Science and TechNatural Disasters


Tropical Storm Calvin moves toward Hawaii, could bring flash flooding

Tropical Storm Calvin is expected near Hawaii's Big Island Tuesday night.
Posted at 8:22 PM, Jul 18, 2023

tropical storm is headed toward Hawaii's big island, bringing with it heavy rain, high surf, strong winds and possible flooding and mudslides.

Satellite imagery showed Tropical Storm Calvin moving swiftly west toward the island, traveling at 22 mph with maximum sustained winds of about 50 mph at 11 a.m. HST Tuesday, which is 5 p.m. EST. That prompted the National Weather Service to warn Hawaii County residents to prepare for storm impacts ahead of Tuesday evening, when Calvin is expected to pass very close to the area.

The National Weather Service's forecast states the storm's wind speeds will steadily increase through Wednesday as it grows closer to Hawaii, with potentially damaging winds possible across most of the state. There's also a possibility of heavy showers and flash flooding, most likely in the Southeast part of the Big Island and Maui's north and east shores, before the storm weakens Wednesday night.

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By Thursday, Tropical Storm Calvin will likely weaken into a tropical depression, the NWS said, as it moves away from the Hawaiian Islands.

From Tuesday to Thursday, total rainfall could reach up to 6 to 10 inches. Forecasters have issued a flood watch and will upgrade to a flood warning if it begins, which will warn residents to move to higher ground and avoid flooded roads. 

Tropical Storm Calvin was forecast as a major hurricane late last week — the third of the Pacific hurricane season — but it weakened in recent days when it crossed the Pacific Ocean's cooler waters.

The National Oceanic and Atmospheric Administration, or NOAA, had predicted the 2023 Pacific hurricane season would contain 14 to 20 named storms and 7 to 11 hurricanes. The influence of a strengthening El Niño, though, could likely result in higher numbers.