the image, different from more recent models I'll show for comparison. In any case, we can see the telltale red tongue of warm water extending off Peru (left side of the image), signaling a strong El Niño. But notice all of the blue water in the North Pacific, which represents below normal water temps in 1997. This is much different when we look at the water temps leading up to the "Godzilla" El Niño of 2015-16 (model from NOAA Coral Reef Watch):

Sure, we see the telltale tongue of warm water extending off Peru (center of this image), but notice what's absent: blue, colder water elsewhere in the Pacific. In fact, the North Pacific was dominated by marine heat waves in 2015 (coined "The Blob"). Overall though, with the North Pacific so warm in 2015 there was less difference between warmth in the El Niño zones and the rest of the North Pacific. Differences in temperature determine weather, which is likely why 1997-98 saw over 30" of rain in parts of SoCal while 2015-16 saw just 10". El Niño warming was stronger in 2015, but so was the rest of the North Pacific, resulting in a different weather pattern compared to 1997-98.

If we now take a look at the present state of El Niño, we see something similar to 2015, not 1997 (model from NOAA Coral Reef Watch):

El Niño warmth is evident off Peru. But waters are exceptionally warm in the North Pacific too. If we put a measurement on this difference between the El Niño zones compared to the rest of the North Pacific, the 1997-98 event was about Δ4°C. But today the difference is about Δ2°C.

Although media coverage of El Niño's Kelvin Waves has been largely misleading, it distracts from the fact that we need to prepare for the worst. When headlines become hyperbole, they're sadly seen as crying wolf, as though the whole thing should be discounted. But it shouldn't. Instead, the 2.6°C forecast for this year's El Niño is a warning to make immediate preparations. No one can say with a high degree of certainty if this winter will be similar to 1997-98, 2015-16, or other El Niño seasons. There is a high "likelihood" of above average rainfall and powerful winter swells. And even though that is "probability", it warrants preparation.

Kelvin Waves and El Niño as a whole are still in the nascent stages of science and our overall understanding. As I mention more than once in Wave by Wave, we're just a few specs of carbon on a water-filled rock that's spinning over 1,000 mph while racing around a modest star at a blinding 67,000 mph within an insignificant solar system housing a handful of planets traveling through a galaxy at 514,000 mph that's whipping through a universe at 1.3 million mph. You, I, and everything on Earth will never be in the exact same place in space ever again — even from second to second we enter new cosmic territory as we hurtle through the universe. And as we barrel through the cosmos, our planet spins and rotates through numerous cycles. We can use science to work within these cycles to gauge what might occur as these same cycles influence Earth's climate and give us insight — but not assuredness.

Our world of waves and weather is a constantly moving target. The short term — let alone the long term — forecast needs much more monitoring. But as long as I have your support then I can continue to keep an eye on the Pacific to keep you posted. Please remember this report is funded by reader donations and your help is needed to keep it alive (see why here).

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Here's a brief look at how the next few days are breaking down so far:

Monday the 21st should run waist high at most spots with occasional pluses at standout south facing breaks.

Tuesday the 22nd looks about waist to chest at south facing breaks and waist high at west facing spots.

Wednesday the 23rd looks about chest high at south facing breaks and waist to chest high at west facing spots.

Thursday the 24th, at the very least should run chest high at south facing breaks; however, Odalys may bring chest to head high sets to south facing spots (I'll confirm in my Tuesday report). West facing breaks should run waist to chest.

Friday the 25th looks similar: same for the southern hemi and question marks on Odalys.

Saturday the 26th, so far, looks about chest max at south facing spots (depending on Odalys).

Sunday the 27th will likely run waist to chest at south facing breaks.

Monday the 28th could see significantly sized forerunners come ashore ahead of powerful swell from Polo Tuesday the 29th. I'll need a couple more days to see how this will likely unfold.

 

Weather Outlook:
Today (Sunday the 20th) we're entering an interesting time weather-wise as the North Pacific transitions away from summer; NorthPac activity is winding up; but the tropics are becoming hyperactive. This puts more variables in play than usual with variations in our weather now through the beginning of October.

Today, this low pressure system is making its way into SoCal, increasing the onshore flow (model by NOAA MAG):

A good deal of cloud cover is pushing into SoCal from that low, making for a fairly cloudy day today. As that low pushes farther into SoCal Monday and Tuesday it should thicken up the marine layer and possibly bring drizzle to many coastal spots. That low should exit to the east for the second half of the week but no major high pressure is expected to backfill it; instead, weak high pressure centered over east Texas will barely extend into SoCal, allowing an onshore flow to stay in place — albeit weaker than the first half of the week.

A trough of low pressure should pass to the north of SoCal Friday (25th) to give the onshore flow a bit of a boost, with only slight weakening of the onshore flow for the weekend of the 26th-27th.

The bigger news is potential rain from Polo by Thursday the 1st as that storm is expected to drift northward, allowing a trough of low pressure to tap into Polo's moisture plume. Here is an early, long-range rain accumulation model showing where rain would hit the most (model by NOAA MAG):

We can see the rain trail Polo could leave in its wake before slamming across Pt. Conception with heavy rain there, less farther south. That though is a 300-hour model, making it far too early to call today, but definitely worth watching.

Taking all of this into account, here's how I'm calling SoCal beach weather for the next few days:

Today (Sunday the 20th) should AM marine burn-off around midmorning but high clouds should drift overhead most of the day. Max beach temps should reach the low 70s.

Monday the 21st should see AM marine layer, burn-off by early afternoon, and max beach temps in the low 70s. Morning drizzle is possible.

Tuesday the 22nd should see AM marine layer, burn-off by noon, and max beach temps in the low 70s. Morning drizzle is possible.

Wednesday the 23rd should see AM marine layer, burn-off midmorning, and max beach temps in the mid 70s.

Thursday the 24th should see AM marine layer, burn-off by midmorning, and max beach temps in the mid to upper 70s.

Friday the 25th should see AM marine layer, burn-off by midmorning, and max beach temps in the mid to upper 70s.

 

Wind Outlook:
Winds at 7:00 AM light and variable most everywhere. Afternoon onshores should run 10-15 mph.

Monday the 21st should see AM light and variables turn onshore to 10 mph by noon and run 15 mph by early to mid afternoon.

Tuesday the 22nd should see AM light and variables with a slight southerly element, onshore by noon to 10 mph, then 15-20 mph by early to mid afternoon.

Wednesday the 23rd should see AM light and variables with afternoon onshores 8-12 mph.

Thursday the 24th should see AM light and variables with afternoon onshores 8-12 mph.

 

Until my next report (Tuesday), take care, be safe, and smile in the lineup!

—Nathan

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