Moderate to locally breezy trades will occur through the remainder of the week. Stable and dry conditions will be the main theme the next several days. Typical summertime, albeit infrequent, windward and/or upslope mauka quick passing light showers.
Weak upper and mid level ridging across the Central Pacific is providing just enough subsidence to result in warm and fairly dry weather, primarily isolated showers, the next couple of days. A large area of 1032 mb surface high pressure located south of the Aleutian Islands is creating a tight enough pressure gradient toward lower equatorial pressure to create continued moderate to locally breezy trade winds the next several days. As was the case yesterday, the next few days will be less humid and generally more pleasant under continued moderate trade flow.
The lower levels are void of any significant features that would indicate any short term deviation from the recent pattern. Morning soundings indicate a near 6k ft inversion depth that is deep enough to support repeat showers. Locally stronger winds gusting to near 25 to 30 mph will be commonplace atop higher terrain and through lee valleys and/or slopes into early next week. Amped up trades will hang with us into early next week as subtle strengthening of the North Pacific surface high puckers up winds a touch past Sunday. Most diurnal rain accumulation will measure in the hundredths of an inch. Greater rainfall will likely focus across windward upslope areas, in particular Big Island's Hilo, Puna and Ka'u Districts and Haleakala's eastern slopes on Maui. Generally, as evidenced in recent soundings, mid to upper ridging will remain in control helping to maintain dry mid-levels (20-40% %RHs between 5-10k ft). This scenario will result in infrequent 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 deeper moisture reaches higher depths per weaker ridging slinking further west.
The National Hurricane Center is monitoring three distinct areas of convection between 100W and 140W. All of these areas have a higher chance for tropical cyclone (TC) formation late this week or weekend. Deterministic model guidance has struggled with consistency on future development and track of potential TCs. Ensemble members that spin these eastern Pacific disturbances up into TCs and send them west are still in the minority. Google Deepmind is also struggling on how to handle the active convection south of 14S between 130W and 140W this morning, NHC's area of a high likelihood of TC formation. The model does send its ensemble members of various strengths due west into a less sheared environment south of the trade belt over Hawaii and over warmer waters through next week.
Moderate trades expected through the period. Low cigs and SHRA over windward and mauka slopes. MVFR conds in heavier SHRA, otherwise VFR prevails.
AIRMET Tango is in effect for mod low-level turb lee of terrain and may be needed for a few days.
Moderate to locally strong trades will persist through this weekend as a broad high pressure remains far north of the state. A Small Craft Advisory for the typically windier waters around Maui County and the Big Island will continue through tonight and likely need to be extended for the next several days.
A small, long period south southwest swell will continue to fill in today, peak this tonight through Friday morning, then slowly fade through the weekend. This swell will help bump surf along south facing shores to above seasonal averages and could approach high surf criteria at its peak.
Surf along east facing shores will remain rough and choppy due to persistent trade wind swell. A small, medium period east swell from Tropical Storm Iselle may fill in Friday, peak Saturday before slowly fading into early next week.
Surf along north facing shores will remain tiny to flat.
Small Craft Advisory until 6 AM HST Friday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
