Heavy rains, big surf, and strong winds: Here’s what to expect from Douglas and when

Updated: Jul. 24, 2020 at 2:02 PM HST
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HONOLULU, Hawaii (HawaiiNewsNow) - As Hurricane Douglas barrels toward the state, emergency management officials are urging residents to prepare now for potential impacts this weekend.

A hurricane watch is in effect for the the Big Island and Maui County along with surrounding coastal waters. This means at least tropical storm force winds of 39 to 73 mph are expected within 48 hours.

The Central Pacific Hurricane Center said damaging winds may begin as early as Saturday night across parts of Maui and the Big Island. The winds could spread westward to the rest of the state on Sunday.

Here’s what Maui County and the Big Island should initially prepare for:

  • There could be some damage to roofing and siding materials, along with damage to porches, awnings, carports and sheds.
  • A few buildings could have window, door and garage door failures.
  • Mobile homes could be damaged, especially if they are unanchored.
  • Unsecured, lightweight objects could become dangerous projectiles.
  • Several large trees may be snapped or uprooted. This could happen in greater numbers where trees are shallow rooted.
  • Fences and roadway signs may be blown over.
  • Some roads will be impassible due to large debris, and more in urban or heavily wooded places.
  • A few bridges, causeways and access routes will be impassable.
  • Scattered power and communication outages are possible, especially in areas with above-ground lines.

A flash flood watch will also take effect Saturday evening through Monday for Maui County and the Big Island. Flooding rain will be possible as early as Saturday night on Maui and the Big Island, and the chance for flooding will increase for much of the state on Sunday.

The flood threat could persist for parts of the state into Monday.

Storm total rainfall of 6 to 10 inches, with some locally isolated areas to 15 inches, will be possible. The highest rainfall will favor windward areas, but leeweard areas could also experience flooding.

  • Major rainfall flooding may prompt evacuations and rescues.
  • Rivers and tributaries may rapidly overflow their banks in multiple places.
  • Small streams, creeks, canals, arroyos and ditches may become dangerous rivers.
  • In mountain areas, destructive runoff may run quickly down valleys and increase the possibility of rockslides and mudslides.
  • Flood control systems and barriers may become stressed.
  • Flood waters can enter many structures in multiple communities, with some structures becoming uninhabitable or washed away.
  • There are many areas where flood waters may cover escape routes.
  • Streets and parking lots can become rivers of moving water with underpasses submerged.
  • Driving conditions will become dangerous. Many road and bridge closures, with some roads and bridges weakened or washed out.

Large swells arriving ahead of Douglas will produce dangerous surf along east and southeast-facing shores, especially on the Big Island and Maui.

Large and rough seas will build rapidly Saturday night and Sunday on exposed east and southeast facing shores and may produce damaging surf, significant beach erosion and overwash onto vulnerable coastal roads, especially during high tide.

  • Localized inundation with storm surge flooding will be possible, mainly along immediate shorelines and in low-lying spots, or an areas farther inland near where hgiher surge waters move ashore.
  • Sections of near-shore roads and parking lots will become overspread with surge water.
  • Driving conditions will be dangerous in places where surge water covers the road.
  • Expect moderate beach erosion. Heavy surf will also breach sand dunes, especially in usually vulnerable locations.
  • Strong rip currents can occur.
  • Minor to locally moderate damage can occur to marinas, docks, boardwalks and piers.
  • A few small craft can be broken away from moorings.

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