9A.7 Can rapidly developing African easterly waves be distinguished by their satellite signatures over West Africa?

Wednesday, 30 April 2008: 9:30 AM
Palms GF (Wyndham Orlando Resort)
Michael W. Douglas, NOAA/NSSL, Norman, OK; and J. F. Mejia and K. Knapp

One goal of the recently completed NASA-AMMA field program over the eastern Atlantic Ocean was to collect observations to help determine how prediction of hurricane formation over the eastern tropical Atlantic can be improved. One aspect of our research has been to analyze African easterly waves with in-situ and satellite data; here we describe the differences in the satellite-signatures of developing and non-developing waves from an analysis of historical METEOSAT imagery. The imagery provides a unique perspective because of its spatial resolution (10 km) and frequency, which is sufficient to resolve the diurnal cycle. We first identify, by inspection of Hovmoller diagrams, the tropical waves during the period July-September for years for which the METEOSAT imagery is available. Then we identify those waves that developed into so-called “Cape Verde” storms – those that formed relatively far east in the Atlantic. The difficulty of this classification procedure is discussed. Composites of the satellite imagery as a function of latitude and of month will be shown. The amplitude of the diurnal cycle will also be presented for both the rapidly developing and non-developing waves. The usefulness of these results in “predicting” eastern Atlantic rapid cyclogenesis is then discussed.
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