Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
450 FXHW60 PHFO 271358 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 358 AM HST Sat Apr 27 2024 .SYNOPSIS... Breezy east to east-southeast winds will continue to gradually ease through early next week. A plume of moisture will produce passing showers across windward and mountain areas through today. A drier weather pattern is expected Sunday into early next week with light to moderate east to east- southeast winds. Winds should be light enough for sea breezes to develop during the day and land breezes at night, especially early next week. && .DISCUSSION... Latest satellite and radar imagery shows scattered light to moderate showers mainly along windward and mountain areas with some showers making it to leeward zones, especially for Kauai County. Shower activity is expected trend down along windward zones. Leeward areas will see a increase in clouds and showers this afternoon as seabreezes develop. Gentle to breezy east to east-southeast winds appear to have developed over the state overnight. A ridge of high pressure north of the state will shift south today, further weakening and veering winds out of the east- southeast, especially over the western half of the state. Breezier winds will persist along windward areas and lighter winds will develop along leeward areas today as a result. A drier air mass is expected to move in by Sunday, so overall we should less showers on Sunday as well as lighter winds with sea breezes developing over many leeward areas Sunday afternoon. For early next week, high pressure will be centered far northeast of the state, while a low pressure system shifts north of the state. We will continue to be in a hybrid wind pattern early next week with light to breezy east-southeast winds over windward areas and generally light winds over leeward areas. Due to limited moisture, we are not expecting much rainfall early next week, but some light passing showers should be expected over windward areas, as well as some light showers over leeward areas during the afternoon with the sea breezes developing. For the second half of next week, guidance continues to show a some discrepancies between the ECMWF and the GFS. The ECMWF shows a much deeper upper level trough with a surface trough developing near the state. This setup would continue the hybrid tradewind and land/seabreeze pattern. Meanwhile, the GFS shows a much weaker upper level trough, with the surface high north of the state with strengthening trade winds during the second half of the week. The forecast as been updated to favor GFS for now, but will likely change over the next several days as model guidance narrows on a solution. && .AVIATION... E trade winds will continue to gradually ease and veer to the ESE this weekend, especially over the smaller islands, where wind speeds will trend toward light by tonight. AIRMET Tango for low- level turbulence will be pared back later this morning, removing at least Kauai and Oahu. Showery and stable low clouds have increased in coverage overnight, in response to a developing low-level trough over the area. Mountain obscuration in windward areas requires AIRMET Sierra, where periods of MVFR VIS/CIG in SHRA may be briefly punctuated by short-lived IFR VIS in +SHRA. Guidance indicates the trough will linger today, thus supporting continued periods of MVFR conditions over windward areas. The veering of the low-level flow is expected to support the development of the "Maui vortex" by this afternoon, which typically impacts Kahului airport (PHOG) with significant low- level wind shear. && .MARINE... A 1031 mb surface high, centered around 1200 nm northeast of the state and low about 1100 nm northwest of Hawaii is producing east-southeast winds over the western half of the state and moderate to locally strong easterly winds over the eastern half of the state. Winds will weaken slightly over the next few days as the high weakens and the low shifts north of the state. A Small Craft Advisory (SCA) will remain in effect for most waters and channels surrounding Big Island, Maui, and Molokai. The advisory may be scaled back late this weekend as winds weaken and shift out of the east-southeast. Surf heights will remain below advisory thresholds for all shores through the forecast period. A small northwest, medium period swell is forecast to subside by this evening. Thus, small surf can be expected along north and northwest facing shores through the remainder of the weekend. Breezy trade winds will produce choppy, rough surf along east facing shores through at least this evening. Conditions are expected to improve on Sunday. Meanwhile, expect small surf along south and southeast facing shores through the forecast period with occasional pulses of 1 to 2 foot medium to long period swell. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Sunday for Maui County Windward Waters-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters. && $$ DISCUSSION...Almanza AVIATION...Birchard MARINE...Bedal