Hawaii Island Weather Update for November 23rd, 2020
A Flash Flood Watch has been issued for the Island of Hawaii through Wednesday morning (November 25th). More wet weather with the possibility of heavy rains and thunderstorms in some areas is expected through Wednesday.
Published by: HIRSC - Weather Team
info@hiradioscannercommunity.com
FLASH FLOOD WATCH IN EFFECT FROM 6 PM HST THIS EVENING THROUGH
LATE TUESDAY NIGHT...
.Recent and persistent rainfall, especially over the east end of
the island chain, has caused soils to become saturated and streams
to be elevated along windward areas of Maui and the Big Island. An
upper trough moving into the area along with abundant low level
moisture, creates the potential for flash flooding.
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...FLASH FLOOD WATCH IN EFFECT FROM 6 PM HST THIS EVENING THROUGH
LATE TUESDAY NIGHT...
The National Weather Service in Honolulu has issued a
* Flash Flood Watch for Maui and the Big Island.
* From 6 PM HST this evening through late Tuesday night
* Saturated soils along with potentially heavy or persistent
rainfall.
* Windward areas will have a greater potential for flooding
rainfall.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
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.
Monitor later forecasts and be prepared to take action if a Flash
Flood Warning is issued. If you experience heavy rain or rising
water, head to higher ground immediately.
National Weather Services (NWS) - Outlook for the State of Hawai'i
Synopsis
Breezy trade winds will continue Tuesday with a gradual decline during the second half of the week. Moisture riding in on the trades will focus showers mainly over windward and mauka areas. An upper trough moving in from the west will help to spark a few thunderstorms through Wednesday. A weak frontal band may move across the area late Friday or Saturday accompanied by a period of showers. A cool and dry airmass will follow in the fronts wake.
Discussion
Anticipate an update to the forecast shortly due to a refinement of the thunderstorm areas for the next couple of days. The driving force for thunderstorms will be from an upper level trough moving in from the west. Overall have expanded the area where thunderstorms may occur based on the latest model guidance, including some of the higher resolution models, through Wednesday. Additionally, a thunderstorm did develop over the Kona slopes this afternoon, and will similar conditions expected tomorrow, have added thunderstorms there for tomorrow afternoon. In general, the threat for thunderstorms will follow the upper level trough axis as it swings in from the west tonight, and then moves over the central islands Tuesday afternoon/evening. The latest runs show the trough holding together a little more as it reaches the Big Island, which in part explains the expansion of the thunderstorm areas. High pressure to the far north-northeast continues to bring breezy trade winds to the region. Although winds are expected to gradually decrease as the high weakens, they have been a little slower to decrease than originally expected. Showers will continue to be carried in on the trade winds, and in areas on Maui and the Big Island which have received a decent amount of rain recently, there is the possibility of flooding. A Flash Flood Watch is in effect for those islands, with the greatest concern being on the windward sides of the islands. At this time, it looks like some drier weather over the islands for Thanksgiving, in a more typical trade wind weather pattern. Trade winds are expected to once again be on the increase over the next weekend as high pressure builds north of the state. The increasing trades may help to push a dissipating front over the islands late Friday or Saturday, leading to a period of increased in showers primarily over northeast facing slopes. A cooler and drier airmass will follow in the fronts wake Saturday night and Sunday.