Hurricane Awareness: Forecasting
July 20, 2012
Statements, Watches and Warnings
One part of the mission of the National Weather Service (NWS) is to save lives and protect property by issuing watches, warnings, forecasts, statements, and other pertinent information. These products are used by emergency management and response personnel, broadcast meteorologists, and the public.
During hurricanes and tropical storms, the National Hurricane Center and local National Weather Service Offices across the country share in the responsibility for providing critical weather information to the public. To do so, the Hurricane Center and local offices closely coordinate on the forecast, in order to provide consistent information to the public. Consequently, the normal zone forecasts may be delayed during these situations.
To make accurate forecasts, forecasters rely on a combination of observations, analyses, statistics, and computer generated guidance in making their predictions.
Standard observing equipment such as satellites, buoys, and land based observations are all important in locating and tracking the storm. In addition, reconnaissance aircraft fly through the storms to take and collect special observations and to drop specialized instruments called dropsondes into the storms to gather additional information.
As these storms approach land, RADAR observations become increasingly important. Quality, quantity, and timeliness of remote sensing observations are critical for accurate and timely forecasts and warnings. Once the observations have been collected, the data are checked for quality, analyzed, and used as the starting conditions for a variety of weather prediction models.
The weather prediction models start with the observed conditions and perform millions of calculations to generate predictions of the hurricane track and intensity and of the general conditions of the atmosphere surrounding the storm. Both the National Hurricane Center and local offices evaluate these computer predictions, coordinate and collaborate, and decide on a consistent forecast to be released to the media and the public.
Once the coordination is complete, both the National Hurricane Center and the local National Weather Service Office are responsible for issuing a variety of forecast, watch, and warning products to the public.
As with all weather-related threats, the National Weather Service relies on a watch and warning program to alert the public to the potential dangers from tropical storms and hurricanes.
Tropical Storm Watch/Hurricane Watch
A Watch is issued when tropical storm/hurricane force winds are possible along the coast within 48 hours. If you haven't done so prior to the issuance of the watch, it's a good time to begin preparations for the potential storm, especially for those actions that require extra time.
Tropical Storm/Hurricane Warning
A Warning is issued when tropical storm/hurricane force winds are expected along the coast within 36 hours. Once the warning has been issued, you should complete any preparatory actions and get to a safe location.
Once the storm arrives, stay in the safe location until the storm has completely passed. Don't be fooled by the eye of the storm, which can mislead people into thinking that the storm is over. Winds and rain will increase rapidly immediately after the eye passes overhead.
While the National Hurricane Center issues Hurricane and Tropical Storm watches and warnings for the coast, the local National Weather Service Office is responsible for issuing numerous watches, warnings, and advisories for various local hazards associated with or preceding the storm, both along the coast and inland. These include:
Did You Know?In 2006, the National Hurricane Center began issuing public forecasts of wind probabilities for various locations along the coast. These numbers are generated statistically, and due to the uncertainty in forecasting the track in intensity, the numbers may seem rather low. Especially days before landfall, don't be fooled by the low probabilities. Even though your probability is low, you may be in the area most likely to be hit by the storm.
- Coastal Flood
- Inland Tropical Storm/Hurricane
- Flash Flood
- Severe Thunderstorm
While issued separately, these watches and warnings are generally summarized by each local National Weather Service Office in Hurricane Local Statements. In addition, the local office issues a variety of forecasts and information statements during hurricanes or tropical storms.
In addition to tropical storm/hurricane watches and warnings, the National Hurricane Center and the Tropical Prediction Center issue numerous other products that can be very useful in tracking and assessing the potential hazards from tropical systems. These include:
- Tropical Weather Outlooks (Issued 4 times daily from June 1st to Nov. 30th)
- Public Advisories (Issued every 6 hours as needed)
- Intermediate Public Advisories (Issued every 2 to 3 hours as needed)
- Forecast/Advisories (Issued every 6 hours as needed)
- Discussions (Issued every 6 hours as needed)
- Wind Probability Forecasts (Issued every 6 hours as needed)
Question of the Day
This Hurricane Awareness information was prepared in partnership with the National Weather Service Forecast Offices in Gray, Maine, in observance of Hurricane Awareness Week in New England.
For additional information about hurricanes and hurricane safety, visit the National Hurricane Center's web site at: http://www.nhc.noaa.gov/