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Pacific Storm and Surf Forecast
Updated: August 18, 2010 9:03 PM
Buoys: Northern CA - Southern CA - Hawaii - Gulf of Alaska - Pacific Northwest
Buoy Forecast:
Northern CA - Southern CA - Hawaii - Gulf of Alaska - Pacific Northwest
Pacific Links:  Atmospheric Models - Buoy Data - Current Weather - Wave Models
Forecast Archives: Enter Here
A chronology of recent Mavericks Underground forecasts. Once you enter, just click on the HTML file forecast you want to review (e.g. 073199.html equals July 31, 1999). To view the maps that correspond to that forecast date, select the html file labeled 073199 maps.html
Swell Potential Rating = 3.0 - California & 2.5 - Hawaii
Using the 'Summer' Scale
(See Swell Category Table link at bottom of page)
Probability for presence of largest swells in near-shore waters of NCal, SCal or Hawaii.    
Issued for Week of Monday 8/16 thru Sun 8/22
Swell Potential Rating Categories
5 = Good probability for 3 or more days of Significant swell
4 = Good probability for 1-2 days of Significant swell
3 = Good probability for 3 or more days of Intermediate/Advanced swell
2 = Good probability for  1-2 days of
Intermediate/Advanced swell
1 = Good probability for 3 or more days of Impulse or Windswell
0 = Low probability for 1-2 days of Impulse or Windswell   

3 Southern Hemi Swells Push North
Focus is the US Mainland - Hawaii to Get a Taste


New Swell Classification Guidelines (Winter)

Significant: Winter - Swell 8 ft @ 14 secs or greater (11+ ft faces) for 8+ hours (greater than double overhead). Summer - Head high or better.
Advanced: Winter - Swell and period combination capable of generating faces 1.5 times overhead to double overhead (7-10 ft) Summer - Chest to head high.
Intermediate: Winter - Swell and period combination generating faces at head high to 1.5 times overhead (4-7 ft). Summer - Waist to chest high.
Impulse/Windswell: Winter - Swell and period combination generating faces up to head high (1-4 ft) or anything with a period less than 11 secs. Summer - up to waist high swell. Also called 'Background' swell.

We've returned from vacation and forecasts are now being updated and will be posted regularly.  Also an issue associated with our wave and weather model servers has been fixed. We appreciate your patience during this outage.

On Wednesday (8/18) North and Central California was getting minimal southern hemi swell in the knee to thigh high range with local windswell at exposed west doing maybe thigh high as well. Southern California was effectively flat up north but clean with knee to thigh high windswell sets at better breaks. Down south southern hemi swell was generating surf in the thigh to maybe waist high range on the better sets on occasion and pretty clean. Hawaii's North Shore was flat and clean. The East Shore was getting waist high.cgius tradewind generated east windswell with moderately chopped conditions. The South Shore was near flat with rare sets in the thigh high range and pretty lumpy though wind was effectively calm. 

The forecast for North and Central CA on Thursday (8/19) is for southern hemi swell building to thigh high with windswell about 2 ft on the face. Friday things pick up slightly with south angled southern hemi swell to 3.5 ft on the face and windswell 2.5 ft.  Saturday southern hemi swell builds to 4.5 ft with windswell up to 3 ft. Sunday southern hemi swell drops to 4 ft faces/chest high with windswell again at 3.0 ft/waist high. Monday (8/23) reinforcing southern hemi swell moves in with waves up to 4.5 ft/shoulder high with windswell still at 3.5 ft. Southern California is to see minimal southern hemi swell on Thursday (8/19) being r.cgiaced with new south angled southern hemi swell on Friday at waist to chest high pushing near head high on Saturday.  Sunday (8/22)  new southern hemi swell moves in from an even more southerly angle at just under head high fading from shoulder high on Monday while more southern hemi swell builds under it.  The North Shore of Oahu is to maybe see little northwest swell at waist high on Thursday then dropping off with no ridable surf forecast over the coming weekend and beyond.  The East Shore to see east short period windswell at knee high Thursday (8/19) holding into Saturday, then dropping off after that. The South Shore is to see south angled southern hemi swell on Thursday (8/19) at head high early dropping from shoulder high Friday fading from thigh to waist high early Saturday. Nothing is expected on Sunday then new very south angled swell is expected to Monday at thigh to waist high early but not going anywhere from there.  

Up north no swell producing fetch is forecast over the next 7 days other than bare minimal local generated short period windswell for Central CA, and not even that till early next week.  Down south a solid gale pattern developed with one system producing up 40-46 ft seas in the far southeast Pacific on Thurs/Fri (8/13) with swell arriving in HI later today and in CA on Fri/Sat (8/21).  A second larger system developed in the far Southeast Pacific Sun/Mon (8/16) producing 46-47 ft seas targeting South America excellently with decent energy pushing up into the US West Coast by Sunday (8/22) but from a very southerly angle. And yet a third system developed in the Southeast Pacific Mon/Tues (8/17) with up to 40 ft seas pushing due north.  Significant class swell from this system is expected into the US West Coast on Tues/Wed (8/25) with lesser energy into Hawaii as early as Mon (8/23). No other swell producing weather system are to follow. 


Current marine weather and wave analysis.cgius forecast conditions for the next 72 hours

North Pacific

On Wednesday (8/18) the North Pacific jetstream was weak but cohesive generally tracking  directly over the Aleutian Islands with a trough pushing south of there back over Kamchatka.  But wind speeds in all location were 90 kts or less offering no real support for development of gale class weather systems at the oceans surface.  Over the next 72 hours an energetic ridge is to build over the Western Gulf of Alaska with winds to 120 kts, but all pushing up over the Eastern Aleutians only supporting the development of high pressure there. Some of this energy is to spill over the eastern flank of the ridge, but there is not signs of a trough developing.  Beyond 72 hours another push of winds energy is to start building over the grater North Pacific with winds speeds at 110-120 kts and aligned mostly west to east tracking just south of the Aleutians starting Mon (8/23), though no clear signs of a trough is forecast.  This suggests no real support for gale development at the oceans surface..  Still, some early signs of a Fall pattern appear to be trying to take hold. 

At the surface on Wednesday (8/18) a broad area of high pressure at 1028 mbs remained locked over the Eastern Pacific centered in the Western Gulf of Alaska.  It was not ridging into the US West Coast meaning only a light north winds flow at 15 kts was being generated over Cape Mendocino offering little in terms of local windswell production potential. It's southern edge was only  lightly pushing over the Hawaiian Islands generating 15 kt trades there an little in terms of windswell production potential there.  Over the next 72 hours more of the same is forecast with the high perhaps ridging only mildly stronger into Cape Mendocino with winds there to maybe 20 kts on Friday (8/20) and trades over Hawaii holding at 15 kts.  Maybe a little better odds for windswell pushing down into Central CA at best, and then even that is to be fading by later Saturday (8/21). Trades to hold unchanged over Hawaii.


North Pacific Animations: Jetstream - Surface Pressure/Wind - Sea Height - Surf Height


California Nearshore Forecast
On Wednesday (8/18) high pressure at 1034 mbs was positioned 1900 nmiles west-northwest of Northern CA and was barely ridging into the coast generating north winds at 10-15 kts off Cape Mendocino producing minimal if any short period northwest windswell. The gradient that has been in control all summer was almost gone. But by Thursday the high is to start ridging east some with north winds building to 15 kts over all of North and Central CA by late in the day, then focusing on Cape Mendocino by Friday (8/20) with winds to 20 kts there offering limited odds for windswell generation, but also pushing into the coast of Central CA warbling things up a bit. A generalized fetch of 15 kt north winds is to continue pushing over Central and North CA Saturday then building to 20-25 kts on Sunday making a mess of things. Finally on Monday (8/23) the gradient is to lift north and focus on Cape Mendocino with 20-25 kt north winds there, while pulling away from the Central CA coast. Windswell production to be on the upswing with conditions starting to improve south of there. The gradient is to hold over Cape Mendo into at least Wed (8/250 producing 25 kt north winds and windswell, while an eddy flow takes over Central CA waters.  Southern CA is to remain protected from all of this in terms of warble and chop production is concerned.           


South Pacific

On Wednesday (8/18) the southern branch of the jetstream continued flowing flat over the 65S latitude from under New Zealand at 110 kts there and then weaker  all the way to the Southeastern Pacific. The remnants of a trough were present in the far Southeast Pacific pushing north to 48S, but it was almost pinched off and looking to be on it's last legs with little wind energy associated with it. Over the next 72 hours a strong ridge is to build over the Southwest Pacific pushing south well into mainland Antarctica totally eliminating any odds for supporting gale development there. All energy in the east is to remain tracking east at 60S or south of there offering no support for surface level gale development there. Beyond 72 hours much of the same is forecast, with the big ridge holding in the west. A small trough is to develop in the extreme Southeast Pacific generally east of even the California swell window offering support for gale development only for South America.  In all, not a good pattern is forecast. 

At the oceans surface the remnants of what was a pretty good gale were circulating in the far Southeast Pacific with 30-35 kt south winds up at 42S 120W.  Previously on Monday AM (8/16) this gale produced 40-45 kt south winds at 50S 142W fading to 35-40 kts at 44S 132W on Tuesday AM (8/17) resulting in peak seas of 40 ft at 18Z on Tuesday at 43S 132W fading to 38 ft in the evening at 40S 130W.  The good thing about this system is all fetch was aimed due north, directly up the 187 degree path to NCal and the 191 degree path to SCal.  There even some potential for sideband swell to directionally spreed west into the Hawaiian swell window up the 165-170 degree track. Rough data has swell arriving in Southern CA on Mon (8/23) with period 20 secs and size tiny but building maybe reaching 2 ft @ 20 secs late (4 ft faces), peaking at sunset on Tues (8/24) pushing up to 4.6 ft @ 17 sec (7.8 ft faces with sets to 10 ft).  Swell to be holding on Wednesday at 5.2 ft @ 16 secs (8.5 ft faces with sets to 10.5 ft and bigger at top spots).  Swell to be settling down on Thursday with swell 4.8 ft @  14-15 secs (7 ft faces) and fading through the day. Swell Direction:  190 degrees. Swell to hit Northern CA on Mon (8/23) with period 21 secs and size tiny but building maybe reaching 1.6 ft @ 21 secs late (3.5 ft faces), building through the day Tues (8/24) pushing up to 4.2 ft @ 18 secs late (7.6 ft faces with sets to 10 ft).  Swell to be maxing on Wednesday at 5.0 ft @ 16-17 secs (8.5 ft faces with sets to 10.5 ft and bigger at top spots).  Swell to be settling down on Thursday with swell 4.8 ft @ 14-15 secs (7 ft faces) and fading through the day. Swell Direction: 187 degrees. Even some small swell is to reach into Hawaii for Monday (8/23) with pure swell 1.6 ft @ 18 secs (3 ft faces) from 170 degrees lingering into Tuesday.   

Otherwise no swell producing fetch is forecast. 


First Gale
Previously a gale developed southeast of New Zealand on Wed (8/11) tracking generally due east on the 53S latitude line producing 40 kt west winds and seas initially in the 32 ft range, making it in-tact the whole width of the South Pacific. By late Thursday (8/12) it gathered some strength with winds still 40 kts resulting in seas of 40 ft at 54S 133W but again aimed mostly east. By Friday AM (8/13) up to 46 ft seas were reported at 56S 121W pushing out of the CA swell window and again aimed mostly to the east. Utility class sideband swell is likely pushing north towards Hawaii and the US West Coast, but the extreme sideband nature of this swell will limit size in all locations. Unfortunately due to server problems we were not able to capture all the required data from this gale, so there is some uncertainty regarding the forecast below.  

Hawaii:  Expect swell arrival on Wed (8/18) with pure swell to 2 ft @ 17-18 secs late (3.5 ft faces). Swell to build to 3 ft @ 15-16 secs (4.5-5.0 ft faces) by early Thursday (8/19), then starting to fade later in the day.  Swell to continue fading from 3 ft @ 13-14 secs (4 ft faces) on Fri (8/20).  Swell Direction: 186-188 degrees

South CA:  Expect swell arrival at sunset on Thurs (8/19) with pure swell reaching 1.6 ft @ 20 secs (3 ft faces).  Swell to build through the day Friday (8/20) to 2.6 ft @ 18 secs  (4.5 ft faces with sets to 5.5 ft).  Swell to be fading after that from 3 ft @ 16 secs (4.5 ft faces) on Sat (8/21) but being overrun by another southern hemi swell.  Swell Direction: 196 degrees

North CA:  Expect swell arrival at sunset on Thurs (8/19) though not rideable (less than 1.5 ft ) with period at 21 secs.  Swell to build through the day Friday (8/20) to 2.0 ft @ 18 secs  (3.6 ft faces with sets to 4.5 ft).  Swell to be fading from 2.3 ft @ 16 secs (3.5 ft faces) on Saturday (8/21) but also being overrun by another southern hemi swell.  Swell Direction: 194 degrees     

Second Gale
On  Sat/Sun (8/15) yet another gale formed in the far southeast Pacific generating 40-45 kt southwest winds.  Seas were modeled to 42 ft Sunday Am at 45S 115W building to 47 ft in the evening at 44S 105W and then fading from 46 ft at 43S 100W Monday AM.  All this was outside the California swell window, though some fragments of energy from early in this systems life invariably pushing up the great circle paths to the north. This is really a reach of a forecast given the limited data available. Also ASCAT wind data was not conclusive. In reality, whatever swell was generated will appear as a second pulse of the First Gale swell (above).  No energy from this system was in the Hawaii swell window.     

 South CA:  Expect swell arrival at sunset on Saturday (8/21) with pure swell reaching 2.3 ft @ 18 secs (3 ft faces).  Swell to peak on Sunday (8/22) at 2.6 ft @ 16-17 secs (4.0-4.5 ft faces), dropping from 2.6 ft @ 15 secs (4 ft faces) on Monday (8/23).  Swell Direction: 188 degrees

North CA:  Expect swell arrival at sunset on Saturday (8/21) with pure swell reaching 1.6 ft @ 18 secs (2.5 ft faces).  Swell to peak on Sunday (8/22) at 2.3 ft @ 17 secs (4.0 ft faces), dropping from 2.6 ft @ 16 secs (4 ft faces) on early Monday (8/23).  Swell Direction: 185 degrees  


South Pacific Animations: Jetstream - Surface Pressure/Wind - Sea Height - Surf Height




Marine weather and forecast conditions 3-10 days into the future

North Pacific

Beyond 72 hrs high pressure is to finally start surging a bit to the east ridging into Central CA on Monday (8/23) with 20 kt north winds building over the state from Pt Conception northward.  Local windswell to start mildly building. A modest gradient is to quickly form over Cape Mendocino on Tuesday with winds there to 25 kts and windswell building some, while nearshore winds over Central CA die if not an eddy flow taking over. This pattern is expected to hold into at least Thurs (8/26). Trades to remain pretty weak over Hawaii until Wed (8/25) and then not increasing in speed any holding at 15 kts, just covering a broader area.  Local short period windswell to gain a few inches in size there then. 

MJO/ENSO Update (
reference):   As of Wednesday (8/18) the Southern Oscillation Index (SOI) continued solidly in the positive range. The daily SOI was up to 25.13 and has been that way in excess of 30 days. The 30 day average was at 17.90 with the 90 day average up to 11.25.  This looks like the Inactive Phase of the MJO was in full control.  

Wind anomalies as of Wednesday (8/18 at the 850 mb level (approx 5000 ft up) as defined by models indicated another surge of the Inactive Phase in effect with anomalous east winds blowing hard over the Philippines and extending east midway to the dateline and west to a little beyond India. This pattern is to hold through 8/20 with easterly anomalies extending east over the dateline, then start fading with anomalies barely reaching mid-day to Central America by 8/25. East anomalies are to totally fade out by Sept 4, but there is to be no sign of a much needed Active Phase developing. 

We believe the remnants of El Nino are just about gone from the upper atmosphere. The expectation is that we'll fall back into some form of a moderate La Nina Pattern (where the Inactive Phase takes control) for later 2010 into 2011. NOAA seems to support that.cgian too per the latest ENSO update. 

Sea Surface Temp anomaly data (8/16) indicates that cooler than normal waters continue to expanded their grip on the equator covering solidly from South America west to the dateline and beyond are in fact getting cooler and covering a larger area over time, extending the whole way to almost New Guinea.  It remained  downright cold just off Ecuador and then from a point south of Hawaii to just west of the dateline, a clear signal of strong easterly winds there and solid upwelling. Feeder bands of much colder than normal water continued building off the US West Coast and South America reaching to the dateline, only serving to reinforce the existing pattern, suggesting stronger than normal high pressure has built in both hemispheres and upwelling is in full effect. Good for sea life and the food chain, bad for storm production. Looks like a classic La Nina setup. This is a turn for the worse and only seems to be getting stronger. At the same time a massive buildup of warmer than normal waters continues in the Atlantic almost bleeding into the far Eastern Pacific, of concern to hurricane forecasters there. We'll see if upper level winds support development of hurricane activity or whether residual upper level shear from El Nino will chop the tops of developing systems. Suspect shear will be gone by the heart of hurricane season in the Atlantic.

Below the surface on the equator no Kevin Wave activity was present and if anything colder than normal water was building strong over the dateline and pushing east (sort of like a cold Kelvin Wave). This pocket was -3 degs below normal. Not good. 

Over the entire Equatorial Pacific trades were blowing all the way to the Philippines and beyond, with easterly anomalies now in control of the entire Western Pacific, though normal conditions in the East. But the Pacific current that runs along the equator turned abruptly from flowing to towards South America to flowing towards the west in mid-March (2010), right as the SOI started it's impressive drive into positive territory and the storm machine abruptly shut down. And it has not wavered since.  This suggests trade wind anomalies might be a byproduct of the Pacific equatorial current change and not the other way around.  And if anything, the change in the current might actually foretell a coming change in the trades, and then with the advent of the trade wind change, it only serves to reinforce the current in a self a.cgiifying loop, until such time as the cycle runs it's course and the self feeding system collapses over a multiyear period. At that time the current then switches direction, and a whole new self-enforcing cycle stars anew. Something to consider (regarding the formation and El Nino/La Nina).     

El Nino is effectively gone and slowly losing it's grip on the global upper atmospheric weather pattern. Still some lingering impact might continue through the Summer of 2010, but likely not enhancing the  storm track in the South Pacific any longer. A slow transition to a normal if not cooler than normal conditions (La Nina) is expected through Nov 2010, and the signs continue to point to a La Nina pattern for the long term future. 

See more details in the   El Nino update.


South Pacific

Beyond 72 hours there is no indication of any swell producing weather systems forecast for the Southern Hemi out  7 days.

Details to follow...


External Reference Material: El Nino Southern Oscillation (ENSO), Madden Julian Oscillation (MJO), Pacific Decadal Oscillation (PDO), Southern Oscillation Index (SOI), Kelvin Wave

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Local Interest

Interview with Stormsurf: Coastviews Magazine has written up a very nice article on Stormsurf in their latest edition. You can read it here:

Stormsurf Hi-Res Coastal Precipitation Models Upgraded Though a bit late in the season, on 3/20 we i.cgiemented the same basic technology used in our new snow/ski models into the coastal hi-res precipitation models. So now you can not only determined whether rain is forecast for your area, but also snow. And not just light, medium or heavy snow like most sites, but the exact snowfall amount (in inches) for each 3 hr frame of the animation. Here's a sa.cgie, but now this approach is used in all our precipitation models.

Stormsurf Precip Models Upgraded! On 2/20 we upgraded some of the broader precipitation models driven by the hi-def GFS model to include snow fall. The algorithm used is similar to the recently released snow models for the Southwest US in that the areas where snow is expected are identified and the exact amount of snow forecast over a 3 hr window is e.cgiicitly color coded. For East and West Coast US interests the following links provide good exa.cgies:
West Coast:
East Coast:

Stormsurf Weather Models have all been upgraded! Over the New Years break we installed all new and upgraded weather models. Also new are experimental snow models for the Southwest US. Take a look here:

Read about Eric Nelson and Curt Myers, the makers of Ride-On and other Big Wave Surf Movies here:

Ride On! Powerlines new big wave epic is now available on DVD. Get the entire big wave story of the 2008-2009 season here:

Click here to learn more about Casa Noble Tequila! Casa Noble Tequila If you are looking for an exquisite experience in fine tequila tasting, one we highly recommend, try Case Noble. Consistently rated the best tequila when compared to any other. Available at BevMo (in California). Read more here:

Interview With Stormsurf:  The crew at worked with Stormsurf on a feature about why surfers should be able to read wave charts themselves. They are firm believers that a little learning can go a long way to help your surfing.  This is a great article to help convince your friends that they can benefit from being able to read the data themsleves rather than just relying on the forecasts of others.  See the full thing here:  Create Your Own Surf Forecast with Stormsurf

Wave Model Upgrade Status Report: At this point we believe the installation of the new wave models is complete, with no problems being reported, the server stabilizing and the much requested return of the old style hemispheric Surf Height models now operational (again) and running side-by-side along the new ones. We thank you for your patience and input as we went though this process.  Your feedback helps guide our efforts and ultimately results in a better product for everyone.  Now we're off to start providing better menus to some wave model products most of you probably haven't uncovered yet (site specific graph and text forecasts), updateing the wave model FAQs and then upgrading the Weather Models.  

New Wave Model Facts: Click HERE to read more about the new wave models. Important info.

Story About Stormsurf: The folks at SurfPulse (and specifically author Mike Wallace) have written up a really nice article about Stormsurf, complete with some good pics. Learn about how we came to be and a little of where we are going. Check it out here:

Stormsurf Video: Just for fun - here's a clip about Stormsurf that ran on Bay Area TV a while back. Thought you might enjoy it:

Time Zone Converter By popular demand we've built and easy to use time convert that transposes GMT time to whatever time zone you are located. It's ion left hand column on every page on the site near the link to the swell calculator.

Need Chiropractic Help? Visit our friends at Darrow Chiropractic. Not only will Dr. Darrow fix you up, he might give you some big wave surfing tips too! See more here:

Stormsurf Google Gadget - Want Stormsurf content on your Google Homepage? It's si.cgie and free. If you have Google set as your default Internet E.cgiorer Homepage, just click the link below and a buoy forecast will be added to your Google homepage. Defaults to Half Moon Bay CA. If you want to select a different location, just click on the word 'edit', and a list of alternate available locations appears. Pick the one of your choice. Content updates 4 times daily. A great way to see what waves are coming your way! .xml

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Surf Height-Swell Height Correlation Table


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