Current Conditions | ||
Temp | ![]() | 0.2 C |
RH | ![]() | 13 % |
Wind | ![]() | E 8 mph |
Road | ![]() | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 992 FXHW60 PHFO 241351 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 351 AM HST Sun Jan 24 2021 .SYNOPSIS... Strong high pressure northeast of the area will maintain locally strong trade winds over the islands through much of the coming week. Windward areas will remain rather rainy. Rainfall will likely become more widespread tonight through Wednesday as a low aloft deepens northwest of the area. && .DISCUSSION... A strong 1041 mb high far north of the area is producing locally strong northeast to east trade winds over the main Hawaiian Islands. Windward areas have broken low clouds, while leeward areas have partly cloudy skies. Radars show numerous showers moving over windward areas with some of these showers spreading leeward on the smaller islands. These conditions will continue through the day today The global models show a northwest to southeast trough aloft deepening west of the islands over the next few days. This trough will destabilize the atmosphere over the islands. The trough will also cause the low level flow to veer out of the southeast and bring very moist air towards the islands. Increased rainfall is likely starting tonight, especially over the Big Island of Hawaii. The global models disagree on how much of the moisture will move over the islands, so there is quite a bit of uncertainty in how widespread and heavy the rainfall will be. The global models show the trough aloft lifting northwest starting Wednesday night as a ridge aloft builds over the area from the north. The atmosphere over the islands will become more stable and the moist air will move away to the west. That should bring a decrease in rainfall for the second half of the week, with showers focused over mainly windward areas. && .AVIATION... A strong high pressure system far north of the islands will maintain locally windy east to southeast winds through Monday. Scattered to numerous rain showers remain in the forecast today with the highest shower coverage developing over mountains and along east facing slopes. Expect brief periods of MVFR conditions in showers along the eastern slopes of most islands, extending into the southeastern slopes of the Big Island. AIRMET SIERRA remains in effect for Tempo Mountain Obscuration above 2500 feet along north through east sections of Oahu and Kauai due to MVFR ceilings in showers. AIRMET TANGO remains in effect for Moderate Turbulence below 8000 feet over and immediately southwest through northwest of all island mountains. && .MARINE... Strong east-southeast winds associated with high pressure will continue over the Hawaiian waters through the upcoming week. Rough conditions with seas at and above the Small Craft Advisory level of 10 ft will be the result across exposed waters. Surf along east facing shores will remain rough due to the aforementioned strong onshore winds locally and upstream across the eastern Pacific driving large seas through the area. The advisory in place will continue through much of the week. Surf along north and west facing shores will steadily lower through Monday as the northwest swell eases. Heights should dip below advisory levels for all exposed north and west facing shores by tonight. Large scale pattern change across the Pacific featuring a blocking pattern setting up east of the Date Line will translate to an end to the active period that began in the second half of December. Surf will respond and drop well below the January average Monday through midweek (near flat levels except for areas exposed to trade wind energy). For the long range, guidance shows the current storm developing off the coast of Japan tracking northward tonight through Wednesday across the far western Pacific to the western Aleutians/Bering Sea. Wave models reflect this and show small, long-period energy arriving through the day Thursday out of the west-northwest, then trending up out of the northwest Friday and Friday night. Large errors typically associated with these sources lead to low forecast confidence. Surf along south facing shores will trend up Tuesday through midweek, as an out-of-season Tasman source arrives. Nearshore PacIOOS buoy at Samoa reflected this source moving through 24 to 48 hrs ago, which increases confidence locally. Surf should drop and return to normal levels through the second half of the week. && .HFO WATCHES/WARNINGS/ADVISORIES... Winter Weather Watch until late Tuesday night for the summits of Mauna Loa and Mauna Kea on the Big Island of Hawaii. High Surf Advisory until 6 PM today for north and west facing shores of Niihau, Kauai, Oahu and Molokai and north facing shores of Maui. High Surf Advisory until 6 PM Sunday for west facing shores of the Big Island. High Surf Advisory until 6 PM Monday for east facing shores of Kauai, Oahu, Molokai, Maui and the Big Island of Hawaii. Small Craft Advisory until 6 PM Wednesday for all Hawaiian waters. && $$ DISCUSSION...Donaldson AVIATION...Bohlin MARINE...Gibbs Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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