HONOLULU - Forecasters at the National Weather Service in Honolulu are expecting a shift in the weather over the Hawaiian Islands as we head into the weekend. According to an early morning update, increased rain chances are anticipated starting today and continuing through the weekend, especially on the western half of the state. Light to locally breezy trade winds are expected to persist until the end of the week, with showers focusing on windward, mauka, and higher elevation areas. Stable and drier conditions should resume by early next week.
As detailed in a National Weather Service discussion, a high-pressure system north and northeast of the islands is currently dominating the weather pattern, bringing showers mostly to windward areas. The Big Island's windward slopes have seen the most precipitation, with amounts generally under a quarter of an inch. An influx of mid to low level moisture today will likely thicken cloud cover an increase shower activity, especially on the windward and upslope regions. Winds have also been strong in certain central and north areas, hitting sustained speeds of 25 to 30 mph with gusts over 40 mph.
The approach of a weak mid to upper low or trough from the west will cause geopotential heights to fall and potentially bring more rain, particularly over Oahu and Kauai, from late Friday through Sunday. Rainfall could become heavy at times, depending on the movement of the upper low and moisture advection. The overall pattern, however, is not expected to cool enough to induce thunderstorms over the weekend, even though there's a possibility of isolated offshore storms.
For aviation, moderate to locally breezy trades are predicted through tomorrow. Windward and mauka locations, along with the South Kona slopes of the Big Island, may experience low ceilings and rain showers. The aviation outlook includes AIRMETs Sierra and Tango, which cover mountain obscuration for windward sections and low-level turbulence below 7,000 feet downwind of island terrain.
Marine conditions feature high pressure remaining far northeast of the state, with fresh to strong trades expected to continue before easing over the weekend. A Small Craft Advisory is in effect for windy areas around Maui County and the Big Island until Friday morning. Surfers should expect below-average surf on south facing shores today, with a slight increase expected over the weekend due to incoming swells. Rough and choppy conditions will persist on east facing shores, while north facing shores will stay mostly flat.
In terms of fire weather, the upcoming wet pattern should alleviate concerns for the next few days. Trade winds are slated to be light to breezy through the day, with showers increasing starting late tonight through the weekend. After the weekend, a return to drier and more stable weather could elevate fire risks in leeward areas that miss out on significant rain.
