The 23rd Conference on Hurricanes and Tropical Meteorology

4A.10
TROPICAL CYCLONE STRUCTURE CHANGE AS REVEALED BY ONE-MINUTE SATELLITE IMAGERY

John A. Knaff, NOAA Colorado State University, Ft. Collins, CO

The new generation of Geostationary Operational Environmental Satellites (GOES) have improved capability for rapid interval imaging. During Super Rapid Scan Operations (SRSO) and Rapid Scan Operations (RSO) imagery is collected over fairly large areas at one, and seven and a half-minute intervals, respectively. The SRSO imagery offers 22 images an hour with two segments of 1-minute interval images, allowing for regularly scheduled operational scans. A series of science tests were carried out during the Summer of 1995 using the GOES-9 satellite before it became operational, including several SRSO cases of hurricanes. These cases, which did not have interruptions for routinely scheduled imagery have 48 images per hour and include observations of hurricanes Felix, Luis and Marilyn.
This talk will discuss tropical cyclone structure and the evolution of that structure in some of the SRSO hurricane cases. The first topic of this presentation will concern the evolution of the upper level winds as manually calculated from convective overshoots, cirrus clouds and visible cloud features. Here, changes of convective activity in the eyewall are examined for changes in upper level vorticity within a degree latitude of the center. The second topic will concern itself with the tracking of convective asymmetries in the eyewall. In examining the SRSO imagery it becomes rather clear that new convection forms in the forward quadrant (with respect to motion) of the hurricane's eyewall and rotates around, often dissipating in the rear quadrant (with respect to motion). The rotation of such anomalies are examined for their relationship to small changes in motion, particularly the well documented trochoidial oscillations often seen with intense hurricanes.

The 23rd Conference on Hurricanes and Tropical Meteorology