Hawaiian residents and visitors alike are bracing for an increased chance of rain, as forecast by the National Weather Service (NWS) in Honolulu. According to their latest weather forecast, a developing wet trade wind pattern is set to bring in higher rainfall to the islands, potentially heavy at times, along with a smattering of thunderstorms through Saturday. The mountain areas on the windward side are expected to see the highest amounts of rainfall.
The NWS reports that there are two upper-level lows approaching the islands from the north, which will be bringing divergent winds along their southern and eastern flanks, encouraging the formation of thunderstorms. Enhanced showers are expected to be caused by a mix of instability around the upper low and convergent lifting of the trade winds, which force unstable clouds up the windward mountain slopes. "For today we expect to see easterly trade winds into the moderate to locally breezy range with increasing clouds and showers as the upper low moves in from the north and low level cloud bands riding in from the east begin to converge over the island chain," the NWS noted.
The wet conditions are predicted to persist for much of the week across all the Hawaiian Islands, with the heaviest showers likely over Niihau, Kauai, and Oahu. Additionally, the Big Island may encounter thunderstorms as early as Thursday. Despite the potential for over 2 inches of rain in some locations, the NWS has not yet issued a flood watch but indicated that it might be necessary as the pattern evolves and they can more accurately assess the threat of flooding in specific areas.
There's a brief respite expected on Sunday as the upper low drifts westward, but a similar pattern is forecast to follow on its heels. A weak upper low is projected to drift in near Kauai and Oahu by Monday, fostering yet another bout of wet trade wind weather extending into next Wednesday. "Stay tuned," advises the NWS, signaling the likelihood of this continuation in the weather pattern.
For aviators, the NWS predicts moderate to breezy easterly trade winds with increased cloudiness and showers. MVFR conditions and isolated IFR conditions in heavier showers are anticipated, mainly over windward and mountainous regions. While no AIRMETs are currently in effect, the NWS anticipates issuing them later for mountain obscurations and upper-level turbulence.
The marine forecast similarly calls for moderate to fresh trade winds with a Small Craft Advisory in place for certain areas around Maui County and the Big Island until Thursday morning. As the upper low approaches, there’s also a chance for thunderstorms in marine areas later into the weekend.
When it comes to fire weather, the wind speeds and humidity levels are expected to stay below critical thresholds. However, with unstable conditions, increasing wet weather trends, and the chance of locally heavy rain and thunderstorms are in the forecast, which should somewhat mitigate fire risks.
