Marine Weather and Tide Forecast for Hilo, HI

DISCUSSION
Light showers were mainly over Maui as of 3 PM HST, with a bit less cloudiness than usual in most windward areas. Winds were light, averaging 5 to 15 mph. Sea breezes had developed on the leeward side of most islands.

A weak surface pressure gradient was leading to healthy sea breeze development across most leeward areas, but this will change tomorrow and Monday as trade winds pick back up a bit. This will shift the focus of showers to windward and mauka areas for the next couple of days. A band of moisture is forecast to move in from the east Sunday night, enhancing overnight showers. The surface gradient is expected to weaken Tuesday and remain weak through Friday, leading to a return of sea breezes from late morning to early evening. This will result in higher-than-normal chances of showers in leeward areas once again. Moisture is forecast to be higher over the eastern half of the state after Monday, so that's where the best chance of showers should develop.

AVIATION

building surface high northeast of the islands will allow gentle to moderate trades to strengthen to moderate to fresh background levels tonight and Sunday. A stable and somewhat dry air mass will maintain mostly VFR conditions. Isolated MVFR ceilings have developed over leeward and interior this afternoon and can be expected to develop again Sunday afternoon in the more sheltered leeward and interior areas. A band of moisture riding in with the trades will increase clouds and showers slightly along windward and mauka areas starting Sunday.

No AIRMETs are in effect.

MARINE
A long-period south southwest (200 degree) swell will build tonight and peak Sunday night into Monday before gradually declining through the rest of the week. Near shore buoys, including Lanai and Barber's Point, show wave heights increasing this afternoon with a the dominant 22 second period. Expect the swell to continue to fill in tonight into Sunday morning. Surf heights will increase along exposed south and west facing shores with surf heights reaching advisory levels. A High Surf Advisory has been issued beginning tonight and continuing through Monday night. Surf could also reach warning levels Sunday night into Monday (advisory along west facing shores), but confidence is a bit lower over 24 hours out from the forecast peak. Will continue to monitor buoys and future guidance for the possibility of upgrading.

This swell will also coincide with the peak monthly tides which will add the potential for significant wave runup on top of the aforementioned minor coastal flooding potential during the first half of next week. Once the peak swell passes, south shore surf will remain elevated through much of the week due to the slow decline of this large south swell and a series of continued overlapping southerly swells.

Very little swell energy is arriving along north facing keeping surf tiny to flat. A small bump in surf is possible for north- facing shores early next week with the arrival of a small northwest swell and a smaller north swell. Gentle to moderate east-northeasterly winds expected through next week as a weak front is held up to the north and west of Hawaii. Surf along east facing shores will remain small as a result.

A Coastal Flood Statement has been issued for minor coastal flooding of vulnerable low-lying coastal roadways, docks, boat ramps and other coastal infrastructure. Peak monthly high tides combined with water levels that are running higher than predicted will lead to minor flooding potential around the daily peak tide, which will be during the late afternoon and early evening hours, through at least Tuesday. While minor coastal flooding is expected along all shorelines, the combination of the south southwest swell, King Tides and the daily high tide will make low-lying coastal areas along south and west shores susceptible to more widespread coastal flooding through the first half of next week.

HFO WATCHES/WARNINGS/ADVISORIES
High Surf Advisory until 6 AM HST Tuesday for Big Island South- Big Island Southeast-East Honolulu-Ewa Plain-Honolulu Metro- Kahoolawe-Kauai South-Kauai Southwest-Kipahulu-Kohala-Kona-Lanai Leeward-Lanai South-Maui Central Valley South-Maui Leeward West- Molokai Leeward South-Molokai Southeast-Niihau-South Haleakala- South Maui/Upcountry-Waianae Coast.