SoCal Forecast
Updated most Sundays, Tuesdays, and Thursdays

Thursday January 21, 2021 5:50 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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Today (Thursday) we have mostly moderate NW ground swell in SoCal. Light to moderate southern hemi comes into the mix Friday. A change in the North Pacific pattern will then bring in a series of NW ground- and wind-swell combos, with a very sizable swell due early next week. More NWers are being watched for the end of the month into the beginning of February. Condition-wise: numerous rain storms aimed at SoCal; onshore winds in the forecast; the tide swings wide shortly; and water temps are fair but likely to drop in a few days.

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Early this morning, periods were primarily running 13 and 17 seconds from 295°.

Most west facing breaks were running chest high. Direct south facing breaks can expect wrap running waist high.

Water Contact Advisory: Rain is on the way for an extended period, which can increase high bacteria levels in the surf zone from runoff. As a reminder, there is a risk of increased bacteria levels for at least 72 hours following any measurable rain-event, during which time water contact should be avoided.

Swell Forecast and Schedule
Buoys in the outer waters off SoCal were running 5-6'. Nearshore buoys were running 1.8-2.5'.

Tide levels are moderate now but swing wider in a few days as we approach a Full Moon Thursday the 28th. Today we have a 4.3' high around 4:00 AM, a 1.5' low around 11:30 AM, a 2.6' high around 5:30 PM, and a slackwater, 2.2' low around 9:30 PM.

Water temps were running 57-59° in most of SD and OC yesterday. LA was running 57-59°. VC and SB were running 54-57°. Note that water temps may drop starting this weekend into next week as storms approaching the region increase NW winds in the outer waters, causing upwelling.

Swell-wise: Today we're seeing swell from the first in a series of storms being affected by that newly developing North Pacific pattern you might recall from my earlier reports. This will also have a major impact on our weather and winds through the rest of the month, with significant change on the horizon. There's a lot to cover in today's report, but before getting to that, it's time once again for me to ask for your support for my forecasting efforts and consider a donation. I posted a new donation progress report, which shows that donations slightly exceeded the goals for 2020. A big thanks to everyone who donated! In return, I carried over that excess balance to get 2021 going, and a few donors have chipped in this month as well, which will be tallied in the next progress report. But we're a long ways from meeting the 2021 donation goal, so anything you can do now (or sometime soon) would be very much appreciated. Now back to our regularly scheduled programming...

Up until now, January was blessed with an ideally draped jetstream/storm-track that looked like this (models by NOAA MAG):

But the jetstream (green) now being bent northward in the Gulf of Alaska by high pressure, prevents storms from the Western Pacific to build stronger seas past the Aleutians:

The blue circle around the Gulf's high pressure shows the key to this new pattern. The biggest swells we had this month grew into wave monsters once they passed the Aleutian longitudes, starting out small in the Western Pacific, growing to around 35' seas south of the Aleutians, and then growing further with 50' or higher seas once entering the Gulf of Alaska as the jetstream — unblocked at the time — allowed storms to continue their forward progression. That's now coming to an end as high pressure asserts itself in the Gulf of Alaska, setting up a wave blockade for ground swell formation, but opening the door (big time) for wind swell, rain, and winds as those same storms being blocked by the Gulf high, will get a rebirth when the clockwise spinning high swirls them south along the west coast, mostly over water like so:

Low pressure systems (circled in red) would pick up plenty of moisture on their overwater treks to bring precip to SoCal at times, along with onshore winds. A slew of these low pressure systems are lining up to take this NorthPac wet express, with the forecast filled with ground/wind-swell combos, rain, and varying degrees of onshore wind.

As mentioned though, today's swell, which should peak Friday the 22nd, was the first to encounter this pattern, which didn't yet have the southerly leg of the jetstream to drop it south to SoCal for a round of wind swell. So this should top out at chest max Friday, and be mostly ground swell.

With NW swell less impressive Friday the 22nd, we should see the addition of light to moderate southern hemi at south facing breaks Friday into Saturday from small-scaled storm activity that swirled about in the lower latitudes a little over a week ago. Nearshore data-point forecasts continue to show potential for chest max waves at south facing breaks, but wave models leaned more toward waist to chest at best, which is how I'm calling it. Swell should be angled from around 200° with periods 16 seconds.

Saturday the 23rd into Sunday the 24th should see the next NWer affected by that blocking pattern — but it'll be a mere teaser for what'll be waiting behind it (I'll get to that next). This should bring chest to head high waves to west facing breaks with a mix of ground swell (60%) and wind swell (40%), peaking Sunday the 24th. Swell should be angled from 300-310° with periods 14 and 10 seconds.

Monday the 25th (building) into Tuesday the 26th (peak) is in for a major NW wind/ground-swell combo. The ground swell portion of the combo is from this impressive looking dude swirling up 40-45' seas in the Western Pacific:

NOAA's OPC, btw, shows a small area reaching 50'+ in this fetch's center. In any case, the more significant portion of the swell combo would occur in a few days when the jetstream swirls that system up and over the Gulf, and then south along the west coast of the U.S., eventually landing smackdab off the coast of SoCal with a massive wind swell fetch:

That red arrow I popped on that model shows how seas well over 20' would sit just off the coast. This would easily bring DOH wind swell to west facing breaks with top wave face height running about 15'. The ground swell portion of its WestPac position would be easily head high+. Wind swell though would be dominant, and bigger. As for timing, it looks like this will hit SB/VC by mid morning Monday the 25th and reach SD by nightfall into early AM Tuesday the 26th. Swell should be angled from 300° (or higher) from the wind swell, and about 290° from the ground swell. Periods should run 18 seconds from the ground swell, and 10-13 seconds from wind swell. Conditions may be rough as well (see below for more). Rip current risk will be extremely high. And bacteria levels from rain pose danger as well. Swell should back off temporarily Wednesday the 27th.

Notice also those other two systems on that last model above: one in the Gulf, and another in the Western Pacific. Each is lined up to take the round-about route to drop more waves and weather on SoCal.

Thursday the 28th into Friday the 29th looks like the next round of NW combo swell, with size estimates so far coming in at least a couple feet overhead at west facing breaks. Once again this would be wind-swell-dominant with swell angled mostly from 300-310° and periods 10 seconds or so. Since this is reliant on coastal proximity, it's based on long range, 160h+ models, putting it in the somewhat likely category for now — but with confidence.

In the mix would be background southern hemi from this an unseasonable system in the Tasman Sea that popped up this week (model by FNMOC):

Even though that pumped up 35-40' seas, this is a tough region to pull in swell for SoCal as numerous island obstacles stand in its way. SoCal's south facing breaks should see waist to chest max Friday the 29th with swell angled from 220-230° and periods 18 seconds. Sets, and waves per set, would likely be infrequent. Also, NW wrap may overshadow this, making it hard to notice.

Monday the 1st would see the next combo swell; however, some models are hinting at a shift in high pressure to the east, which would result in this being more ground- than wind-swell. This is way out on the long range, making it too early to call today. I'm on it...I'll keep you posted.

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

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

Saturday the 23rd should run waist to chest high every in the early AM with swell building into west facing breaks during the morning, more so later in the day.

Sunday the 24th looks about chest to head high max at west facing breaks. Southern hemi backs off, leaving south facing breaks relying on NW wrap.

Monday the 25th should see NW wind swell and ground swell build during the day, reaching SB early to mid AM, and SD late in the day. Peak wave size on arrival should be DOH at west facing breaks. Conditions look poor and hazardous.

Tuesday the 26th should see the NW combo peak in the early AM with DOH waves lingering through the morning, dropping off in the afternoon.

Wednesday the 27th looks about chest to head high at west facing breaks.

Thursday the 28th, so far, looks about head high to a few feet overhead at west facing breaks.

Friday the 29th, so far, looks similar.

Saturday the 30th, so far, would likely drop to chest to at times head high at west facing breaks.

Sunday the 31st, so far, looks about chest max at west facing breaks..

Monday the 1st, so far, has potential for overhead surf at west facing breaks.

Weather Outlook
Today we're between major weather events: the Santa Ana is gone, but rainy weather is setting up from that pattern I talked about above, with the jetstream poised to drive storm after storm south to SoCal. For now though, SoCal sits under mostly sunny skies with beach max temps today in the mid to maybe upper 60s. That changes tomorrow.

Rain should begin Friday, lasting through the rest of the month, with some days wet, and others dry. Cutting to the chase, here's how rain totals are looking right now for the period of 1/22 through 2/1 (model by NOAA MAG):

According to that GFS model, coastal SB could see 3-5" (up to 10" in SB mountains); VC would see 3-4"; LA coast would be around 2-3"; and OC and SD would run up to 2".

As for timing: Friday would be dry most everywhere during a good portion of the morning with cool temps in the upper 50s. Rain would reach SB and VC sometime in the afternoon or early evening, then LA, OC, and SD later in the afternoon or evening. Rain would last a good portion of the day Saturday. This would initially bring about 0.1-0.25" of rain to most of the coast.

Rain should clear Sunday with temps still cool in the upper 50s max at the coast; however, rain is likely to come into most areas in the evening as the next low dives much farther south before swinging into SoCal. Rain would likely start after dark Sunday, and become heavy Monday. Rain totals from this round are looking heaviest in OC and SD from a southerly moisture tap, bringing 0.5" to the OC and SD coasts; 0.1-0.25" farther north.

Tuesday would clear out with beach max temps in the mid 50s.

Wednesday begins the next round of rain, hitting SB pre dawn, VC around dawn, LA shortly after dawn, and OC mid to late morning. SD is looking less affected, with rain possibly not reaching that far south until Wednesday night or Thursday morning. Rain would continue (moderately) Wednesday, off and on Thursday, and then potentially very heavy Thursday night (28th) into Friday (29th), clearing Saturday (30th). This is looking like a damaging, high-flood-potential event with very high rain rates, raising concern for mudslides/debris-flows. Rain totals from this particular round could reach up to 3" in SB, 2" in VC and LA, and 1-2" in OC and SD. Beach max temps around this time would be in the mid to upper 50s.

Saturday the 30th looks clear so far, with the next possible rainmaker coming ashore Sunday the 31st. That one looks light so far, with some rain lingering into Monday the 1st.

Tuesday the 2nd would likely start a drying trend as most models favor high pressure building over the American West.

Wind Outlook
Winds at 6:00 AM were light and variable most everywhere. Afternoon onshores should run 9-14 mph. Friday will likely see early AM offshores to 5 mph and afternoon onshores to 15 mph. Saturday will likely see onshores pick up early and reach 15 mph in the afternoon. Sunday should see onshores pick up by midmorning and reach 20 mph in the afternoon. Monday looks blown out with onshores over 20 mph early, reaching 30 mph at times in the afternoon. Tuesday will likely see weaker onshores, but still 15+ mph early.


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


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