UPDATE 8/3/15: Guillermo

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

Tropical Storm Guillermo strengthened slightly Monday night, holding maximum sustained winds of 70 miles per hour as it approaches the Big Island.

Central Pacific Hurricane Center image, as of 11 p.m. Monday.

As of the Central Pacific Hurricane Center’s 11 p.m. advisory Tropical Storm Guillermo was located 485 miles east of Hilo. The storm is moving to the northwest at 12 miles per hour.

A Tropical Storm Watch remains in effect for the Big Island and Maui County

Tropical Storm conditions are possible as early as Wednesday. The center of Guillermo is expected to pass 170 miles northest of Hilo Wednesday afternoon.

*** Updated at 8 p.m. to include information from the Central Pacific Hurricane Center’s 8 p.m. intermediate update. ***

Guillermo has maximum sustained winds at 65 mph with higher gusts and steady weakening is still expected. continues to move northwest at 10 mph. This motion is expected to continue through Wednesday. On this forecast track the center of Guillermo is expected to pass about 140 miles northeast of the Big Island on Wednesday and about 100 miles northeast of Maui on Wednesday night.

Image: NWS Satellite 9:30 p.m.

Tropical Storm conditions are possible on the Big Island of Hawaii and in Maui County on Wednesday. Total rainfall amounts of 1 to 3 inches with isolated maximum amounts near 7 inches (in higher terrain) are possible. Large swells ahead of the system are expected through midweek.

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

A tropical storm watch has been issued for Tropical Storm Guillermo.

As of the Central Pacific Hurricane Center’s 5 p.m. update, Tropical Storm Guillermo was about 515 miles to the east of Hilo. The storm continues to travel in a northwest direction, at a speed of 10 miles per hour.

Maximum sustained winds are at 65 mph.

Although Tropical Storm Guillermo is tracking to the northeast of the state, CPHC forecasters warn that tropical storm conditions could still impact the Big Island and Maui County.

A tropical storm watch means that conditions condusive to a tropical storm are possible over the next 48 hours.

***Updated at 3 p.m. to include information from the National Weather Service’s 3 p.m. update.**

The National Weather Service has modified their rain, surf and wind forecast for the islands. The High Surf Advisory will remain posted through 6 p.m. Tuesday with wave heights of 6 to 10 foot faces tonight and 5 to 8 feet Tuesday. A Tropical Storm Warning has been issued for offshore waters beyond 40 nm and out to 240 nm.

Image: NWS Warning Map

It is likely that Hawaii will fall at least within the periphery of the storm and would likely see rain and wind associated with Guillermo. Abundant tropical moisture associated with Guillermo’s vast moisture field will bring the potential for heavy rainfall and flash flooding Wednesday and Thursday. The intensity of both wind and rain will highly depend on guillermo’s eventual path.

UPDATED WEATHER FORECAST: If the track holds true the forecast is calling for partly sunny skies on Tuesday with scattered showers for windward spots and isolated showers for leeward areas. Variable winds are forecasted around 15 mph.

Wednesday: Mostly cloudy skies are expected with heavy rain and south winds from 15 to 25 mph.

Thursday: Mostly cloudy skies are forecasted with a chance of heavy rain during the day for windward spots then scattered showers at night. A slight chance of heavy rain exists for leeward areas during the day, then isolated showers at night. Southeast winds are forecasted around 15 mph.

Keep in mind, this is all subject to change with even little adjustments to the track and intensity of Guillermo as the system continues to approach the Hawaiian Islands.

***Updated at 11:00 a.m. to include information from the Central Pacific Hurricane Center’s 11 a.m. update.***

As of the Central Pacific Hurricane Center’s 11 a.m. update, Tropical Storm Guillermo was 560 miles ESE of Hilo, 620 miles ESE of Kailua-Kona and 590 miles E of South Point. Maximum sustained winds are now at 65 mph with higher gusts. Guillermo is ragged in appearance and continues to weaken as forecasted. The system is now moving northwest at 12 mph. This motion is expected to continue through Wednesday.

Image: NHC – Monday August 3, 2015 11 a.m.

The forecasted track has again been nudged slightly north. On this track, the center of Guillermo is forecast to pass approximately 150 miles northeast of the Big Island on Wednesday. Tropical storm force winds extend 140 miles from the center.

The CPHC says a watch may be issued later today or tonight. They refrained from issuing a watch during this update because of the northward shift and weaker winds.

***Updated at 8:20 a.m. to include information from the Central Pacific Hurricane Center’s 8 a.m. update.***
As of the Central Pacific Hurricane Center’s 8 a.m. update, Tropical Storm Guillermo was about 600 miles to the east-southeast of Hilo. The storm continues to head in a northwest direction at a rate of about 10 miles per hour.

***Original story posted at 6:28 a.m.***

As forecasted, Guillermo continues its slow weakening trend, now a tropical storm with maximum sustained winds of 70 mph. The storm, located about 735 miles ESE of Kahului, 790 miles ESE of Kaunakakai and 765 miles ESE of Lanai City. Guillermo is looking more disorganized as it continues to move WNW at 10 mph.

The track forecast has been nudged slightly north since yesterday.  Having said that, it’s important to focus on the entire forecast cone and not uniquely on the middle line of the track. Track error looking this far out into the future can still be hundreds of miles wide as evidenced by how vast the error cone gets that far out in time.

Central Pacific Hurricane Center image as of 5 a.m. Monday.

If this track remains true, Guillermo should reach our southeastern offshore waters by Tuesday at tropical storm strength, then approach the Big Island sometime Wednesday morning and track along the smaller islands on Wednesday and Thursday.

Guillermo is experiencing unfavorable conditions for further development. Vertical wind shear is starting to tear the system apart as it tracks north over cooler waters.

Tropical storm force winds now extend 125 miles from the center so it’s always good to remember that even if the center of the storm is not tracking right for the islands impacts can extend well away from the center.

In fact, although no watches or warnings are in effect at this time. We anticipate a tropical storm watch may be issued as early as this afternoon or evening depending on what happens today.

Central Pacific Hurricane Center image as of 5 a.m. Monday.

Having said that, impacts to the islands from Guillermo will start to show today. Large swells ahead of Tropical Storm Guillermo are expected to spread from east to west through the island chain. Big, dangerous surf is expected for east facing shores through about midweek. A High Surf Advisory is in effect and could be upgraded to a warning depending on conditions.

As far as weather effects, it’s still a little too early to talk about any specific wind conditions for the islands, but it is now very likely that the large field of moisture associated with Guillermo will bring periods of heavy rain and potential for significant flooding statewide from late Tuesday through Thursday.

Details of timing, exact location and amount of rainfall are still very uncertain and depend on where Guillermo actually ends up going and with what strength.