What is the Role of Deep Convection in the Intensification of Tropical Cyclones?

Tuesday, 19 April 2016: 2:00 PM
Ponce de Leon A (The Condado Hilton Plaza)
John E. Molinari, University at Albany/SUNY, Albany, NY

DeMaria et al. (2012) showed a surprising negative correlation between lightning frequency (a good measure of deep convection) in the storm core and tropical cyclone intensification over subsequent periods of 6, 12, 18, and 24 hours. Tao and Jiang (2015) argued that rapid intensification proceeds from periods where shallow convection dominates and deep convection is nearly absent. Many authors have argued that development of a low-level vortex is preceded by the existence of a strong midlevel vortex and thus a cold core in the lower troposphere (Raymond et al. 2007, 2014; Nolan 2007). This configuration should suppress deep convection and is thus consistent with the above arguments. Modeling studies by Wang (2014) also show the importance of relatively shallow convection in tropical cyclone development. Conversely, numerous previous papers have shown a high correlation between convective outbreaks in the tropical cyclone core and subsequent intensity increases. How can both be true?

DeMaria had a second result, that enhanced lightning in outer rainbands is accompanied by subsequent deepening over all time scales from -6 to 24 hours. This also contradicts many previous results in the literature arguing that outer region heating (such as in the development of a secondary eye wall) will weaken the storm.

In my talk I will try to sort out these paradoxes and contradictions.

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