Summer officially ends tomorrow, and a string of swells from the North are headed towards Hawaii, marking the start of Autumn. Early season on the North Shore is typically a bit more inconsistent and unpredictable, although last year one of the best Pipe swells of the season hit in late September.
Looking at the Waimea Bay buoy model (@buoy51201), we can see a triad of swells in the current forecast. The first and smallest of the group, fills on Thursday and holds through Friday (4.9 feet at 12.8 seconds, 326°).
A larger, more Northerly swell builds quickly early Sunday morning, peaking in the afternoon (9.2 feet at 14.1 seconds). This swell will most likely result in a high-surf advisory being posted for all North facing shores, the first event of this size for the 2010-2011 season.
Looking ahead 7-days, there is another swell forecast to hit on Tuesday, September 28th. This swell is more of a straight North, with a slightly shorter period of 12.9 seconds. Keep an eye on the model to see how this swell develops, as the 7-day forecast is often subject to correction.
All in all, a lot of action during the next week. We recommend following the Northwest Hawaii buoy (@buoy51101) for real-time observations, as it roughly provides an 8-10 hour precursor for Oahu. For the more Northerly events, the Northern Hawaii buoy (@buoy51000) is a good one to keep an eye on.