SoCal Forecast
Updated most Sundays, Tuesdays, and Thursdays

Sunday April 11, 2021 6:45 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 (Sunday) NW wind swell continues to be the main feature for SoCal surf but that will change shortly. Once wind swell wanes over the next couple of days, moderate southern hemisphere ground swell builds during the second half of the week, lasting for a while. Light to moderate NW ground swell is likely to come into the mix this coming weekend. We may see bigger NW swell during the second half of next week. Around the same time, we could see the first of two southern hemi swells come ashore, the second of which could be bigger over the weekend of the 24th-25th. We could then see our next NW swell around the 25th-26th from a rare development in the North Pacific. Condition-wise: onshore flow digs into SoCal shortly; morning marine layer thickens with drizzle/precip in the forecast; winds trend onshore for a bit; tide levels are moderate despite our current lunar event; and water temps are mostly unphased from potential upwelling.

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Current Conditions:
Early this morning, periods were primarily running 10 seconds from 315° and 13 seconds from 185°.

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

Buoys in the outer waters off SoCal were running 9-11'. Nearshore buoys were running 1.9-3.7'.

Tide levels are fairly moderate for daytime sessions despite a New Moon cresting tonight. Today we have a 0.3' low around 4:00 AM, a 4.5' high around 10:00 AM, a 0.5' low around 4:00 PM, and a 5.2' high around 10:00 PM.

Water temps have been unphased for the most part from upwelling, despite recent outer water winds. There has been a slight drop in the outer waters, but nearshore temps remain unchanged; in fact, they've warmed in some spots. SD has been running 61-63°. OC was varied yesterday with Huntington 59°, Newport 65°, and San Clemente 66°. In LA, many buoys have been running 59-63°. In VC, Ventura Harbor reported 58° yesterday morning, and Channel Islands Harbor reported 54° this morning. SB Harbor reported 60° overnight.

Surf Forecast:
Wind swell continues today and to a somewhat lesser degree Monday from this dual-jetstream pattern you may recall from my last report (model by UQAM):

The northerly (polar) jet dipped south late last week, setting up a storm track to drive a series of low pressure systems southeast through Washington, Idaho, and the Rockies. These lows stayed far enough away from the coast to keep pressure gradients — and subsequent winds/wind-swell ‐ moderate. The second, southerly (subtropical) jet is positioned over SoCal and will actually intensify around the middle of the week. This feature is more weather- than wave-affecting, keeping an onshore flow in place — something I'll touch on further in the Weather section below. In any case, wind swell should continue with similar size Monday and then back off Tuesday. Although a robust onshore flow will be affecting SoCal weather then, there won't be much pressure difference along the west coast to kick up much in the way of wind-swell-producing winds; instead, pressure will be predominantly low with high pressure hard to come by: no high pressure to interact with the lows; thus no gradients; thus no wind swell. Winds though will trend onshore, but not strong enough to kick up fetch in the outer waters. As far as surf goes, we should see a dramatic drop to knee to waist high wind swell by Tuesday at west facing breaks, which is perfect timing for our next swell.

Wednesday the 14th (building day) through Sunday the 18th remains on track for a moderate round of somewhat sporadic southern hemisphere ground swell from this activity you may recall from earlier reports near New Zealand:

Although this peaked with 35' seas, this stayed on a nearly direct easterly course, sending SoCal less of its energy; however, some reform action (note the two blobs of purple) should keep this going for a few days. So although SoCal's south facing breaks should see waist to chest high sets from this by Thursday the 15th (with Wednesday being the building day), swell should last into the weekend (17th-18th) and then fade to about waist max Monday the 19th. Note though that the easterly course means we'll see sporadic sets with many sets hovering around waist high, and then some sets (or waves in sets) running chest high (with occasional pluses possible at standouts). Swell is not likely to be consistent from set to set either. Swell should be angled from 205-210° with periods 18 seconds.

Saturday the 17th into Sunday the 18th, as the moderate southern hemi swell continues, we'll likely see an injection of NW ground swell from these two systems (model generated from NFCENS data):

Neither system is all too impressive with the first one (in the Gulf) having maybe 20-25' seas max, and the second one (near the Aleutians) being similar. Models aren't in total agreement on these; in fact, nearshore data — that generates the surf charts here on WaveCast — show ho-hum size. Working the numbers on the models (using good old fashioned math) this morning shows that west facing breaks can expect waist high ground swell waves Saturday the 17th, with a slight increase (waist+) Sunday the 18th. Swell would be angled from about 295-300° with periods 13 seconds. This is only out on the 72h models, so confidence is high that this weekend will see waist to chest high waves at south facing breaks from the southern hemisphere, and waist high waves at west facing breaks from this Gulf-Aleutian duo. Both swells would drop by Monday the 19th, more so Tuesday the 20th.

Conditions, btw, look fairly ideal this coming weekend (at least by Sunday...by the looks of things so far) as high pressure builds Sunday the 18th into Monday the 19th, which would make for clearer skies, warmer temps, and weaker onshores (if not offshore in the AM). This would be a rare — and brief — break in the onshore flow that dominates the weather forecast.

Wednesday the 21st has a decent chance of seeing WNW ground swell from this fetch that's expected to form in the lower latitudes of the Gulf of Alaska (model by FNMOC):

This is stepping into long-range-land, with this 180-hour model a bit dubious, but most models are in agreement today that this would eventually peak about 1,100 nautical miles from SoCal, which is close enough to put SoCal's west facing breaks into chest high waves. Swell would be angled from 285-290° with periods 13 seconds. I'll have to see how this plays out over the next few days.

Wednesday the 21st into Thursday the 22nd could also see southerly ground swell from the first of two systems that are forecast to break off Antarctic and drift north once nearing Pitcairn longitudes (model by FNMOC):

Storm #1 is in fair agreement across the models with enough juice to send SoCal's south facing breaks sets running chest high on Wednesday the 21st; however, a few models are less aggressive, coming in at waist high. Being on the short-range models, I'll be able to nail that in my next report. In any case, swell should be angled from 190° with periods 16-18 seconds.

The weekend of the 24th-25th could see bigger swell from storm #2 on that southern hemi model; however, this is where models diverge further. FNMOC's NAV (for instance) shows a massive fetch, and another model or two lean that direction, but other models yawn at it being a paper tiger with no teeth. This second swath of swell would arrive on the 24th-25th, but it's too early to start calling size right now. Either way, swell would be angled from 190° with periods 16-18 seconds.

Sunday the 25th and/or Monday the 26th is the ETA for our next swell. This would be a NW ground swell from a Fujiwhara that would form in the North Pacific (model by NOAA MAG):

As one storm swirls and subsumes the other, the combined storm would drop to fairly low latitudes in a deep trough of low pressure, which could send somewhat sizable WNW ground swell to SoCal. This is too far out on the long range to call right now, but I'm on it, and I'll keep you posted.

Here's how the day-to-day is breaking down so far, but first, here's an ad to help pay the bills:

Monday the 12th looks about waist to chest at west facing breaks and waist high at south facing spots.

Tuesday the 13th looks about waist high everywhere.

Wednesday the 14th looks about waist to chest high at south facing breaks and knee to waist at west facing breaks.

Thursday the 15th looks about chest high at south facing breaks (but sets sporadic with many sets only waist high) and knee to waist at west facing spots.

Friday the 16th looks similar.

Saturday the 17th should see waist to at times chest high sets at south facing breaks and waist high waves at west facing spots. Both from ground swells.

Sunday the 18th looks similar.

Monday the 19th should see southern hemi ground swell back off to waist high at south facing breaks. West facing spots will likely run knee to waist high.

Tuesday the 20th, so far, looks about knee to waist high everywhere.

Wednesday the 21st, so far, is expected to run chest high at west facing breaks and waist to chest at south facing spots.

Thursday the 22nd, so far, looks similar.

Friday the 23rd, so far, also looks similar.

Saturday the 24th could see a boost in southern hemi ground swell...more on that in my next report.

Weather Outlook:
A robust onshore flow gets underway later today through the rest of the week as a trough of low pressure digs south to SoCal, and a large area of low pressure parks itself over a large portion of the American West, like so (model by NCAR):

That is one heck of a large area of low pressure, which is forecast to just sit and spin for much of the week, peaking Tuesday into Wednesday. So while today should have minimal marine layer, max beach temps will start to cool, topping out in the low to maybe mid 60s today as that low starts to work its way into the region.

Monday sees the low start to dig in its heels and whip up AM marine layer with coastal eddy development likely. Look for a late AM burn-off Monday with max beach temps right around 60°.

Tuesday sees a heftier, moister onshore flow as the trough and low sit and spin across the region, bringing the chance for light AM precip/drizzle, late burn-off, and max beach temps in the upper 50s to maybe 60°. Wednesday looks similar.

Thursday into Friday sees some reprieve from the onshore-ness. Although a trough of low pressure remains draped over the region, that large low pressure system dominating the American West will weaken and exit to the east. This should allow a slightly weaker onshore effect Thursday, with drizzle unlikely, but AM marine layer practically certain with a mid to late AM burn-off, and max beach temps right around 60°. Friday should be a tick warmer with burn-off maybe a smidge earlier.

Saturday looks like a transition day (so far) before high pressure makes a temporary comeback Sunday (18th). This would result in an earlier burn-off Saturday with beach max temps in the low to mid 60s, with clearer skies Sunday with warmer temps. I'll need to see how this plays out on the models over the next few days,

Wind Outlook:
Winds at 7:00 AM were light and variable most everywhere. Onshores should pick up this afternoon and reach 15 mph by mid afternoon. Monday should see AM light and variables with onshores picking up mid to late AM, reaching 15mph early afternoon. Tuesday is looking at onshores early 5+ mph, perhaps 10+ mph late morning, and 15-20 mph in the afternoon. Wednesday will likely see AM onshores to 5 mph, picking up by noon, and reaching 15 mph in the afternoon.

 

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

—Nathan

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