Waipahu, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

551
FXHW60 PHFO 160122
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
322 PM HST Fri May 15 2026

.SYNOPSIS...
An upper level low is bringing unstable conditions, heavy rain,
and thunderstorms to parts of the state through tonight. A flood
watch is in effect for central and eastern islands through 6 AM
HST Saturday. This low will slowly move away from the state
Saturday into Sunday, diminishing the chance for heavy rain. Wet
trades will build back in Sunday through Tuesday, becoming more
typical trades thereafter. This pattern should then last into next
weekend.

&&

.DISCUSSION...
Showers and thunderstorms continue over the region, with the
largest concentration of thunderstorms over Oahu and the near
shore waters west of Oahu as of 3 PM HST. Heavy rain was
occurring, and gages showed rapid rises on numerous streams across
Oahu. A flood warning has been issued. Please exercise caution
during this warning as water may flow over roads, and may be
deeper than if first appears. Winds were gusting 25 to 35 mph
near the stronger showers and thunderstorms, but otherwise winds
were averaging 5 to 15 mph.

An upper level low centered near Kauai was moving slowly
southeast this afternoon. This low is expected to gradually weaken
and move east and then northeast tonight. The cold air aloft
associated with this low will help provide unstable conditions
through tonight, and therefore we have extended the flood watch
for Oahu and Maui County, and added Big Island. Kauai seems to be
too far west now to have a significant threat of flooding, so they
were removed from the watch. Where the watch remains, it goes
through 6 AM HST Saturday.

As the low moves away from the islands Saturday into Sunday, the
atmosphere will become more stable, and even though lots of low
level moisture will remain with us through Tuesday, the chance of
flooding will decrease. Trade winds will return Sunday after
another day of southeast winds Saturday. Once the trades return,
they are expected to remain over the state through the end of next
week. Initially, the increased moisture from this current system
will bring wet trades Sunday through Tuesday. After Tuesday, more
typical trade wind showers should be with us through the end of
the week.

&&

.AVIATION...
Surface trough near Kauai this afternoon will result in gentle to
moderate trade to ESE winds (90 to 120 degrees) across the state.
Upper low tracking over the western half of Hawaii will
destabilize the atmosphere producing scattered heavy showers and
thunderstorms across Oahu through the rest of the afternoon, with
isolated coverage across Maui County and the Big Island. Guidance
forecast most showers decreasing in coverage and intensity
overnight.

SIGMET Zulu is posted for thunderstorms across Oahu and adjacent
waters this afternoon. AIRMET Tango is posted for tempo moderate turbulence
all islands elsewhere from 150 to FL380 due to the upper low. AIRMET
Sierra is in effect for tempo mountain obscurations above 2000
feet for entire area of Oahu and Maui County. The upper low is
expected to weaken tonight through Saturday.

&&

.MARINE...
This afternoon, an upper low and its associated surface trough
near Kauai is continuing to support unstable conditions across the
western and central coastal waters. Thunderstorms capable of
gusty winds, torrential downpours, extensive lightning, and
possibly small hail will remain possible into the evening hours,
primarily from the Kauai Channel eastward. Meanwhile, a late
morning advanced scatterometer pass showed that background flow
has decreased below Small Craft Advisory (SCA) levels, so the SCA
that was previously in effect has been cancelled. Background winds
will remain slightly east southeasterly this weekend at moderate
to fresh levels. By Saturday, the upper disturbance will be moving
northeast away from the state, with stability slowly returning to
the region. As a result, expect decreasing thunderstorms and
heavy showers across the waters. A more typical easterly trade
wind patter will return next week.

A small, medium period north northwest (320-330 degree) swell
that peaked last night will continue to slowly decline this
evening into tonight. Surf along north and west facing shores will
follow suit, easing during the weekend.

A mix of small, medium to long period south swells will maintain
small surf along south-facing shores this weekend. A series of
gale lows passing south of New Zealand should send small south
swell energy into the southern waters through next week. Surf
should lift to summer averages around Sunday and hold through
Wednesday. Moderate to fresh trades will maintain rough and
choppy surf along east-facing shores.

Tides will peak around 2.5 to 3.0 ft MLLW this weekend. Combined
with a small south swell bump, water levels will peak near or
above 3.0 ft as early as tomorrow. Minor overwash of low lying
coastal areas will be possible during times of high tide.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for Big Island East-Big Island
Interior-Big Island North-Big Island South-Big Island Southeast-
Big Island Summits-Central Oahu-East Honolulu-Ewa Plain-
Haleakala Summit-Honolulu Metro-Kahoolawe-Kipahulu-Kohala-Kona-
Koolau Leeward-Koolau Windward-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-Oahu North Shore-Olomana-South Haleakala-South
Maui/Upcountry-Waianae Coast-Waianae Mountains-Windward
Haleakala.


&&

$$

DISCUSSION...Parker
AVIATION...Foster
MARINE...Vaughan