textproduct: Honolulu

SYNOPSIS

The flooding threat will remain through the day primarily across the windward areas of the eastern half of the state. Conditions will generally be improving from this evening through Friday, but some localized downpours will continue for windward areas through Friday. For Oahu and Kauai, weather conditions will continue to improve this afternoon with fair trade wind weather expected over the next few days. A weak front will push through on Sunday with strong northerly trades following behind Sunday into Monday.

UPDATE

No major changes this morning. A Flood Watch remains in effect for Maui County and the Big Island today. Latest 12Z high res models continue to show the heaviest rainfall over east and southeast facing areas of Maui and the Big Island. Some mid level dry air is expected to fill in west to east across the state today, which should generally decrease the threat for flash flooding tonight. But at the lower levels, abundant moisture will remain through Friday, so we will likely continue to see some localized heavy showers continue through Friday across windward and mauka areas for the eastern half of the state. For rest of the state, a drier trade wind pattern is expected with some passing showers from time to time.

PREV DISCUSSION

Issued at 359 AM HST Thu Oct 29 2026 The overall synoptic scene has undergone little change overnight. A diffuse, meandering low level trough of low pressure laying within a conditionally unstable moist air mass will be the channel in focusing return rain episodes through the afternoon. Shortwave energy rounding the base of the upper trough whose axis lies just west of 170W will pass over the state today. This may provide the extra lift needed, along with early day cloud breaks allowing more sun to the surface and destabilizing the boundary layer, to initiate repeat rounds of light to moderate rainfall. While higher resolution NWP guidance has failed at properly placing where the higher precipitation will fall, ensemble modeling has been consisting telling the tale of primarily higher QPF being focused along more eastern-facing exposures. Low level trade flow will assist in keeping better organized rain anchored or pinned across windward and upslope east-facing mauka regions. Therefore, with antecedent 24 hour rainfall of over a foot across areas of eastern Maui, along with little change in the large scale of a southwest positioned upper level low and associated slowly eastern-moving low level trough located near the Alenuihaha Channel early this morning, the Flash Flood Watch has been extended through this afternoon for Maui and Hawaii Counties.

While it is hard to determine which areas will receive the most rain, little change in the synoptic pattern within this moist fairly unstable environment ensures that those that receive another inch or more on top of already soaked grounds will experience the greater probability of flooding. The highest low to mid layer moisture will travel east of the state Friday as the broad upper low southwest of the island chain begins to wobble west in response to the passage of a North Central Pacific upper trough this weekend. A cooler and drier air mass behind this trough will descend upon the state early next week. The associated surface front is forecast to reach the islands and back trades around to north northeast late Sunday or early Monday. In the meantime, lingering lower to middle layer moisture over the islands will ensure cloudier skies and periodic trade shower activity, especially over windward locales and upslope mauka, this weekend. The passage of this trough will usher in a much drier air mass where dew points are forecast to fall into the lower 60s by Monday afternoon. A backing near 1030 mb surface high north of the region will tighten the downstream pressure gradient over the islands enough to significantly strengthen early to mid week trade winds. Breezy to locally strong trades at higher elevation will persist, as will much drier conditions, through at least next Thursday.

AVIATION

Generally disorganized -SHRA/SHRA for much of the island chain with lesser coverage for Kauai. More organized SHRA/+SHRA for Maui with lowering VIS/CIGS for PHOG and to a lesser extent PHJH. Additional areas of showers elsewhere from Oahu to the Big Island generally focusing on windward TAF locales. VFR/MVFR is fairly common with periods of IFR under heavier and more persistent SHRA/+SHRA. This should continue through the day and at least into the early portion of the evening. Coverage of SHRA wanes a little overnight with increasing trade winds for tomorrow.

AIRMET Sierra for mountain obscuration remains in effect abv 020 for Oahu through the Big Island. Conditions look to remain fairly consistent through much of the day.

AIRMET Tango for Turbulence remains in effect from Molokai to the Big Island. Moderate turbulence between 100-FL200. Oahu AIRMET has been cancelled for improving conditions. AIRMET Zulu is in effect for light ice from Molokai to the Big Island in layer 140-FL200. Oahu has been removed from the AIRMET for improving conditions.

MARINE

This morning, a diffuse trough over the islands continues to support showers and isolated thunderstorm chances, particularly across the central and eastern waters. This trough will weaken near the Big Island today, allowing ridging to the north to drive moderate to fresh easterly winds over most waters, but southerly lighter winds will remain near the Big Island. The trough will move south of Big Island Friday, and moderate to locally fresh trades will prevail Friday night into the weekend. A Small Craft Advisory for the windier waters and channels around Maui County and the Big Island is likely late this weekend into early next week. The current northwest swell will gradually decline as a small short period north-northeast swell will fill in Friday and maintain small surf. A larger, long-period northwest swell will arrive late Saturday and may push surf above the High Surf Advisory threshold Sunday. The swell will shift more northerly and may briefly build further on Monday before dropping Tuesday.

Surf along south facing shores will slowly rise through this evening, peak Friday just below High Surf Advisory levels, and gradually decline through the weekend. By early next week, surf looks to remain tiny to small through the forecast period.

Surf along most east-facing shores will remain small and choppy through today but will rise Friday with the wrapping north to north- northeast swell energy, producing periods of moderate surf. Strong northeast winds and a large, rough north- northeast swell are possible Sunday night and Monday.

FIRE WEATHER

Issued at 359 AM HST Thu Oct 29 2026 Due to the recent rain and light wind, fire weather concerns will remain low through Saturday. A front is expected to arrive early next week. Breezy to locally strong north northeast winds and drier conditions are expected in the wake of this boundary passage late Sunday or early Monday. Thus, fire weather concerns will be on the rise through next week.

HFO WATCHES/WARNINGS/ADVISORIES

Flood Watch until 6 PM HST this evening for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Haleakala Summit-Kahoolawe-Kipahulu- Kohala-Kona-Lanai Leeward-Lanai Mauka-Lanai South-Lanai Windward- Maui Central Valley North-Maui Central Valley South-Maui Leeward West-Maui Windward West-Molokai Leeward South-Molokai North- Molokai Southeast-Molokai West-Molokai Windward-South Haleakala- South Maui/Upcountry-Windward Haleakala.