Monday, September 26^th – Tuesday, October 4^th

Local Weather Outlook –

Trade winds gradually building through the week…

A weak, surface ridge of high pressure extended from the Pacific northwest to Hawaii thanks to a cold front slowly passing north of Hawaii. The East trade flow of 5-10mph on Sunday was not strong enough overcome the development of widespread sea breezes. The cold front should devolve into a shearline and maintain very light E-ENE trade flow on Monday. Like Sunday, sea breezes will be common for many spots in the afternoon. By Tuesday, the shearline should wash out and allow high pressure north of Hawaii to build. ENE trades should trend upward by a half to one notch on Tuesday (5-15mph), still light enough for sea breezes for the leeward coast. Speeds should reach moderate levels by Thursday and hold into next week. Shower activity will be rather limited during this transition period. A return to more typical windward and mauka showers is in store after midweek.

Surf Outlook –

North Shore: Progressively larger NNW swells this week…a moderate event to start next week?

Recent/Now: On Sunday afternoon, surf in the country was out of the NNW at tiny levels of 1.5’ Hawaiian scale or less and dropping. This event peaked towards midday Saturday. The source was a cut-off low north of Hawaii that aimed 30-40mph winds mostly to the west of Hawaii. Angular spreading enabled some of that energy to reach Hawaii. With the lack of trade wind wrap, most spots should drop to near flat on Monday.

Next: Last Thursday, a trough over the Bering Sea dug southward and emerged equatorward of the Aleutians and just east of the dateline. Winds peaked late Friday into Saturday at 25-35mph. Although the aim was highest east of Hawaii, the longer fetch duration and length should spell decent surf potential. Short to medium period forerunners from the NNW should arrive towards midday Tuesday with a very slow rise to 1.5’ before dark. It should peak late Wednesday at 1-2’+. Top sets could approach 3’. It should slowly drop on Thursday with 2.5’ sets becoming less frequent in the afternoon. It should be down to traces by Friday.

Next: A stronger storm is predicted to track straight east and track along the Aleutian Islands. As it does, a short fetch of 35-45mph winds is captured eastward and well past the dateline. Moderate to long period forerunners of 15-17 seconds from the NNW should arrive Friday morning. Surf should rise to 1-2’+ by the afternoon. It should peak early Saturday morning at 2-3’ occ. + and slowly drop through the day. Heights should be down to 1-2’+ by Sunday.

Finally (Potentially moderate): Models have been in good agreement showing now-Tropical Storm Kulap strengthen into a typhoon and recurve NE over the NW Pacific over the course of this week. Although the initial NE track is not ideal, the storm should grow in size with near-hurricane force winds aimed at Hawaii. The storm is then modelled to slow in its forward speed and track more eastward as it hugs the Aleutians on Friday. This would result in a captured fetch of 45-60mph winds past the dateline and produce, by far, the biggest swell so far this season. Very long period forerunners of 20-23 seconds from the NNW could arrive late or overnight Sunday. Surf could rise to 3-5’ by Monday morning and 4-6’ by the afternoon. It could peak overnight, and Tuesday could start off at 4-6’+, or borderline medium-large. This event is still quite far out in time, and lots could change. Stay tuned…

Outlook: An active spell of surf could continue into the first week of October as storm activity blossoms over the NW Pacific. There are signs that strong high pressure could build over the NW Pacific and block the storm track, leading to a slower period after the first week of October into mid-month.

South and West Shores: SSW turning South swell dropping this week but more fun coming next weekend…

Recent/Now: Surf early Sunday was 2-3’ occ. 4’ from the SSW at the focal reefs of the South Shore. The source was a strong storm that emerged from south of New Zealand Sep 15-17 with 45-55mph winds. This was the second in a back-to-back series of storms. It peaked with a higher deepwater swell than the first but at a lower period (15 seconds versus 17 seconds). With both parameters accounted for, the first storm boasted slightly larger surf last Thursday. The second storm maintained a NE tilt in the fetch as it traversed across the south Pacific. Winds, however, dropped to 30-40mph. Surf from this source will taper off and shift from more to the south: 1-2’ occ. 3’ early Monday, 1-2’ occ. + early Tuesday, 1-2’ early Wednesday, and 1-occ. 2’ early Thursday.

Next: A fairly strong, compact, fast-moving system emerged from well south of New Zealand on Sep 22. It mostly had a zonal track, which is unfavorable for surf locally. It could maintain long period background SSW swell for surf of 2’ or less late Thursday into Friday.

Finally: A modest storm with decent equatorward extent began to develop on Saturday, Sep 24. It continued to reach northward as it tracked towards the central south Pacific with 35-45mph winds aimed fairly well at Hawaii. Forerunners of 16-18 seconds from the SSW-S should arrive late Saturday. Surf should rise to 1-2’ occ. + by Sunday morning and 1-2’ occ. 3’ by the afternoon. It should peak overnight and slowly drop from 1-2’ occ. 3’ on Monday to 1-2’ occ. + on Tuesday.

Outlook: Models highlight a large, broad storm with strong winds following closely behind on Sep 28-29. It could bring a SSW swell that peaks at near the summer average Oct 6. Stay tuned…

East Shores: Small, bumpy surf prevailing through the period after midweek…

Recent/Now/Finally: Surf on Sunday was minimal at 1-1.5’ due to locally weak trades. Similar conditions should hold into Tuesday before surf ticks up a notch midweek. Stronger trades over and upstream of Hawaii should bring surf from the ENE up to 1-2’. A potential further uptick in trades early next week could add a few 2.5’ sets into the mix.

Outlook: The ECMWF model continues to depict a very strong storm developing roughly 1,400 nautical miles NNE of Hawaii on Friday and Saturday. In fact, it shows winds of 45-55mph aimed highest east of Hawaii. The GFS model had previously called for this scenario but has since thrown it out over the last several model runs. If this storm develops as indicated by ECMWF, it could bring a moderate NNE-NE swell for Hawaii early next week. Otherwise, nothing else of significance is noted in the long term.

Surf Climatology HERE