Forecast for impending tropical cyclone continues to call for heavy rainfall, possible wind for parts of Hawai‘i

National Hurricane Center forecasters in an 11 p.m. Aug. 20 update reported the forecast for Tropical Depression Two-C continues to show heavy rainfall and windy conditions possible for parts of the Hawaiian Islands this weekend and early next week.

The storm — with sustained winds of 35 mph, just under tropical storm force classification, with higher gusts — was moving west-northwestward at 10 mph and was about 780 miles southeast of Hilo.

That general motion is expected to persist during the next several days, with the center of the system still forecast to pass south of the Big Island this weekend and then the smaller main Hawaiian Islands by early next week.

Gradual strengthening also continues to be in the forecast for the next couple of days, with Two-C expected to become a tropical storm likely today (Aug. 21).

Rainfall totals of 5 to 10 inches, with maximum amounts of 15 inches, are forecast around the Big Island, with rainfall of 1 to 2 inches, and a maximum of 3 inches, expected on windward Maui.

The remainder of the islands can expect a possible 1 to 2 inches of rain.

Rainfall totals also could be higher in some localized areas and could produce life-threatening flooding and mudslides, especially in locations of steep terrain and especially areas recently impacted by Hurricane/Tropical Storm Lala.

Heavy rainfall will begin to impact the Big Island late Saturday night, spreading westward across the remainder of the islands Sunday into Monday.

There also is a risk of wind and wave impacts regardless of the exact track and intensity of the storm system.

Swells generated by the storm are expected to affect parts of the island chain this weekend and could cause life-threatening surf and rip current conditions.

The storm is expected to take a gradual turn west later during the weekend.

Track guidance remains in generally good agreement; however, the updated National Hurricane Center forecast is slightly south of previous forecasts.

Satellite imagery indicates convective coverage associated with Tropical Depression Two-C changed little between the 5 p.m. and 11 p.m. updates Thursday.

Environmental conditions appear favorable for gradual strengthening during the next few days as the storm system approaches Hawai‘i. The cyclone is forecast to stay over warm waters and within a moist environment, with light to moderate vertical wind shear.

Guidance shows a gradual weaking trend, however, beginning by early next week because of drier mid-level air and increasing vertical wind shear.

Everyone in Hawai‘i should keep a close eye on the storm system and monitor the latest forecast updates from National Weather Service forecasters in Honolulu. They also will issue any advisories, watches or warnings, when necessary.

Members of the public also should already have preparedness plans in place.

The next complete advisory for Tropical Depression Two-C will be issued at 5 a.m. today.