• Tuesday, September 25, 2018
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Weather service lists potential impacts of Olivia

  • COURTESY NOAA

    This enhanced satellite image shows Tropical Storm Olivia off Maui late Wednesday morning.

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Olivia is drenching Maui County and the National Weather Service has warned of potential effects on the islands, including tropical storm-force winds over 39 mph and higher gusts; flooding rain, with isolated amounts of 15 inches possible, especially over windward areas; and high surf and storm surge spreading east to west across the islands early this week, especially for eastern shores. Weather service forecasters have issued the following list of potential impacts and preparedness advice:

Wind

Tropical storm conditions are hitting Maui County Wednesday, followed by Oahu later in the morning. Remember that wind gusts can be much stronger near higher terrain, and in the upper floors of high-rise buildings. Winds can also be especially gusty through gaps between mountains and where winds blow downslope. Protect against dangerous wind having possible significant impacts across Oahu and the islands of Maui County. Potential impacts in this area include:

>> Some damage to roofing and siding materials, along with damage to porches, awnings, carports, and sheds. A few buildings experiencing window, door, and garage door failures. Mobile homes damaged, especially if unanchored. Unsecured lightweight objects become dangerous projectiles.

>> Several large trees snapped or uprooted, but with greater numbers in places where trees are shallow rooted. Several fences and roadway signs blown over.

>> Some roads impassable from large debris, and more within urban or heavily wooded places. A few bridges, causeways, and access routes impassable.

>> Scattered power and communications outages, but more prevalent in areas with above ground lines.

>> Also, protect against hazardous wind having possible limited impacts across the remainder of the state.

Flooding rain

Showers will continue to increase over the main Hawaiian Islands Wednesday. Olivia is expected to produce total rainfall accumulations of 5 to 10 inches in some areas, with isolated maximum amounts of 15 inches possible, especially in higher terrain. This rainfall may produce life-threatening flash flooding. Up to 6 inches of rain had already fallen over parts of Maui by Wednesday morning. Protect against life-threatening rainfall flooding having possible devastating impacts across Molokai, Maui, and the Big Island. Potential impacts include:

>> Extreme rainfall flooding may prompt numerous evacuations and rescues.

>> Rivers and tributaries may overwhelmingly overflow their banks in many places with deep moving water. Small streams, creeks, canals, arroyos, and ditches may become raging rivers. In mountain areas, deadly runoff may rage down valleys while increasing susceptibility to rockslides and mudslides. Flood control systems and barriers may become stressed.

>> Flood waters can enter numerous structures within multiple communities, some structures becoming uninhabitable or washed away. Numerous places where flood waters may cover escape routes. Streets and parking lots become rivers of raging water with underpasses submerged. Driving conditions become very dangerous. Numerous road and bridge closures with some weakened or washed out.

>> Protect against life-threatening rainfall flooding having possible limited to extensive impacts across the rest of the state.

>> Much of this rainfall will be focused on windward areas of the islands, especially from Oahu through the Big Island. However, flooding is still a significant threat for all areas.

Storm surge

Large swells generated by Olivia will impact the main Hawaiian Islands through Wednesday night. This will result in dangerously high and potentially damaging surf, mainly along exposed east-facing shores. Protect against locally hazardous surge having possible impacts across east-facing coastlines of Oahu and the islands of Maui County. Potential impacts in this area include:

>> Localized inundation with storm surge flooding mainly along immediate shorelines and in low-lying spots, or in areas farther inland near where higher surge waters move ashore.

>> Sections of near-shore roads and parking lots become overspread with surge water. Driving conditions dangerous in places where surge water covers the road.

>> Moderate beach erosion. Heavy surf also breaching dunes, mainly in usually vulnerable locations. Strong rip currents.

>> Minor to locally moderate damage to marinas, docks, boardwalks, and piers. A few small craft broken away from moorings.

>> Elsewhere across the Hawaiian islands, little to no impact is anticipated.

Other coastal hazards

Large and dangerous surf and strong rip currents are expected along east-facing shores of Oahu and Maui County from Olivia. Prepare for overwash of low lying areas and roadways with localized beach erosion around high tide. A high surf warning is in effect for east-facing shores of Oahu and Maui County, and a high surf advisory is in effect for east facing shores of the other islands.

Precautionary/ preparedness actions

>> Evacuations: Listen to local official for recommended preparedness actions, including possible evacuation. If ordered to evacuate, do so immediately.

>> Now is the time to complete all preparations to protect life and property in accordance with your emergency plan.

>> Ensure you are in a safe location before the onset of strong winds or possible flooding. Failure to adequately shelter may result in serious injury or loss of life.

>> Always heed the advice of local officials and comply with any orders that are issued.

>> Remember, during the storm 9-1-1 Emergency Services may not be able to immediately respond if conditions are unsafe. This should be a big factor in your decision making.

>> Keep cell phones well charged. Cell phone chargers for automobiles can be helpful, but be aware of your risk for deadly carbon monoxide poisoning if your car is left idling in a garage or other poorly ventilated area.

>> It is important to remain calm, informed, and focused during an emergency. Be patient and helpful with those you encounter.

>> If you are a visitor, be sure to know the name of the city or town in which you are staying and the name of the county in which it resides.

>> Listen for these locations in local news updates. Pay attention for instructions from local authorities.

>> Rapidly rising flood waters are deadly. If you are in a flood-prone area, consider moving to higher ground. Never drive through a flooded roadway. Remember, turn around don’t drown!

>> If in a place that is vulnerable to high wind, such as near large trees, a manufactured home, upper floors of a high-rise building, or on a boat, consider moving to a safer shelter before the onset of strong winds or flooding.

>> Closely monitor weather.gov, NOAA Weather radio or local news outlets for official storm information. Be ready to adapt to possible changes to the forecast. Ensure you have multiple ways to receive weather

warnings.

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For more information: ready.gov, getagameplan.org, and redcross.org.

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