Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 04/19/2026 11:10:00 PM UTC

                        
798
FXHW60 PHFO 191310
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
310 AM HST Sun Apr 19 2026

.SYNOPSIS...

An upper-level trough will will bring increased high clouds and
renewed chances for isolated heavy showers and thunderstorms
this afternoon and Monday. Light winds favor chances for mainly
afternoon showers Tuesday and Wednesday, followed by rebuilding
trade winds Thursday and Friday.


&&

.DISCUSSION...

Today and tomorrow, trades will weaken further and will shift out
of the east-southeast across the western half of the island
chain, while another upper-level trough brings instability, mainly
tonight into Monday morning. For now, it appears that the deepest
moisture and highest chances for widespread rainfall will remain
along the surface trough northwest of Kauai, but isolated heavy
showers or a thunderstorm remain possible around Kauai. Elsewhere,
expect afternoon interior showers and possibly a thunderstorm on
Big Island, and another item to monitor will be a chance for
localized anchored heavy showers along the Koolau Mountains of
Oahu tonight. Even though moisture does not appear to be
significant on Oahu, the expected veering flow with height has a
tendency to produce heavy rain events on the Koolau.

Chances for heavy rainfall look to diminish Tuesday and Wednesday.
The upper level trough should move off to the east late Monday,
allowing a weak ridge aloft to settle over the state. The GFS and
ECMWF are hinting that the surface trough that had been lingering
northwest of Kauai will be pushed over the western end of the
island chain. This would favor light and variable winds over most
areas with higher rainfall chances over island interiors during
the late morning and afternoon hours. Trade winds are expected to
rebuild Thursday and Friday.

&&

.AVIATION...

Predominately light northeasterly winds among some land-sea
breezes will remain in place through the next several days under
high pressure well northeast of the Hawaiian Islands and a surface
trough lingering to the west. Some terminals may experience some
mid- to high-clouds and embedded light showers, resulting in
brief periods of MVFR conditions. Otherwise, expect VFR conditions
to prevail across most terminals through the period.

No AIRMETs in effect.

&&

.MARINE...

A high pressure system far north of the state will slowly drift
eastward this weekend. Easterly trade winds diminish tonight as a
trough to the northwest of the islands develops into a weak low
pressure system by Sunday. The resulting weakness in the ridge
causes winds to veer southeasterly and diminish over the western
Hawaii region from Sunday into early next week. By Thursday the
high pressure ridge builds back in north of the state with
fresh easterly trade winds returning to the region lasting through
next weekend.

A small pulse of medium period swell energy from the northwest
should produce a slight bump in north facing surf heights into the
morning hours. Another small, medium period northwest swell will
move into the region by Monday night and continue through
Wednesday. A moderate, medium period northeast swell arrives
Tuesday and peaks on Wednesday, bringing moderate surf to north-
facing shores, before slowly declining through the end of the
week.

A series of overlapping small south swells will move into the
region this week keeping surf heights on the small side. Surf
heights along east facing shores also remain small due to weaker
trade winds until the arrival of the small medium period northeast
swell building into the Hawaii region from Tuesday through
Thursday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$


DISCUSSION...Walsh
AVIATION...Pierce
MARINE...Bohlin