Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
649 FXHW60 PHFO 171322 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 322 AM HST Tue Sep 17 2024 .SYNOPSIS... Moderate to locally fresh trade winds will hold through the week. A drier trade wind pattern will filter today into weekend, with light to moderate showers focused over windward slopes. && .DISCUSSION... Latest satellite and radar imagery shows numerous light to moderate showers mainly over windward and mauka regions compared to more moderate to locally heavy showers earlier this evening. The past 12 hour rainfall totals rain range from .10 to .30 of an inch for the coastal windward locations on Kauai .01 to .30 of an inch for windward areas of the other islands. Radar and satellite imagery shows an area of less clouds and showers that should move over the state later this morning and afternoon in tandem with the diurnal minimum precipitation trend. However, expect humid conditions to linger as dew points remain elevated in the low to mid 70s. The surface high pressure north of the state that is driving the moderate to locally fresh trade winds. The high is expected to ease slightly during the second half of the week allowing for a brief decline in the trades around Thursday and Friday. While a ridge aloft will bring stability, a mid- level trough will linger nearby into Wednesday, which will keep shower chances a bit higher than normal. Dew points are expected to fall into the upper 60s over most leeward areas late Wednesday into Thursday, bringing some relief from the humidity. Drier conditions are due Thursday and Friday and likely persist into Saturday. While a ridge aloft will maintain stability over the islands through much of the week, an upper-level trough will persist to the west. The main effect of this feature will be periods of high clouds overhead. Models suggest that a low aloft may develop Sunday and Monday and north of Kauai. At this time, it does not look like it will affect local weather significantly. && .AVIATION... High pressure far north and northeast of Hawaii will maintain breezy trade winds through forecast period. Stable conditions will prevail, with only limited areas of low ceilings and temporary MVFR conditions over windward areas. Aside from afternoon clouds over Kona slopes of the Big Island, VFR conditions will prevail. With the increased trade winds, AIRMET Tango for low-level turbulence over and downwind of terrain is in effect. This AIRMET will likely continue through the day. && .MARINE... High pressure north of the state will maintain moderate to locally strong trade winds through Wednesday. The trades may ease off ever so slightly Thursday and Friday as the high to the north weakens, before rebounding back to moderate and locally strong levels this weekend. A Small Craft Advisory (SCA) is now in effect for the typically windy waters around the Maui and the Big Island through 6 AM Thursday. East shore surf will hold near seasonal levels through Wednesday, then slowly lower Thursday through early next week. A mix of southeast, south and southwest swells will keep some small surf rolling into south facing shores through the weekend. A slight bump in south shore surf is possible early next week as a slightly larger southwest swell moves into the islands. North shore surf will remain very small through the weekend. A nice bump in north shore surf is possible early next week as a long period northwest swell arrives. The combination of high astronomical tides and water levels running around 0.6 to 0.8 feet higher than predicted will produce localized coastal inundation around the time of high tide this afternoon. A Coastal Flood Statement remains in effect highlighting potential impacts. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Almanza AVIATION...Shigesato MARINE...Jelsema