| Current Conditions | ||
| Temp |  | 0.9 C |
| RH | | 25 % |
| Wind | | ESE 7 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 621 FXHW60 PHFO 250639 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 839 PM HST Mon Jul 24 2017 .SYNOPSIS... A drier, more comfortable trade wind regime will be building across the area tonight and Tuesday as high pressure strengthens across the area. And this regime will persist into the upcoming weekend. Showers riding in with the trades will favor the windward and mountain areas. Lee areas of the smaller islands will be dry. Leeward Big Islands will get their usually afternoon and evening clouds and scattered showers. && .DISCUSSION... The uncomfortable air mass brought on by the remnants of tropical cyclone Fernanda continues to exit the main Hawaiian Island this evening. It is being nudged out by a much more comfortable trade wind air mass. There is a sign that this air mass is here, by noting the dew point reading from Kahului airport where it has lowered from 74 degrees at 4 pm HST to 71 at 7 pm. Also, the the trades are apparently back, blowing out of the NE at 13 mph with gust to 22 at Kahului Airport. The upper level trough that aided with the flare ups of thunderstorms earlier this morning, is still located 240 miles west of Kauai this hour. The models are weakening this trough overnight and into Tuesday. Thus, it will no longer be a factor to our local weather. The shower activity over on Oahu will continue to subside in the next hour. Expect trade wind showers to take over after midnight on Oahu. The last of the tropical elements should vacate Kauai by noon Tuesday. Once the trades become established, it will be here for the rest of the week with precipitable water (PW) values of around 1.50, 1.65 inches. These values translate to more or less of a typical trade wind regime with showers likely for the nights and mornings across the windward and mountain areas, and drier during the afternoon hours. A light shower or two will leak over into the lee areas of the smaller islands, particularly during the nights and morning. Lee side of the Big Island will maintain their usual afternoon clouds and scattered showers, lasting well into the night, but shifting from the interior to along the coast as the evening progresses. The return of the trades will be that of a nice breeze, at moderate to locally strong speeds. The trades then ease off slightly to moderate speeds on Wednesday night. This comes after the surface high supplying the islands weakens slightly from 1031 mb to 1029 mb some 1300 miles NE of the islands. It remains at moderate speed to until Friday night when the trades strengthens to locally strong for the weekend. && .AVIATION... A low pressure system, associated with the remnants of Fernanda, will continue to move north away from the state tonight. Moderate trade winds will return to the islands by morning bringing drier and more stable air to the region. Expect mostly VFR conditions with a few areas of low clouds lingering in the overnight hours. There are no AIRMET's in effect. However, stronger winds may produce low level turbulence over and downwind of mountain ranges by Tuesday afternoon. && .MARINE... The trade winds are gradually spreading across the area from east to west this evening as the remnants of Fernanda, located just west of Kauai, moves further away from the islands. The trade winds have already reached Maui with Kahului airport coming in at 15 mph and gusts to 23. The models are suggesting the trades to be locally strong once it comes in tonight. Thus, the Small Craft Advisory (SCA), slated to go into effect at 6 am HST Tuesday, will go into effect shortly at 9 pm. The SCA will continue through Wednesday night for the typically windy zones around Maui County and the Big Island. The high to the northeast is expected to weaken Thursday through the weekend, resulting in winds easing during this period. Moisture associated with the surface trough near Kauai may interact with a broad upper air feature west of the area. This interaction could result in a slight chance for thunderstorms over coastal waters northwest of Kauai. One final large high tide of the month will occur tonight. This tide may result in coastal flooding in some areas. A Special Weather Statement (see SPSHFO product on our website) is posted to highlight the potential hazards. No significant swells are expected through the week. Surf will likely remain below high surf criteria on all beaches. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory to 6 AM HST Thursday for Maalaea Bay, the Pailolo and Alenuihaha Channels, and waters south of the Big Island. && $$ DISCUSSION...Lau AVIATION...Bohlin MARINE...Kinel Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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