Big Island needs to brace for another tropical storm; heavy rainfall forecast to begin Saturday night

With the Big Island still recovering from last weekend’s deadly and destructive Hurricane Lala, the Hawaiʻi County Civil Defense Agency and the National Weather Service are closely monitoring two tropical systems in the Pacific Ocean.

The closest one is forecast to bring heavy rain to the Big Island, beginning on Saturday night.

The National Hurricane Center says a disturbance in the East Pacific Ocean has developed into Tropical Depression Two-C. It now has sustained winds of 35 mph and is about 960 miles east-southeast of Hilo as it moves west-northwest at 16 mph.

On the forecast track, the center of the system is expected to pass near or south of the Big Island of Hawaiʻi this weekend.

While it is too early to determine the exact track, intensity, magnitude or potential impact Tropical Depression Two-C, Big Island residents should — for the second time in less than 2 weeks — prepare for a possible tropical cyclone and severe weather.

Rainfall

Heavy rainfall associated with Tropical Depression Two-C is expected to impact the Big Island late Saturday night, spreading westward to the other Hawaiian Islands Sunday into Monday, according to the 5 a.m. Thursday advisory of the National Hurricane Center.

It is expected to produce rainfall totals of 5 to 10 inches with maximum amounts of 15 inches across the Big Island. Rainfall totals of 1 to 3 inches with maximum amounts of 5 inches are expected across the remainder of the Hawaiian Islands this weekend and early next week.

“This rainfall may produce life-threatening flooding and mudslides, especially in steep terrain and over areas that were recently affected by Lala,” the National Hurricane Center wrote.

Winds and surf

“There is a risk of wind and wave impacts in the Hawaiian Islands regardless of the exact track and intensity of the system. Watches may be required for portions of the Hawaiian Islands Thursday night or Friday.”

The cyclone is expected to be in a mostly favorable environment for the next couple of days, which should allow for gradual strengthening to a high-end tropical storm or a category one
hurricane as the system moves toward the Hawaiian Islands, the forecast said.

Swells generated by the depression are expected to affect portions of the Hawaiian Islands ths weekend, and could cause life-threatening surf and rip current conditions.

Storm’s name
Tropical Depression Two-C will be named once it reaches tropical storm strength of winds 39 mph or greater.

If that happens in the Central Pacific, it will be named “Moke,” a commonly used direct equivalent to the name “Moses” in historical Hawaiian records and family genealogies. If it forms while still in the East Pacific, it would mean the return of “Iselle” — the same name of the hurricane/tropical storm that devastated portions of the Big Island in August 2014.

Second tropical disturbance

A second area of low pressures is expected to form several hundred miles off the coast of Mexico. Gradual development of this system is expected, with a tropical depression expected to form this weekend as it moves north-northwest.