/Hurricane Douglas to swipe Hawaii, producing flooding rain, damaging winds and huge waves

Hurricane Douglas to swipe Hawaii, producing flooding rain, damaging winds and huge waves





Hurricane Douglas approaches Hawaii on the morning of July 25. (RAMMB/CIRA)

Hurricane Douglas is rapidly closing in on the Hawaiian Islands. While it has weakened below major hurricane status, the current forecast brings it on a dangerous trek through the Pacific archipelago starting tonight and lasting into early Monday.

If Douglas makes landfall in Hawaii as a hurricane, it will become the third storm in the modern record to do so. Many other storms have weakened rapidly on approaches similar to that of Douglas, torn apart by strong upper-level winds that tend to be present, as well as cooler ocean temperatures.

Hurricane watches are in effect for the Big Island and Maui while Oahu was placed under a hurricane warning.

“The close passage of Douglas brings a triple threat of hazards, including but not limited to damaging winds, flooding rainfall, and dangerously high surf, especially along east facing shores,” the Central Pacific Hurricane Center wrote.

Hanna’s impending landfall comes at a time when the United States continues to be gripped by the coronavirus pandemic, which complicates storm shelter and relief operations as social distancing requirements and other prevention efforts are taken into account. Currently, FEMA as well as state agencies are tasked with responding to both the coronavirus and the storm.

In an interview about the storm, Honolulu Mayor Kirk Caldwell said, “This is a double whammy.” That was in reference to the fact that covid-19 is surging in the state as Douglas approaches.

State officials are urging people to shelter at home and only leave as a last resort.




Advice from the Oahu Emergency Management Office. (Twitter)

Hurricane Douglas peaked earlier in the week as a Category 4 Hurricane, with maximum sustained winds of 130 mph. However, Douglas has steadily weakened as it tracks over waters that are cooler than required to power the most intense tropical cyclones. Water temperatures where it maximized its intensity were close to the mid-80s, whereas it’s currently traversing waters in the mid-70s.

Rounding the base of a large high pressure area to its north, Douglas is moving quickly toward Hawaii. With a forward speed of 18 mph, the storm had maximum sustained winds of 90 mph as of 11 a.m. Hawaii time.

Besides cooler waters, the Pacific Hurricane Center points to “relatively low vertical wind shear values [that are] forecast to affect the tropical cyclone during the next day or so,” indicating a relatively slow decrease in strength is likely in the near term.

Large waves that Douglas has kicked up are already impacting the islands, and they’ll only grow in size and intensity during the short term. The CPHC expects: “life-threatening surf and rip current conditions for a couple of days.” Local inundation and beach erosion are also anticipated.

By Sunday afternoon, Hurricane Douglas is forecast to pass about 30 miles north of the island of Maui and have sustained winds of 80 mph. Tropical storm conditions (sustained winds greater than 39 mph) are anticipated there, with hurricane conditions (sustained winds greater than 74 mph) possible should the track shift slightly south.

Sunday night, Douglas is forecast to pass over Kauai as a strong tropical storm.

The current forecast brings Douglas directly over Oahu Sunday evening as a hurricane with 75 mph winds.

NWS Honolulu writes, “Damaging winds may begin as early as late tonight across parts of Maui and the Big Island, possibly spreading westward to the rest of the state on Sunday.” They also point out that there should be limited focus on the track, given widespread impacts across the island chain. Localized winds higher than other places may also occur in mountainous regions as well as high rises, they warn.

Flooding rain may end up the most widespread feature of Douglas across the islands.

The local NWS forecast calls for as much as five to 10 inches of rain as the storm passes, with some amounts of up to 15 inches possible. Significant flooding is anticipated along rivers and tributaries. This may be enhanced on the north side of the islands where winds will blow onshore, although flooding is possible just about anywhere.




Forecast rainfall as Douglas passes Hawaii. (weatherbell.com)

The current track forecast shows that Hurricane Douglas may come within 30 miles of Honolulu, which is the main logistical hub for the island chain.

Since Douglas is a fairly small tropical cyclone, small shifts in its track or intensity fluctuations can mean major differences for the islands in its projected path. Should Douglas swing farther north, impacts could be significantly lessened, although large waves and gusty winds are likely in just about any scenario.

“Even if the center remains offshore, severe impacts could still be realized over the islands, as they extend well away from the center,” the NWS warned.

Although it is a warm-weather island destination, Hawaii’s location in a cooler area of sea surface temperatures has historically protected it from anything but the rare hurricane strike. There have only been two hurricane landfalls in modern times; Category 1 Hurricane Dot in 1959 and Category 4 Iniki, which caused widespread damage on Kauai in 1992. Both of those curved northward from the south, where there is a shorter trip across cool waters, rather than moving in from the east like Douglas is.

Due in large part to human-caused global warming, increasing water temperatures and a somewhat shifted storm track in a warming world may bring increased hurricane threats to Hawaii moving forward.

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