National Weather Service Raw Text Product
Displaying AFOS PIL: AFDHFO Product Timestamp: 2019-07-09 19:45 UTC
Previous in Time Latest Product Next in Time
View All PHFO Products for 09 Jul 2019 View All AFD Products for 09 Jul 2019 View As Image Download As Text
726 FXHW60 PHFO 091945 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 945 AM HST Tue Jul 9 2019 .SYNOPSIS... As moisture associated with the remnant of Barbara moves away from the area, a more typical trade wind weather pattern will resume, and humidity will diminish somewhat. The light to moderate trade winds will deliver clouds and a few brief showers to windward areas through the week. There is some potential for an increase in moisture to fuel showers near Kauai on Saturday, and near the Big Island late in the weekend. && .DISCUSSION... The slug of moisture associated with the remnant of Barbara is moving W and away from the islands this morning, as somewhat drier air begins to filter in from the E. A ridge of high pressure to the N is supporting moderate to locally breezy trade winds while a mid- level ridge to the N is supporting an increasingly stable island atmosphere. In the meantime, a few heavy showers are seen in cloud plumes peeling off the islands, with one batch of showers over Oahu leeward waters this morning having formed within a plume off Lanai. Additionally, showery low clouds have been streaming into windward Big Island all morning, with additional clouds and showers extending about 150 miles to the E. A trend toward a more typical, and somewhat less humid, trade wind weather pattern is expected over the next 24 hours or so. This pattern will remain in place through the week, potentially continuing into the weekend. A mid-level ridge to the N will change little through the week, and will keep trade wind showers limited in intensity and coverage for most of the period. Models depict a weak trough aloft moving toward the islands from the NE Friday/Saturday, with the trough dissipating just N of Kauai. Associated moisture and modest instability is, for now, expected to remain just N of the islands, but this feature could increase trade showers near Kauai around the end of the week. The only other potential interruption to the benign trade wind weather pattern is a tropical disturbance that is expected to pass S of the Big Island Sunday/Monday. Associated moisture may bring an increase in windward showers to the Big Island, but confidence remains low as to the details. && .AVIATION... Relatively strong high pressure well to the north-northeast is providing the state with mostly east-southeast trade winds which will be breezy to windy throughout the day. These winds are expected to begin reducing is speed as the high weakens tonight into Wednesday. AIRMET Tango for low-level turbulence below 8,000ft is expected through the day today but we may be able to cancel this AIRMET by this evening after the winds weaken. There is a lot of moisture above Hawaii and it will not take much of a lifting mechanism to kick off showers, some of which could be heavy at times, especially if there are any lengthy periods of daytime heating this morning. If we do see any heavy showers, they will probably occur near the mountains or possibly on the inner portions of the islands. Expect MVFR conditions, especially on windward parts of the islands from Oahu southeast to the Big Island and passing MVFR conditions across the rest of the state. AIRMET Sierra for mountain obscuration is currently in effect for the windward areas of Oahu, Molokai, Maui, and the Big Island at least through the morning with some areas maybe seeing mountain obscurations into the overnight hours tonight. && .MARINE... The northern extent of the surface trough remnant of Barbara appears to be about 100 nm southwest of Kauai this morning. As it moves westward today, its direct influence on Hawaii weather will continue to diminish. Although there are no longer gales in the Alenuihaha Channel and waters south of the Big Island, the pressure gradient remains tight enough to keep Small Craft Advisory (SCA) conditions in the typically windier waters around Maui County and the Big Island through tonight. While winds may briefly drop below the SCA threshold for these areas Wednesday, a new surface high is forecast to build far north of the state later this week, prompting another SCA. The locally strong trade winds continue to produce elevated rough surf along east facing shores this morning according to the nearshore buoys. Therefore, a High Surf Advisory (HSA) remains in effect for east facing shores of most islands through mid-afternoon today. Surf is expected to gradually lower later this afternoon through mid-week. The combination of a declining south-southwest swell and a small southeast swell will likely keep surf heights near or slightly above the summer average along exposed shores through mid-week. New long- period, south-southwest swells beginning to arrive Friday are expected to cause HSA level surf this weekend into next Monday. Elsewhere, a small northwest swell is expected to arrive late Wednesday for a slight bump in surf along exposed shores of some of the smaller islands Wednesday night through Friday. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory until 4 PM HST this afternoon for East facing shores of Kauai Oahu Molokai Maui Big Island. Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Birchard AVIATION...Chevalier MARINE...TS