A high surf warning is also in effect for east-facing shores of the Big Island. It was located about 470 miles east-southeast of South Point, Hawaii.
On Aug. 6 at 4:40 a.m. EDT (0840 UTC) NASA's Aqua satellite found coldest temperatures of strongest thunderstorms (yellow) in Tropical Storm John were as cold as or colder than.
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The storm will continue moving west after it passes by Hawaii.
Two new tropical storms were strengthening off Mexico on Monday and both were projected to reach hurricane force while marching northwestward parallel to the coast, bringing heavy surf.
Closer to the US mainland, Hurricane John is strengthening in bathlike ocean water south of the Baja Peninsula. It is moving northeast at 12 mph with its tropical-storm-force winds extend outward up to 45 miles from the center. It will not affect any land areas.
Debby is the fourth-named storm of the season.
The U.S. National Hurricane Center says Tropical Storm John is expected to strengthen rapidly and become a hurricane by Monday afternoon and a major hurricane by Tuesday.
During last year's historically active, ferocious and deadly season, Harvey and Irma alone caused close to $200 billion in damages, according to ICAT, the catastrophe insurance concern.
The risk of a hurricane striking the United States during the remainder of the summer is lower than average, experts said in an updated seasonal forecast released Thursday.