textproduct: Honolulu

SYNOPSIS

Heavy rain will continue over Leeward Big Island while conditions improve over the western end of the state. Wet weather will continue through the week.

SHORT TERM UPDATE

Issued at 847 AM HST Sun Mar 15 2026

The kona low has lifted well north of the area and the surface low is approaching 40N early this morning. However, the islands remain enveloped in the southern periphery of large scale cyclonic flow aloft which itself is anchored over the central North Pacific. Deep moisture is remains established over and upstream of the Big Island while dry mid-level air is wrapping in from the south over Kauai. This dry air was evident in this morning's Lihue sounding which indicated weak capping developing around 6kft. Further east, morning satellite and radar reveal meaningful showers persisting over Leeward Big Island. Strong SW flow will continue to capitalize on orographic lift in maintenance of continued showers over this area until the next wave of deep moisture arrives this afternoon. This will represent another opportunity for heavy showers to train over the Leeward and potentially SE slopes of the Big Island. It is unlikely to be as intense as yesterday as large scale large scale forcing has waned substantially, but actively cooling cloud tops upstream nonetheless indicate potential for deep convection and heavy rainfall capable of producing flash flooding. Confidence is high that the Flood Watch will remain in place through tonight for the Big Island. It remains unclear whether this activity will reach Maui, but current trends suggest that may miss to the south. In that case, consideration would be given to ending the Flood Watch for them this afternoon.

Over the western end of the state, an upper wave pivoting over the area is maintaining weakly convergent low-level flow centered in the Kauai Channel at press time. This convergence combined with weak instability is allowing a band of deep but relatively low-intensity showers to develop and stream northward over Oahu. Intruding dry air has seemingly already brought an end to this activity over Kauai. These showers will gradually work east through today reaching Molokai late this evening in a weakening state as forcing peels off to the northeast. Given the saturated ground, nuisance flooding is certainly plausible over Oahu during the next several hours. Finally, the Wind Advisory will remain in place through at least noon, but current observations suggest it may be a bit tenuous, especially in light of the steadily weakening background wind field.

For the summits, strong winds persist and the High Wind Warning will remain in place. The Winter Storm Warning likewise remains in place, though dewpoints have risen to 33F and rain is currently observed on the summits. Little change in the thermal profile is expected during the next 24 hours, so observed ptype trends will dictate whether the WSW will remain in place through tonight.

PREV DISCUSSION

A strong kona storm positioned north of the Hawaiian Islands continues to generate moderate to heavy showers over the eastern half of the state, namely Maui and the Big Island. Persistent rainfall has resulted in island-wide flash flood warnings across the Big Island, persisting through the much of the morning. Meanwhile, conditions across the western half of the state have begun to improve, allowing several previously issued hazard products to be cancelled. However, a new rainband has developed and moved over Kauai, expected to move over Oahu later this morning. Latest guidance suggests a gradual depicts an overall downward trend in rainfall across the Hawaiian islands within the next 24 to 36 hours, as the primary rainbands shift east of the state by early Monday morning.

Based on the latest observations and model guidance, the High Wind Warning for Maui County and Big Island has been downgraded to a Wind Advisory, with exception of the summits of Big Island and Haleakala on Maui. Additionally, the Wind Advisory elsewhere was extended for portions of Kauai and Oahu, where locally strong winds of 20 to 30 mph and gusts up to 50 mph along windward sloping areas. The Wind Advisory will remain in effect until 6 PM HST this evening, to be reassessed with the next forecast cycle.

Showery conditions are expected to persist into early next week as the kona storm weakens and shifts northeast of the islands with the final push of upper-level support. As the system departs, winds across the state will steadily diminish and the coverage of heavier showers will decrease. However, a light and variable wind pattern is anticipated to develop, which will maintain periods of unsettled weather through much of the upcoming week.

The extended forecast beyond Monday remains somewhat uncertain as model solutions continue to evolve. Current guidance indicates an upper-level troughing pattern will persist across the region, supporting light and variable winds along with periodic showers and the potential for isolated thunderstorms through the remainder of the week. Toward the latter of the week, some models suggest broad high pressure may begin to build over the region, potentially allowing trade winds to return. Given the uncertainty at this range, future forecast updates will refine the expected evolution of this pattern.

AVIATION

Issued at 852 AM HST Sun Mar 15 2026

Low cigs and SHRA continue across the islands. This entire system is moving northeastward. A few isol TSTMs are possible over the Big Island. As far as the winds, they have begun to weaken slightly and veer more west-southwesterly over the western end of state, but still remain gusty in some spots especially over the windward portions of those islands. Over Maui and the Big Island, breezy and gusty winds are still possible through today.

AIRMET Sierra is in effect for mtn obsc for all islands except Kauai. AIRMET Sierra for IFR is no longer in effect for the Big Island, but brief and isolated IFR conditions are still possible today.

AIRMET Tango remains in effect for mod mid-upper level turb between 130 and FL330. It is is also in effect for turb downwind N thru E of terrain statewide. Conds should continue this morning and gradually improve west to east.

Light icing is possible between 130 and FL260 as mid-high clouds continue moving through the islands. These conds are expected to gradually improve today.

MARINE

The powerful kona storm will weaken as it moves northeast and away from the area during the next few days, with conditions improving over the coastal waters. Winds have dropped below Gale force over the coastal waters, therefore the Gale Warning has been cancelled and replaced with a Small Craft Advisory (SCA), which is in effect for all zones through 6 PM this evening. The SCA may need to be extended for portions of the waters around the Big Island tonight. Winds will ease below advisory levels across all waters by Monday and then remain light and variable Tuesday and Wednesday. Ridging is forecast to strengthen north of the islands late in the week, which should bring a return of moderate to fresh trade winds.

Strong southerly winds will keep large and rough surf in place along south facing shores today, with the surf then trending lower tonight and Monday. A new long period south swell will arrive late Monday night and Tuesday, giving a nice and extended boost to south shore surf through late next week.

A moderate sized short-period west swell associated with the kona storm will affect north and west facing shores during the next couple days, but surf will remain below advisory levels. The one exception is over west facing shores of the Big Island, where advisory level surf is expected today. As a result, a High Surf Advisory has been issued for west facing shores of the Big Island through 6 pm this evening. The short-period swell will lower Monday night and Tuesday, while a new medium-period north- northwest swell fills in. This north-northwest swell could bring surf up to advisory levels Tuesday night and Wednesday, with the swell then shifting more northerly and lowering below advisory levels Thursday into next weekend.

Surf along east facing shores will remain well below normal levels through the middle of the week, before trending upward Thursday into next weekend as trade winds return over and upstream of the islands.

HFO WATCHES/WARNINGS/ADVISORIES

Wind Advisory until 6 PM HST this evening for Big Island Interior-Big Island North-Big Island South-Big Island Southeast- Central Oahu-Kauai East-Kauai Mountains-Kauai North-Kohala-Kona- Koolau Leeward-Koolau Windward-Maui Central Valley North-Maui Windward West-Molokai North-Molokai Southeast-Molokai Windward- Oahu North Shore-Olomana-South Maui/Upcountry-Waianae Mountains- Windward Haleakala.

Flood Watch through late tonight for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast- 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.

High Wind Warning until 6 PM HST this evening for Big Island Summits-Haleakala Summit.

High Surf Advisory until 6 PM HST this evening for Kohala-Kona.

Winter Storm Warning until 6 AM HST Monday for Big Island Summits.

Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters- Maalaea Bay-Maui County Leeward Waters-Maui County Windward Waters-Oahu Leeward Waters-Oahu Windward Waters-Pailolo Channel.