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 Thursday (7/8) North and Central California had waist high ruffled north angled short period locally generated windswell with leftover pieces of southern hemi Swell #5S running about the same size underneath. Southern California was getting thigh to waist high leftover remnants of Swell #5S up north with barely noticeable wrap around northwest windswell intermixed and clean. Down south leftovers of Swell #5s were waist to maybe chest high and a bit warbled by modest west wind. Hawaii's North Shore was flat with clean conditions. The East Shore was getting knee high tradewind generated east windswell and lightly chopped. The South Shore was small to flat with no southern hemi swell of interest occurring.
The forecast for North and Central CA is for no real rideable surf coming from either the south or north expected on Friday. Then a little north windswell is forecast on Saturday at thigh high pushing maybe chest high Sunday then back to thigh high Monday (7/12). Southern California is to see no more southern hemi swell on Friday with things going flat and staying there through the weekend other than knee to thigh high north windswell possible on Sunday (7/11). Low odds of thigh high southern hemi background swell building in by Monday. The North Shore of Oahu is to possibly see some dateline windswell later on Saturday (7/10) at waist to near chest high on Saturday pushing shoulder high early Sunday (7/11) then fading from waist high on Monday. The East Shore to see east tradewind generated windswell Friday maybe at thigh high pushing waist high steady through the weekend into the early week. The South Shore is to see no real swell until Saturday (7/10) when southern hemi swell arrives at waist high or so, fading some Sunday then back later Monday at near waist high.
Up north a broad area of low pressure continues to be forecast for the dateline and Western Gulf on Fri-Sat (7/10) possibly generating 35 kt west winds and 18 ft seas pushing towards Hawaii initially and 40 kt west winds and 28 ft seas pushing towards the Pacific Northwest. Down south a gale is forecast to push under New Zealand on Sat (7/10) and lifting northeast with 32-36 ft seas, then regenerating and tracking further northeast into mid-next week with up to 36 ft seas over the time period. Possible swell to result initially for Hawaii and then the US West Coast. But is remains too early to know if any of this will really occur. At least there something to monitor.
SHORT- TERM FORECAST
Current marine weather and wave analysis plus forecast conditions for the next 72 hours
On Thursday (7/8) the North Pacific jetstream was tracking generally flat west over the 45N latitude with a decent trough developing on the dateline with 140 kt northwest winds flowing into it offering decent odds to support surface level low pressure development. Over the next 72 hours that trough is to hold into Friday (7/9) continuing support for gale development, then all energy is to streak off to the east and northeast lifting up towards Alaska, reducing odds of gale development in that region. Beyond 72 hours the jet is to continue flowing generally flat west to east on the 45n latitude, but no wind energy or troughs of interest are forecast to be present, likely minimizing odds for gael formation.
At the surface on Thursday (7/8) the usual area of high pressure off California had retrograded west and weakened to 1024 mbs, with no windswell producing northwest winds indicated. Trades remained light (15 kts) over the Hawaiian Islands too as a result of weakening high pressure over the Eastern Pacific. But of more interest was a gale low positioned just east of the dateline at 980 mbs producing 30-35 kt west winds off it's southern quadrant generating 17 ft seas pushing a bit towards Hawaii. This is expected to result in swell of up to 4 ft @ 12 sec (4.5 ft faces) for North Shore of Oahu starting late Saturday and building into Sunday AM (7/11) from 315 degrees. Over the next 72 hours this gael is to deepen on Thursday evening with pressure supposedly down to 968 mbs with a decent sized fetch of 40 kt west and northwest winds building at 46N 173W and holding there, up to 45 kts Friday AM at 47N 171W then fading from 40 kts in the evening at 47N 166W. This fetch is to be aimed mostly towards the Pacific Northwest down into Northern CA. Seas are modeled jumping to 25 ft Fri AM at 47N 171W, then 28 ft in the evening at 48N 166W and fading from 28 ft Saturday AM at 48N 161W. If that occurs some degree of decent 14-15 sec period swell could result pushing into Central CA and points north of there early next week. This was once considered a long shot, but is looking more like a genuine possibility. Regardless, this system is 2100 nmiles away from the US West Coast and whatever swell does arrive will experience much decay on the long journey east. Still, for July it would be a rare treat indeed.
North Pacific Animations: Jetstream - Surface Pressure/Wind - Sea Height - Surf Height
California Nearshore Forecast
On Thursday (7/8) high pressure at 1026 mbs was positioned 110 nmiles west of Cape Mendocino and having no impact on the US or Canadian West Coast with light winds generally in control. No change is forecast until Saturday when high pressure eases a little east and north winds build to 25 kts off Cape Mendocino, but reaching no further south than Pt Arena then retreating some. Maybe some warble to result, but no chop south of there. .A weak flow is to persist over Central and Southern CA waters until perhaps Thurs (7/15), and even then only north winds to 15 kts forecast. In generally a light mid-summer wind pattern is indicated.
On Thursday (7/8) the same old split and fragmented jetstream pattern remained in control of the South Pacific. The southern branch of the jet was tracking east down at 65S over the northern edge of the Antarctic ice pack eliminating odds for development of surface level low pressure over exposed waters of the South Pacific. Over the next 72 hours more of the same is forecast initially, then a gently building trough is forecast taking hold southeast of New Zealand on Sat (7/10) with 130 kts winds building on Sunday pushing northeast through it offering good support for gale development down at the oceans surface. Beyond 72 hours that trough is to hold and continue tracking northeast Monday (7/12) through slowly almost pinching off Tuesday and Wednesday while moving into the East Pacific and out of the US Swell window by late in the workweek. Still some decent odds are suggested to support surface level gale formation.
At the oceans surface low pressure had developed directly adjacent to the East Coast of New Zealand generating a small fetch of 40 kt south winds, but the fetch itself was sinking south. Maybe 25 ft seas are to result, not enough to generate swell of interest. Over the next 72 hours a broad area of gale force winds area to develop in association with e 960 mb low southeast of New Zealand starting Friday night (7/9) with 40 kt west-southwest winds at 60S 170E building to 45-50 kts Sat AM (7/10) from the southwest to south at 57S 175W then rapidly fading to 35 kts in the evening at 55S 162W. Sea are modeled to 32 ft Sat AM at 59S 178W pushing to near 36 ft in the evening at 57S 167W, then fading fast with maybe some 30 ft residual expected Sunday AM at 53S 160W. This is on the 187-181 degree tracks to Hawaii and the 206-203 degree tracks to California, all pretty well shadowed by Tahiti. Possible swell generation potential for Tahiti, with sideband energy for Hawaii and shadowed and somewhat indirect energy for the US West coast.
South Pacific Animations: Jetstream - Surface Pressure/Wind - Sea Height - Surf Height
Marine weather and forecast conditions 3-10 days into the future
Beyond 72 hrs weak high pressure is to try to have a toe-hold off Cape
Mendocino Sat/Sun (7/11) producing limited north winds there at 20-2t5 kts resulting in small short period north windswell before retrograding and dissipating. This high is to also stimulate trades over the Hawaiian Islands at 15-20 kts Sat (7/10) offering a little more hope for some windswell along east facing shores. A bit of a fade is forecast, then a weak return of high pressure is forecast Tues (7/13) limited to Cape Mendocino, only to dissipate again 24 hours later. Small windswell for Central CA at best. But after that a near neutral pressure pattern is to take hold of the entire North Pacific with no swell producing fetch forecast into Thurs (7/15).
MJO/ENSO Update (reference): As of Thursday (7/8) the Southern Oscillation Index (SOI) remained in positive territory. The daily SOI was at 10.16 and has been positive for 13 days running. The 30 day average was up to 4.53 with the 90 day at 7.01. This is looking like the start of a modest run of the Inactive Phase of the MJO.
Wind anomalies as of Wednesday (7/7) at the 850 mb level (approx 5000 ft up) as defined by models suggested light east anomalies holding over a small area in the West Pacific centered near the Philippines indicative of a fading pulse of the Inactive Phase of the MJO. A small and fading area of westerly anomalies indicative of the Active Phase of the MJO were still trying to hold on over Central America, not dying as fast as previous forecast. The Inactive Phase is trying to linger lightly over the Pacific with easterly anomalies forecast to over the Philippines 7/17 the dissipate. A neutral wind pattern is to take over then with the Active Phase of the MJO fading out.
We believe the remnants of El Nino will try to linger in the upper atmosphere for a while longer. But in reality, they are almost gone. The expectation is that we'll fall back into some form of a light to moderate La Nina Pattern (where the Inactive Phase takes control) for later 2010 into 2011.
Sea Surface Temp anomaly data (7/1) indicates that cooler than normal waters have developed over a moderate strip on the equator from South America drifting west to the dateline and are in fact getting cooler and covering a larger area over time, extending the whole way to almost New Guinea now. And feeder bands of colder than normal water have developed pushing 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. 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 -4 degs below normal. Not good.
Over the entire Equatorial Pacific trades were blowing all the way to the Philippines and beyond, but only in the normal range. But there has begun to be some signs of slight easterly anomalies developing, which is to be expected given all the other data. This is typical for this time of the year but is likely to change towards an increased easterly flow as Fall approaches symptomatic of La Nina.
El Nino is effectively gone and slowly losing it's grip on the global upper atmospheric weather pattern. Still some lingering impact is to 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 new El Nino update.
Beyond 72 hours the models indicate a secondary fetch of 45 kt south to southwest winds are to build south of Tahiti on Sunday evening (7/11) at 52S 160W and shadowed by Tahiti relative to the US West Coast but lifting steadily northeast and quickly moving out of the shadow while holding in the 45-50 kts range covering a generally small area into Wednesday AM (7/14) at 40S 122W. Seas projected in the 32 ft range. Some decent potential for swell mainly for Central America with decent odds for the US West Coast and maybe sideband energy into Tahiti. Hawaii is to be pretty far off and great circle route from this fetch though.
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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Surf Height-Swell Height Correlation Table