Incorporation of equatorial wave modes into tropical synoptic meteorology: Is It worth the trouble?

A brief review will be given of the influence of equatorial wave modes on the tropical weather, including their possible role as tropical cyclone pre-cursors. The talk will focus on the issue of whether tropical synoptic meteorology practices could benefit from including such equatorial waves. Incorporation of equatorial waves into forecasting requires clear-cut "synoptic models" (LaSeur, personal communication 1975). We will attempt to fuse the equatorial wave model with those currently in use.

Equatorial waves are quite difficult to make use of in practice. They are often visible only after filtering the data. Such filters are much less accurate in a real-time forecasting situation than in a research calculation. Choosing among possible filters is difficult, and all potentially suffer from aliasing of tropical cyclones. These problems will be contrasted with the possible benefits. Among the latter are the gains in understanding and interpreting what we see. Some questions directly addressable using equatorial wave theory are: (i) why convection occurs well east of lows rather than at their centers; (ii) why storms form on the edge of the monsoon trough; and (iii) why background convergence and easterly vertical wind shear play a key role in disturbance growth.

Some of the difficulty with adopting equatorial waves into tropical synoptic meteorology relates to old controversies between the climatological and perturbation schools in tropical meteorology (Palmer 1951). An attempt will be made to define a framework for viewing weather in the tropics that is based on previous work by Webster and Chang (1988) and others. The conceptual separation of waves and background forms the basis for this framework.