Report Date & Time: December 16, 2018 7:00 AM
By forecaster: Nathan Cool
Get notified when this report is updated. Sign-up for our free email forecast and be notified as soon as this report is posted.
Today (Sunday) we have a good deal of NW ground swell in SoCal. Much bigger NW ground swell is due to build into SoCal Monday. Another NW swell is being tracked for Thursday. Smaller NW swell is on the radar right now for next week. Condition-wise: slight rain chances in the forecast yield to mild weather later this week; winds remain moderate for the most part this week; the tide swings wide as the week progresses; water temps are fair for this time of year; and advisories are in effect.
This morning, periods were primarily running 12 seconds from 290°.
Most west facing breaks were running head high with occasional overhead pluses at standouts; however, there is island shadowing around parts of OC where size was more along the lines of chest high. South facing breaks were running chest high.
Hazardous Surf Warning: A hazardous surf warning is in effect this week. The NWS has also issued high surf advisories. Monday and Tuesday will be exceptionally hazardous as the bigger swell comes ashore; however, today's swell, and the swell coming in Thursday will also increase rip current and along-shore current risks and other hazards as well. Caution is strongly advised.
Swell Forecast and Schedule
Buoys in the outer waters off SoCal were running 8-10'. Nearshore buoys were running 2.7-3.9'.
The tide swings wide as the week progresses as we approach a Full Moon Saturday the 22nd. Today we have a 4.5' high around 5:00 AM, a 2' low around 11:30 AM, a 3.3' high around 4:30 PM, and a 1.3' low around 10:30 PM.
Water temps were running 61-62° in most of SD yesterday. OC was running 58-62°. LA was running 60-62° yesterday, although Cabrillo reported 58°. VC and SB have been running 59-60°.
Swell-wise: Today we're on the back side of swell #3 of the 4 swells that have been bringing swell to SoCal. The finale though will be much bigger, hitting SoCal during the day Monday.
Monday the 17th will see strong surf build into SoCal from north to south, with size varying at times during the day due to a "peak" swell event sent to the west coast when the storm creating this swell maxxed out at 51', but only for a brief time Friday night. Most of this storm's swell maximum time housed 40-45' seas when it was 1,600 nautical miles from SoCal, and this morning seas were measured at 33-38' at a distance of 1,100 nautical miles from SoCal. This factor alone (max seas being short-lived) means there will be heavy surf during the day Monday and Tuesday, but there will likely only be a 6- to 10-hour window for the biggest surf in SoCal at a certain point on Monday. But that's not all — there are other complicating factors affecting the forecast for SoCal.
Besides the short-lived peak swell timeframe (about 6-10 hours), exceptionally long-period swells like this, housing periods 20-22 seconds, behave much differently than shorter period swells do, as the longer periods shoal uniquely from spot to spot, which is widely varied throughout SoCal's curvey coastline with islands and channels adding to the variety of complex bathymetry (the contour/topography of the ocean floor). This means that one spot could be seeing massive waves while just up the coast another spot is much smaller. But, this isn't all that needs to be consider.
To complicate things even further, this storm has a massively wide fetch spanning an area in the Gulf that would be equal to about 3/4 the size of the entire continental U.S. This means that the incoming angle will vary widely, with the primary energy being accompanied by secondary energy. The entire swell energy spectrum from this particular swell will range from 270-320°; however, that's not the "primary" energy, nor is it for any particular time. From the center of the system's fetch, where the primary energy was sent during the swell-maximum Friday night, SoCal can expect a swell angle from 290-300°. While that will be the primary swell angle for about 70% of the swell, the remained will come in from 270-290° and 300-320°. And, on top of that, as the storm moved quickly to the west coast, its swell angle steepened; for instance, early this morning the fetch center was angling swell at SoCal from 305°, which will be arriving in SoCal late Monday into Tuesday. So not only will there be a wide swath of swell, but the primary angle will change throughout the day with peak swell coming in from 290-300°, and then 300-305° as the swell continues later in the day Monday into Tuesday. This also means there will be varying degrees of island shadowing, especially around OC.
As for timing: The peak swell should arrive in SB per-dawn to early AM Monday; VC early AM; LA mid AM; OC late AM; and SD by early afternoon Monday. That though is for the peak swell, but heavy surf will precede and follow it.
As for size: The peak swell is expected to produce breaking waves at SoCal's west facing breaks running 12-18' on the faces. But, with all the complicating factors I mentioned above, size will vary widely between spots, and at various times during the day as well. There is also a chance for bigger rogue waves at times on Monday.
Hazards will abound with an exceptionally high risk of rip currents and along-shore currents. Swells like this can create waves that quickly rush far up onto shore, which have been known to sweep bystanders out to sea. Stay off rocks and jetties, and remain a far distance from the shoreline. There is also a slight chance for rain in SoCal, mostly north of LA. See the Weather section below for more on that.
Tuesday the 18th should still see heavy swell, but size is expected to back off to DOH max at west facing breaks with pluses possible in the early AM at standouts. Swell should back off further Wednesday (head high+).
Thursday the 20th is expected to see the next NW swell from a Western Pacific storm that should peak south of the Aleutians in the next 24 hours with maximum seas in the 40' range, staying at a decent distance of around 2,000 nautical miles (farther away than the storm bringing Monday's swell). Running the numbers this morning, it looks like west facing breaks will see surf running 2-4' overhead, angled from 295° with periods 18-19 seconds.
The next potential swell for SoCal looks like a mild mix of NW from a Gulf storm on the 120h models that could get some reform when it nears the west coast (on the 150h+ models). This probably wouldn't be much, likely chest high or so for west facing breaks around the 24th or 25th. And then, some light southern hemi could come ashore on the 25th-26th from a small French Poly storm that's starting to swirl up right now, likely enough to bring waist high waves to south facing breaks. The NW though is out on the long range, and conditions remain El Niño-esque in the North Pacific, conducive to greater storm development. So although the NW'er for Christmas time looks moderate right now, I'll need to see how that plays out in the coming days, I'll keep you posted.
Here's how the day-to-day is breaking down so far:
Monday the 17th is expected to see heavy NW swell build from north to south into SoCal. The peak swell should arrive in SB per-dawn to early AM Monday; VC early AM; LA mid AM; OC late AM; and SD early afternoon Monday. When this peak swell hits, size is expected to run 12-18' on the faces at west facing breaks not affected by island blockage or the other complicating factors mentioned above.
Tuesday the 18th is expected to run DOH with pluses at west facing breaks, with peak swell in the morning, smaller later in the day.
Wednesday the 19th is expected to run head high to slightly overhead at west facing breaks.
Thursday the 20th is expected to run 2-4' overhead at west facing breaks.
Friday the 21st is expected to run head high to a couple of feet overhead at west facing breaks.
Saturday the 22nd is expected to run chest high at west facing breaks.
Sunday the 23rd, so far, is expected to run waist high at west facing breaks.
Monday the 24th, so far, looks about waist to chest high at west facing breaks.
Tuesday the 25th, so far, looks about chest high at west facing breaks.
An onshore flow is in place with weak high pressure over SoCal. Beaches should top out in the low to mid 60s today. A weather front linked to Monday's swell-maker is expected to swipe its tail end through SoCal tonight into Monday morning, with light rain likely in SB, somewhat likely in VC, but dry elsewhere. Rain totals could reach up to 0.2" in SB, maybe up to 0.1" in parts of VC, but trace to dry elsewhere. VC's 0.1" may even be a stretch. Rain, if any, should clear out mid to late AM. Beach temps should run in the mid 60s Monday. High pressure then builds into SoCal Tuesday for clear skies, but beach temps should remain in the mid 60s. Wednesday sees high pressure and offshore flow warm beaches into the high 60s, then 70 or so Thursday. The high should break down Friday with temps dropping to the high 60s.
Winds at 7:00 AM were calm to lightly offshore in most spots. Afternoon onshores are expected 8-12 mph. Monday is expected to see AM light and variables with a northerly element, possibly a bit NNW in the early AM around VC and SB, but NNE from LA south. Afternoon onshores Monday should max out in the 8-12 mph range, with some southerly element possible. Tuesday should see light offshores in the AM 5-10 mph and afternoon onshores to 10 mph. Wednesday is likely to see AM offshores 7-12 mph, and afternoon onshores to 10 mph. Thursday is looking at AM offshores in the 5-8 mph range and afternoon onshores 8-12 mph.
Until my next report (Tuesday), take care, be safe, and smile in the lineup!