Hurricane “Olivia,” the 15th named storm of the 2018 Pacific hurricane season, is intensifying as it tracks toward Hawaii. Little change in strength is forecast through late Monday (HST), with gradual weakening possible starting sometime Tuesday, September 11. It is important to not focus on the exact forecast track and intensity when planning for Olivia, NHC said. Persons on all of the main Hawaiian Islands should continue preparing for the likelihood of direct impacts from this system Monday and early Tuesday, September 10 and 11. Those impacts could include intense flooding rainfall, damaging winds, large and dangerous surf, and storm surge.
At 09:00 UTC on Monday, September 10, the center of Hurricane “Olivia” was located about 880 km (545 miles) ENE of Hilo and 1 140 km (705 miles) E of Honolulu, Hawaii. Its maximum sustained winds were 140 km/h (85 mph), making it a Category 1 hurricane on the Saffir-Simpson scale.
The system is moving W at 15 km/h (9 mph) with minimum central pressure of 980 hPa.
This general motion is expected to continue through early Monday (HST), followed by a turn toward the WSW starting late Monday. This WSW motion is expected to continue through Tuesday evening. On this forecast track, tropical storm conditions are possible over some parts of Hawaii starting Tuesday.
Hurricane “Olivia” on September 9, 2018. Credit: NASA/NOAA Suomi NPP/VIIRS
A Tropical Storm Watch is in effect for Oahu, Maui County, including the islands of Maui, Molokai, Lanai and Kahoolawe, and Hawaii County. A Tropical Storm Watch means that tropical storm conditions are possible in the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. A Tropical Storm Warning may be required for some areas that are in the watch area on Monday. Interests on Kauai and Niihau should closely monitor the progress of Olivia, NHC said.
Olivia is expected to produce total rainfall accumulations of 254 to 381 mm (10 to 15 inches). However, isolated maximum amounts of 508 mm (20 inches) are possible, especially over windward sides of Maui and the Big Island. This rainfall may produce life-threatening flash flooding.
Large swells generated by Olivia are expected to continue to increase across the main Hawaiian Islands. Surf will build as Olivia approaches, and may become damaging along some exposed east facing shorelines starting Tuesday or Wednesday, September 12.
It is important to not focus on the exact forecast track and intensity when planning for Olivia, NHC said. Persons on all of the main Hawaiian Islands should continue preparing for the likelihood of direct impacts from this system Monday and early Tuesday. Those impacts could include intense flooding rainfall, damaging winds, large and dangerous surf, and storm surge.
Regardless of the exact track and intensity that Olivia takes as it approaches the islands, significant effects often extend far from the center. In particular, the mountainous terrain of Hawaii can produce localized areas of strongly enhanced winds and rainfall, even well away from the tropical cyclone center.