SoCal Forecast
Updated most Sundays, Tuesdays, and Thursdays

Tuesday September 21, 2021 6:20 AM
By Nathan Cool


Surf Charts for SoCal

Rincon | Ventura, C-St. | County Line | Malibu | Hermosa | Huntington Beach
Trestles | Old Mans | Oceanside | Beacons | Sunset Cliffs

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At a glance:
Today (Tuesday) we have mostly moderate NW ground swell with background southern hemi swell in SoCal. Another shot of NW ground swell is due Thursday into Friday, and a slightly bigger NW ground swell is due Sunday. The weekend also sees southern hemi ground swell build, peaking early next week. There's a chance of seeing fairly good-sized NW ground swell by the middle of next week, with wind swell following shortly after. Condition-wise: offshore conditions flip quickly; precip chances tease the forecast; the tide is swinging wide; and water temps are varied.

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Current Conditions:
Early this morning, periods were primarily running 13 seconds from 300° and 14 seconds from 200°.

Most west facing breaks were running waist to chest high. Direct south facing spots were mostly waist high.

Buoys in the outer waters off SoCal were running 7-9'. Nearshore buoys were running 1.6-2.3'.

Tide levels are swinging wide from the Full Moon yesterday. Today we have a 0.2' low around 4:30 AM, a 5.3' high around 10:30 AM, a 0.9' low around 4:30 PM, and a 5.3' high around 10:30 PM.

Water temps were varied in SoCal. In SD and OC yesterday many spots were reporting 63-65°, but San Clemente warmed to 71°. In LA, Cabrillo warmed a tad to 63°, Zuma remained steady at 64°, Hermosa reported 66°, and Santa Monica buoy has been running 66-68°. In VC, Channel Islands Harbor in Oxnard has been running widely from 58-66° over the past 24 hours, most recently reporting 65° last night. SB Harbor reported 61° last night.

Surf Forecast:
All eyes remain focused on the North Pacific as seasonal change is getting underway — and rather quickly at that. We do have one southern hemisphere ground swell headed our way over the weekend into early next week; before then, and shortly after its arrival, northern hemi swells get all the attention.

Today we're seeing swell from the first of three NorthPac storms you might recall from my earlier reports (see earlier model here). Swell from storm #1 is what we're seeing today (model generated by XyGrib from NFCENS data):

Conditions have shifted offshore but will shift quickly. I'll get into the details of that and potential for weird weather in the Weather and Wind sections below. Wave-wise, today's NW swell should linger to a somewhat lesser degree Wednesday, with fewer chest high waves at west facing breaks.

Thursday the 23rd into Friday the 24th should see swell from storm #2, which had heftier seas in the 25' range, but that storm took a more northerly course, sending SoCal waist to chest high waves that should peak sometime during the day Thursday into early Friday morning. Swell should be angled from 300° with periods 14 seconds. This, btw, is when weather and winds could start going wonky.

Sunday the 26th remains on track to see better sized NW ground swell from storm #3 (model generated by XyGrib from NFCENS data):

After breaking off Kamchatka, this should stir up seas in the 25-30', but take a slight northerly route into the Gulf of Alaska. Running the numbers today on the 24-hour models, this remains at chest high for SoCal's west facing breaks, with swell angled from 300-305° and periods 16 seconds. Note that this is based on the majority of models this morning. The GFS model, which is used to generate surf charts here on WaveCast and some other forecasting sites, shows a weaker storm, so the charts show smaller swell in the waist high range building Sunday into Monday. I'm calling it based on the majority of models: chest high at west facing breaks with ETA early Sunday morning.

Overlapping with that NW'er is southern hemi ground swell that should slowly build Saturday the 25th and Sunday the 26th, and then peak Monday the 27th from this system that originated southeast of New Zealand and moved northward, growing along the way (model generated by XyGrib from NFCENS data):

Saturday the 25th and Sunday the 26th are looking at waist high waves at south facing breaks from this, but then Monday the 27th should run chest high. Swell should linger in the waist to chest high range Tuesday the 28th through Friday the 1st thanks to some reform action in the low latitudes. Swell should be initially angled from 205°, and at its peak swell would be angled from 190°. Periods should run 16-18 seconds.

Tuesday the 28th into Wednesday the 29th could see fairly good-sized NW ground swell. All long range models show something forming about 5 to 6 days from now, but the NFCENS is way bullish showing this impressive fetch (model generated by XyGrib from NFCENS data):

The purple blob in the center would be 30' seas, which is hefty to say the least from this proximity. If the NFCENS has it right, then SoCal's west facing breaks would see head high sets; FNMOC's NAV model works out to chest max; and the GFS model would be waist to chest. Being out on the long range, 144-hour-plus models, I'll need a few more days to see how this takes shape.

Following that potential ground swell could be an injection of NW wind swell. Many of the 200-hour-plus models show strong NW winds picking up along the coast around the middle of next week, which could increase wind swell Wednesday the 29th through Friday the 1st from a super deep trough that could push through SoCal (see Weather section below for more on that). Note that the GFS disagrees with this; hence, the surf charts won't align with my forecast. I'll keep an eye on it, and I'll keep you posted.

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Here's how the day-to-day is breaking down so far:

Wednesday the 22nd should run waist high everywhere with occasional chest high pluses at standout west facing spots.

Thursday the 23rd is expected to run waist to at times chest high at west facing breaks and knee to waist at south facing spots.

Friday the 24th is expected to run waist to chest high at west facing breaks and knee to waist at south facing spots.

Saturday the 25th is expected to run waist high everywhere.

Sunday the 26th is expected to run chest high at west facing breaks and waist to at times chest high at south facing spots.

Monday the 27th is expected to run chest high at most breaks.

Tuesday the 28th looks about chest at south facing breaks and waist to chest at west facing spots.

Wednesday the 29th, so far, holds a chance of seeing enough NW ground swell and wind swell to put west facing breaks into the head high range; however, models are highly conflicted from this point forward, making it too early to call either way. I'll have more on this and extend the forecast in my next report (Thursday).

 

Weather Outlook:
Weather will shift widely over the next few days. Today we're sitting under high pressure that's dominating the American West, but the offshore effect is not yet as strong as models have been forecasting. Models continue to show a moderate Santa Ana peaking between 8:00 AM and 10:00 AM this morning, but even at 7:00 this morning winds were light most everywhere, although about 20 mph offshore in some of the wind-prone mountain locations. There is a slight onshore flow at the surface, especially near the coast, so many spots can expect some marine layer this morning, but burn-off should be quick by midmorning (maybe late morning in some spots) with beach max temps in the mid to upper 70s. Wednesday looks similar.

Thursday is when things go haywire on the models as they struggle to deal with that cut-off low that'd retrograde across SoCal (trekking east to west, opposite of normal). See earlier model here. This morning, some models have backed off on that scenario, but more than 50% of the models show this low driving smackdab through SoCal (model by FNMOC):

In that scenario, which FNMOC's NAV and the CMC models agree with, some precip would hit the SoCal coast. These could be outliers, especially since the CMC keeps waffling on it, so I'll put the idea of precip Friday into the weekend in the 10% probability; my gut tells me there's zero chance of precip.

In any event, an onshore flow will get underway by Thursday (Wednesday afternoon, actually) into the weekend. This should bring back notable AM marine layer Thursday through the weekend with late AM burn-offs. Max beach temps should reach the low 70s Thursday, slightly cooler Friday, and then upper 60s this weekend.

After a brief interlude of warming high pressure early next week, we could see a very hefty trough of low pressure makes it way through SoCal (model by FNMOC):

No surprise, models are conflicted on this; however, not to the degree they are on the cut-off low for the end of the week since this trough would reside in the jetstream, making it easier to call. I'll hold off for now as we're venturing into long-range-land. I'll have more on this in my next report.

 

Wind Outlook:
Winds at 7:00 AM were light and variable most everywhere with a slight offshore element. Offshores should pick up a bit through mid morning, reaching 5-10 mph, and then shifting lightly onshore this afternoon to around 10 mph. Wednesday should see AM offshores in the 4-8 mph range, but turning onshore by mid to late morning, reaching 15 mph onshore in the afternoon. Thursday is looking at AM light and variables, but with afternoon onshores in the 15-20 mph range; however, this is where models begin to struggle with the retrograding, cut-off low, so I'll need to hold off until my next report to nail down the end of the week and weekend winds.

 

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

—Nathan

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