Weekend Impact Expected in Hawaii, Tropical Storm Ana Forecast

According to catastrophe modeling firm AIR Worldwide, Tropical Storm Ana is located 315 miles south-southwest of Hilo, Hawaii, with maximum sustained winds of 70 mph and a minimum central pressure of 994 mb. While Ana is gradually strengthening, and may achieve hurricane status later today, the storm is expected to weaken slightly tomorrow. Ana is forecast to bring heavy rains to the Big Island of Hawaii this afternoon, as well as potentially damaging surf along the island’s south and southeastern shores.

“Tropical Storm Ana is forecast to pass south of the Hawaiian archipelago this weekend,” said Scott Stransky, manager and principal scientist at AIR Worldwide. “Currently moving west-northwest with a forward speed of 14 mph, Tropical Storm Ana is anticipated to affect Hawaii’s Big Island by this afternoon, bringing heavy rain and high waves. A tropical storm watch is currently in effect for Hawaii County. Rainfall accumulations of 6-8 inches are expected on the Big Island; significant rainfall may also occur in the rest of the Hawaiian Islands over the weekend.”

According to AIR, winds from Tropical Storm Ana may pose a hazard to nonstructural components, particularly to roof cover and exterior cladding. There may be some airborne debris, which could damage unprotected windows or other fragile cladding on both engineered and non-engineered buildings. Most insured residential structures on Hawaii’s west coast—the region of the Big Island that is closest to Ana’s forecast track are made of wood, with about 40% of these being single-wall wood frame construction. Generally, load-bearing walls in these buildings are made of thin plywood boards and thus are quite susceptible to wind damage.

Stransky noted, “At Ana’s forecast wind speeds—accounting for the storm’s anticipated strengthening and subsequent weakening over the next 24 hours, as well as for the forecast track, which has shifted south in the last 24 hours—wind damage is likely to be limited to roof coverings, signage, and trees. Ana is anticipated to bring heavy rainfall to the Big Island of Hawaii starting this afternoon; total rainfall may be 6 to 8 inches, with up to 12 inches possible in some locations.”

Stransky concluded, “Then, through the weekend, Ana is forecast to bring heavy rains to the rest of the Hawaiian Islands as the storm continues to sweep west-northwest, keeping to the south of the archipelago. Particularly in mountainous regions, this heavy rainfall may lead to flash flooding and mudslides. Ana may also bring large swells to the island chain through the weekend, with surf that may cause damage to exposed south and southeast shorelines.”

Source: AIR Worldwide