Hawaii Island Weather Update for March 1st, 2020
Wet, Windy and Unsettled conditions are expected to persist through Monday and slowly improve through the week. Gusty trade winds along with moderate to heavy showers have been happening throughout East Hawaii and occasionally crossed over into West Hawaii districts.
A handful of weather advisories remain in effect for Hawaii Island.
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Report from: HIRSC Team - Utah Section/Weather Unit
info@hiradioscannercommunity.com
Synopsis
Windy trade winds can be expected over the next couple of days thanks to strong high pressure far north northeast of the state. An unstable airmass across the area caused by an upper level low will allow for some locally heavy showers and possible thunderstorms today. The high and the upper low will weaken over the next few days with trade winds diminishing and the airmass becoming more stable. A new strong high will build in far north of the area later in the week with trade winds strengthening once again. Passing showers will tend to favor windward and mauka areas and be highly dependent on incoming moisture availability.
Discussion
Strong high pressure is centered far north northeast of the state. This places the islands in a rather windy trade wind environment. Meanwhile, an upper-level low is centered just to the east of the Big Island. This is causing the air mass to be rather unstable in the island vicinity. Satellite and radar imagery shows numerous showers embedded within the trade wind flow providing for passing showers across most of the state, especially for windward and mauka areas. The instability is allowing for some thunderstorm development with lightning being detected mainly over the waters just to the north and east of the state. Thus we can expect passing showers and possible thunderstorms to occur today especially over the east end of the state which lies closer to the upper low. A Winter Weather Advisory is in place for the high summits of Maui and the Big Island while a Wind Advisory is in place for most areas of the state. The surface high will remain nearly stationary over the next few days while gradually weakening. This will allow for a lowering in wind speeds across the area. Meanwhile, the upper low will also be weakening while drifting northwestward. This will eventually allow for a more stable airmass in the island vicinity. Showers will still tend to favor windward and mauka areas but the threat for thunderstorms will be diminished. Trade winds will diminish even more Wednesday and Thursday as a frontal system passes by far north of the state. Some passing showers will remain in the forecast mainly for windward and mauka areas. A new strong high will build in north of the area on Friday with trade wind speeds ramping back up to breezy to locally windy levels. Showers will continue to favor windward and mauka areas with the winds sufficiently strong enough to blow some showers over to leeward areas at times. Shower frequency will be high dependent on incoming moisture availability.
Aviation
High pressure sitting stagnant north of the islands will continue to produce moderate to strong northeasterly trade winds today across the islands. A low-pressure system centered slightly east of the islands will bring an increase in shower activity, mainly affecting the windward sections, though a few showers could spill over the terrain and into leeward areas a well. In addition, isolated thunderstorms may occur due to the unstable air aloft associated with this feature. Periods of MVFR conditions will be present along the windward sides of the islands with isolated MVFR conditions on the leeward sides due to mountain obscuration from low clouds and showers. AIRMET Sierra remains in effect for mountain obscuration across windward sections of Molokai, Maui, and the Big Island. These conditions should improve later this morning. AIRMET Tango remains in effect for low-level turbulence over and downwind of the terrain of all islands. These conditions will likely persist through this evening.
Marine
Strong east-northeast trades associated with a robust high far northeast of the state will continue into Monday before trending down. Pailolo and Alenuihaha Channels, Maalaea Bay and waters around South Point on the Big Island will remain near gale-force levels through this time. In addition to the blustery conditions, showers and thunderstorms associated with an upper low in the area will continue to impact the area, especially the windward waters. Some of these showers and storms will produce winds in excess of 35 knots and locally higher seas. Guidance shows a surface trough approaching and moving through the waters from east to west through the first half of the week. Winds and seas should respond and begin to trend down locally. Surf along east facing shores will steadily rise through the day due to the strong trades over and upwind of the islands. Heights may climb toward warning levels by tonight. If seas climb to levels well above predicted, a warning will become a possibility for east facing shores. Surf along north and west facing shores will continue to lower today as the northwest swell fades. This will be the beginning of a quiet stretch for north and west facing shores, which may continue through the week. Some of the trade wind energy, however, may wrap into exposed north facing shores each day. Surf along south facing shores will remain small with mainly background southerly swells moving through.
HFO Watches/Warnings/Advisories
Wind Advisory until 6 AM HST Monday 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 Monday for Kauai Windward, Oahu Koolau, Olomana, Molokai Windward, Maui Windward West, Windward Haleakala, South Big Island, Big Island North and East. Winter Weather Advisory until 6 PM HST this evening for Haleakala Summit, Big Island Summits. Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters.
WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 6 PM HST THIS EVENING * WHAT...Freezing rain expected. Some snow expected on the Big Island summits. Additional snow accumulations of up to 3 inches. Winds gusting as high as 40 mph. * WHERE...Haleakala Summit and Big Island Summits. * WHEN...Until 6 PM HST this evening. * IMPACTS...Travel could be very difficult, leading to road closures. Summit roadways will likely become dangerously slippery due to patches of ice mixed with areas of snow, with reduced visibility at times. PRECAUTIONARY/PREPAREDNESS ACTIONS A Winter Weather Advisory means that periods of snow, sleet, or freezing rain will cause travel difficulties. Postpone travel plans to the summits until weather conditions improve, as warmer and drier conditions are expected by Monday.
HIGH SURF ADVISORY REMAINS IN EFFECT UNTIL 6 PM HST MONDAY * WHAT...Surf will be 8 to 12 feet. * WHERE...East facing shores of Kauai, Oahu, Molokai, Maui and the Big Island. * WHEN...Until 6 PM HST Monday. * IMPACTS...Moderate. Strong breaking waves and currents will make entering the water dangerous. Several days with these conditions will likely lead to significant beach erosion in some areas. PRECAUTIONARY/PREPAREDNESS ACTIONS... Beachgoers, swimmers, and surfers should heed all advice given by ocean safety officials and exercise caution.
WIND ADVISORY REMAINS IN EFFECT UNTIL 6 AM HST MONDAY * WHAT...Northeast to east winds 20 to 35 mph with gusts near 50 mph with stronger gusts possible in showers. * WHERE...All areas except the summit of Haleakala on Maui, and the highest summits on the Big Island. * WHEN...Until 6 AM HST Monday. * IMPACTS...Winds this strong are capable of causing localized power outages, downing tents or other temporary structures, as well as breaking tree branches. PRECAUTIONARY/PREPAREDNESS ACTIONS Motorists, especially those in high profile vehicles, are urged to drive with caution. Secure trash cans, lawn furniture, and other loose objects that can easily be blown around by strong wind gusts.
Maunakea Access Road Information Update for March 1st, 2020 @ 13:25 (1:25 pm):
Aloha, The access road to the summit of Maunakea is closed at the Visitor Information Center at an elevation of 9,200 feet due to below freezing temperatures, high humidity, snow, and icy road conditions. The latest forecast also calls for more ice, snow flurries, and fog. We are currently under a Winter Storm Advisory until 6:00 p.m. today. Road and weather conditions will continue to be monitored and this message will be updated as these conditions change. Maunakea Rangers thank you for your patience and understanding. Mahalo, Maunakea Rangers