Cyclogenesis in a Tropical Wave Critical Layer: Vertical Structure of the "Wave Pouch" and Impacts of the Large-scale Environment

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

This effort will address the genesis of tropical cyclones (and antecedent regions of low pressure and near-surface cyclonic wind patterns termed tropical depressions) through further study of the "marsupial paradigm." This conceptual model refers to a theory of hurricane formation in which the translation speed of one type of parent atmospheric disturbance (termed an "easterly wave") is matched the environmental flow so as to create a protective zone (or so-called "pouch") in which developing small-scale cyclonic circulation(s) are protected from hostile environmental conditions until further strengthening occurs. This study will be supported by data to be collected during the 2010 NSF-supported PREDICT (PRE-Depression Investigation of Cloud-systems in the Tropics) field campaign involving the NSF/NCAR GV research aircraft as well as complementary resources being provided by NASA and NOAA. This research will focus on conditions within the meso-alpha scale wave pouch region (having 200-2000 km horizontal extent), its interaction with the larger-scale environment, and impacts of this interaction on ultimate tropical cyclone formation. It will incorporate flight-level, dropsonde and radar data from the PREDICT field campaign, with reanalysis data, various satellite datasets, and the WRF-ARW numerical model to address three main questions: 1) Is a well-defined wave pouch a necessary condition for tropical cyclone development, and if so, how does it form? 2) Why do some waves exhibiting a deep pouch fail to develop into a tropical storm? 3) How does the Saharan Air Layer (SAL) affect tropical cyclogenesis, and why do some wave pouches provide protection from dry air intrusion while others do not? The intellectual merit of this effort centers on exploitation of the focused PREDICT dataset in conjunction with numerical model simulations conducted in the marsupial framework to lead to better understanding of tropical cyclogenesis. Broader impacts of this research include the education and training of two graduate students and the integration of tools and products into classroom learning activities, as well as support for an investigator drawn from an underrepresented group. Benefits to society will come through the increased understanding of tropical cyclogenesis and associated increases in warning lead time for hurricane formation.