textproduct: Honolulu

SYNOPSIS

Light to moderate background trade winds will prevail, allowing sea breezes to develop in sheltered leeward areas each day through Monday. A brief increase in windward showers is expected Monday night into Tuesday, especially for the easternmost islands. Moderate trade winds will begin building back into the region during the second half of the week, becoming locally breezy again by the weekend.

SHORT TERM UPDATE

No updates made. Previous forecast is on track.

PREV DISCUSSION

This afternoon, mostly to partly sunny skies are observed across much of the smaller islands, with the exception of a few clouds developing over sheltered leeward locations due to localized sea breezes as a result of weak to moderate background winds. Over the Big Island, typical interior cloud buildups have also developed, with only a few light showers noted and little in the way of rainfall accumulations today. CIMSS Precipitable Water imagery shows much drier air over the state today compared to recent days.

A weak low in the mid and upper levels is located just east of the Big Island. Over the next few days, this feature will linger and then move off to the northeast, with little effect on island weather. However, an area of enhanced moisture associated with a trough east of the islands will make its way westward, reaching the eastern end of the state by late Monday. As this feature quickly moves through, windward showers are anticipated to increase, especially for the Big Island and Maui. The remaining islands may see a slight increase in windward and mauka showers as well.

By Wednesday, a moderate trades will build back into the region, strengthening to become locally breezy by the end of the week. Showers will generally favor windward and mauka areas throughout the rest of the week, especially during the overnight through morning periods. An additional band of moisture approaching from the east could bring another uptick in showers late this week into next weekend.

AVIATION

Light to moderate trade winds are expected through Monday. Isolated afternoon clouds and showers are possible over terrain sheltered/leeward areas due to the light winds. Windward and mountain areas will generally see limited shower activity. An incoming surface trough east of the state will provide an increase in showers to windward areas of the Big Island Monday night. Expect MVFR conditions within any showers, and VFR to prevail elsewhere.

AIRMET SIERRA remains in effect on the Big Island from Apua Point to South Cape to PHKO to 15 nm NE of PHKO for tempo mountain obscuration above 2500 feet due to low clouds and showers. However, conditions will likely improve over 10Z tonight.

MARINE

Moderate to locally fresh trade winds continue through Tuesday before decreasing by mid-week into the light to moderate range. Slight day to day fluctuations are expected, then trades are expected to strengthen towards the end of the week as high pressure builds north of the area.

A long-period south swell will hold through Monday, producing elevated surf along south and west-facing shores, but it will remain below advisory levels. South shore surf will decline gradually Tuesday into Wednesday, but a new long-period south swell arriving late Wednesday will provide another bump in surf for Thursday and Friday.

A small long period northwest swell will keep small surf in place tonight for north-facing shores. Surf could decrease a little on Monday morning before another small, long-period northwest swell arrives Monday afternoon and peaks Tuesday. This swell is expected to boost north shore surf to moderate levels. A moderate mid period north-northwest swell is possible by the end of the week into the weekend, depending on the evolution of a projected low in the north Pacific. However, confidence is low given differences in model solutions with this feature.

Surf along east-facing shores will remain small as local winds remain fairly weak with only slight variations each day. Small, moderate-period west and east swells generated by multiple Pacific tropical cyclones continue to move through the islands through Monday.

FIRE WEATHER

Light to moderate background winds will continue for the first half of the week. Dry air will bring relative humidity levels down to near-critical values for parts of the state through late this afternoon and again on Monday afternoon. However, winds will be light and KBDI remains below 500 statewide. Inversion heights range from near 3000 feet over the western end of the state to near 8000 feet over the eastern end.

HFO WATCHES/WARNINGS/ADVISORIES

None.