Atlantic tropical cyclogenesis—satellite analysis
Raymond M. Zehr, NOAA/NESDIS, Fort Collins, CO
The initial positions of each tropical storm and hurricane from the Best Track data can be used to indicate where and when tropical cyclogenesis occurs. Satellite image analysis provides a wealth of additional information on the genesis period for each tropical cyclone.
Animations of high resolution multi-spectral geostationary images are used to track the tropical cyclone scale circulation center back in time. Typically, this circulation center originates at mid-levels in association with a mesoscale convective system (MCS). The MCS's can be objectively identified by the centroid of IR temperature defined cold cloud areas at their maximum extent. However, it is at times difficult to distinguish the center that eventually becomes the cyclone center from the broad center of the pre-existing tropical disturbance. Nevertheless, this distinction can often be made, and the pre-existing systems, usually easterly waves, can be tracked back in time for many days. Total precipitable water analyses using a microwave satellite algorithm applied to a composite of polar orbiting satellite data are shown to be very useful in tracking easterly waves. When tropical cyclones form primarily from upper-level forcing, the animated water vapor images show this evolution.
A few detailed case studies show tracks of the key features identified with satellite analysis and depict the transformation of an easterly wave to a tropical storm. More limited case studies of the genesis periods of all Atlantic named tropical storms for 2004-2005 will be summarized.
The case studies will be supplemented with numerical model analyses, and discussed in terms of several conceptual models of tropical cyclogenesis.
In anticipation of the next series of GOES (GOES-R), the improved Meteosat-8 image products will be examined with a case study. Other satellite products, such as scatterometer winds and microwave images are also being evaluated as part of this project.
Extended Abstract (280K)
Session 10B, Tropical Cyclogenesis II
Wednesday, 26 April 2006, 3:30 PM-5:30 PM, Regency Grand Ballroom
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