textproduct: Honolulu

SYNOPSIS

Breezy trade winds will persist through much of the week with minor fluctuations as surface high pressure holds north of the state. Pockets of moisture moving in the trades will focus rainfall over windward and mauka areas with showers briefly passing over leeward areas. An area of deeper moisture may enhance showers on windward Big Island and Maui County Friday and Saturday.

DISCUSSION

A ridge of high pressure north of the state is driving breezy trades across the state. Satellite and radar imagery show widely scattered to numerous, light to moderate showers focusing along windward and mauka areas with frequent showers spilling over to leeward areas of the smaller islands. The sounding profiles this morning are fairly elevated between 7,000 to 8,000 ft which reasons with the frequency of showers spilling over to leeward area. For the past 6 hours, rainfall totals for leeward areas range from 0.10 to 0.24 inches for the smaller islands. Windward locations range from 0.20 to nearly 1.0 inch of rainfall for the wetter areas.

Breezy and stable trade winds will continue through today as the ridge remains north of the state. Showers should trend down this morning for the western half of the state but pick up slightly for the eastern half of the state as an area of moisture sags south.

Little change is expected tonight through at Thursday. Trades will remain breezy as a surface ridge holds to the north, and additional pockets of moisture will focus showers over windward and mauka areas, particularly during the overnight and early morning hours.

There remains a high chance of tropical cyclone gradually developing far southeast of the state within a few days. Most guidance tracks the main tropical cyclone feature well south of the islands over the weekend. GFS and ECMWF show the northern flank of a broad pool of deep moisture grazing over windward Big Island and possibly reaching as far north as Maui County. There remains about a 12 hour difference between the GFS and ECMWF models, with the GFS increasing showers as early as Friday morning and clearing the moisture Saturday. A tropical cyclone, or broad area of low pressure, passing south of the state could also lead to a period of stronger trade winds this weekend as other surface ridge builds in from the northwest, as shown in the ECMWF runs. However, GFS shows only a minor fluctuations thus confidence is low at this time.

AVIATION

Breezy trades expected for next few days. Low cigs and SHRA will continue over windward and mauka locations with some spillover into leeward areas. MVFR conds in SHRA, otherwise VFR prevails.

AIRMET Sierra is in effect for mtn obsc for the smaller islands and windward Big Island. Conds should improve mid morning.

AIRMET Tango remains in effect for mod turb lee of terrain and should remain in effect for next few days.

MARINE

Fresh to strong trade winds will persist for most of the week across most coastal waters as high pressure remains in place north of the region. Small Craft Advisory (SCA) conditions will likely persist across many zones throughout the week due to a combination of winds and seas. Additionally this weekend, a tropical cyclone could pass far south of the state. According to National Hurricane Center, there is a high chance of tropical cyclone formation in the next 7 days.

Surf along north and west-facing shores will continue to decrease through today as the current small north-northwest swell fades and shifts more northerly. A more significant moderate, long- period northwest swell will arrive tonight into Thursday morning and will easily push north and west shore surf to advisory levels for Thursday into Friday. An additional medium-period moderate swell is expected to fill in on Saturday, likely prolonging moderate to large surf action into the weekend.

A compact fetch of gales passing east of New Zealand last week Friday should produce some waves slightly above average around Friday into Saturday along south facing shores. East-facing shores will see continued moderate trade wind swell as strong trade winds remain. Surf along east- facing shores will stay elevated and choppy through much of the week with the strong trades.

FIRE WEATHER

Persistent rainfall will likely limited the widespread availability of receptive fuels. Breezy winds will continue during the next several days, generating moderate fire weather conditions. The inversion near Big Island will range from 6000 to 8000 ft over the next few days.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 AM HST Friday 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.