20th Conference on Weather Analysis and Forecasting/16th Conference on Numerical Weather Prediction


Convective Towers in Eyewalls of Tropical Cyclones Observed by the TRMM Precipitation Radar in 1998–2001

Owen A. Kelley, George Mason University, Fairfax, VA and NASA/GSFC, Greenbelt, MD; and J. Stout

It is difficult to forecast the intensity of a tropical cyclone, and improving such forecasts would improve public safety. One possible indicator of cyclone intensification is a convective tower in a cyclone’s eyewall. The TRMM Precipitation Radar (PR) is the first space-borne radar that is capable of resolving the detailed vertical structure of convective towers. Since it was launched in 1997, the PR has flown over enough tropical cyclones to make possible a statistical study of convective towers in eyewalls.

We locate approximately one hundred TRMM PR overflights of tropical cyclones whose eyewalls are entirely or mostly within the PR swath. We discuss different definitions of convective towers. We choose a definition that is easy to implement in an automated search and that locates those towers that are most often associated with tropical cyclone intensification. Next, we describe the vertical and horizontal structure of convective towers in cyclone eyewalls. We contrast the structure of towers within eyewalls with those outside of eyewalls. Last, we quantify how often cyclone intensification is associated with the presence in the eyewall of at least one PR pixel that is a convective tower. We find that intensifying cyclones are more than twice as likely to have a convective tower in their eyewall than non-intensifying cyclones. In particular, 50% of weak, intensifying cyclones (categories 1 or 2 on the Saffir/Simpson scale) have a convective tower, vs. 20% of weak, non-intensifying cyclones. Thirty-five percent of strong, intensifying cyclones have a tower, vs. 15% of strong, non-intensifying cyclones.

extended abstract  Extended Abstract (396K)

Poster Session 1, Monday Posters
Monday, 12 January 2004, 2:30 PM-4:00 PM, Room 4AB

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