Marine Weather and Tide Forecast for Kahului, HI

DISCUSSION
Our weather continues to be dominated by a large, sprawling, persistent 1035 mb surface high centered over the far NE Pacific.
This high will probably continue to be there for the next 10 days.
This leaves the islands in a gentle to locally breezy trade wind pattern, where weak troughs and areas of convergence can temporarily veer local background flow to the ESE like we see today. A few small showers have popped up on the northwestern sides of the islands today, but overall any convection has greatly underperformed the CAMs owing to the subsidence and very warm air aloft seen in the mid- levels in the 00z soundings.

The models agree on fairly normal summertime weather continuing through the next week or so, with hard-to-time areas of shallow moisture convergence riding in on the trades. These will not get any help from the mid-levels, where very warm temperatures and ridging will keep strong subsidence in place above the trade wind inversion.
We will still see some trade wind showers from time to time, favoring overnights and early mornings windward. After today, the pressure gradient strengthens a bit more for a minor peak in trade winds about Saturday, before easing up just a bit.

Kilauea volcano episode 51 is ongoing, but we have recieved only very localized reports of tephra in the closed area of the park so far. Continuing to ride with a Special Weather Statement unless we get some evidence of more widespread problems. Model guidance shows low level winds 10000 feet and below would likely push any ash cloud toward the WSW, while winds at about 15000 feet and higher would carry any ash able to reach that height toward the N or NNE.

AVIATION
A few small sea breeze showers were able to develop on the leeward sides of most islands this afternoon due to the lighter trade wind flow. Light to moderate trades will strengthen slightly late tonight through Thursday. Expect mainly scattered low clouds and showers favoring windward and mauka areas. Brief MVFR conditions are possible in passing showers, but VFR should prevail across the state.

SIGMET Papa is in effect over and just northwest of the Kilauea summit area of the Big Island due to the latest fountaining episode of the ongoing eruption.

MARINE
High pressure far north of the islands and very broad weak troughing to the west will continue to lead to a slightly veered and lighter trade wind flow across the coastal waters through tonight. Then the pressure gradient between the high to the north sagging south and a couple of lows developing to our south and southwest will strengthen across the area, causing an uptick in trade wind speeds Thursday night into the weekend. As the trades gradually strengthen to fresh to strong levels, a Small Craft Advisory will likely be needed for the typical windier channels and waters around Maui and the Big Island.

A small, long-period west-northwest (280 to 290 degrees) swell from former Super Typhoon Bavi has arrived, peaking through Thursday before gradually subsiding into the weekend. This swell is overlapping for some west-facing shores with a gradually fading small, medium-period southwest (210 to 220 degrees) Tasman swell that is currently bringing near-average surf to south-facing shores. A series of small, long- to medium-period south-southwest (190-200 degrees) swells will arrive starting Thursday night into the weekend, keeping surf slightly below summer average. Then an overlapping moderate, long-period south swell (180 degrees) will arrive early next week, bringing the potential for above-average (though sub-advisory) surf.

As mentioned previously, the west-northwest swell from former Super Typhoon Bavi has arrived and is bringing a slight uptick in surf along exposed north-facing shores this afternoon. This surf will hold into Thursday before gradually fading and returning north shores to flat to tiny status for the weekend.

Surf along east-facing shores will be slightly below seasonal averages through Thursday with lighter trade winds. Surf may then climb back up a notch as trades strengthen through the weekend.
Then early to midweek next week, there's potential for a small, long- to medium-period swell to arrive, generated from Tropical Storm Elida.

Peak monthly high tides combined with water levels that are running slightly higher than predicted will likely lead to minor flooding along the shoreline and in low-lying coastal areas this afternoon as we approach high tide. A Coastal Flood Statement is in effect through 9 PM tonight.

HFO WATCHES/WARNINGS/ADVISORIES
None.