The system designated Potential Tropical Cyclone One-C strengthened Wednesday as it tracked westward toward the Hawaiian Islands, prompting forecasters to urge residents and visitors to prepare for heavy rainfall, flooding and gusty winds beginning late this week.
Where the system is and what it could bring
At 11 a.m. Wednesday, the Central Pacific Hurricane Center placed the center of the system about 895 miles east-southeast of Hilo and roughly 1,100 miles east-southeast of Honolulu. The cyclone was moving west at about 9 mph with maximum sustained winds near 40 mph, up from 35 mph earlier in the day.
Forecast models and official guidance indicate the storm is likely to become a named tropical storm — expected to be called Hernan — by Friday at the latest. The hurricane center gave the system a 90% chance of becoming a tropical cyclone within 48 hours and over the next seven days.
Rainfall and flooding risks
The greatest hazard from the system is expected to be heavy rainfall. The National Weather Service and hurricane center are forecasting widespread totals of 5 to 10 inches across much of the island chain, with isolated maximum amounts up to 20 inches in favored locations. Those amounts could produce life-threatening flooding and dangerous mudslides, particularly across steep and mountainous terrain on Hawaiʻi Island and in parts of Maui County.
"Residents and visitors should prepare now," the National Weather Service in Honolulu said, warning the system could bring strong winds, heavy rain, flooding, mudslides and dangerous surf.
Wind, surf and timing
Tropical-storm-force winds already extend as far as 275 miles northeast of the storm’s center, and forecasters said wind impacts will increase across the islands regardless of the system’s exact track. Alongside the rain bands, gusty winds may down trees and power lines and contribute to hazardous marine conditions.
Heavy showers are expected to begin affecting the Big Island as early as Friday, spreading to Maui by the start of the weekend and continuing to impact much of the rest of the Hawaiian Islands through the weekend as the system approaches or passes nearby.
What officials are saying
Both the Central Pacific Hurricane Center and the National Weather Service emphasized that pinpointing which specific locales will receive the highest rainfall remains uncertain. Forecasts could change as the system organizes and its track becomes clearer, so officials urged close attention to updates over the next 48 to 72 hours.
Preparedness steps
Officials recommend residents and visitors take steps now to prepare for heavy rain, flooding and possible high winds:
- Review and update emergency plans and evacuation routes, especially for those in flood-prone or steep areas.
- Secure outdoor furniture, loose objects and any items that could be blown around by gusty winds.
- Stock emergency kits with water, nonperishable food, flashlights, batteries and medications for at least 72 hours.
- Avoid driving through flooded roadways; turn around, don’t drown.
- Monitor official sources — CPHC, NWS Honolulu and local county emergency management — for watches, warnings and alerts.
| Item | Current value / forecast |
|---|---|
| Location (11 a.m.) | ~895 miles ESE of Hilo; ~1,100 miles ESE of Honolulu |
| Movement | West at ~9 mph |
| Maximum sustained winds | 40 mph (as reported) |
| Rainfall forecast | 5–10 inches widespread; up to 20 inches isolated |
| Chance of becoming tropical cyclone | 90% within 48 hours / 7 days |
Local impacts and next steps
Forecasters noted the highest rainfall potential currently favors Hawaii island and Maui County, though the exact distribution of heavy rain could shift as the system evolves. In addition to flash flooding and landslides in steep terrain, communities along exposed shorelines should expect dangerous surf and elevated coastal hazards as the storm draws nearer.
Residents and visitors should remain alert for any tropical storm or hurricane watches that could be issued by early Thursday and should follow instructions from county emergency management offices. With sea-surface temperatures unusually warm this season and an ongoing El Niño contributing to elevated activity in the eastern Pacific, officials stressed vigilance for the next several days.
Updates will be issued by the Central Pacific Hurricane Center and the National Weather Service as new data arrive. Monitor local radio, official social feeds, and county communications for watches, warnings and evacuation guidance.
