Much of the state remains under a tropical storm watch as a weakening but still concerning Tropical Storm Guillermo continues its slow northwesterly progress toward Hawaii waters.
The National Weather Service issued the watch for Hawaii island and Maui County on Monday afternoon. Other islands may be included later as Guillermo continues on course to pass just north of the state, according to forecasters.
A watch means that tropical storm conditions are likely within 48 hours.
Guillermo was downgraded from a hurricane to a tropical storm overnight between Sunday and Monday and continued to weaken throughout the day. Even so, weather service officials warn that the storm is still capable of bringing heavy rain and the potential for flooding and strong winds to the islands from late Tuesday night through Thursday.
Guillermo had sustained maximum winds of 70 mph with higher gusts at 11 p.m. Monday, according to the Central Pacific Hurricane Center. Tropical storm-force winds extend 140 miles from the center. At 11 p.m. the storm was centered 485 miles east of Hilo and 680 miles east-southeast of Honolulu and was moving west-northwest at 12 mph.
On Monday evening, hurricane center forecasts estimated that the center of Guillermo would pass about 140 miles northeast of the Big Island on Wednesday and approximately 100 miles northeast of Maui by Wednesday evening.
The margin of error for the track 48 hours ahead of the storm is about 85 miles in each direction, so the storm could still pass directly over the islands, bringing tropical storm-force winds and heavy rain.
Even if the storm passes north of the islands, Guillermo is about 350 miles wide, and Hawaii will still see some rain, possibly heavy rain Wednesday and Thursday.
“Although Tropical Storm Guillermo shows signs of weakening, we strongly encourage residents and visitors to prepare themselves and their families for potential severe weather,” said Doug Mayne, administrator of Hawaii Emergency Management.
“There is some uncertainty associated with weather forecasting, so we need to plan for the worst and hope for the best.”
The National Weather Service issued a flood potential outlook, citing the possibility of heavy rain and flooding throughout the islands Wednesday and Thursday. The amount of rain and wind is still uncertain.
“While the forecast track keeps the center of Guillermo northeast of the main Hawaiian Islands, a significant deviation to the left of the track would have the potential to bring tropical storm conditions to the Big Island or Maui County,” hurricane center forecasters said Monday afternoon.
“When accounting for the size of the system, there remains enough uncertainty to warrant issuance of a tropical storm watch for Hawaii and Maui counties,” the forecasters said. “Other counties may be added later as needed.”
Most of the heavy rain and winds are north of the center. So if it follows the current track, the state could avoid the worst of it.
The weather service Monday afternoon cited high seas and strong winds in a tropical storm warning for Hawaii offshore waters beyond 40 nautical miles out to 240 nautical miles including the portion of the Papahanaumokuakea Marine National Monument east of French Frigate Shoals. Northeast wind up to 23 mph and seas up to 9 feet were expected Monday afternoon, officials said.
“It is still too soon to determine with certainty which islands are most likely to experience the greatest impacts from Guillermo. It is also important to note that significant impacts can extend well away from the center,” forecasters said.
A high-surf advisory for the eastern shores of Oahu, Hawaii island, Kauai and Maui is posted through 6 p.m. Tuesday.
In anticipation of the storm, Hawaii Volcanoes National Park will close at 5 p.m. Tuesday. The closure will extend to Mauna Loa Road from Kipukapuaulu to the Mauna Loa lookout, as well as the Namakanipaio campgrounds and A-frame cabins. The visitor centers, restrooms, lava tube, front-country trails, steam vents and other popular features will remain open.
Haleakala National Park announced it will close backcountry areas for hiking, camping and cabin use at noon Wednesday. The areas will remain closed until the storm threat is resolved.
All backcountry campers and cabin users have already been informed of the closure, according to park officials.
On Monday afternoon the Coast Guard issued a message urging mariners to secure their boats and boating equipment, and move large boats to protected marinas.
“It may be advisable for smaller boats to be pulled from the water and stored in a place that is not prone to flooding and is protected,” the Coast Guard message stated. “Regardless of location, all loose items aboard vessels should be secured or removed.”
The Coast Guard further advised all mariners and beachgoers to monitor the progress and strength of the storm and to heed all warnings from lifeguards and public health and safety officials.
As Guillermo weakens, a new storm system is developing in the Eastern Pacific and is expected to become a tropical depression later in the week as it moves toward the Central Pacific, according to the National Hurricane Center in Miami. The developing storm is about 1,000 miles southwest of Baja California.
Guillermo’s wind will likely be from the northeast, so windward and mauka areas will see most of the rain and wind. But leeward sections will also see some effects.
