Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
763 FXHW60 PHFO 240705 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 905 PM HST Sun Jun 23 2024 .SYNOPSIS... High pressure north of the state will maintain breezy trade winds the next couple of days. Showers will favor windward coasts and slopes. Trades will slightly weaken around the middle of the week with an increase in shower activity late in the week. && .DISCUSSION... The downstream pressure gradient from a 1030 mb high centered approximately 950 miles north northwest of Kauai remains tight enough across the region to maintain breezy to locally windy trade winds through Tuesday. A Wind Advisory is in effect for Big Island summits. Easterlies at the summits will reach 45 mph and gust to around 55 mph through the overnight hours. Expect these winds to begin trending down through the daylight Monday morning hours. The state will remain under the stabilizing influence of mid-level ridging as the islands reside along the southeasterly periphery of a 700 mb ridge positioned to the northwest. Evening radar and satellite imagery show relatively drier conditions compared to last night with widely scattered weak trade showers traveling across the isles. Expect these conditions to continue overnight with showers favoring windward exposures. Higher mid-level moisture advecting in and deepening a more moist boundary layer the next few days, along with the emergence of the jet draped across the southern half of the state, should be the impetus to increased shower coverage that will produce a few hundredths of an inch more rain within those communities that typically stay wet during a normal summertime trade pattern. Aside from some brief afternoon showers over the Kona slopes of Big Island, leeward areas will remain mostly dry. Little to no movement of the lower and upper ridge planted north of the islands through Tuesday ensures breezy trades 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 will weaken the lower level pressure gradient enough to subtly suppress trade flow to more gentle magnitudes through the middle of the week, although easterlies will still remain breezy along ridge lines and within those valleys parallel to trade flow. Lowering mid to upper heights, with periodic ribbons of higher moisture passing to the west, will increase shower frequency and areal coverage later in the week. The development of a mid to late week upper level trough/cut-off low east northeast of the islands will move north of the area this weekend. This scenario will certainly boost weekend rain chances as the low moves north of the state the last few days of June. && .AVIATION... Breezy to locally windy trades will continue through Monday. Showery cloud bands embedded in the trade flow will produce periods of MVFR conditions across windward/mauka areas of each island, particularly through the overnight and early morning hours. 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 Monday morning. 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 roughly 900 nm north of the state will remain stagnant through early this week and help to drive fresh to strong easterly trades. The Small Craft Advisory (SCA) remains in effect through Monday night for all local waters south and east of Maui County. Trades weaken slightly Tuesday into mid- week as the high moves east northeastward, away from the islands. Surf along east-facing shores will remain rough and choppy through Monday followed by a gradual downward trend during mid-week as trades weaken slightly. Expect slightly elevated surf, near or slightly below seasonal norms, along south facing shores through Tuesday as a small, medium period, south swell moves through. However, this should be short-lived, with a downward trend expected by Tuesday night. More small, medium to long period, south swells will return Wednesday night through the weekend. Nearly flat conditions along north facing shores expected through mid day Monday. A small, medium period, northwest swell will bring tiny surf to north facing shores late Monday through mid- week. && .HFO WATCHES/WARNINGS/ADVISORIES... Wind Advisory until 6 PM HST Monday for Big Island Summits. Small Craft Advisory until 6 PM HST Monday for Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel- Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Blood AVIATION...Gibbs MARINE...Thomas