textproduct: Honolulu

SYNOPSIS

Moderate to breezy east southeast winds and mainly stable conditions are expected this weekend. A significant pattern change will begin early next week as a deep low pressure system evolving northwest of the islands turns winds from the south. This southerly flow will allow deep tropical moisture to move northward and overrun the state. This scenario will increase the chances for heavy rainfall, thunderstorms and strong winds next week. These impacts have a higher probability of starting over the western waters and from Oahu westward late Monday. This activity is forecast to advance east and impact the entire island chain through the middle and latter part of next week. The slow- moving nature of this system to the west signals that this active weather pattern may persist into next weekend.

SHORT TERM UPDATE

Issued at 914 AM HST Sat Mar 7 2026

A surface ridge axis just west of the island chain is what is ultimately maintaining a relatively pleasant start to this first Saturday of March. Scattered cumulus moving in on predominant east flow and piling up along windward upslope mauka as convective blow off cirrus from a line of thunderstorms a few hundred miles west of Niihau passes across within upper level westerlies. Generally partly cloudy conditions with late morning upper 70s warming a few more degrees into the lower 80s along more wind protected, leeward coastal areas...remaining in the upper 70s in windward communities. Lower elevation dew points in the mid 60s, along with a fairly stout breeze, will make for a comfortable day within non-wind protected areas. Today's rain behavior will typically be confined to windward, east or southeast-facing spots and within higher terrain where more overcast and rain will keep temperatures in the 60s between 3-5 k ft. A mainly clear leeward, partially to overcast windward Saturday night with occasional quick-hitting trade showers going into Sunday sunrise. Tomorrow will be very similar to today concerning temperature, sky and rain chances. The pattern begins to undergo some major change later Monday, especially from Oahu westward, as the next upper low and its associated features begin to evolve far northwest of the state.

PREV DISCUSSION

A notable shift in the large-scale pattern is expected to unfold across the Hawaiian Islands during the upcoming week. The current dry and fairly stable regime, characterized by moderate to locally breezy east-southeast trade flow, will hold in place through the weekend. Conditions will then begin to change late Monday into Monday night as a deep upper trough develops and amplifies northwest of the islands, bringing a multi-faceted weather event to the state that could include heavy rainfall with flash flooding potential, strong to severe storms, and strong kona winds.

Model guidance continues to indicate a strong jet streak, with core winds around 120 to 140 kt at 250 mb, digging southeast along the western flank of the evolving trough. As this occurs, the trough is expected to acquire a more negative tilt and expand toward the island chain. The islands will increasingly come under the influence of the jet streaks left-exit region, promoting enhanced upper-level divergence aloft. This large-scale ascent, combined with smaller shortwave disturbances rotating around the base of the trough, could generate periods of organized convection through much of next week, potentially beginning as early as Tuesday.

At the surface, global and ensemble guidance are fairly consistent in depicting a broad cyclonic circulation developing northwest of the state by early next week in response to strong upper height falls. Central pressures near 985 to 990 mb are possible with this feature remaining well northwest of the islands. The resulting pressure pattern will support strengthening south to southeast winds across the state, allowing a plume of deep tropical moisture to surge northward into the region. Precipitable water values are expected to climb into the 1.7 to 2 inch range by Tuesday over the western islands, then spread across the remainder of the state by midweek.

The evolving thermodynamic and kinematic environment, including upper height falls, cooler air aloft, and increasing deep-layer shear, will favor episodes of heavy rainfall with embedded thunderstorms. Combined with broad confluent south-southeast flow and island terrain effects, this pattern could support training and anchored convection, particularly along favored terrain, such as the Koolaus. This raises the potential for significant flooding concerns if heavier rainfall bands persist over the same areas. In addition to the heavy rainfall threat, some storms could become strong, and occasionally severe, by the middle of next week with locally damaging winds possible.

Impacts may begin to develop across the western islands as early as Monday night as the leading edge of the moisture plume reaches the state. The risk for heavy rain and thunderstorms will likely expand eastward across the remainder of the island chain Tuesday into Wednesday as deeper moisture and stronger forcing for ascent overspread the region.

While details regarding the exact timing and location of the heaviest rainfall remain uncertain, confidence continues to increase that a prolonged period of unsettled and potentially impactful weather will affect the islands next week. Flooding impacts could become more pronounced over time as soils become saturated and stream levels and reservoirs become elevated. Residents and interests across the state should continue to monitor forecasts through the weekend as this system comes into better focus and details regarding the timing and location of impacts become clearer.

AVIATION

Issued at 914 AM HST Sat Mar 7 2026

Scattered to broken high clouds will move over the state today. Brisk east southeast flow across Hawaii expected today with a slight weakening by Sunday. Winds will carry in scattered clouds that will anchor over southeast slopes and bring isolated MVFR ceilings and brief mountain obscurations, increasing a bit tonight across Kauai and Big Island.

AIRMET Tango in effect for tempo moderate turbulence below 7000 feet across downwind slopes (south across northwest facing). Expect this AIRMET to continue through the day then dropping off tonight or Sunday. Directional LLWS possible at the PHOG/OGG runway.

MARINE

Issued at 914 AM HST Sat Mar 7 2026

Strong high pressure far to the northeast of the state will maintain fresh to strong trade winds through the weekend, with the strongest winds over the typically windy areas around Maui County and the Big Island. A Small Craft Advisory is now in effect from the windward Oahu waters and Kaiwi Channel eastward through 6 pm Sunday, with the exception of Maalaea Bay. This SCA may need to be extended for portions of the marine area through Sunday night. A front approaching from the west will ease the trades and shift them southeasterly on Monday, with the winds then becoming southerly and increasing to fresh to strong levels Tuesday and Wednesday.

Surf along east facing shores will remain elevated and choppy through the weekend, trend downward on Monday, then lower below normal levels Tuesday through late next week.

A series of west-northwest swells will keep some small surf in place along north and west facing shores during the next 7 days, but surf will remain well below advisory levels. A small to moderate sized north swell is possible around Thursday and Friday of next week.

Surf along south-facing shores will remain small through early next week, with the exception of areas exposed to trade wind swell wrap. Rough and choppy conditions appear to develop Tuesday and continue through late next week as southerly winds increase in advance of a front. A series of small long period south swells will also move through Monday through late next week.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Sunday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters-Kaiwi Channel-Maui County Leeward Waters-Maui County Windward Waters-Oahu Windward Waters-Pailolo Channel.