Storm Douglas – Hawaii Braces for 'Triple possibility'

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Forecasters predicted three to six inches of rain on the main Hawaiian islands, possibly contributing to flash flooding and landslides.

About Hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain or squalls. Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane (), typhoon (), tropical storm, cyclonic storm, tropical depression, and simply cyclone. A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; in the south Pacific or Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.”Tropical” refers to the geographical origin of these systems, which form almost exclusively over tropical seas. “Cyclone” refers to their winds moving in a circle, whirling round their central clear eye, with their winds blowing counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The opposite direction of circulation is due to the Coriolis effect. Tropical cyclones typically form over large bodies of relatively warm water. They derive their energy through the evaporation of water from the ocean surface, which ultimately recondenses into clouds and rain when moist air rises and cools to saturation. This energy source differs from that of mid-latitude cyclonic storms, such as nor’easters and European windstorms, which are fueled primarily by horizontal temperature contrasts. Tropical cyclones are typically between 100 and 2,000 km (62 and 1,243 mi) in diameter.
The strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth’s rotation as air flows inwards toward the axis of rotation. As a result, they rarely form within 5° of the equator. Tropical cyclones are almost unknown in the South Atlantic due to a consistently strong wind shear and a weak Intertropical Convergence Zone. Conversely, the African easterly jet and areas of atmospheric instability give rise to cyclones in the Atlantic Ocean and Caribbean Sea, while cyclones near Australia owe their genesis to the Asian monsoon and Western Pacific Warm Pool.
Coastal regions are particularly vulnerable to the impact of a tropical cyclone, compared to inland regions. The primary energy source for these storms is warm ocean waters. These storms are therefore typically strongest when over or near water, and weaken quite rapidly over land. Coastal damage may be caused by strong winds and rain, high waves (due to winds), storm surges (due to wind and severe pressure changes), and the potential of spawning tornadoes. Tropical cyclones also draw in air from a large area—which can be a vast area for the most severe cyclones—and concentrate that air’s water content (made up from atmospheric moisture and moisture evaporated from water) into precipitation over a much smaller area. This continual replacement of moisture-bearing air by new moisture-bearing air after its moisture has fallen as rain, may cause multi-hour or multi-day extremely heavy rain up to 40 kilometers (25 mi) from the coastline, far beyond the amount of water that the local atmosphere holds at any one time. This in turn can lead to river flooding, overland flooding, and a general overwhelming of local man-made water control structures across a large area.
Though their effects on human populations are often devastating, tropical cyclones can relieve drought conditions. They also carry heat energy away from the tropics and transport it toward temperate latitudes, which may play an important role in modulating regional and global climate.

Hurricane Douglas: Hawaii Braces for 'Triple Threat'

About Douglas:

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Hurricane Douglas moved north of Hawaii early on Monday, sparing the islands the direct hit that forecasters had feared.CreditCredit…Ronen Zilberman/Agence France-Presse — Getty Images
  • Published July 26, 2020Updated July 27, 2020, 10:19 a.m. ET

Hurricane Douglas moved north of Hawaii zearly on Monday, sparing the islands the direct hit that forecasters had feared. The hurricane pelted some areas with winds of 90 miles per hour and torrential rains as it passed by Oahu on Sunday, the National Hurricane Center reported. A hurricane warning was canceled early on Monday for the western islands of Kauai and Niihau, and forecasters expected the storm to pass north of the islands.

Hurricane Douglas: Hawaii Braces for 'Triple Threat'

If Douglas, which was downgraded to a Category 1, had made landfall over the islands, it would have been only the third hurricane in modern times to do so.

The hurricane was moving rapidly away from Kauai, but it will remain a hurricane until it passes west of the island, the hurricane center said. Maximum sustained winds neared 90 m.p.h. early on Monday, and heavy surf and rainfall were expected to pound the main islands, the center said.

But the force of the storm was forecast to weaken during the next 48 hours.

Only two storms since modern record-keeping started in 1900 are known to have struck the islands: In 1992, Hurricane Iniki hit Kauai as a Category 4 storm, killing six people and causing about $3 billion in damage. In 1959, Hurricane Dot caused about $5.5 million in damage.

Though the islands avoided a direct hit, the combination of high water levels, storm surge and large breaking waves could raise water levels by as much as two feet above normal tides near the center of the storm, the center warned.

Forecasters predicted three to six inches of rain on the main Hawaiian islands, possibly contributing to flash flooding and landslides.

Earlier in the day, Maui County asked residents to shelter in place or move to an emergency shelter immediately if they lacked a safe place to weather the storm. Much of the county has already been through the brunt of the storm with minimal damage, said Mayor Michael Victorino of Maui County.

Tourism has been severely affected by both the storm and the coronavirus pandemic, Mr. Victorino said. On any given day, the county received about 8,000 visitors. Over the last few days, there have been less than 50 visitors per day, which has made the job of emergency management much easier.

“That was the blessing,” Mr. Victorino said. “We didn’t have to work so hard and concern ourselves with the visitors.”

Upon entering the state, all travelers have a mandatory 14-day self-quarantine. Maui’s visitors are sheltering in place at hotels, Mr. Victorino said. If it becomes dangerous, local shelters can separate those who are self-quarantining or who have the coronavirus.

Thirteen shelters opened on Sunday in Honolulu, including the Hawaii Convention Center, which can hold 1,600 people, with social distancing, Honolulu’s mayor, Kirk Caldwell, said at a news conference on Saturday.

Officials have warned that space at the shelters may be constricted because of social distancing policies. Gov. David Ige of Hawaii said the authorities would monitor capacity at the shelters and open more if necessary.

In Maui County, which has about 167,000 residents, fewer than 30 people have gone to a shelter, Mr. Victorino said.

In a statement on Sunday morning, the hurricane center emphasized that residents should not focus on the exact forecast track or intensity of Douglas.

“Due to Douglas’s angle of approach to the islands, any wobble in the track could lead to significant differences in where the worst weather occurs,” the center said. “Even if the center remains offshore, severe impacts could still be realized over the islands, as they extend well away from the center.”

Mr. Ige on Thursday issued a pre-landfall emergency proclamation that authorized state funds for quick disaster relief.

“We don’t just focus on the wind,” Mr. Feltgen said on Friday about the storm. “You have to look at the water impacts on this thing as well. Very heavy rainfall.”

Marie Fazio, Daniel Victor and Christine Hauser contributed reporting.

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