Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
782 FXHW60 PHFO 230657 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 857 PM HST Sat Jun 22 2024 .SYNOPSIS... High pressure north of the state will maintain breezy trade winds the next few days. Showers will primarily favor windward coastal and mauka slopes. Trades will slightly weaken around the middle of next week with a possible increase in shower activity late next week. && .DISCUSSION... The downstream pressure gradient remains tight enough across the islands from a 1030 mb high centered approximately 950 miles north of Oahu to maintain breezy trades well into next week. The Hawaiian Islands remain under the stabilizing influence of the southeasterly periphery of a mid-level ridge located northwest of the region. Radar depicts widely scattered showers moving in on these trades and affecting across most windward locales this evening, especially at elevation, with the highest rainfall focused over all windward mauka slopes this evening. Drier air working its way into the state from the northeast on Sunday will limit overall shower activity to just light, isolated showers confined to windward mauka regions. Slightly higher mid- level moisture advecting in Monday may increase shower coverage and produce a few hundredths of an inch more rain over those communities that typically receive more rain during normal trade flow. Little to no movement of the lower and upper ridge planted north of the islands through the middle of next week ensures daily breezy trade flow under partly to mostly cloudy windward skies, mostly to partly sunny leeward skies. High pressure at all levels begins to transition east during the latter half of the week. This may weaken the pressure gradient enough to subtly suppress trade flow to more gentle magnitudes, although easterlies will still remain breezy along better exposed windward ridge lines and within more east-to-west orientated valleys. Lowering mid to upper heights, with periodic ribbons of higher moisture, will increase shower frequency and areal coverage later in the week. The possible development of an upper level disturbance east or northeast of the islands will boost weekend rain chances as we close out the month of June. && .AVIATION... Breezy to locally windy trades will continue through Monday. Showery cloud bands embedded within trade flow will produce periods of MVFR conditions across windward/mauka areas of each island, particularly through the overnight and early morning hours each day. Conditions will improve through the late morning and afternoon periods. AIRMET Sierra remains in effect for tempo mountain obscuration for windward slopes of most islands, which will likely continue through the early Sunday morning hours. AIRMET Tango remains in effect for mod low-level turb over and downwind of island terrain due to the breezy trade winds. This AIRMET will continue through Monday. && .MARINE... Surface high pressure, centered around 850 nm north of the state, will remain nearly stationary over the next several days and help generate strong easterly trades. A Small Craft Advisory will remain in effect for all local waters through Monday night. Trades are expected to decrease slightly Tuesday through midweek as the aforementioned surface high drifts northeast away from the islands. Surf along east-facing shores will remain rough and choppy through early next week due to the strong trades locally and upstream of the state. A gradual downward trend is expected Tuesday through midweek. Surf along south-facing shores remains slightly elevated tonight into Sunday as a small medium to long period south swell moves through. This should be short-lived, with a downward trend expected early next week. Despite a blocking high that has set up over our typical swell window southeast of New Zealand, a gale has formed northeast of this high with the head of the fetch aimed at the islands within the 180 to 200-degree directional band. Given the shorter travel distance, surf associated with this source should trend up late next week. Surf along north-facing shores will remain nearly flat on Sunday. A small, medium period, northwest swell will bring tiny surf to north-facing shores by early next week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters- && $$ DISCUSSION...Blood AVIATION...Gibbs MARINE...Thomas