UPDATE 8/4/15: Guillermo Forecast

***Updated at 11:10 p.m. to include information from the Central Pacific Hurricane Center’s 11 p.m. advisory.***

Tropical Storm Guillermo is once again showing signs of weakening as it faces strong shearing.

As of the Central Pacific Hurricane Center’s 11 p.m. advisory, Tropical Storm Guillermo was about 315 miles east-northeast of Hilo. The storm’s maximum sustained winds dropped to 65 miles per hour and is moving to the west-northwest at 8 mph.

Forecasters expect Tropical Storm Guillermo to continue to hold its current track over the next few days while picking up speed slightly. On its current track, the center of the storm is expected to pass 175 miles to the north-northeast of the Big Island Wednesday night.

A Tropical Storm Watch remains in effect for the Big Island as well as Maui County. A  Flash Flood Watch is also in effect until 6 p.m. Thursday.

***Updated at 5 p.m. to include information from the Central Pacific Hurricane Center’s 5 p.m. update.***

Moisture on the fringe of tropical storm Guillermo has started moving over the Big Island producing locally heavy rain. A Flash Flood Watch remains posted.

The latest Central Pacific Hurricane Center forecast estimates the center of Guillermo will pass approximately 150 miles northeast of the Big Island on Wednesday night, and approximately 120 miles north- northeast of Maui Wednesday night.

Tropical Storm Guillermo is now 345 miles E of Hilo, 410 miles E of Kailua-Kona and 400 miles E of South Point. Maximum sustained winds are still at 70 mph and the system is moving WNW at 9 mph.

Image: NWS satellite at 5:30 p.m. on August 4, 2015

The forecast calls for a steady weakening with Guillermo becoming a tropical depression after day 3. The forecast track has been nudged slightly closer to the islands with this forecast update and a bit slower as well. Because of these changes, the Tropical Storm Watch will remain posted.

A jog to the right, north or east means we will see lesser effects from this storm. Whereas, a jog to the left, south or west could mean tropical storm conditions for parts of the state.

Movement and intensity forecasts overnight will determine whether watches and advisories are upheld or cancelled.

***Updated at 1:45 p.m.***

A Flood Advisory has been posted for parts of the Big Island until 4:30 p.m. At 1:13 p.m. radar showed heavy rain between Na’alehu and Hawaiian Oceanview Estates. Radar was showing rainfall rates of up to 3 inches per hour.

The area of heavy rain is expected to remain over mainly rural areas. The National Weather Service advises the public to stay away from streams, drainage ditches and low-lying areas prone to flooding. Rainfall and runoff can also cause hazardous driving conditions due to ponding, poor breaking action and reduced visibility. Remember, never try to cross fast-flowing or rising water in your vehicle or on foot.

Image: NWS satellite at 1:45 p.m. Tuesday August 4, 2015

Guillermo is still a tropical storm with maximum sustained winds at 70 mph. As of the 2 p.m. CPHC update, the storm is 370 miles E of Hilo, 435 miles E of Kailua-Kona and 420 miles E of South Point. The system slowed down a bit and is moving WNW at 8 mph.

A Tropical Storm Watch is still in effect for the Big Island. The chance for tropical storm force winds is 4 percent for Hilo. This represents a general downward trend since the last forecast. Keep in mind, tropical storm force winds are still possible Wednesday into Wednesday night and if the track changes, the forecast also changes as a result. For more forecast guidance and detailed weather prediction, see previous posts.

***Updated at 10:50 a.m.***

A Flash Flood Watch is in effect until 6:00 p.m. Thursday for Maui and the Big Island. Abundant moisture from Tropical Storm Guillermo moving over the area. Excessive runoff may result in rock and mudslide in steep terrain. Fast-moving water may create life-threatening situations.

11 a.m. CPHC forecast track

The track has again been nudged north as of the 11 a.m. update. Guillermo is forecast to remain well northeast of the Hawaiian islands at its closest point of approach. If this motion continues and there is no significant deviation to the left of the forecast track, the Tropical Storm Watch for the Big Island and Maui County may be cancelled later today or tonight.

Guillermo is now 390 miles E of Hilo, 455 miles E of Kailua-Kona and 445 miles E of South Point. Maximum sustained winds are still at 70 mph as of the 11 a.m. CPHC update and the system is moving NW at 10 mph. The system should weaken and dissipation is expected in 72 hours.

***Updated at 8:15 a.m. to include updated information from the Central Pacific Hurricane Center.***

As of the Central Pacific Hurricane Center’s 8 a.m. update, Tropical Storm Guillermo continues to hold its stregnth as maximum sustained winds remain at 70 miles per hour with higher gusts.

Central Pacific Hurricane Center image, as of 8 a.m. Tuesday.

CPHC says that little change in stregnth is expected Tuesday, but a slow weakening trend is anticipated Wednesday.

The storm is currently 415 miles east of Hilo and is traveling at a rate of 10 mph.

Forecasts predict that Tropical Storm Guillermo will pass 215 miles northeast of Hilo on Wednesday afternoon.

***Original story posted at 5:39 a.m.***

Tropical Storm Guillermo is a bit stronger this morning than it was for much of yesterday, now a tropical storm with maximum sustained winds of 70 mph. The storm, located about 420 miles E of Hilo, 490 miles E of Kailua-Kona and 475 miles E of South Point, continues to move NW at 12 mph.

The track forecast has the system continuing in this general motion through today. Tonight and Thursday Guillermo is expected to shift WNW.

If this track remains true, the center of Guillermo should pass 215 miles northeast of Hilo Wednesday afternoon and around 165 miles north of Maui Wednesday night with tropical storm force winds currently extending about 175 miles from the center. The moisture field extends even beyond that.

Image: NWS satellite 5:15 a.m.

There is potential for slight strengthening today but the system looks a little less organized this morning compared to late last night. We’re seeing warmer cloud tops and less thunderstorm activity on satellite. Slow and steady weakening is expected from then on as vertical wind shear takes over again and starts to tear the storm apart. Sea surface temperatures are still sufficiently warm to sustain a hurricane so we can’t rule that out from the possibilities.

A Tropical Storm Watch is posted just in case the system decides to jog left of the expected track. If that happens, tropical storm conditions are possible within the next 48 hours somewhere within the watch area.

Image: CPHC 5 a.m. August 4, 2015

A watch is typically issued before the possible arrival of tropical storm force winds which make continuing outside preparations dangerous. Having said that, the probability of tropical storm force winds is currently 11 percent for Hilo and 13 percent for Kahului. Which is a general downward trend from yesterday.

The chance for heavy rain and thunderstorms continues Wednesday and Thursday. Total rainfall amounts of 1 to 3 inches with isolated maximum amounts near 7 inches (in higher terrain) are possible. If the system tracks closer to us, those numbers could go up. If Guillermo tracks farther away from us, rainfall amounts will be lower. Winds are expected to remain below 39 mph but only a slight shift left could result in higher winds so we need to keep watching.

A High Surf Advisory is still in effect through today for the Big Island and large swells are expected through much of the week.

DETAILED WEATHER FORECAST UPDATE:

Based on the current track (5 a.m.), tonight we expect mostly cloudy skies with showers likely in windward locations and frequent showers after midnight. Leeward spots should be partly cloudy to start with a mostly cloudy afternoon and a chance of heavy rain after midnight. Northeast winds are expected around 15 mph.

Wednesday we expect cloudy skies and heavy rain for windward spots with a slight chance of thunderstorms. Leeward areas have a slight chance of thunderstorms and / or heavy rain through the day with heavy rain likely overnight. Variable winds are expected around 20 mph.

Thursday we expect mostly cloudy skies for windward areas with a chance of heavy rain during the day then scattered showers at night. Leeward spots have a slight chance of heavy rain through the day and isolated showers at night. Southeast winds are expected around 15 mph.

Friday and Saturday we should get our easterly winds back around 15 mph. Mostly cloudy skies are expected with scattered showers for leeward spots. Windward areas will also get scattered showers and then showers are likely at night.