Seasonality and Geographic Distribution of Highly Precipitating Tropical Easterly Waves

Tropical easterly waves (TEWs) are important drivers of tropical rainfall, making significant contributions to summertime and annual rainfall across much of the tropics, and driving some extreme rainfall events. However, the location and timing of the rainiest TEWs is not well studied therefore better understanding the climatology of when and where TEWs are associated with excessive rainfall may help predict rainy TEWs and their impacts. Using twenty years of objectively tracked TEWs and associated precipitation, we identify the rainiest TEWs by both rainfall at individual times and total rainfall over the wave’s life normalized by wave lifespan. Initial results show that most highly precipitating TEWs occur over tropical oceans in a band roughly corresponding with the ITCZ. For TEWs in the northern hemisphere, the rainiest tracks occur during the months with the most TEW activity, July through September, while the rainiest individual times are spread across July through December. While we expect higher counts of TEWs with enhanced precipitation during the months of peak activity (July through September), the persistence of rainy times past the peak of TEW activity suggests additional factors, either tropical or extratropical, result in highly precipitating times later in the year and highlights the importance of understanding TEWs that occur outside of the summer season. In the southern hemisphere, where fewer TEWs occur, the rainiest individual times and tracks both occur October through March. Further planned analysis will separate TEW tracks and points by region of occurrence and whether the points occur over land or ocean, and identify the rainiest times in the land/ocean subsets.