Midlatitude Influence on the Genesis of an Early Season Eastern North Pacific Tropical Cyclone

Tropical waves are the primarily source for eastern North Pacific (EPAC) tropical cyclones. Many, but not all, of the precursor tropical waves can be tracked back to Africa. The term tropical wave is generic in nature, referring to a trough, or cyclonic curvature in the tradewind easterlies. Perturbations within the tradewind easterlies can interact with a favorable background environment in the EPAC basin in the development of tropical cyclones. Since any coherent perturbation within the tradewind easterlies can loosely be termed a tropical wave, the source for a tropical wave is not always from Africa. If tropical waves that lead to the development of a tropical cyclone in the EPAC do not have to move off the coast of Africa, what other source can develop a precursor tropical wave? In order to answer this question, this study will analyze the source of a tropical wave which was the precursor for an early season EPAC tropical cyclone, Tropical Storm Alvin in May 2013.