Example of NOAA's experimental tropical cyclone surface "wind speed" probability graphic.

September 30, 2005 — With the 2005 Atlantic Hurricane Season well on its way toward becoming one of the busiest in recorded history, several experimental graphical and text products available for public comment and evaluation are getting a workout.

NOAA’s experimental tropical cyclone surface wind speed probability products provide users with information that enhances their ability to make preparedness decisions specific to their situations. Where the existing strike probability product is a statement about the "close" approach of the center of a tropical storm or hurricane, the experimental wind speed probability product is about the actual weather potentially impacted areas could expect. The wind speed probabilities provide the chances of surface winds for tropical storms and hurricanes. Probabilities are produced for three intervals: 1) tropical storm winds of at least 39 mph, 2) winds at least 58 mph and 3) hurricane winds 74 mph and greater.

A graphical multicolored format uses concentric ellipses to show cumulative probabilities for each of the three wind speeds at 12-hour intervals out to 120 hours (e.g. 0-12 hours, 0-24 hours, etc.). These cumulative probabilities indicate the overall chance that the particular wind speed will occur at each location during the designated period.

NOAA is producing this experimental product along with the standard advisory package for each active cyclone in the Atlantic and Pacific basins. Pending public comment and final NOAA approval, the TCSWSP product could become operational in 2006 and replace the Atlantic strike probability text and graphic products, which would then be discontinued.

Improving Hurricane Forecasting Capabilities and Communication
NOAA is testing this experimental product as part of its continuous effort to provide a suite of products so users can make informed decisions. This is especially important for anyone dealing with hurricanes.

NOAA meteorologists forecast if, then possibly where, a storm will make landfall, when it would come ashore, and how strong it would be if it does. Forecasters issue a hurricane watch when hurricane conditions are possible 36 hours in advance and a warning when hurricane conditions are expected within 24 hours. Emergency managers and local/state officials rely on this information to make decisions on whether to evacuate areas in the path of the hurricane.

Example of NOAA’s hurricane “track” forecasts.

While still challenging, NOAA’s hurricane forecasts have improved over the last few decades. Improvements in NOAA’s hurricane “track” forecasts have allowed the NOAA National Hurricane Center to lengthen its forecasts from three to five days, and NOAA researchers are now focusing their efforts on improving hurricane intensity. These improvements in hurricane forecasting may help explain why hurricane-related deaths have decreased in recent years, despite the fact that the nation’s coastal regions continue to develop.

No matter how accurate NOAA’s hurricane forecasts are, they do little good if they do not get out to the user and/or the user does not understand how to interpret them. For example, NOAA was concerned residents in hurricane prone areas did not clearly understand some hurricane forecast products, especially the relatively new five-day NOAA hurricane track forecasts (characterized by a single black line surrounded by the cone of uncertainty). While some users focused solely on the black center line, the area to which users should pay close attention is the cone of uncertainty because it more accurately reflects track uncertainty inherent in any forecast.

Example of NOAA’s hurricane "strike probabilities" graphic.

“It’s not necessarily the center of the storm that is going to cause the most damage; it’s the dangerous storm surge that occurs near landfall, the broad expanse of strong wind, heavy precipitation and tornadoes that can spread well inland along the path of the storm,” said Max Mayfield, director of the National Hurricane Center in Miami. “This is exactly what we saw with hurricanes Katrina and Rita. A hurricane’s damaging effects can span many hundreds of miles away from its center.”

Not only is the purpose of the experimental TCSWSP product to supplement other NHC forecast products, it is also focusing on this very issue — depicting the uncertainly associated with size and intensity of the storm, not just its location.

Example of NOAA's experimental tropical cyclone surface "wind speed" probability graphic.

Small Probabilities are Still Significant
It is important for users to realize probabilities that many seem relatively small may still be quite significant, since they indicate there is a chance a damaging or potentially extreme event may occur that warrants preparation to protect lives and property, according to Richard Knabb, meteorologist and hurricane specialist at the National Hurricane Center. Just consider the potentially immense cost in terms of lives and property of not preparing for an extreme event, even if the chances at an individual point are only one in 20 (five percent) or one in 10 (10 percent) that the event will occur.

Comments on Experimental Forecast Products Sought
Through November 15, 2005, NOAA’s National Weather Service is seeking public comments on the experimental TCSWSP product to determine the benefit and usefulness of the product and product formats. Electronic submission of comments is encouraged via email to Tc.Probgraphic@noaa.gov.

NOAA forecasters constantly strive to improve their ability to convey forecast information and educate the public how to most effectively use that information. NOAA’s experimental TCSWSP product is just one example of this effort. The product provides users with information that enhances their ability to make preparedness decisions specific to their own situations. After viewing this product the user should come away realizing the impacts of a hurricane can be felt far beyond the center of the storm and the uncertainty associated with the hurricane’s forecast track, intensity and size.

Relevant Web Sites
NOAA National Weather Service

National Hurricane Center

NOAA Hurricanes Page

Hurricane Preparedness

Hurricane Awareness

NOAA Historical Hurricane Tracks

Media Contact:
NOAA Weather Service Public Affairs, (301) 713-0622