2009 NSF-PREDICT Dry Run: what have we learned?

In support of the NSF-PREDICT, NOAA-IFEX and NASA-GRIP Dry Run exercises during the 2009 hurricane season, a real-time wave tracking algorithm and corresponding diagnostic analyses based on a recently proposed tropical cyclogenesis paradigm was applied to tropical easterly waves in the Atlantic basin. In this study, the synoptic and meso-alpha scale structure of the developing and non-developing waves was examined, and different scenarios of wave evolution were identified based on the kinematic structure of the wave pouch: fast propagating waves without a pouch, waves with a shallow pouch confined primarily above the boundary layer or within the boundary layer, and waves with a relatively deep pouch extending from 600-700 hPa to near the surface. Easterly waves without a pouch or with a shallow pouch did not develop. Although not all waves with a deep pouch developed into a tropical storm, our diagnoses show that a deep wave pouch extending from 700 hPa to 950 hPa had formed at least 24 hours prior to genesis in all the sixteen named storms which originated from monochromatic tropical easterly waves over the Atlantic during June-October 2008-2009. Illustrative examples for each scenario are presented herein using the GFS analysis data and satellite imagery. Our results support the hypothesis that a diabatically activated wave pouch extending from near the surface to the lower troposphere is a necessary condition for tropical cyclone formation.