Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
986 FXHW60 PHFO 290104 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 304 PM HST Sun Apr 28 2024 .SYNOPSIS... East southeast winds continue through Thursday supporting drier weather from Oahu eastward while Kauai experiences periods of enhanced showers today and Monday. A return to a breezy trade wind pattern is in store for the end of the week. && .DISCUSSION... The Hawaiian islands remain on the poleward side of the Pacific jet through the week while a somewhat progressive mid-latitude pattern produces mean troughing centered around 170W longitude. Consequently, low pressure and a weak background gradient prevail over the western end of the state while breezy ESE persist over the eastern islands as high pressure settles along the west coast of the CONUS. Drier air has filtered in today as evidenced by decreased cloud cover compared to yesterday and precipitation-free conditions in most locales. However, some moisture continues wrapping around the Big Island and is supporting a few afternoon showers over Kauai and vicinity. PoPs remain appropriately higher there while drier and sunnier conditions prevail elsewhere. This may be the case on Monday afternoon as well as the weak gradient gives rise to expanding sea breezes over Kauai coincident with a mid- level shortwave grazing the islands from the north. This should further reduce stability over Kauai and may result in a couple locally heavy showers over interior or leeward zones during Monday afternoon. The high res guidance offers a similar picture which increases forecast confidence. Any afternoon convection will diminish with the loss of diurnal heating Monday evening. The pattern will remain generally stagnant through at least Tuesday. Wednesday into Thursday will represent a transition period back to a typical easterly trade wind pattern. Global model consensus indicates that a low will close off over or near the islands immediately south of expansive ridging building over the Central Pacific. This will set the stage for a breezy and weakly stable easterly trade wind pattern settling in by week`s end. && .AVIATION... Drier air has moved in across the majority of the state today, with very little in the way of showers this afternoon. A N-S oriented low cloud band is currently moving toward the Big Island from the east. This could bring a period of enhanced low clouds and showers through tonight for windward portions of the Big Island and Maui. Rainfall amounts should be rather limited, given the dry and stable air aloft, but brief periods of MVFR conditions are possible in any heavier showers that develop. Otherwise, light to moderate ESE trades will persist for the next couple of days. With the lighter ESE flow and decreased cloud cover, afternoon sea breeze activity is expected across wind- sheltered areas, with some inland/leeward cloud buildups and a few light showers possible. && .MARINE... Surface high pressure far northeast of Hawaii and an approaching front to the northwest will drive breezy east southeast winds through tonight, mainly for windward waters and through the channels surrounding Maui County and the Big Island. The high will slide east while a low pressure system will edge closer Monday and Tuesday allowing winds to weaken. By mid-week, high pressure will rebuild to the northeast and allow trade winds to strengthen. A Small Craft Advisory for winds is in effect for most waters and channels surrounding Big Island, Maui, and Molokai through tonight. Surf heights will remain below advisory thresholds for all shores through the forecast period. A small northwest, medium-period swell will persist through mid-week with small surf expected. Breezy east or east southeasterly flow will produce choppy surf along east facing shores through tonight, then decrease as winds begin to taper off. Small, short-period southeast, and small medium-period south swell will continue into mid-next week. Surf heights along the south facing shores should remain near or slightly below seasonal norms. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Monday for Maui County Windward Waters-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters. && $$ DISCUSSION...JVC AVIATION...TS MARINE...Foster