Wali is no longer a tropical storm, but remains a threat that may bring thunderstorms and up to a foot of rain in some areas this weekend, forecasters said.
The storm was about 765 miles east southeast of Hilo and 980 miles away from Honolulu at 11 a.m. on Friday, moving northwest at 13 mph.
Forecasters downgraded Wali to a tropical depression at 11 a.m. Sustained winds are near 35 mph with higher gusts. The rain clouds associated with Wali extend about 600 miles from the center, and rain remains the main threat from the storm, forecasters said.
The winds from the storm are expected to weaken even more by the time the storm reaches the islands. But what’s left of Wali, likely a mass of humid weather and rain clouds, will still bring widespread heavy rains and the potential for flooding when its outer bands reach the Big Island on Saturday and the rest of the islands by Sunday morning.
"Widespread rainfall amounts of 5 to 10 inches are expected with up to 12 inches locally," forecasters said.
Another weather system in the upper atmosphere about 280 miles north of Oahu, is also moving toward the state and the combined effects of both systems will add instability to the weather around Hawaii this weekend.
"The winds are coming from opposite directions, so that’s going to sort of rip the storm apart," said Matthew Foster, a meteorologist in the Honolulu office of the National Weather Service. But the interaction of the two systems over Hawaii will also increase the chance of heavy rain over the islands.
Wali’s remnants will likely linger until Tuesday, increasing the potential for flooding.
A flash-flood watch is in effect for Hawaii from Saturday night through Monday.
"The main risk for flooding Saturday night is for the windward Big Island and Maui, and for all islands Sunday and Monday," forecasters said in a weather advisory.
Residents will first notice Wali’s approach Saturday as the humidity increases. The storm is also likely to cut off the cooling northeast tradewinds and bring muggy southeast Kona winds.
The state Department of Land and Natural Resources is closing or monitoring the following state park and forest areas this weekend as a precaution in anticipation of heavy rains and possible flash flooding:
» Muliwai Trail and Waimanu Valley campground. Campers holding permits are being notified. It should reopen Tuesday.
» Makawao Forest Reserve and Kula Forest Reserve, including Polipoli Spring State Park., effective noon Saturday.
» Kalalau Trail may be closed. DLNR will monitor the weather and close the trail if weather conditions warrant.
» Kayakers on the Wailua River are advised to be aware of possible rising waters and debris.
Foster said the rains will be widespread, but are most likely to fall in windward areas and southeastern slopes.
"It’ll be pretty persistent," he said.
The forecast for Honolulu and southern shores of Oahu calls for a 70 percent chance of rain on Sunday and Monday and a 50 percent chance of rain Saturday night and Tuesday.
Until the humidity and rain from Wali arrives on Saturday evening, forecasters expect typical tradewind weather on Friday, windward and mauka showers Saturday morning and mostly sunny to partly cloudy weather with isolated showers elsewhere.