Satellite products and imagery with Hurricane Isabel

During the past few years the satellite data and products for monitoring and analyzing hurricanes have expanded. For example, the MODIS (Moderate Resolution Imaging Spectroradiometer) aboard the NASA EOS (Earth Observing System) provides 250-meter spatial resolution visible images, along with truecolor images and 38 spectral bands at 1 km resolution. In contrast, the Dvorak technique for estimating hurricane intensity using satellite images was introduced in the 1970s and it continues to be useful as a primary analysis tool. However, considerably more satellite data sets are now available to supplement the Dvorak technique that were not available in the 1970s.

A survey of satellite products and imagery will be presented to illustrate the life cycle of Hurricane Isabel during 3-18 September 2003. Hurricane Isabel persisted at or near Category 5 intensity for three full days. Fortunately it weakened to Category 2 intensity when in went ashore in North Carolina on 18 September.

Geostationary satellites provide tracking and intensity information along with motion derived wind vectors. With Hurricane Isabel, GOES SRSO (Super Rapid Scan Operations) images were available on seven consecutive days. The TRMM (Tropical Rainfall Measuring Mission), SSMI (Special Sensor Microwave Imager), and the NOAA satellites’ AMSU (Advanced Microwave Sounder) all have microwave images that depict ice and water distributions that cannot be measured in the infrared spectrum. The AMSU also directly measures the upper layer hurricane warm core for which algorithms have been devised to estimate hurricane intensity and size. Scatterometers provide estimates of satellite winds over the oceans that can be used to estimate the intensity of weak tropical cyclones and also depict the outer wind patterns with hurricanes. MODIS and NOAA’s AVHRR (Advanced High Resolution Radiometer) have sensors from polar orbit with 1 km resolution IR images that reveal features not well depicted by the lower resolution geostationary images.