Light and breezy trades with light showers primarily occurring along windward exposures and higher terrain. A plume of moisture moving south of the islands will increase rain chances over the eastern end of the state through Monday, followed by drier mid week conditions. Brewing disturbances within the eastern Pacific will need to be monitored for tropical cyclone development the next few days.
An upper ridge centered northeast of the islands has its axis draped southwest over the region. This feature has provided enough stability, as evidenced by the upstream stratiform clouds, to maintain partly cloudy and relatively dry conditions today. Upper ridging will gently back off the next couple of days with the result being a deeper, more moist resident boundary layer. This will assist in producing greater clouds and more widespread rain caught up within moderate trade flow, especially for the windward communities of Big Island and Maui. An area of higher moisture southeast of Big Island will pass across the eastern half of the state through early Monday. This more moist air mass will primarily impact Big Island but may clip Maui County and Oahu through early Monday. This will likely be the cause for more frequent, mainly windward and upslope mauka, showers today and tomorrow. Locally heavy rainfall is also possible on Big Island and windward Maui through Monday morning. If enough early day Sun heats up Mauna Kea and Mauna Loa's (primarily western) slopes, in tandem with this higher moisture flux from the south, there is a non-zero chance for an isolated thunderstorm or two to develop this afternoon. Despite increased cloud cover, the day will still warm up in the statewide average middle to upper 80s. Trades will be welcome with many coastal, low lying spots experiencing the mugginess as dew points remain in the low 70s.
Once this slug of southern moisture advects west southwest of the area Tuesday, a drier air mass will briefly pass through during the middle of the week. Clearer skies and limited shower activity with breezy trades not undergoing much change Tuesday through Thursday.
There are increasing probabilities that an easterly wave located about 1,000 miles east-southeast of the islands, or near 10N140W, will develop a low center and strengthen into tropical cyclone by mid week. The NHC has assigned a 90 percent probability of tropical cyclone development over the next seven days. The majority of the NWP guidance, from deterministic to AI ensembles, still track a tropical cyclone toward the state later this week. While still too early to definitively discuss the details of a potential tropical cyclone impacting Hawaii, this active area will warrant close monitoring the next few days. Please refer to the latest NHC forecasts concerning this potential development and evolution. If not already finalized, NOW is the time to begin finishing up your Hurricane Plan(s) and be ready to execute the plan when the time comes.
Moderate to fresh trades expected for the next several days. Low cigs and SHRA should mainly impact windward and mauka spots. MVFR conds likely in heavier SHRA, otherwise VFR prevails.
AIRMET Sierra is in effect for mtn obsc for windward locations of all islands.
AIRMET Tango is in effect for mod turb downwind of island terrain. This AIRMET will likely be needed for next several days.
Fresh to locally strong trade winds will persist through at least Wednesday as high pressure remains anchored northeast of the state. A Small Craft Advisory (SCA) has been extended for the typical windy channels and waters around Maui County and the Big Island through Monday afternoon. Borderline conditions will likely continue through at least Wednesday, which may prompt further extensions of the SCA. Later in the week, the focus will shift to the deep tropics southeast of the state. A tropical cyclone is likely to develop over the next few days and have an effect on local winds, seas and weather as early as Thursday.
Continued small overlapping south-southwest swells will produce south shore surf near August average through Monday and near to above average surf on Tuesday. A larger swell will arrive Tuesday night and may push surf to the High Surf Advisory level late Wednesday through Friday. This swell should slowly decrease next weekend.
Along east-facing shores, short-period trade wind swell will generate surf just below August average through Thursday. An increase in southeast swell is possible Friday and next weekend generated by a tropical cyclone that is likely to develop southeast of the islands over the next few days. Aside from wrapping trade wind energy, surf along north-facing shores will remain flat to tiny through the week.
Due to a combination of peak monthly high tides and water levels running higher than predicted in a few locations, a Coastal Flood Statement is in effect for minor coastal flooding possible around the afternoon high tide through at least Tuesday. Tides will be decreasing on Wednesday, but coastal flooding may continue to be possible around high tide for locations where water levels are running highest.
Small Craft Advisory until 6 PM HST Monday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
