Vorticity-based detection of tropical cyclogenesis

M.M. Gierach, M.A. Bourassa, P. Cunningham, J.J. O'Brien, P.D. Reasor

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


Ocean wind vectors from the SeaWinds scatterometer aboard the Quick Scatterometer (QuikSCAT) satellite and Geostationary Operational Environmental Satellite (GOES) imagery are used to develop an objective technique that can detect and monitor tropical disturbances associated with the early stages of tropical cyclogenesis in the Atlantic basin. The technique is based on identification of surface vorticity and wind speed signatures that exceed certain threshold magnitudes, with vorticity averaged over an appropriate spatial scale. The threshold values applied herein are determined from the precursors of 15 tropical cyclones during the 1999-2004 Atlantic Ocean hurricane seasons using research-quality QuikSCAT data. The choice of these thresholds is complicated by the lack of suitable validation data. The combination of GOES and QuikSCAT data is used to track the tropical disturbances that are precursors to the 15 tropical cyclones. This combination of data can be used to test detection but is not as easily used to examine false alarms. Tropical disturbances are found for these cases within a range of 19-101 h before classification as tropical cyclones by the National Hurricane Center. The 15 cases are further subdivided based upon their origination source (i.e., easterly wave, upper-level cutoff low, stagnant frontal zone, etc.). The primary focus centers on the cases associated with tropical waves, because these waves account for the majority of all Atlantic tropical cyclones. The detection technique illustrates the ability to track these tropical disturbances from near the coast of Africa. Analysis of the pretropical cyclone (pre-TC) tracks for these cases depicts stages, related to wind speed and precipitation, in the evolution of a tropical disturbance within an easterly wave to a tropical cyclone. © 2007 American Meteorological Society.
Original languageEnglish
Pages (from-to)1214-1229
Number of pages16
JournalJournal of Applied Meteorology and Climatology
Issue number8
Publication statusPublished - 2007


  • Precipitation (meteorology)
  • Satellite imagery
  • Storms
  • Tropics
  • Vorticity
  • Wind
  • Geostationary Operational Environmental Satellite (GOES) imagery
  • Ocean wind vectors
  • Pretropical cyclone
  • Quick Scatterometer (QuickSCAT)
  • Tropical disturbances
  • Tropical waves
  • Meteorology
  • cyclogenesis
  • easterly wave
  • GOES
  • hurricane
  • satellite imagery
  • scatterometer
  • tropical cyclone
  • vorticity
  • wind velocity
  • Atlantic Ocean


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