UPDATE: The flash flood watch is in effect tonight and Monday for Niihau, Kauai and Oahu.
Moisture associated with former tropical cyclone Howard along with an unstable air-mass will provide for the possibility for locally heavy rainfall and possible thunderstorms.
- A flash flood watch means that conditions may develop that lead to flash flooding. flash flooding is very dangerous.
- You should monitor later forecasts and be prepared to take action should flash flood warnings be issued.
A flash flood watch was issued for all islands Sunday morning through Monday afternoon.
Abundant moisture from the remnants of tropical cyclone Howard and an upper trough moving near the islands will bring a conducive environment for heavy rain and thunderstorms.
Saturated grounds from recent rain events will exacerbate the threat of flash flooding from the forecast rainfall.
The best chances for flash flooding will be over the northern end of the state.
“We do not expect the same level of rainfall as we did with Tropical Storm Darby, but with the ground still saturated from that event, heavy rains could still lead to flooding, road closures, and possible utility outages,” said Honolulu Mayor Kirk Caldwell.
Last week, city crews cleared stream heads in Laie, Hauula, Waipuhi, Pokiwai, Punaluu, and Kailua. Residents are urged not to dump green waste or other items in stream beds as they can be washed downstream during severe rains.
The city departments of environmental services and design and construction will be monitoring sewer flows throughout the storm. Oahu Transit Services is prepared to move Handi-Vans and buses from their overnight storage lot in the event of heavy rains.
If you have a flood-related emergency, call 911 immediately.
A high surf advisory is also in effect from 6 a.m. Saturday to 6 a.m. Sunday for Hawaii Island and Maui County, and noon Saturday to 6 a.m. Sunday for Oahu and Kauai.
A surface low associated with Howard will build easterly swells Saturday and produce advisory-level surf with waves expected to reach 6-9 feet along east-facing shores.
To the east of Howard is Ivette, which is currently a tropical storm.
Ivette is expected to weaken and as it nears the islands next week, it will likely also be storm remnants.
The following tips were provided by the city Department of Emergency Management:
Hawaii residents need to consider the following actions to prepare for possible flooding and flash flooding.
- Get out of areas subject to flooding. This includes dips, low spots, washes, etc.
- Avoid already flooded and high velocity flow areas. Do not attempt to cross flowing streams.
- If driving, be aware that the road bed may not be intact under flood waters. Turn around and go in another direction. Remember, turn around, don’t drown!
- If the vehicle stalls, leave it immediately and seek higher ground. Rapidly rising water may engulf the vehicle and its occupants and sweep them away. Remember, it’s better to be wet than dead!
- Be especially cautious at night when it is harder to recognize flood dangers.
- Do not camp or park your vehicle along streams and washes, particularly during threatening conditions.
- If advised to evacuate, do so immediately.
- Move to a safe area before access is cut off by flood water.
- Continue monitoring National Oceanic and Atmospheric Administration (NOAA) Weather Radio, television, or emergency broadcast stations for information.
Before the flood:
- Consider securing sand bags and other flood protection items if your home or business is in a flood prone area or has experienced flooding in the past.
- Bring in outdoor furniture and move important indoor items to the highest possible floor. This will help protect them from flood damage.
- Keep gutters and drains free of debris.
- Do not dispose of yard waste or trash into streams or estuaries. Keep them clear to alleviate flooding.
- Review your homeowner’s policies to understand what may or may not be covered by your flood insurance.
During the flood:
- Minimize vehicle travel or better yet, plan to stay at home until weather conditions improve and any watches or warnings are cancelled.
- Avoid areas subject to sudden flooding.
- If you come upon a flowing stream where water is above your ankles, STOP! Turn around and head in another direction.
- Do not open sewer or utility covers to drain flood waters.
- Children should NEVER play around high water, storm drains or viaducts.