The National Weather Service Forecast Office in Honolulu, Hawaii issues the following watches, warnings, and advisories when weather threatens Hawaii.
Watches are issued to allow time for preparation and planning for weather threats that are expected, but have not arrived yet.
Warnings are issued when a threat is occurring or imminent, and immediate action is needed to protect life and property.
Advisories are issued when weather conditions impact our lives in ways that are not a direct threat to life and property but ignoring them may lead to hazardous conditions.
This presentation provides more information about the differences between watches, warnings, and advisories.
- Can there be a Watch and Warning in effect at the same time?
- Yes. Watches generally cover longer time periods and highlight the possibility of a threat that may develop at some time in the future. Warnings are issued for specific threats in particular areas as they develop and require immediate action to protect life and property.
- Tornado Watch
- A Tornado Watch means that strong thunderstorms capable of producing tornadoes are possible. If you are in the area of a Tornado Watch, you should be prepared to take shelter from thunderstorms. Tornadoes may develop with little warning. Tornado Watches are generally issued for 6 hour periods.
- Tornado Warning
- A Tornado Warning means that a tornado is occurring or developing in a strong thunderstorm. If you are in the area of a Tornado Warning you should stay inside, away from windows, and be prepared for strong winds and large hail. If you see a tornado and/or are in its path, go to the central portion of a substantial structure, like a building, and seek shelter under a heavy piece of furniture if possible, or in a closet or other small protected room. Tornado warnings are generally in effect for less than 1 hour.
- Severe Thunderstorm Watch
- A Severe Thunderstorm Watch means that strong thunderstorms capable of producing winds of 58 mph or higher and/or hail 1 inch in diameter or larger are possible. If you are in the area of a Severe Thunderstorm Watch, you should be prepared to take shelter from thunderstorms. Severe Thunderstorm Watches are generally issued for 6 hour periods.
- Severe Thunderstorm Warning
- A Severe Thunderstorm Warning means that thunderstorms capable of producing winds of 58 mph or higher and/or large hail of 1 inch diameter or greater are occurring or could form at any time. If you are in the area of a severe thunderstorm, you should take shelter indoors immediately, avoid windows and be prepared for high winds and hail. Severe Thunderstorm Warnings are generally in effect for an hour or less.
- Flash Flood Watch
- A Flash Flood Watch means heavy rain leading to flash flooding is possible. If you are in the area of a flash flood watch you should be prepared for heavy rains and potential flooding. Flash Flood Watches may be issued up to 12 hours before flash flooding is expected.
- Flash Flood Warning
- A Flash Flood Warning means that flooding is occurring or will develop quickly. If a Flash Flood Warning is issued for your area, take shelter and/or move to high ground as necessary. Never drive or walk across a flooded roadway.
- Flood Advisory
- A Flood Advisory means nuisance flooding is occurring or imminent. A Flood Advisory may be upgraded to a Flash Flood Warning if flooding worsens and poses a threat to life and property.
- High Wind Watch
- A High Wind Watch is issued when sustained winds exceeding 40 mph and/or frequent gusts over 60 mph are likely to develop in the next 24 to 48 hours. For summit areas, high wind watches are issued when sustained winds are expected to exceed 45 mph and/or frequently gust over 60 mph. If you are in an area for which a High Wind Watch has been issued you should prepare secure loose objects outdoors that may blow about and avoid outdoor activity that exposes you to high winds.
- High Wind Warning
- A High Wind Warning is issued when sustained winds exceeding 40 mph and/or frequent gusts over 60 mph are occurring or imminent. For summit areas, warnings are issued for winds exceeding 45 mph and/or frequently gusting over 60 mph. Wind warnings may be issued up to 24 hours ahead of the onset of high winds. If you are in an area where a high wind warning is in effect you should avoid activities that expose you to high winds. Loose objects may be blown around. Tree limbs may break and fall. Power lines may be blown down.
- Wind Advisory
- A Wind Advisory is issued when sustained winds of 30 to 39 mph and/or frequent gusts to 50 mph or greater are occurring or imminent. For summit areas the sustained wind range is 30 to 45 mph. Wind advisories may be in effect for 6 to 12 hours. If you are in an area where a wind advisory is in effect you should secure loose objects that may be blown about outdoors and limit activity that may expose you to high winds.
Summit Areas Only
- Winter Storm Watch
- A Winter Storm Watch is issued when more than 6 inches of snow and/or ice accumulation of more than 1/4 inch are expected in a 24 hour period. Winter Storm Watches may be issued 24 to 48 hours in advance of the onset of the winter storm.
- Winter Storm Warning
- A Winter Storm Warning is issued when more than 6 inches of snow and/or ice accumulation of more than 1/4 inch are occurring or imminent. Winter Storm Warnings may be issued as much as 24 hours in advance.
- Blizzard Warning
- A Blizzard Warning is issued when sustained winds of 35mph or above along with falling/blowing snow reducing visibilities to 1/4 mile or less.
- Winter Storm Advisory
- A Winter Weather Advisory is issued when falling snow of 1-6 inches and/or ice accumulation of less than 1/4 inch in a 24 hour period is occurring or imminent, and/or when ice has formed on roadways or is expected, and/or when snow is blowing and drifting.
- Wind Chill Warning
- A Wind Chill Warning is issued when wind chill reading reach below -10 degrees F for three or more hours.
- Wind Chill Advisory
- A Wind Chill Advisory is issued when wind chill readings are between 0 and -10 degrees F and an average wind speed above 15 mph for six or more hours.
- High Surf Warning
- A High Surf Warning is issued when waves reach threshold criteria for a particular island and shoreline. High Surf Warnings may be issued up to 24 hours ahead of the arrival of the swell and may remain in effect for several days.
- High Surf Advisory
- A High Surf Advisory is issued when waves reach threshold criteria for a particular island and shoreline. High Surf Advisories may be issued up to 24 hours ahead of the arrival of the swell and may remain in effect for several days.
- Small Craft Advisory
- A Small Craft Advisory is issued for the coastal waters when winds of 25-33 knots and seas 10 feet or higher are occurring or forecast.
- Gale Warning
- A Gale Warning is issued for coastal, offshore, and high seas areas when winds of 34- to 47 knots not associated with a tropical cyclone are occurring or forecast.
- Storm Warning
- A Storm Warning is issued for coastal, offshore, and high seas areas when winds of 48-63 knots not associated with a tropical cyclone are occurring or forecast.
- Tropical Storm Watch
- A Tropical Storm Watch is issued when tropical storm force winds (39-73 mph) are expected within the next 48 hours.
- Tropical Storm Warning
- A Tropical Storm Warning is issued when tropical storm force winds (39-73 mph) are expected within the next 36 hours.
- Hurricane Watch
- A Hurricane Watch is issued when hurricane force winds of 74 mph or greater are expected within the next 48 hours.
- Hurricane Warning
- A Hurricane Warning is issued when hurricane force winds of 74 mph or greater are expected within the next 36 hours.
- Fire Weather Watch
- A Fire Weather Watch is issued when there is a high potential for the development of a Red Flag event. Fire Weather Watches may be issued 12 to 72 hours prior to the expected onset of criteria.
- Fire Weather Warning
- The criteria for Red Flag events is a Keetch-Byram Drought Index (KBDI) greater than or equal to 600, relative humidity equal to or less than 40 percent, and winds greater than 20 mph. Red Flag Warnings alert of the potential for widespread ignitions or control problems with new or existing fires.
On very rare occasions weather conditions may also warrant the issuance of the following:
- Dense Fog Advisory
- A Dense Fog Advisory is issued when visibility is reduced to 1/4 mile or less. This advisory is issued for radiation type fog that occurs most often in the valleys of Central Oahu and Maui. Motorists are urged to use extreme caution when driving in areas of dense fog.
- Excessive Heat Advisory
- An Excessive Heat Advisory is issued for elevations at or below 3000 feet when daytime Heat Indices (HI) of 105 degrees F or greater and nighttime HI values of 80 degrees F or greater are expected for 2 consecutive days or longer. During periods of excessive heat you should drink plenty of water, avoid unnecessary exertion, and seek shelter in a well-ventilated or air-conditioned building. Extra care and attention should be given to very young children and the elderly.
- Freeze Warning
- A Freeze Warning is issued when air temperatures are forecast below 32 degrees F for elevations at or below 6000 feet.