Current Conditions | ||
Temp | ![]() | 1.8 C |
RH | ![]() | 29 % |
Wind | ![]() | NNE 12 mph |
Road | ![]() | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 582 FXHW60 PHFO 170224 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 424 PM HST Sat Jan 16 2021 .SYNOPSIS... Wet weather is on the way as a strong cold front approaches the state Sunday into Monday. This front will quickly advance down the island chain Sunday night, then stall around the Big Island Monday through Tuesday. Heavy showers and isolated thunderstorms will be possible along and ahead of this front. Cool and strong northerly winds are expected following the frontal passage over the western end of the state early next week. Trade winds may return late next week. && .DISCUSSION... As a strong cold front approaches the state Sunday, we will see the winds shift toward the south and southwest on Sunday. By Sunday afternoon, the front is expected just northwest of Kauai and will begin to bring the threat of heavy rain and isolated thunderstorms. The cold front is expected to continue to move down the island chain Sunday night through Monday with the threat of heavy rain and isolated thunderstorms along and ahead of the front. Right behind the front, we will see gusty northerly winds (potentially reaching advisory levels beginning Sunday night) and cool conditions will follow with dewpoints dipping into the 50s for Kauai and Oahu. There remains subtle differences in the global models on how far east the front will progress before stalling. But the GFS and ECMWF remains in fairly good agreement with he front stalling near Maui or the Big Island. Either way, the Big Island and Maui will remain rather wet on into Wednesday, which could result in localized flooding concerns. Winter weather conditions are also expected over the Big Island summits as early as Monday, but more likely by Monday night into midweek due to a combination of the deep moisture axis associated with the front hanging up or stalling and cold temperatures aloft arriving with the shortwave trough. A Winter Storm Watch could be possible for the summits if the boundary looks to set up over the Big Island. As we head on into Thursday, high pressure will build in northeast of the area resulting in strengthening trade winds. Moisture associated with the frontal boundary is then forecast to move back westward likely providing for a wet trade wind pattern to set up across the state. With the differences in the long range models continuing, changes to the forecast our possible next week. && .AVIATION... Light to moderate easterly trades will persist through this afternoon, then shift to southeasterly tonight ahead of an approaching frontal system. Expect shower activity to increase slightly tonight, as moisture deepens, with brief periods of MVFR ceilings and visibility possible. By late in the day on Sunday, the aforementioned front will begin to push across Kauai and bring scattered to numerous showers and a slight chance of thunderstorms. No AIRMETs are currently in effect. && .MARINE... In summary, expect giant surf to continue through the island chain tonight and decline tomorrow. A potent cold front will move down the island chain late tomorrow night into Monday. Another large NW swell will fill in Monday. High Surf Warning is in effect as the largest NW swell of the winter season rapidly moves down the island chain, with peak surf heights of 40 to 50 feet (with locally higher waves) along exposed shores tonight and into tomorrow. PacIOOS Waimea buoy swell heights and period have been on the rise all day and currently at 16 feet 18 seconds. Offshore NDBC 51001/51101 buoys have started to show a slow decline in swell height which are now running in the 18 feet 17 second range. The swell may have peak already for Kauai. The swell is still anticipated to peak late this afternoon to early evening for Oahu, and in the evening for Maui. A High Surf Advisory remains in effect for exposed N and W facing shores of the Big Island as the swell is expected to peak locally overnight. The swell will gradually diminish from NW to SE tonight through Sunday night, but a new NW swell arriving Monday will likely push surf to warning levels once again, with peak surf heights lower than today's swell. The Small Craft Advisory is still in effect for most waters except Maalaea Bay, as E/SE winds have eased below SCA criteria, but seas continue to build around the islands due to the giant NW swell moving through the island chain. A Marine Weather Statement is in effect due to the potential for surges and significant wave action in and near exposed harbors. Due to the period and size of the NW swell, some (much reduced) swell may wrap into select S and E facing shores. A vigorous cold front will rapidly approach the islands from the NW, tomorrow and tomorrow night, providing a brief period of light to moderate S to SW winds. The front will initially bring the potential for locally heavy showers and slight chance of thunderstorms as it moves relatively quickly through Kauai and Oahu Sunday night, and then slows to a stall and dissipates over Maui County and the Big Island Monday. A Gale Watch is in effect for all coastal waters around the smaller islands as a strong high to the NW of the islands will continue to support strong to gale force NE winds behind the front. The moisture from the dissipated frontal boundary may retrograde back west Tuesday as an upper level trough moves over the islands from the NW. This setup may increase the potential for heavy showers trade showers and thunderstorms along the remnant boundary through mid-week. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Warning until 6 PM HST Sunday for Niihau-Kauai Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu Koolau-Olomana-Molokai-Maui Windward West-Maui Central Valley- Windward Haleakala. High Surf Advisory until 6 PM HST Sunday for Kona-Big Island North and East-Kohala. Small Craft Advisory until 6 PM HST Sunday for all Hawaiian waters except Maalaea Bay- Gale Watch from Sunday evening through late Monday night for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters- Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel. && $$ DISCUSSION...Kino AVIATION...Thomas MARINE...Almanza Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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