Nolo crosses the date line as a Category 3 hurricane and becomes a typhoon

Hurricane Nolo crossed the international date line on Sunday and, by the naming rule that splits the Pacific, became Typhoon Nolo. The Associated Press, citing the fix before the crossing, said it was a Category 3 hurricane with maximum sustained winds of 115 mph, 185 km/h, on Sunday morning Hawaii time. Once it was west of the line, the Japan Meteorological Agency logged maximum sustained winds of 100 mph, 162 km/h, and a westward motion of 19 mph, 30 km/h, on Monday morning Japan time.

The drop from 115 to 100 mph is a change of basin and of agency scale as well as a change in the storm. The Joint Typhoon Warning Center and the Japan Meteorological Agency do not always print the same one-minute or ten-minute wind. The public fact is the pair of fixes: Category 3 on the Hawaiian side of Sunday morning, typhoon at 100 mph on the Japanese side of Monday morning. The name does not change. The label does.

Nolo's recent track is short enough to list. It passed near Hawaii as a hurricane about a week earlier, weakened to a tropical storm, and regained hurricane strength on Friday. It is forecast to keep moving west and to weaken gradually. No coastal warning for a populated island was attached to the Monday morning fix. Hurricane Rachel, a separate storm, was still heading west on a path away from Mexico.

Satellite analysts filled in structure that the advisory does not. The Cooperative Institute for Meteorological Satellite Studies at Wisconsin posted 10-minute GOES-18 infrared imagery from 2300 UTC on 3 October to 0000 UTC on 5 October, showing Nolo intensifying from Category 1 to Category 2 as it approached 180 degrees longitude, then continuing west. The eye widened on the approach. The coldest cloud-top temperatures in the deep convection were about minus 77 Celsius. Lightning, from the GOES-18 lightning mapper, was intermittent and less frequent in the eyewall than in the outer bands.

A synthetic aperture radar pass from Canada's RCM-2 satellite at 1800 UTC on 4 October measured surface winds as high as 121.35 knots in the northwest quadrant. That is about 140 mph, above the 115 mph advisory wind, which is what a single radar look at the strongest quadrant often shows against a storm-wide maximum. The number is a point sample, not a new category.

The date line is an administrative boundary. The ocean under Nolo does not change at 180 degrees. Shipping and aviation do. A hurricane east of the line is the responsibility of the Central Pacific Hurricane Center. A typhoon west of it is the Japan Meteorological Agency's. The rename is the handoff. For mariners already west of the line on Monday, the working wind is the agency's 100 mph, with the Canadian radar pass as a reminder that one quadrant was stronger than that average on Sunday evening UTC.

The next useful fix is whether the westward motion at 19 mph holds and whether the eye, which widened on the approach to the line, starts to fill as the forecast weakening arrives. Until that fix, Nolo is a typhoon on the Japanese chart and a hurricane on Sunday's Hawaiian one, same circulation.