154 FXHW60 PHFO 202008 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 1008 AM HST Fri Dec 20 2019 .SYNOPSIS... Strong high pressure passing north of the islands will produce very windy conditions through Saturday, and possibly into Sunday. An old front will also move through the state through early Saturday, bringing some wet weather to the islands. An area of low pressure west of the state will cause mostly cloudy conditions across the area through the middle of next week. A wet weather pattern could develop around the Christmas holiday, but confidence in the details remains low at this time. && .DISCUSSION... A 1033 mb surface high is centered around 1200 miles north northwest of Kauai, while an old front is located around 50 miles north of Kauai. Water vapor imagery shows an upper level low developing area of low pressure is located around 1200 miles west of the state. Infrarred and visible imagery shows a combination of low clouds and numerous showers moving onto Kauai from the old front (ushered in by the trades) and convective debris cirrus streaming overhead along the eastern edge of the system west of the area. Partly cloudy skies persist across the eastern half of the state. The high will shift eastward well to the north of the islands during the next few days while the old frontal band pushes through the island chain through Saturday. The upper low will lift northward well to the west of the state. Winds are expected to really ramp up along and behind the old remnant front as it pushes through the islands. Very windy conditions are expected to overspread the state tonight through Saturday and possibly linger into Sunday. As a result, a Wind Advisory is now in effect through 6 PM this evening, and a High Wind Warning is in effect from 6 PM this evening through 6 PM Saturday. More uncertainty in the wind forecast begins next week. The GFS drags a front into the island chain during the middle to latter part of the week, while the ECMWF keeps the front west of the state. Given the continued uncertainty in the forecast, will follow a middle of the road solution which results in breezy to windy trades through early next week, with winds shifting around to the southeast and easing during the middle and latter part of the week. As for weather details, trade wind weather will continue through early next week, with an increase in shower coverage and intensity as the old front passes by northwest to southeast today through Saturday. Behind the frontal remnants, it appears that conditions will dry out a bit, with a decrease in shower coverage expected Saturday night. We should see the airmass gradually moisten up by Sunday, with a more typical trade wind shower pattern then expected through the first half of next week. Much uncertainty continues in long range portion of the forecast, with the GFS indicating some heavy rainfall and thunderstorms could be in store for the area Christmas Day through Thursday, while the ECMWF keeps the heaviest rain and thunderstorms west of the state. A considerable amount of mid and high cloud cover is expected today through much of next week. As a result, mostly cloudy conditions will be common statewide. Some thinning in the clouds can be expected at times, but timing the days with more sunshine filtering through will be difficult to pin down until the models come into better agreement. && .AVIATION... A strengthening surface high to the north northwest of the state, combined with a strengthening surface low west of the state, will lead to breezy to windy east northeast trades today. Moderate turbulence is likely today along the leeward side of the mountains with moderate to isolated severe turbulence expected late this evening and into tonight as very windy conditions develop. A dissipating front north of Hawaii will move southward today. This feature will bring thicker cloud cover and more widespread precipitation to Kauai this afternoon, then Oahu this evening into tonight. MVFR conditions and mountain obscuration are likely as shower or squall activity moves through. AIRMET Tango remains in effect for areas over and immediately south thru west of mountains for all islands below 8000 feet due to tempo moderate turbulence. && .MARINE... Strong high pressure is building in north of the area. This will result in rather strong trade winds and rough seas resulting in rather hazardous boating conditions across most of the Hawaiian Coastal Waters. A Gale Warning is currently posted for waters north and west of Kauai and Oahu. This is expected to be expanded to the remaining coastal waters by tonight. Winds are expected to gradually diminish beginning Sunday. However, winds and seas will likely remain elevated enough requiring a Small Craft Advisory for most areas on into early next week. The strong trade winds will produce rather large and rough surf along east facing shores through Sunday. Thus a High Surf Advisory is currently in effect. With the expected drop off in trade winds early next week, surf heights will gradually diminish as a result but are still expected to remain rather elevated. There will be a series of small north and northwest swells through the weekend and on into the middle of next week. Wave Watch III model guidance indicates that none of these swells will be capable of producing advisory level surf. No other significant swells are expected. && .HFO WATCHES/WARNINGS/ADVISORIES... High Wind Warning from 6 PM this evening to 6 PM HST Saturday for Niihau-Kauai-Oahu-Molokai-Lanai-Kahoolawe-Maui Windward West- Maui Leeward West-Maui Central Valley-Windward Haleakala-Leeward Haleakala-Kona-South Big Island-Big Island North and East-Kohala- Big Island Interior. Wind Advisory until 6 PM HST this evening for Niihau-Kauai-Oahu- Molokai-Lanai-Kahoolawe-Maui Windward West-Maui Leeward West- Maui Central Valley-Windward Haleakala-Leeward Haleakala-Kona- South Big Island-Big Island North and East-Kohala-Big Island Interior. High Surf Advisory until 6 PM HST Sunday for Kauai Windward-Oahu Koolau-Olomana-Molokai Windward-Maui Windward West-Windward Haleakala-South Big Island-Big Island North and East. Wind Advisory until 6 PM HST Saturday for Haleakala Summit. Gale Warning until 6 PM HST Saturday for Kauai Northwest Waters- Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu Windward Waters. Small Craft Advisory until 6 PM HST this evening for Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. Gale Warning from 6 PM this evening to 6 PM HST Saturday for Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters- Maui County Leeward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Foster AVIATION...Thomas MARINE...Burke