The Galvez-Davison Index for Tropical Convection

The Galvez-Davison Index (GDI) was developed in an attempt to ease and improve tropical convection forecasting over the Americas. The index considers (a) the vertical distribution of equivalent potential temperature, (b) mid-level warming/cooling associated with upper ridges/troughs and (c) drying/stabilization associated with trade wind inversions. The GDI is a diagnostic tool and can be computed with temperatures and mixing ratios at 950, 850, 700 and 500 hPa. These can be obtained via soundings, model analyses or any alternative desired means.

As a preliminary validation exercise, GDI data computed using GFS model output was compared against cloud top temperatures derived from GOES data. The results are promising. They show that the GDI outperforms other convective instability indices in diagnosing the potential for different tropical convection regimes ranging from isolated shallow cells to widespread deep convection. It even produced better results than the K index, so far considered the most efficient index for tropical convection forecasting in the Americas. Potential applications include both the public and aviation sectors.