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Why are we doing this?
Country WalkThe U.S. is more vulnerable to hurricanes now than at any time in recent decades. Over the last 30 years coastal population growth in the U.S. has increased 4-5% y-1. With only a 1-2% y-1 rate of improvement in official track forecasts, the mean 24-h track error over the last 10 years is 91 nm (170 km). However, 5% of the 24-h track errors over the last 10 years are >200 nm (370 km). To minimize the possibility that a coastal area may be struck without time to prepare, much larger areas are warned than will actually experience damaging winds. While specific track models have indicated up to 15-30% improvement over the past 2-3 years, the average length of coastline warned, 400 nm (730 km), roughly a 4/1 ratio to the track error, has not decreased over the past decade. In fact, it has increased over the 30-year mean of 300 nm (556 km) in response to the emergency manger's desire for longer lead-times (PDT-5, 1998 PDF or HTML).

For over 40 years NOAA's hurricane research field program collected data required to support analytical and theoretical hurricane studies. These studies are designed to improve the underst anding of the structure and behavior of hurricanes. Over the 25 years that the NOAA WP-3D research aircraft have been active, HRD has collected observations in over 80 tropical cyclones. These data sets have enabled the development of new theories, analysis tools and dramatic forecast improvements, e.g.,

  • Flight-level data collected in these storms was instrumental in the development of a new theory on intensity change-the concentric eyewall cycle.
  • The addition of dropwindsonde data sets collected over the surrounding environment of storms into operational forecast models resu lted in a 20-30% improvement in track forecasts-the major justification for the procurement of the NOAA G-IVSP and GPS dropsondes.< /font>
  • The development of remote sensors such as the airborne Doppler radar, C-ba nd Scatterometer, and Stepped Frequency Microwave Radiometer have revolutionized our ability to describe the three-dimensional wind structure of the storm from the surface to the top of the troposphere.

While the data sets collected over the past 20 years have improved track forecasts and our description of mature storm structure, the main purpose for the experiments proposed fo r 2001 is to improve methods for hurricane prediction, in particular forecasts of storm intensity.
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