Hurricanes Miriam and Norman forecast to weaken

Central Pacific Infrared Images

Hurricane Miriam

At 5 a.m. HST (1500 UTC), the center of Hurricane Miriam was located near latitude 18.3 North, longitude 141.2 West. Miriam is moving toward the north near 10 mph (17 km/h). This general motion is expected to continue through tonight. A turn toward the northwest with an increase in forward speed is expected Saturday through Sunday.

Maximum sustained winds are near 90 mph (150 km/h) with higher gusts. Rapid weakening is expected to begin later today and continue through Sunday. Miriam is expected to become a post-tropical remnant low Sunday or Sunday night.

Hurricane-force winds extend outward up to 25 miles (35 km) from the center and tropical-storm-force winds extend outward up to 105 miles (165 km).

The estimated minimum central pressure is 978 mb (28.88 inches).

Miriam peaked at an intensity of 80 knots overnight, a high-end category one hurricane, and it appears likely that this will be as strong as the system gets. Southwesterly shear is forecast to increase further today, with 35 to 50 knots of shear expected over the cyclone tonight through the end of the forecast period, while the system is passing over sea surface temperatures below 26C. Rapid weakening should begin later today, with Miriam expected to drop below hurricane strength late today or tonight, and become a post-tropical remnant low Sunday or Sunday night. The intensity forecast is closely aligned with the latest dynamical and consensus guidance which were all in good agreement.

Hurricane Norman

Tropical Cyclone Norman’s forecast path as of 5 a.m. HST Friday, August 31, 2018.

Tropical Cyclone Norman’s forecast path and earliest reasonable arrival of tropical storm winds as of 5 a.m. HST Friday, August 31, 2018.

At 5 a.m. HST (1500 UTC), the eye of Hurricane Norman was located near latitude 16.7 North, longitude 120.8 West. Norman is moving toward the west-southwest near 8 mph (13 km/h). A turn toward the west and west-northwest with an increase in forward speed is expected over the weekend and into next week.

Maximum sustained winds have decreased to near 130 mph (215 km/h) with higher gusts. Norman is a category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Gradual weakening is forecast, but Norman is expected to remain a powerful hurricane through the early part of next week.

Hurricane-force winds extend outward up to 25 miles (35 km) from the center and tropical-storm-force winds extend outward up to 90 miles (150 km).

The estimated minimum central pressure is 950 mb (28.06 inches).

Slow weakening is forecast through the entire period, although there could be fluctuations in the short-term due to inner core structure evolution. There also appears to be some modest northeasterly shear impinging the northeast portion of the cyclone, which could hamper strengthening. The Decay Statistical Hurricane Intensity Prediction Scheme (SHIPS) intensity model indicates that the shear will persist during the next couple of days. Through the remaining part of the forecast, decreasing sea surface temperatures (SSTs) and the intrusion of a more stable/drier environment from the north should lead to further weakening.

Actions to take whenever a tropical storm or hurricane nears Hawaii

All of Hawaii’s citizens should know what to do during a hurricane, tropical storm watches and warnings. Watches and warnings are prepared for the Hawaiian Islands by the National Weather Service Central Pacific Hurricane Center in Honolulu. When watches and warnings are issued, people should closely monitor the Internet, radio, TV, or NOAA Weather Radio for official bulletins of the storm’s progress and instructions from civil defense authorities. Jim Weyman, director of the Central Pacific Hurricane Center, said, “Although you and your family may have never experienced a hurricane, don’t be complacent! It’s not a matter of if a hurricane will occur, but when one will occur. All of the Hawaiian Islands are at risk for a hurricane and we should all know what actions to take.”

For the Central Pacific Ocean a Hurricane/Tropical Storm Watch means hurricane/tropical storm conditions are possible in the specified area of the Watch, usually within 48 hours.

When a Hurricane or Tropical Storm Watch is issued:

For the Central Pacific Ocean a Hurricane/Tropical Storm Warning means hurricane/tropical storm conditions are expected in the specified area of the Warning, usually within 36 hours.

When a Hurricane or Tropical Storm Warning is issued:

The Central Pacific Hurricane Center (CPHC) issues tropical cyclone warnings, watches, advisories, discussions, and statements for all tropical cyclones in the Central Pacific from 140 Degrees West Longitude to the International Dateline. The season officially begins on June 1 and ends on November 30. However, tropical cyclones can occur at any time. The National Weather Service Forecast Office in Honolulu activates the CPHC when: (1) a tropical cyclone moves into the Central Pacific from the Eastern Pacific, (2) a tropical cyclone forms in the Central Pacific, or (3) a tropical cyclone moves into the Central Pacific from the West.