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Pacific Storm and Surf Forecast
Updated: September 19, 2010 1:08 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 & 3.0 - 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 9/20 thru Sun 9/26
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   

Small Dateline Swell Pushing to California
More Gale Energy Forecast to Follow - Fall is Imminent


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.

On Sunday (9/19) North and Central California was getting the backside of what proved to be a pretty good southern hemi swell with waves still head high with southeast winds on it.and heading down. Southern California was getting rare waist high southern hemi sets with fog and moderate onshore winds generating heavy texture early.  Down south the swell was looking much better with southern hemi swell pushing shoulder to head high and better at top spots and clean though foggy. Hawaii's North Shore is finally starting to move some with northern dateline region swell hitting at head high and maybe a foot or more overhead on the sets and a little warbled but not too bad. There certainly was surf. The East Shore was getting wrap around energy from the North Shore at waist high with lightly chopped conditions. The South Shore was approaching the flat zone with thigh high southern hemi leftovers on occasion and clean.    

The forecast for North and Central CA is for the first small northwest swell of the season arriving at near head high on Monday (9/20) holding into Tuesday AM then heading down Wednesday at waist high. Nothing rideable expected on Thursday or Friday. Southern California is to see fast fading southern hemi swell at maybe chest high at top spots on Monday and gone by Tuesday though little pieces of dateline swell might reach select breaks on Tuesday at thigh high. Nothing rideable is forecast Wed-Fri. The North Shore of Oahu is to see more sideband energy from the dateline arriving at 6.0 ft on the face holding Monday dropping to shoulder high early Tuesday and thigh high early Wednesday. Possible new datelines well arrives for later Thursday at 1-2 ft overhead holding at 1 ft overhead on Friday.  The East Shore to see no rideable surf of interest for the workweek. The South Shore is to see no rideable surf till Thursday when swell from the Tasman Sea filtered by Fiji arrives at shoulder to head high early and is expected to hang around for a while.   

Up north a tropical system tracked from Japan up to the dateline and organized pretty well, positioned just barely south of the Aleutians on Thursday AM (9/16) with 35-40 kt west winds generating one spurt of 28 ft seas at 45N 178W Wed PM into Thursday AM 2500 nmiles away and aimed well at Central CA, then faded to 20 ft late Thursday from 2150 nmiles away and dissipated by Friday AM.  Small swell has already hit Hawaii and is expected to reach into Central CA starting on Monday holding into Tuesday AM (9/21). Another similar gale is expected Sunday evening into Monday with seas in the 28-30 ft range, then fading with remains forecast to reorganize in the Gulf of Alaska Thurs-Sat (9/25).

Down south a gale tracked into the Tasman Sea Thurs AM (9/16) with seas to 38 ft and slowly fading into Saturday AM with seas dropping below 30 ft, all focused very well on Fiji and Northern New Zealand, with limited energy expected to filter through Fiji reaching Hawaii on Thurs (9/23) with less for California days beyond.  But with the North Pacific starting to activate, who cares about the southern hemi now?


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

North Pacific

On Thursday (9/16) the North Pacific jetstream was pushing off the Kuril Islands flowing flat east over the 45N latitude with 140 kt winds almost reaching the dateline, then the energy levels dropped way off as it progressed east almost dissipating right before reaching the US West Coast. There a trough was pushing onshore early. Back on the dateline, though there was wind energy there was no trough present to support gale development though low pressure was present north of the winds energy. Over the next 72 hours the dateline wind energy is to start organizing into a broad but weak trough on Tuesday and Wednesday with winds holding in the 120 kt range and moving into the Western Gulf of Alaska. Limited support for gale development indicated. Beyond 72 hours more wind energy is to be building over the West Pacific at 160 kts slightly ridging over the dateline then falling into the building trough in the Gulf by Thurs (9/23) looking quite nice by late Friday with winds still 160 kts providing improving odds for gale development there. That trough to east east through Sunday (9/26) while the jetstream falls down to 40N off Japan. Looks like a Fall pattern is setting up. And for now, no signs of the dreaded .cgiit jetstream is forecast (yet).  

At the surface on Sunday (9/19) a new gale was building just south of the Aleutians and west of the dateline off Kamchatka at 976 mbs with west winds 40 kts at 50N 170E aimed well up the 308 degree path to Central CA and 30 degrees east of the 327 degree path to Hawaii. Seas were building from 28 ft over a tiny area at 51N 172E. This is to hold into the early evening with seas peaking out at 30 ft at 50N 175E, then fading fast as winds drop to 35 kts or less Monday AM (9/19) and seas fading from 26 ft at 49N 180W. If this comes to pass (likely) some degree of small northwest swell is likely for Central CA starting late in the workweek (Friday 9/24) and fading into the early weekend. Hawaii to also swell swell possibly starting Thursday (9/23). Over the next 72 hours energy from the dateline gale is to slowly drift east into the greater Gulf of Alaska. no immediate development is forecast, but longerterm things are to improve.


Dateline Gale
On Thursday (9/16) remnants of a second tropical system that tracked east from Japan up to the dateline had organized better, positioned just barely south of the Aleutians in the morning with 35-40 kt west winds generating one spurt of 28 ft seas at 45N 178W Wed PM 2500 nmiles away and aimed well at Central CA, then expected to fade to 20 ft late Thursday  at 45N 170W (2150 nmiles away from NCal) then fading from 20 ft Friday AM. Small swell hit Hawaii as expected starting Sunday AM (9/19) at 5 ft @ 13 secs (6.5 ft faces) and is forecast to fade on Monday from 5.5 ft @ 12 secs (6.5 ft faces) from 325 degrees. Central CA is to start seeing swell mid-day Monday at
4.0 ft @ 15 secs (6 ft faces) holding at 5 ft @ 13 secs (6.5 ft faces) by Tuesday AM (9/21).  Swell Direction 297-301 degrees.  


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

No tropical activity of interest is forecast.

California Nearshore Forecast
On Sunday (9/19) weak low pressure at 1004 mbs was moving into British Columbia while weak high pressure at 1022 mbs was di.cgiaced northwest of even Hawaii. This has resulted in a near neutral pressure pattern locally and minimal winds, though a weak cold front associated with the low to the north was dissipating over the San Francisco Bay area. No rain was falling, even though it had been predicted. High pressure is to rebound eastward by Monday (9/20) with northwest winds taking over at 15-20 kts centered over Pt Conception but reaching up into North CA, then lifting north some into Tuesday centered over Central CA again at 15-20 kts nearshore and basically covering the entire state except Southern CA. Warbled and messy conditions expected. Even as a series of gale lows move through the Gulf of Alaska Wed-Sun (9/26) local high pressure is to hold it's ground producing pesky northwest winds at 15 kts over Central CA, though Southern CA is to remain mostly calm and perhaps San Francisco northward to get a break in the mornings.  


South Pacific

Note: Swell that arrived over the weekend was larger and more consistent than expected. We are retroactively labeling it Swell #6S.

On Sunday (9/19) a solid ridge was pushing south over the Central South Pacific reaching down to inland Antarctica and completely suppressing storm development over the region (from New Zealand eastward to nearly the tip of South America). A weak fading trough was centered just south of New Zealand but with no real wind energy associated with it. Over the next 72 hours a new batch of wind energy is to push up into that trough Sunday evening with winds 150 kts, but impacting New Zealand directly and likely providing no windflow to support gale development for our forecast area. That said, the trough is to east east some while weakening and become unobstructed by mid-Wednesday (9/22) providing a little window of opportunity, but weakening very fast. Beyond 72 hours the trough is to dissipate with a weak flat jetstream flow forecast on the 50S latitude traversing the width of the South Pacific.

At the oceans surface on Sunday (9/19) a broad low pressure system at 936 mbs was southeast of New Zealand encased over the Ross Ice Shelf and producing no real winds of interest over ice free waters. High pressure at 1024 mbs had a lock over the Southeast Pacific. No swell was being produced. Over the next 72 hrs a new storm is to quickly wrap up south of the Tasman Sea Sunday evening with 45-50 kt south winds at 56S 155E aimed directly at New Zealand. This fetch is to be lifting northeast and starting to impact the southern tip of New Zealand Monday AM (9/20) with the core still at near 50 kts at 53S 160E (southwest of New Zealand). By evening the fetch is to still be at 45 kts located at 52S 167E moving into the 220 deg swell window for California. 38 ft seas are forecast at 50S 170E, perhaps pushing energy towards CA. Tuesday AM (9/21) a tiny fetch of 45-50 kt south winds is to persist at 51S 172E resulting in near 40 ft seas at 50S 174E over a tiny area and pushing up the 216 degree path to California and unshadowed by Tahiti and the 200 degree path towards Hawaii. The fetch is to be gone by evening. With luck a little pulse of southern hemi swell could radiate towards Hawaii and California, with the ISlands getting the better shot of the energy just due to being closer minimizing swell decay. But with swell from the North Pacific becoming more of a reality, this swell becomes less interesting. Will monitor.


Tasman Sea Gale
At the oceans surface on Thursday (9/16) a broad gale built in the Tasman Sea.
This system started forming south-southwest of Tasmania on Wed (9/15) with 45 kt south to southwest winds pushing mostly into Tasmania, with maybe a little reaching clear of it's south end and tracking up into the extreme southern Tasman Sea. On Thursday 40 kt southwest fetch was finally pushing free and clear of Tasmania reaching to 39S 152E early and up to 36S 165E late resulting in 37 ft seas at 39S 159E (Thurs PM).  Then on Friday additional 40 kt southwest fetch built into the Central Tasman Sea near 40S 160W resulting in 33 ft seas at 40S 170E in the evening. This system faded fast on Saturday AM. Northern New Zealand is to receive the brunt of this swell though an almost equal amount of swell energy is to push up into Fiji starting on Sunday AM (9/19 GMT).

Filtered swell is expected to hit Hawaii late Wed (9/22) at 1.6 ft @ 18 secs at sunset (3 ft faces) building overnight and pushing to 3 ft @ 16 secs (head high to 1 ft overhead) late Thursday (9/23).  Swell to hold at 3 ft @ 16 secs (head high) on early Friday (9/24) then slowly settle down. But still swell of 2 ft @ 14 secs (waist high sets) is expected on Sunday (9/26). Swell DIrection: 215 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 low pressure that was over the dateline is to move to the Gulf of Alaska Wed/Thurs (9/23) with winds to 30 kts aimed pretty well at the US West Coast. Sea possibly to 20 ft or better, but this is purely an early guess by the models. Possible more small swell for the US West Coast with sideband energy pushing down towards Hawaii.  

MJO/ENSO Update (reference):   As of Thursday (9/16) the Southern Oscillation Index (SOI) continued solid in the positive range. The daily SOI was at 19.79 and has been that way in excess of 59 days now. The 30 day average was up to 24.29 with the 90 day average up to 17.68.  The Inactive Phase of the MJO appears to still be in control.  

Wind anomalies as of Wednesday (9/15) at the 850 mb level (approx 5000 ft up) as defined by models indicated the Inactive Phase was still in control with light east anomalies covering the entire width of the tropical Pacific and pushing into Central America. A weak incarnation of the  Active Phase of the MJO was trying to build over the width of the Indian Ocean. This pattern was to continue with easterly anomalies and the Inactive Phase tracking over the Eastern Pacific while fading and pushing into Central America through 9/25 then slowly dissipating into 9/30 while a weak version of the Active Phase and it's much needed westerly anomalies are forecast to try and push into the West Pacific on 9/25, barely making it halfway to the dateline then stalling and dissipating there into 10/5. This is about the same as the previous forecast and might help to build a weak Fall weather pattern over the North Pacific. Also the movement of the Inactive Phase into the Atlantic might help to fuel hurricane development there through the end of Sept.

We believe the remnants of El Nino are just about gone from the upper atmosphere. The expectation is that we'll see a building moderate to moderate.cgius strength La Nina Pattern (where the Inactive Phase takes control) for the remained of 2010 extending well into 2011 and likely to early 2012. In short, the next year and half is going to be tough for surfers on west facing shores in the Eastern Pacific and Eastern Atlantic, though east facing shores of the West Pacific and Atlantic might do well from the Inactive Phase's dominance.     

Sea Surface Temp anomaly data (9/13) indicates that downright colder than normal waters continue to expand their grip on the equator covering solidly from South America west to the dateline and beyond and are in fact getting cooler and covering a larger area over time, extending the whole way to New Guinea.  The coldest waters extended 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 cooler than normal water continued building off the US West Coast and South America sweeping fully to the dateline, only serving to reinforce what is already an impressive La Nina pattern, suggesting stronger than normal high pressure has built in both hemispheres and upwelling is in full effect in the Gulf of Alaska and off South America. This is good for sea life and the food chain (since they tend to like colder waters), but bad for storm production. Looks like a classic La Nina setup. This continues the turn for the worse and only seems to be getting stronger. At the same time a massive buildup of warmer than normal waters has stalled in the Atlantic almost bleeding into the far Eastern Pacific. This was of concern to hurricane forecasters there. But it appears residual upper level shear from El Nino has done a good job of if not chopping the tops off developing systems, at least directing then to the north. But that shear appears to be fading some as we move into the heart of hurricane season in the Atlantic. Regardless of this year, next year might be a very strong hurricane producer, with the El Nino shear gone and a mature La Nina in control.

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 -6 degs below normal (getting colder). Not good. 

Over the entire Equatorial Pacific trades were blowing all the way to the Philippines and beyond. And now from a historical perspective these easterly winds were anomalous, blowing harder than normal from the east to the west, as would be expected looking at all the other data. But this is a rather recent development, with only normal winds indicated prior to 9/11. The interesting twist to all this is that the Pacific current that runs along the equator turned abruptly from flowing towards South America to flowing towards the Philippines in mid-March (2010), right as the SOI started it's impressive drive into positive territory and the North Pacific winter storm machine abruptly shut down. And it has not wavered since. But trades never waiver from the normal range.  This suggests trade wind anomalies might be a byproduct of the Pacific equatorial current change and not the other way around i.e. the trades do not drive the temperature change initially, but the current change does. And then the atmosphere responds in kind to the change, building high pressure and reinforcing the flow and water temps. Said a different way, 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 early Fall 2010, but likely not enhancing the storm track in the South Pacific any longer. A transition to 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 suggestions of weak sporadic pulses of winds energy pushing east under New Zealand. But none are to last more than 24 hours with most of their energy pushing east rather than north. In short, nothing of real interest is indicated.


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:
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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:

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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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