Marine Weather and Tide Forecast for Princeville, HI

DISCUSSION
A high pressure ridge will remain in place north of the Hawaiian Islands through the weekend. This means moderate to locally breezy trade winds for the foreseeable future. The strongest winds this week will likely develop from Tuesday through Wednesday. The main weather variable in the forecast will be slight changes to the cloud cover and shower pattern this week and over the weekend.

This mornings satellite imagery shows an easterly wave (trough)
swiftly moving westward towards the Big Island. This mornings upper air balloon soundings from Lihue and Hilo at 2 AM HST (12Z)
show very stable temperature inversion heights hovering around the 5,500 foot elevation level. This inversion height will lift rather quickly into the 8,000 to 10,000 foot range as the trough moves into Maui and the Big Island later this afternoon. Cloud tops will deepen and shower activity will increase as a result of increasing instability associated with this trough moving through each island.

The timing of these increasing shower trends will vary island by island, the Big Island and Maui will start to see increasing shower trends later this afternoon, Lanai and Molokai will see increasing shower trends by this evening, with Oahu and Kauai picking up enhanced shower trends through the overnight and Tuesday morning hours. This increase in shower activity will be brief as a mid level ridge will build in quickly, stabilizing the atmosphere and decreasing shower trends, as the trough exits the pattern to the west.

Drier and more stable conditions will return from late Tuesday into early Friday, as high pressure will keep a subsidence cap on vertical cloud development. Shower activity will remain isolated during the day over windward mountains during the day time periods, becoming isolated to scattered coverage in the overnight to early morning hours. Any 12 hour overnight rainfall amounts will likely be on the light side due to the strong stability.

Subtle changes in the island cloud and shower pattern will become less stable by late Friday into the weekend, as a weak upper level low injects some instability across the Hawaii Region. A slight increase in shower trends are anticipated mainly during the overnight to early morning hours favoring the windward mountain areas. Confidence in these shower trends are only moderate at this time as the strength of the upper low is currently projected to be on the weaker side of the equation. More details will become clearer later this week, as the time period grows closer, and our confidence on island by island shower trends improve.

AVIATION
A high pressure ridge remains locked in place north of the Hawaiian Islands this week. Moderate to locally breezy easterly trade winds remain in the forecast. Shower trends will increase today and tomorrow as a trough moves westward across the island chain, starting with the Big Island and Maui later this afternoon, and then spreading to the smaller islands through Tuesday morning. Periods of MVFR conditions are expected in any showers, especially affecting windward airfields.

No AIRMETs are in effect, AIRMET Sierra for Mountain Obscuration is possible for the eastern islands later today as clouds and showers increase.

MARINE
A ridge of high pressure will remain far north of the state throughout the week. Moderate to fresh trades will likely continue through today then strengthen to locally strong speeds from Tuesday onward as a weak trough exits the region. A Small Craft Advisory should return to our typically windy waters around Maui County and the Big Island by Tuesday evening.

Surf along south facing shores should see a modest increase over the next few days due to a pair of south and south-southeast swells. A long-period south swell should fill in today and peak on Tuesday near summer averages. As this swell declines a reinforcing swell from the south- southeast should fill in Tuesday or Wednesday. This should maintain surf heights through the middle of the week. Surf should gradually decline Thursday into Friday, but another small increase is expected into the weekend as a new long-period southwest swell arrives from the Tasman Sea.

Surf along east facing shores will continue to remain choppy with surf heights below average due to the lack of strong trades locally and upstream of the state. A sight increase is expected towards the middle of the week as the trades strengthen. A tiny northwest swell could produce some rideable surf along north facing shores today into Tuesday.

FIRE WEATHER
Trade winds will remain in the moderate to locally breezy range into the upcoming weekend. Aside from a period of higher humidity and an increase in shower activity today and Tuesday, the atmosphere will remain rather dry through Friday.

HFO WATCHES/WARNINGS/ADVISORIES
None.