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Hawaii Island Weather Outlook for January 23rd, 2021

Wind Advisory for parts of Hawaii Island remains in effect until Sunday morning (January 24th).

The potential for heavy rainfall (wet weather) is likely for Hawaii Island to begin Sunday evening and continue through mid-week. Snowfall is possible for the summits of Maunakea and Mauna Loa as well.

Published by: HIRSC - Weather Team


* WHAT...East winds 20 to 30 mph, with gusts to 50 mph.

* WHERE...Kahoolawe. Portions of the Big Island, including areas
  along the Hamakua Coast and near South Point. Portions of Maui,
  including areas along the northern and southern slopes of
  Haleakala, as well as the northern coast of West Maui. Portions
  of East Molokai, over and immediately downwind of the mountains.

* WHEN...Until 6 AM HST Sunday.

* IMPACTS...Winds this strong are capable of downing tents or
  other temporary structures, as well as downing trees and
  causing power outages.


Motorists, especially those in high profile vehicles, are urged
to drive with extra caution.



The combination of deep tropical moisture and a disturbance aloft,
could bring periods of heavy rainfall to the state Sunday night
through Wednesday. Heavy rainfall could reach the Big Island as
early as Sunday night, potentially spread to smaller islands on
Monday, with the unsettled weather possibly lingering through the
middle of the week. Although many places are expected to receive
rain, possibly heavy at times, the heaviest rainfall could very well
pass by just to the south of the state.
If it becomes more clear that heavy rainfall and flash flooding
could impact portions or all of the state, a Flash Flood Watch may
eventually be required.

Keep up to date with the latest forecast information through the
Internet (, local media, social media, or NOAA
Weather Radio broadcasts. An updated Hydrologic Outlook will be
issued by 6 AM HST Sunday, if necessary.

Area Forecast Discussion for Hawai'i as of 8:46 pm Saturday evening:


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 Sunday night through Wednesday as a low aloft deepens northwest of the area.


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 to overcast 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 Sunday. 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 surface winds to veer south of east and bring very moist air towards the islands. Increased rainfall is likely starting Sunday night, 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.


Maunakea and Mauna Loa Summits Forecast as of 10:00 pm Saturday evening:

Maunakea Forecast:

Mauna Loa Forecast:

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