A moderate to large medium period north-northwest swell will build into Hawaiian waters through Thursday. Surf heights along exposed north and west facing shores will exceed surf advisory thresholds into Thursday, before steady declining. A High Surf Advisory (HSA) was issued this morning for these areas. An overlapping north-northwest swell will move into the region by Friday, helping to maintain moderate surf heights along north and west facing shores. In the longer range forecast, a deep low pressure system is expected to develop to our north and northeast from Friday into Saturday. This low will likely generate a large north-northeast swell late this weekend, easily exceeding HSA thresholds. Due to the swell angle, heavy surges will be possible along north facing harbors such as Kahului and Hilo on Sunday.

A small long-period south-southwest swell will boost south shore surf heights from Thursday into the weekend, along with a larger out of season south swell possible by early next week. Surf for east facing shores should be rough and choppy today with the increasing trade winds and could also see a little bit of north wrap from the medium period north-northwest swell.