Current Conditions | ||
Temp | ![]() | -3.0 C |
RH | ![]() | 54 % |
Wind | ![]() | SSW 8 mph |
Road | ![]() | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 073 FXHW60 PHFO 071404 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 404 AM HST Sun Mar 7 2021 .SYNOPSIS... Unsettled weather is likely for the upcoming week as an upper level disturbance interacts with tropical moisture. Breezy trade winds will give way to light and variable winds by mid week as a surface trough forms over the state. Strong northeast winds will then follow Friday over Kauai, and to the remaining islands over next weekend. && .DISCUSSION... Although the evening has been rather tame, there are a couple of spots that we are watching closely. The two areas are windward Kauai and windward Haleakala above Hana, where heavy showers are occurring. There has been a significant shift in the wind forecast during the second half of the week. Instead of strong and gusty trade winds through the week, models are suggesting a surface trough forming over the islands Tuesday and remaining in the vicinity of the state through Friday. Strong and gusty northeast winds are expected to build back in to the area next weekend as high pressure passes north of the islands. Another addition to the forecast is a slight chance of thunderstorms has been introduced for the Big Island and windward Maui starting this afternoon and remaining in forecast through at least Monday. The rest of the forecast package is pretty much the same, that is it will be showery for most of the week. This prolonged period of unsettled weather will likely warrant a Flash Flood Watch for most if not all of the islands and a Winter Weather Advisory for the Big Island Summits. An east to west oriented upper level trough with cold temperatures of around minus 13 degrees C is located just north of the islands this morning. An upper low is forecast to form later today west of Kauai as enhanced low level moisture moves toward the Big Island from the southeast. This moisture will then spread up the island chain through Monday night. The upper low then drifts over the islands by Wednesday night and stalls through Friday. The combination of the cold temperatures aloft and the moist air mass near the surface will likely result in an extended period of heavy rains and possible thunderstorms. && .AVIATION... FR conditions prevail at all TAF sites with some brief periods of MVFR conditions at PHLI and PHTO in low clouds and shra. Expect these conditions to continue into the morning hours. AIRMET Sierra is currently in effect for Kauai, Maui and the Big Island due to mountain obscuration. They will be brief periods of MVFR conditions elsewhere along windward slopes through into the morning hours as low clouds interact with island terrain. AIRMET Tango is currently in effect over and immediately south thru west of mountain ranges due to low level mechanical turbulence. && MARINE... The center of a strong surface high pressure system is located more than 1000 nautical miles north of Honolulu early this morning. The forecast guidance continues to indicate the pressure gradient will gradually tighten south of this feature as it moves toward the southeast during the next couple of days. This will produce strong and gusty trade winds across most waters into Tuesday. The strong trade winds are causing the local wind waves to increase over exposed waters. These wind waves combined with a modest north swell are also producing elevated seas over most waters. As a result, a Small Craft Advisory (SCA) is now in effect through early Monday morning for all Hawaiian waters. Expect the SCA to be extended beyond Monday morning for all Hawaiian waters, since the trade winds and elevated seas will likely persist through Monday night. Also, there is a slight chance of thunderstorms in the vicinity of the Big Island from this afternoon through Monday. The strengthening trade winds will likely cause surf to increase along east facing shores from later today and tonight through Monday. As a result, expect a High Surf Advisory (HSA) to be issued for most east facing shores starting tonight or Monday. Once this HSA is issued, it will likely remain in effect for the first few days of the new work week. The latest guidance from the various forecast models is starting to reach some agreement that a surface trough may develop in the vicinity of the islands around mid-week. Assuming this feature does develop, it would likely cause the winds to trend down over some areas by late Tuesday or Wednesday. Stay tuned for updates to future coastal waters forecasts as this scenario continues to become less ambiguous. The current north swell, which was mentioned above, is forecast to slowly decrease today. A small north-northwest swell and a reinforcing north swell are expected to spread across the area later today and tonight. These swells will likely maintain medium surf heights along most north and west facing shores through Monday. As these north-northwest and north swells gradually diminish, expect relatively small surf heights along most north and west facing shores from Tuesday into next weekend. Small, long-period south-southwest swells will maintain small background surf along most south facing shores through Friday. Note that some of the trade wind wrap may produce a localized boost in surf heights along some exposed south and north facing shorelines later this week. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Monday for all Hawaiian waters. && $$ DISCUSSION...H Lau AVIATION...Morrison MARINE...Houston Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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