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Hawaii Island Weather Update for March 11th, 2021

A Flash Flood Watch for the Island of Hawaii has been extended through Friday evening (March 12th).

Published by: HIRSC - Weather Team

info@hiradioscannercommunity.com

FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH FRIDAY AFTERNOON...

The Flash Flood Watch continues for

* Niihau, Kauai, Oahu, Molokai, Lanai, Maui, Kahoolawe and the Big
  Island.

* Through Friday afternoon

* A low west of Kauai will keep the atmosphere moist and
  unstable, maintaining the potential for locally heavy
  rainfall.

* Significant flooding may occur due to the overflow of streams
  and drainages. Roads in several areas may be closed, along
  with property damage in urban or low lying spots due to
  runoff. Landslides may also occur in areas with steep terrain.

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.

 

Synopsis

A wet pattern could linger into the weekend as deep tropical moisture pools northward over the state in response to low pressure west of the area. Saturated grounds and elevated water levels in streams will keep the threat for flash flooding up across the state through Friday, especially over the western end. Light to moderate southerly winds will hold through Friday, then shift out of the north-northeast and become strong over the western end of the state by Saturday as high pressure builds to the north behind a cold front.

Discussion

Deep tropical moisture pooling northward across the state due to an upper trough and surface low positioned to the west will keep the threat for heavy rainfall and flash flooding in the forecast through Friday. Although the threat for localized flooding will remain in place statewide, the best chance will remain over Oahu and Kauai where the better instability is located. As a result, the Flash Flood Watch (FFA) remains in effect through 6 PM HST Friday statewide. In addition to the rainfall, the aforementioned instability associated with the upper trough will be enough to trigger thunderstorms periodically. Guidance depicts the low- level flow remaining in the light to moderate range out of the southerly direction into tonight, then shifting out of the southwest Friday as the surface low to the west begins to lift off to the northeast. Winds should be light enough to keep the land and sea breeze pattern in place through this time. The extended guidance shows the surface low lifting off to the northeast this weekend as a shortwave trough dives southeastward into the area and a cold front passes to the north. Strong high pressure (1040 mb) building to the north in the wake of the front will translate to strong north-northeast winds over the western end of the state beginning Friday night/Saturday. Light winds, however, may linger over the eastern end of the state as the tail- end of the front stalls nearby to the north of the Big Island. Forecast confidence diminishes for early next week due to large differences shown between model solutions.

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