Convective activity in the Gulf of Tehuantepec can be very intense and is frequently linked to the development of tropical depressions and storms that may result in hurricanes once they move further westward. The objective of this study is to characterize the spatial extent and the intensity of the convection that develops in the western end of the Isthmus of Tehuantepec. In particular, we want to assess the role of mesoscale circulations, such as the land-sea breeze and mountain-valley breeze in the spatial organization and temporal evolution of convective activity. It is also of interest to identify the events of low level jets through the Isthmus, associated with synoptic scale features that are frequently observed during the winter months. The jet exit over the Gulf of Tehuantepec, has associated areas of vorticity and convergence/divergence that will also affect the spatial organization of the convection.

We have initiated a climatological study utilizing GOES data, from 1996 to 2002. We have obtained hourly averaged images to observe the daily diurnal variability. The analysis allows the identification of convective cores (based on minimum temperatures) and the extent of the cirrus anvils. The analysis was started using February data, where the events of low level wind jet through the isthmus have been left out of the average, so that the diurnal signal can be observed. During the summer months, we separate the days where there is clear evidence of influence of easterly waves. The preliminary results so far, based on observations from February and September allow the characterization of the diurnal pattern over the mountains. In September, the land-sea breeze signal is stronger and it is possible to observe the convection moving on/offshore.