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Cooperative Institute for Meteorological Satellite Studies / University of Wisconsin-Madison
Tropical Cyclones
Image Enhancements FAQ

Within the various "Images & Movies" pages and "TCTrak" window Infrared images are displayed that have been enhanced using two primary enhancement curves. These enhancements are used to highlight various different features within the imagery, with each enhancement used for different purposes. These two enhancements are named the "BD Curve" and "NHC Curve" enhancements.
BD Curve Enhancement

This enhancement is used a great deal in the research and tropical cyclone forecasting communities who are interested in determining the intensity of these storms. This enhancement is otherwise known as the "Dvorak Hurricane Curve for Tropical Cyclone Classification", and is applied only to infrared (11µm) imagery. The different black/white/gray ranges represent different intensity classifications in the Subjective Dvorak Intensity Classification Technique (NOAA Technical Report NESDIS 11, 1984). The temperature values displayed on the image above are approximate, with the absolute temperature ranges for each gray shade listed below :
         	  GRAY SHADE CODE         TEMPERATURE (Deg C)
         	  Warm Medium Gray          greater than +9
         	  Off White                  + 9 to -30
         	  Dark Gray                  -30 to -41
         	  Medium Gray                -41 to -53
         	  Light Gray                 -53 to -63
         	  Black                      -63 to -69
         	  White                      -69 to -75
         	  Cold Medium Gray           -75 to -80
         	  Cold Dary Gray            less than -81
NHC Curve Enhancement

This enhancement is mainly utilized by the National Hurricane Center/ Tropical Prediction Center in Miami, Florida for enhancement of infrared (11µm) imagery for television, newspaper, and internet displays. This enhancement is typically provided for/by the media since they prefer to work with color imagery rather than simple black & white enhanced imagery. The temperature values listed on the image above are approximate values.
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