Hawaii Island Weather Outlook for January 24th, 2021

A Flash Flood Watch for the Island of Hawaii will go into effect later this evening (Sunday, January 24th). The windward side of Hawaii Island will see the potential for heavy rainfall and flash flooding to occur, however, wet weather is expected islandwide.


Also, a Winter Storm Watch has been issued for the summits of Maunakea and Mauna Loa through Tuesday evening (January 26th), with snowfall being the heaviest being tonight through Monday.

Published by: HIRSC - Weather Team

info@hiradioscannercommunity.com


FLASH FLOOD WATCH IN EFFECT FROM 6 PM HST THIS EVENING THROUGH
TUESDAY AFTERNOON...

The National Weather Service in Honolulu has issued a

* Flash Flood Watch for the Big Island.

* From 6 PM HST this evening through Tuesday afternoon

* Abundant moisture moving in from the southeast will bring the
  threat of flash flooding tonight through Tuesday afternoon for the
  Big Island. The greatest areas of risk will be over windward and
  mountain areas, especially the Hilo, Puna and Kau districts.

* Flood prone roads and other low lying areas may be closed due to
  elevated runoff and overflowing streams. Urban areas may receive
  more significant flooding and property damage due to rapid runoff.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

Be prepared to take action if a Flash Flood Warning is issued. If
you experience heavy rain or rising waters, head to higher ground
immediately.

A Flash Flood Watch means that conditions are favorable for flash
flooding. Flash Flooding is LIFE THREATENING. Do not cross fast
flowing water in your vehicle or on foot.
WINTER STORM WATCH IN EFFECT FROM THIS EVENING THROUGH TUESDAY
AFTERNOON...

* WHAT...Heavy snow possible. Total snow accumulations over 12
  inches possible. Winds could gust as high as 40 mph.

* WHERE...Summits of Mauna Kea and Mauna Loa above 11500 feet.

* WHEN...From this evening through Tuesday afternoon.

* IMPACTS...Travel could be very difficult or impossible.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Watch means there is potential for significant snow
or ice accumulations. If you are planning travel to the summits,
monitor the latest forecasts and consider postponing your trip
until the weather improves.

Maunakea Forecast as of 10:00 am Sunday morning:

Mauna Loa Forecast as of 10:00 am Sunday morning:

Hydrologic Weather Outlook for Hawai'i:

A FLASH FLOOD WATCH HAS BEEN ISSUED FOR THE BIG ISLAND...

Abundant moisture moving in from the southeast will bring the threat
of flash flooding tonight through Tuesday afternoon for the Big
Island. The greatest areas of risk will be over windward and
mountain areas, especially the Hilo, Puna and Kau districts.

Higher confidence in the heavy rainfall and flooding threat has led
to the issuance of a Flash Flood Watch for the Big Island starting
tonight.

This will be the final Hydrologic Outlook issued for this event.
Further hydrologic threat information will be covered by flash flood
watches, flash flood warnings and flood advisories as conditions
warrant.

Keep up to date with the latest forecast information through the
Internet (weather.gov/hawaii), local media, social media, or NOAA
Weather Radio broadcasts.

Area Forecast Discussion for Hawai'i as of 10:10 am Sunday morning:


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.

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