textproduct: Honolulu

SYNOPSIS

An elongated ridge of high pressure north of the state will dominate our weather pattern through tomorrow. Stable conditions with continued breezy to locally strong trades. A upper level low moving in west of the islands tomorrow may pass over the state Friday into Saturday. This feature may enhance showers.

DISCUSSION

Hawaiian Island weather will remain very summerlike the next several days with certain days experiencing thicker cloud cover and slightly higher rainfall. Synoptically, there hasn't been much change the past couple of days. Today's weather will be very similar to recent days. That of breezy trades and infrequent passing upslope windward trade belt showers that, if more organized, may pass over the ridge tops and reach leeward areas. Partly to mostly overcast skies over most windward sites today, mostly sunny or clear over leeward. Afternoon temperatures will top out near 80 F where the clouds are thickest, middle 80s over sunny interior leeward spots. Overnights will cool into the lower to mid 70s where most live. The highest rainfall will be confined to east-facing terrain.

Near or sub-inch pwat morning soundings, low to mid 60 F surface observations and water vapor satellite all support the fact that the resident air mass is still on the dry side. While there will be lobes of higher moisture traveling through upon breezy trades from the east as clustered warm clouds line up east northeast of the island chain, most of the day will remain dry with little to no rain accumulation. The general moisture characteristics of eastern air moving through will remain unchanged...it will be those areas of higher moisture marching through that dictate the haves and have nots in terms of any wetting rain. While trade- facing slopes and upper terrain will pick up the highest daily accumulations, there will be random spots that may pick up a quick tenth or so, especially of those spots experiencing a mostly sunny, very warm start to their day. It will not feel as muggy in non-wind protected areas as winds remain breezy through tomorrow...speeds gradually fall off later this week.

A weak upper low east of the state will move away today as a new low to the west advances to just west of Kauai by Friday morning. This low will pass overhead Friday into Saturday and assist in destabilizing the atmosphere just enough, in tandem with a band of slightly higher mid level moisture passing by from the northeast, to garner a mention of more inclement weather from late Thursday through Saturday. A transitory period early next week as upper riding makes an unimpressive attempt at building in from the west. This will leave the region under a relatively stable, dry last couple days of May. June arrives with more sun, less clouds/rain under weaker trades as a new surface high takes up residence northwest of the islands.

AVIATION

Moderate to breezy trade winds will continue for the next couple of days. Low ceilings and passing showers will be possible over windward and mountain locations at times, especially during the overnight through morning hours each day. Although MVFR conditions will be possible within passing showers, VFR will prevail for most locations.

AIRMET Sierra is in effect for tempo mountain obscuration for N through SE sections of Oahu this morning due to low clouds and passing showers.

AIRMET Tango remains in effect for mod low-level turbulence over and downwind of terrain across all islands. This AIRMET will likely be needed through Wednesday.

MARINE

Fresh to strong east-northeasterly trades will persist through midweek as a strong surface ridge remains north of the state. This will allow the Small Craft Advisory to continue across most Hawaiian coastal waters through midweek. Expect a gradual downward trend through the second half of the week and especially by the weekend as a weakness in the ridge develops due to a front passing far to the north.

A fresh long-period south swell arrives today which will slowly build surf to near the seasonal average through Wednesday before easing Thursday. A more significant long-period south-southwest swell is expected by the weekend due to a storm-force low that passed southeast of New Zealand over the weekend. Satellite data showed a large fetch of 40 to 50 kt winds generating seas of 35 to just over 40 ft, focused toward, or just east of Hawaii along the 190-degree directional band. Expect surf to begin building locally Friday with 20+ second forerunners, then potentially peak around advisory level over the weekend.

Surf along exposed north- and west-facing shores will trend up once again today, peaking at small to moderate levels on Wednesday, before lowering Thursday and continuing to fade through the weekend. Surf along east facing shores will remain rough through midweek, then gradually lower later in the week as the trades ease.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Wednesday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters- Maalaea Bay-Maui County Leeward Waters-Maui County Windward Waters-Oahu Leeward Waters-Oahu Windward Waters-Pailolo Channel.