textproduct: Honolulu

SYNOPSIS

Breezy trades continue well into next week with limited showers directed windward and mauka during this time.

SHORT TERM UPDATE

Benign trade wind pattern through the forecast period as strong longwave ridging approaching 598dm at 500mb remains anchored along 170W longitude. This in turn favors expansive surface high pressure in maintenance of breezy trades through the middle of next week. An uptick in showers for windward and mauka zones is possible next week as moisture off the California coast becomes entrained in the trades, reaching the islands around Wednesday.

The tropics remain remain active with the primary focus at the moment being Tropical Storm Lowell. This system is forecast by NHC to become a hurricane this weekend. Even though it is already around 135W, or about 1500 miles SE of Hilo, weak steering winds delay any potential arrival to/around the Hawaiian islands to beyond the 7 day forecast period.

PREV DISCUSSION

Issued at 425 AM HST Fri Aug 28 2026 Upper and mid level ridging has asserted enough influence across the Central Pacific to still provide the needed subsidence to result in continued warm and dry weather, with only isolated early day windward showers. A large area of 1034 mb surface high pressure located far north of the state is creating a tight enough pressure gradient, in relation to lower equatorial pressure, to result in persistent moderate to locally breezy trade winds. The next few days will feel less humid and generally more pleasant under this moderate trade flow.

The lower levels remain void of any significant features that would indicate any short term deviation from the recent pattern. Morning soundings indicate a 6-7k ft inversion layer depth that is deep enough to support mainly isolated showers. Locally stronger winds gusting to near 25 to 30 mph will occur atop higher terrain ridgetops and through lee valleys and/or slopes. These amped up trades will hang with us through early next week with a potential approaching tropical cyclone being a disrupter to what will be several days of breezy trades. Most diurnal rain accumulation will measure in the hundredths of an inch. Greater rainfall will likely focus across windward upslope areas. Recent regional sounding profiles indicate that mid to upper ridging will remain in control helping to maintain dry mid-levels (20-40% %RHs between 8-15k ft). This scenario will result in less frequent windward exposure showers. Quick-hitting light showers trapped within the trade belt will likely be more recurrent during the nocturnal hours than during the day. The rapid nature of these cells passing over high terrain will have better organized showers wetting leeside communities. The weather pattern will turn more wet going into the middle of next week as higher moisture reaches greater depths as weak ridging slides westward.

The National Hurricane Center is issuing forecast advisories for Tropical Storm Lowell. Long-range models show Lowell will advance toward the state next week. As no distinct center of circulation has appeared with Lowell and it has been drifting, deterministic model guidance have struggled with grabbing onto this system and therefore have lacked any run-to-run consistency. Ensemble members that move Lowell in close vicinity of the island chain in a little over a week still remain in the minority. Google Deepmind's ensemble takes the storm due west then northwest into a less sheared environment south of Hawaii over the Labor Day Weekend.

AVIATION

For 18Z - Moderate trades regime continues. Mostly VFR through the TAF period with some MVFR conditions with passing heavier showers/lower CIGs. Expect low CIGs and SHRA over windward and mauka slopes most areas and reflected as VCSH most TAFs.

AIRMET Tango is in effect for mod low-level turb lee of terrain and may be needed for a few days.

MARINE

High pressure located far north of the waters will remain nearly stationary through the forecast period maintaining moderate to locally strong trade winds. A Small Craft Advisory (SCA) is in effect for the windier waters and channels around Maui County and the Big Island through Saturday. The SCA will likely be extended through the weekend and could be expanded to other zones around Kauai and Oahu waters early next week.

Surf along south facing shores will hold just below advisory levels today as the moderate medium to long period south swell filled in over night. The swell will slowly fade through the weekend. Another south swell similar in size is expected during the middle of next week.

Surf along east facing shores will remain choppy in response to the locally strong trade winds over and upstream of the islands. A small medium period east swell from Tropical Storm Iselle will fill in later today and hold through Saturday. Another round of east to southeast swells are possible next week but remains at high uncertainty due to the potential track and intensity of the storms.

FIRE WEATHER

Issued at 425 AM HST Fri Aug 28 2026 Relatively dry regional air and moderate to locally breezy trade winds will maintain moderate fire weather concerns into early next week. A slight increase in moisture next week will marginally improve conditions.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Saturday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.