7B.4
**Mixed Rossby-gravity waves and Western Pacific tropical cyclogenesis
Michael J. Dickinson, SUNY, Albany, NY
The current work examines the development of a tropical cyclone from an equatorial mixed Rossby-gravity wave using time-filtered ECMWF analyses and observed Outgoing Longwave Radiation (OLR). The equatorial wave in this case exhibited maximum meridional flow at the equator with convection located ahead of the southerly flow in the Northern Hemisphere and ahead of the northerly flow in the Southern Hemisphere, as expected from the analytic mixed Rossby-gravity wave solution. The mixed Rossby-gravity wave developed near 170°E during the active (convective) phase of the Madden-Julian Oscillation (MJO). Associated with the MJO convection was a weak westerly wind burst along the equator. The mixed Rossby-gravity wave propagated westward and intensified within the large scale MJO. Near 145°E the wave moved northwestward with convection developing along the wave axis. Within a 36 hours, the wave becomes a tropical depression. The relationship between the mixed Rossby gravity wave and the subsequent cyclogenesis will be discussed at the conference.
Session 7B, Tropical Cyclogenesis II (Parallel with Sessions 7A and J4)
Wednesday, 24 May 2000, 4:00 PM-5:15 PM
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