Tropical Storm Guillermo has strengthened slightly with a forecast track further north of the islands. Little change in strength is expected through Wednesday morning, with slow but steady weakening anticipated thereafter.
Although the worst of the storm system may pass to the north, a tropical storm watch remains in place for Hawaii and Maui counties, which include the islands of Hawaii, Maui, Molokai, Lanai and Kahoolawe.
A tropical storm watch means tropical storm conditions are possible within the watch area, generally within 48 hours.
Forecasters say it is important not to focus on the exact forecast track. Forecast movement, direction and speed are only estimates, and even small shifts in the track can mean major differences in where the worst conditions will occur. Damaging effects can extend far from the center.
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. 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. Other counties may be added later as needed.
Summary of 11 p.m. information
- Location: 18.9N 147.7W
- About 485 miles E of Hilo, 680 miles ESE of Honolulu
- Maximum sustained winds: 70 mph
- Present movement: NW at 12 mph
- Minimum central pressure: 991 mb
As of 11 p.m. Monday, the storm is about 485 miles east-southeast of Hilo, and 680 miles east-southeast of Honolulu with maximum sustained winds at 70 mph with higher gusts.
The storm system is moving northwest at 12 mph. The center of Guillermo is expected to pass approximately 170 miles northeast of Hawaii Island on Wednesday and about 130 miles northeast of Maui Wednesday night.
The threat of sporadic heavy rains will linger while the storm moves parallel to the islands, about one to three inches of rain could fall for most areas, with more near the mountains.
Large surf could spread from east to west over the islands this mid-week for east-facing shores. As the storm moves closer to Hawaii, the National Weather Service may issue a high surf advisory for east facing shores of most islands.
It is still too soon to determine which islands will experience the greatest impacts from Guillermo.
Large swells traveling ahead of Guillermo will spread from east to west over the Hawaiian Islands through Monday. Surf will steadily build along east-facing shores and will likely become large and potentially life-threatening starting on Monday.
The “hurricane hunters” of the U.S. Air Force 53rd Weather Reconnaissance Squadron conducted its first reconnaissance early Sunday at 4 a.m. as they flew through the storm. Crews dropped special sensors known as dropsondes into the storm to measure wind speeds, pressure and temperature.
The squadron will do round-the-clock observations every 12 hours, and as Guillermo gets closer to Hawaii, a plane will leave every nine hours.