UPDATE | 9 p.m.

• The second Hawaii County Civil Defense audio message concerning Hurricane Guillermo (listen above). No coastal watches or warnings are in effect.

UPDATE | 5:30 p.m.

Coastal Watches/Warnings and 5-Day Forecast Cone for Storm Center, courtesy National Weather Service

• Guillermo is a Category 2 hurricane (maximum sustained winds at 105 mph), but is no longer strengthening according to the latest observations by the National Weather Service. Some strengthening is possible tonight and Saturday. Then, weakening is expected to begin on Sunday.
• Guillermo is 1,335 miles east southeast of Hilo, moving rapidly west northwest at 20 miles per hour.

“The intensity forecast has become somewhat problematic. The reason for the recent arrested development is unclear, although it might be related to dry air entrainment into the northwestern quadrant of the cyclone. However, there is still the opportunity for Guillermo to strengthen a bit more during the next 12 to 24 hours, while the system remains within a low-shear environment and over warm sea surface temperatures. The new intensity forecast is adjusted slightly downward to 95 kt at the 12- and 24-hour forecast times. Thereafter, the cyclone is forecast to move into an upper-level deformation zone between subtropical ridges to the east and west, which is a less favorable environment. Also, sea surface temperatures gradually cool along the forecast track. We have followed the previous forecast trend of gradual weakening, which is in good agreement with the latest SHIPS/LGEM and IVCN consensus guidance. When Guillermo approaches the Hawaiian Islands, it is expected to encounter increasing westerly shear, and the new intensity forecast follows the previous forecast in weakening Guillermo to tropical storm strength.” – National Weather Service

UPDATE | 11:30 a.m.

Coastal Watches/Warnings and 5-Day Forecast Cone for Storm Center, courtesy National Weather Service

• Hurricane Guillermo is “racing” toward the west-northwest near 18 mph and is expected to continue to do so with a gradual decrease in forward speed on Saturday. Maximum sustained winds have increased to near 105 mph with higher gusts. Guillermo is forecast to become a major hurricane tonight or Saturday. No coastal watches or warnings are in effect.

“By the end of the forecast period, when Guillermo is expected to be nearing the Hawaiian Islands, most of the guidance indicate that Guillermo should have weakened to a tropical storm, and so does the NHC forecast.” – National Weather Service

UPDATE | 9:30 a.m.

• Hawaii County Civil Defense have issued their first audio message concerning Hurricane Guillermo (listen above). No coastal watches or warnings in effect.

UPDATE | 6:20 a.m.

Coastal Watches/Warnings and 3-Day Forecast Cone for Storm Center, courtesy the National Weather Service

• Hurricane Guillermo is 1,570 miles east southeast of Hilo and “racing” west-northwestward at about 17 mph, according to the National Weather Service. There are no coastal watches or warnings in effect.
• Maximum sustained winds have increased to near 90 mph with higher gusts. Some additional strengthening is forecast during the next 48 hours, NWS says, and Guillermo is now expected to become a major hurricane over the weekend.
• The latest five day forecast track has Guillermo headed straight for Hawaii, diminished to a Tropical Storm before reaching the Big Island, but in an early morning discussion, forecasters said the track forecast is uncertain.

“The hurricane is racing west-northwestward or 285 degrees at about 15 kt. The cyclone will likely continue on this track and speed for the next day or two while embedded within a layer of deep easterlies to the south of the subtropical ridge. After 48 hours, the hurricane is expected to slow down as it approaches the southwestern edge of the subtropical ridge. By then, the presence of weaker steering currents makes the track forecast uncertain, and even more uncertain as the cyclone approaches the Hawaiian islands in about five days. The NHC forecast is consistent with the solution provided by global models. The forecast is also near the consensus, but heavily weighted on the GFS and ECMWF models.” – National Weather Service on July 31 at 8 a.m. PDT



Guillermo, courtesy the National Weather Service

Tropical Storm Guillermo became a Hurricane on Thursday night.



Coastal Watches/Warnings and 3-Day Forecast Cone for Storm Center, courtesy the National Weather Service

UPDATE | 12 a.m.

• Guillermo is now a category 1 hurricane; the fifth hurricane of the 2015 eastern North Pacific season.
• Hurricane Guillermo is 1,715 miles east southeast of Hilo. The storm is moving toward the west-northwest near 16 mph, and this general motion is expected to continue through Saturday.
• Guillermo is getting stronger. Satellite images indicate that the maximum sustained winds have increased to near 80 mph with higher gusts, and additional strengthening is forecast during the next day or two.
• There are no coastal watches or warnings in effect.

“There is considerable uncertainty in the intensity forecast beyond 48-72 hours, since Guillermo could encounter stronger shear, depending mainly on how far north the cyclone moves late in the forecast period.” – National Weather Service

We will be updating this page with the latest information on Hurricane Guillermo as it becomes available.