FORECAST DISCUSSION

Synopsis

Breezy trade winds will persist across the islands into Wednesday. Low clouds and showers will favor windward and mauka sections, with an increase in trade showers expected over the next few days. A late season front will approach the islands Thursday through Friday, causing our winds to weaken and veer from the southeast, and allowing sea breezes to develop each day. The front may stall near Kauai by the end of this week, then gradually dissipate with trade winds returning during the weekend.

Discussion

Breezy trade winds are pushing clouds up the windward slopes this afternoon with little to no rain falling over the state. Leeward locations have mostly clear skies, other than the Kona slopes where afternoon sea breezes have brought about cloudy skies. Over the next few days, trade winds will continue with clouds and showers favoring the windward areas and mountain slopes, while leeward locations will see partly cloudy skies with a few brief showers. Showers will become more prevalent tonight over windward Kauai and Oahu as increasing moisture moves in from the north. High pressure far north of the state is producing the island trade winds, and the high will continue moving eastward over the next few days. A decaying frontal boundary located between the high and Hawaii, or about 200 miles north of Oahu, will gradually work its way toward the state with an expected arrival time of Tuesday night. The moisture associated with the frontal boundary will bring increasing showers to mainly windward areas with some showers spilling over to leeward locations on the smaller islands. Trade winds look to weaken and turn southeast toward the end of the week as a cold front approaches from the northwest. The current forecast has winds veering southeast ahead of the front Thursday, with widespread afternoon sea breezes forming over leeward areas. The front will likely stall north of Kauai Friday with sea breezes again in the forecast for Friday afternoon. The sea breezes should be enough to kick off afternoon convection over the islands with scattered showers and clouds focused over interior areas. Moderate trade winds return over the weekend with remnant frontal moisture providing showers for windward areas.

Aviation

Mainly VFR conditions are expected at the terminals but there may some brief MVFR conditions at PHLI and PHTO in passing SHRA overnight. Brief MVFR conditions can also be expected over windward slopes as moisture riding in on the trades interacts with terrain. Airmet tango remains posted for low level turbulence over and immediately S through W of mountains of all islands as breezy trade winds continue.

Marine

A small craft advisory remains posted for the windier waters around Maui county and the Big Island, as well as the Kaiwi Channel. The SCA will remain into Tuesday night before winds decrease and veer out of the southeast during the second half of the week. Look for trade winds to rebound over the weekend. A small northwest swell will slowly decline through Tuesday. A new small longer period west-northwest swell is expected to arrive Wednesday and linger through Saturday. Elsewhere, expect background south swell through the week before a noticeable bump in surf heights along south facing shores for the weekend. Trade winds will produce choppy short period surf along east facing shores through midweek.

HFO Watches/Warnings/Advisories

Small craft advisory until 6 am HST Wednesday for Maalaea Bay, Pailolo channel, Alenuihaha channel, Big Island leeward waters, Big Island southeast waters. Small craft advisory until 6 pm HST Tuesday for Kaiwi Channel.

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MORRISON...DISCUSSION AND MARINE BURKE...AVIATION

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