Honolulu's weather forecast is shaping up to be quite eventful, with the National Weather Service predicting a mix of passing showers and moderate trade winds through Monday, followed by lighter winds and an approaching cold front, according to the NWS Honolulu Weather Forecast. The forecast starts off with trades holding steady into Monday, but things will shift come Tuesday when winds become lighter and veer southward as a front from the northwest heads toward the islands.
An earlier analysis highlighted a trough of low pressure that sparked isolated thunderstorms, but those have remained mostly offshore to the west. Meanwhile, parts of Kauai saw rainfall ranging from 0.06 to 2.0 inches overnight. As the day progresses, showers are expected to decrease thanks to a drier airmass moving in, and moderate trades will begin to ease tonight, potentially leading to brief isolated moderate to locally heavy rainfall, particularly along windward and mauka areas. “The Kona slopes of the Big Island as seabreezes strengthen this afternoon into the early evening hours,” as noted by the NWS. Over the next few days, the state should sit in an area of subsidence, with ridging building in from the west and reinforcing a stable trade wind pattern.
Looking ahead, there's less certainty as the week progresses with extended guidance showing variable outcomes regarding the incoming cold front's timing and impact; the Euro (EC) model and the GFS differ significantly, with the former suggesting modest impacts Wednesday night and the latter indicating a wetter pattern starting Thursday morning. For aviation purposes, moderate to breezy east-southeasterly winds will gradually weaken, and conditions are expected to remain mainly VFR, although brief MVFR conditions might occur in passing showers.
In maritime news, a Small Craft Advisory (SCA) is currently in place due to the moderate to strong easterly trade winds, particularly around Maui and Hawaii Counties, but this is set to expire by this evening as the trade winds wane. "Winds flowing around this ridge will produce moderate to locally strong easterly trade winds today, then wind speeds will slowly decrease from Sunday onward," as stated by the NWS. Surf conditions are also on the docket—with the north-northwest swell dying down into Monday, and two new northwest swell pulses anticipated to hit Monday and Tuesday potentially pushing surf heights to advisory levels by Wednesday.
Finally, the fire weather outlook remains below the critical fire threshold today with a slightly drier airmass in place and moderate trade winds that are due to slacken tonight. Looking toward the middle to latter part of the week, light southeast winds are expected ahead of a shift to wetter conditions. The ongoing Small Craft Advisory will hold until 6 PM HST this evening for certain zones, including Maalaea Bay and Big Island Leeward Waters. Keep an eye on conditions as the week unfolds and check back for updates on the approaching cold front's impacts on Hawaii's weather.
