Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
200 FXHW60 PHFO 160639 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 839 PM HST Sun Sep 15 2024 .SYNOPSIS... Moderate to locally breezy trade winds will prevail across the islands through the week and into next weekend. A slug of deep moisture will bring an increase in trade wind showers particularly to windward slopes and coasts as it moves from east to west across the islands tonight through Monday night. Typical trade wind weather featuring mainly windward and mauka showers will return by Tuesday and continue into next weekend. && .DISCUSSION... Currently at the surface, a 1031 mb high is centered around 1600 miles north-northeast of Honolulu, and is driving moderate to locally breezy trade winds across the island chain this evening. Infrared satellite imagery shows a band of low and mid clouds moving into the eastern portion of the state. Mostly cloudy to overcast conditions prevail over windward sections of Maui and the Big Island, while mainly partly cloudy skies are present from Lanai and Molokai westward to Kauai. Radar imagery shows numerous to widespread shower activity over windward and southeast sections of the Big Island, with isolated to scattered showers affecting windward sections of the smaller islands. Main short term focus is on rain chances during the next couple days. High pressure north-northeast of the state will drift westward to a location due north of the islands tonight and Monday, then remain nearly stationary through Thursday, keeping moderate to locally breezy trade winds in place. The high will shift eastward and weaken slightly Friday through next weekend, which could bring a slight easing in the trade wind speed. As for the remaining weather details, a mid-level trough will bring a slug of deeper moisture from east to west across the islands tonight through Monday night. Some showery weather can be expected in windward areas as this batch of deeper moisture moves through. We should see a return back to more typical trade wind weather beginning Monday afternoon over the Big Island and by Tuesday morning over Kauai. Typical trade wind weather featuring mainly windward and mauka showers and the occasional leeward spillover will then continue into next weekend. && .AVIATION... High pressure centered far north of the state will maintain moderate to breezy trades over the next few days. Clouds and showers will generally favor windward and mauka areas, though the temperature inversion heights will remain elevated enough to allow occasional showers to pass over island terrain into leeward areas. A plume of deeper moisture is moving into the southern end of the state this evening, affecting primarily east and southeast portions of the Big Island and Maui. This plume may then expand across windward portions of the rest of the state through tomorrow. MVFR conditions, and possibly isolated IFR, are expected in heavier showers tonight. Elsewhere, VFR conditions are expected to prevail. AIRMET Sierra is in effect this evening for east and southeast facing slopes of the Big Island and Maui to account for mountain obscuration due to low clouds and showers. These conditions will likely persist into tomorrow morning. AIRMET Sierra may need to be expanded to include other windward areas later tonight or tomorrow. With locally breezy trade winds prevailing across the state, AIRMET Tango remains in effect for low-level turbulence over and downwind of terrain. This AIRMET will likely continue through tomorrow. && .MARINE... Moderate to locally strong trade winds will hold through Wednesday, as a strong surface high meanders far north northeast of the islands. A Small Craft Advisory (SCA) remains in effect for the typically windy waters around the Big Island and Maui County through Tuesday night, though the advisory may need to be extended through Wednesday. The high will weaken and move eastward late Wednesday and Thursday, leading to a slight decline in the trades into the moderate to fresh range. Surf across most shores will be below seasonal average through the week. Surf along east facing shores will remain choppy through Wednesday due to persistent trades locally and upstream of the islands. A decrease in trade winds will cause east shore surf to decline Thursday and Friday. South facing shores will continue to decline over the next few days. A small southwest pulse out of the Tasman Sea could produce a slight rise in surf Friday. Aside from trade wind wrap, surf along north facing shores will be minimal through Wednesday, and a tiny northwest swell will be possible Thursday or Friday. The combination of seasonally high astronomical tides and water levels running around 6 inches higher than predicted will produce localized coastal inundation each afternoon through Tuesday. A Coastal Flood Statement has been issued to highlight these conditions. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Jelsema AVIATION...Farris MARINE...Shigesato