Marine Weather and Tide Forecast for Hilo, HI

DISCUSSION
The latest surface analysis continues to show a dissipating trough just north of Maui this afternoon providing for a slight increase in clouds and showers across the windward Maui waters. Otherwise, conditions were rather tranquil today with light and variable winds and limited shower chances. Little change is expected through most of tonight.

Southerly winds will begin to increase late tonight into Saturday ahead of a significantly stronger and more moisture-laden front.
Model guidance remains in fairly good agreement and continues to show the front approaching Kauai County late Saturday, then moving eastward towards Oahu on Sunday, before stalling somewhere over the western end of the state Sunday night into Monday. The main difference between this front and those of recent memory is the increased upper level support provided by a 120 kt southwesterly jet. This jet will help deepen the front and provide a narrow corridor of strong uplift. This in turn will result in a mature jet-front system that will support the development of a band of heavy rain and isolated thunderstorms. There is still some uncertainty where this band will setup, but based on the latest guidance decided to issue a Flood Watch for Kauai, Niihau, and Oahu from midnight Sunday through late Monday night.

Upon the departure of supporting upper dynamics on Tuesday, the surface low escorting the front toward the Hawaiian Islands will move far north and weaken. Lingering moisture will keep some showers across the area on Tuesday. Another surface low looks to develop near the dateline on Monday, then dive southeast towards the islands mid to late next week. The will send another front that approaches the state from the northwest, then stalls over the western end of the state. There is still some uncertainty with how strong this front will be, but expect additional showers to continue through the rest of the week.

AVIATION
Light to gentle south to southeastly winds over the state will allow for sea breezes to develop this afternoon that could increase chances of MVFR cigs and SHRA over interior areas. VFR conds expected to prevail. Moderate southerly winds will develop over the western half of the state tonight as another front approaches the state from the northwest. Moderate to strong southwesterly winds will fill in around Kauai and Oahu Saturday along with increasing chances of IFR/MVFR conds.

No AIRMETs in effect.

MARINE
Light variable winds prevail through the near term before transitioning to fresh southerlies late tonight into Sunday. SW winds in advance of an approaching front may briefly reach the Small Craft Advisory threshold for the western waters. Isolated thunderstorms will be possible during this time.

Moderate, medium period NW swell gradually declines through Saturday. N pulse will move through today and Saturday in maintenance of elevated surf into weekend. A developing gale just NW of the offshore waters will send a similar moderate, medium period NW swell toward the state. This swell will advance through area waters Sunday and Monday increasing surf to the High Surf Advisory (HSA) threshold. A mix of smaller, medium period N swells will arrive this weekend. These swells will maintain elevated surf along exposed N shorelines into early next week.

Surf along E shores remains small during the next several days given the lack of trades. Expect minimal background surf for S shores. S and SW exposures will see increased short period fresh swell and wind waves emanating from strengthening SW flow ahead of the approaching front. This will particularly be the case for Kauai and Oahu.

FIRE WEATHER
Conditions will remain below critical fire weather thresholds through the forecast period. Winds are expected to remain light to moderate, with relative humidity steadily increasing as a front approaches from the northwest late Saturday, then stalls over the western end of the state Sunday and Monday. Additional showers chances expected mid to late next week as another front approaches, then stalls across the western half of the state.

HFO WATCHES/WARNINGS/ADVISORIES
Flood Watch from late Saturday night through late Monday night for Niihau-Kauai Leeward-Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central Oahu-Waianae Mountains-Kauai North- Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain- Koolau Windward-Koolau Leeward.