Looks like a solid South swell will mark the start of Summer in Hawaii, as the forecast model is currently showing some long-period energy hitting Buoy 51003 on Tuesday, June 21.
Look for (1) 19-second forerunners early Tuesday morning from 188°, with swell heights increasing throughout the day into Wednesday. (2) Wave heights are forecast to be biggest Wednesday as the South swell continues to fill in, then (3) maintain their size through early Thursday before declining into the weekend.
Depending on your location, travel times from the buoy may range from 3-8 hours, with more Southerly breaks (Big Island) seeing almost no delay from the real-time reports. If the swell arrives as forecast, Oahu will likely see the largest surf sometime Wednesday afternoon.
Keep an eye on @buoy51003 for real-time reports beginning on Tuesday morning, as those will be the best indicators of the actual swell size. Note that strong Northeast wind swell may mask some of the early forerunners, so be sure to also check the nearshore buoys, such as Lanai and Barbers Point, which are shielded from these effects.