Equatorial tropical weather is influenced by many types of disturbances with varying temporal and spatial scales. One important category of disturbances are equatorial wave modes. Not only do they impact tropical weather directly, they can influence the time and location of tropical cyclogenesis. These features have been examined extensively in the literature, though mainly from a theoretical approach. Few have tried to apply the theoretical models of these waves to synoptic features seen in the data, especially for equatorial Rossby waves. To gain a better perspective of the control that these waves have over equatorial tropical weather, would be insightful to examine daily weather maps for the presence of these features.

Considering the above, this presentation will focus on one specific case study of an equatorial Rossby wave train in the Western Pacific during the Northern Hemisphere summer of 1991. ECMWF gridded analyses have been used in conjunction with outgoing longwave radiation (OLR) to track this wave train. A 15-30 day band-pass filter has been applied to all data in an attempt to isolate these waves from background features (i.e. MJO and monsoon trough) as well as equatorial waves with shorter temporal scales (i.e. mixed Rossby gravity waves, westward inertial gravity waves, etc.).

Beginning in mid-August, an equatorial Rossby wave train clearly develops in the Western Pacific and persists over a two month period. In addition, eleven tropical cyclones form in association with this very regular feature. In the talk, this case will be discussed further in detail, specifically focusing on the synoptic structure and motion of this wave train.