Hurricane Lowell is passing close to the Hawaiian islands, and the warnings issued for it illustrate something about tropical cyclones that is easy to miss: the centre of a storm and its effects are not the same thing.

As of Sunday’s advisories, Lowell was a Category 3 hurricane with maximum sustained winds reported between 115 and 125 miles per hour and a central pressure around 943 millibars, moving north-northwest at about 6 miles per hour. Its centre is forecast to pass just west of the main islands overnight on Monday, then slow by Wednesday. Gradual weakening is expected through Tuesday.

Who is under what

The warnings are layered, and the distinctions are meaningful.

Kauai County — the islands of Kauai and Niihau — is under a tropical storm warning, meaning tropical storm conditions are expected. A hurricane warning covers parts of the Papahānaumokuākea Marine National Monument in the Northwestern Hawaiian Islands, from Nihoa to French Frigate Shoals, along with offshore waters. The entire state is under a flood watch through Tuesday afternoon.

A warning is issued roughly 36 hours before conditions are expected to arrive, on the reasoning that outdoor preparation becomes difficult or dangerous after that point. A watch means conditions are possible, typically within 48 hours. The gap between them is the window in which useful action can be taken.

Forecast wind on Kauai is 35 to 45 miles per hour with gusts to 60, and the National Weather Service noted that the wind threat had increased from its previous assessment. Rainfall of 6 to 10 inches is expected on Kauai with up to 14 inches possible in places, 4 to 8 inches on the Big Island, and 2 to 4 inches on Maui and Oahu. Storm surge of 1 to 3 feet is forecast for Kauai. Seas offshore could reach 19 feet by Tuesday.

Why a near miss is not a miss

Hurricane-force winds extend outward up to about 50 miles from Lowell’s centre. Tropical storm-force winds extend up to 175 miles. That difference is the entire reason a storm tracking to the west of the islands still produces warnings across them.

Rainfall follows an even wider footprint than wind, and in Hawaii the terrain amplifies it. Steep volcanic slopes force moist air upward, which increases rainfall, and the water then runs off quickly into narrow valleys. The National Hurricane Center has warned that the rainfall could produce significant flash flooding and mudslides. The combination of surge and high tide is expected to flood normally dry coastal areas.

This is why the category number is a poor guide to what a storm will do to a particular place. The Saffir-Simpson scale measures sustained wind speed only. It says nothing about size, forward speed, rainfall or surge — and in mountainous islands, water is usually the greater hazard.

What islands do differently

The Kauai Emergency Management Agency has told residents to fill fuel tanks, charge devices, refill prescriptions, keep enough food and water, and be prepared to stay home for several days. Residents have been boarding up and stocking supplies. The state Department of Transportation warned that flights could be cancelled on Sunday and Monday, and a small craft advisory covers several channels.

The instruction to prepare for several days at home is the island-specific part. On a continental coast, people can drive inland and supplies can be trucked in once roads reopen. On an island, evacuation inland is limited by geography, and resupply depends on ports and airports that are themselves closed by the same weather. Preparation has to substitute for the movement that is not available.

Two other cyclones are active in the East and Central Pacific, including Tropical Storm Karina, well east-northeast of Hilo. Neither is expected to affect Hawaii. The Central Pacific season runs until 30 November.

Track forecasts are updated every six hours by the National Hurricane Center and the Central Pacific Hurricane Center, and anyone in the affected area should rely on those rather than on any single snapshot, including this one.

Sources

• National Hurricane Center and Central Pacific Hurricane Center advisories, 6–7 September 2026
• National Weather Service Honolulu warnings and watches, including wind threat assessments
• Honolulu Star-Advertiser, Kauai, Niihau under tropical storm warning as major Hurricane Lowell approaches, 6 September 2026
• CBS News, Hurricane warning issued for western Hawaii as Lowell approaches, 7 September 2026
• PBS NewsHour / Associated Press reporting on wind field and rainfall forecasts
• County of Kauai and Kauai Emergency Management Agency public advisories, 6 September 2026