85th AMS Annual Meeting

Tuesday, 11 January 2005
Idealized Numerical Simulation of the Evolution of Tropical Cyclone Electrification, Lightning, Microphysics, and Kinematics at Landfall
Alexandre O. Fierro, Univ. of Oklahoma, Norman, OK; and L. M. Leslie, E. R. Mansell, and J. Straka
Poster PDF (645.6 kB)
Effects of Landfall on the Evolution of Tropical Cyclone Electrification, Lightning, Microphysics, and Kinematics.

Alexandre O. Fierro*1, Lance M. Leslie1, Edward R. Mansell2,3, Jerry M. Straka1, William H. Beasley1 1 School of Meteorology, Univ. of Oklahoma, Norman, OK 2 Cooperative Institute for Mesoscale Meteorological Studies, Univ. of Oklahoma, Norman, OK 3 NOAA/ NSSL, Norman, OK

Astract

Strong tropical cyclones (TC), named hurricanes in the Atlantic basin, and typhoons in the northwest Pacific Ocean, are known for their destructive power associated with extremely strong winds, storm surges and torrential rainfall. Many populated coastal regions are threatened yearly by these extreme events. Thus, it is of primary importance to acquire a better understanding of their internal dynamics in order to improve forecasting capabilities. With the advent of increasingly powerful computing resources, numerous idealized numerical studies in the past 50 years have reproduced with success some of the main features of TC observed in nature. The availability of increasingly detailed observational studies is crucial in assessing the reliability of these numerical experiments. In this study, emphasis is placed on the importance of improving our knowledge of the TCs microphysical and electrical structure, to reduce model forecast errors in track and intensity predictions. Many numerical and observational studies have demonstrated the impact of orography/land on TC evolution, morphology and motion. There is a general agreement that TCs tend to weaken and also tend to deviate more from their initial track well offshore, as they interact with orography/land. Further motivation for this work find its support in previous observational studies, which stressed the importance of more systematic monitoring of any change in TC lightning flash activity. The latter could be a very useful source to determine the distribution of the convective precipitation (most importantly at landfall, providing advance warnings for potential flooding) and the severity of the weather (as the latter are also likely to originate from embedded supercells). Nevertheless, little is known about the actual changes occurring within the hydrometeor field and microphysics of a hurricane during landfall (on flat or mountainous terrain) and in turn how these changes influences on the TCs electrical activity and intensity fluctuations. This work is intended to help answer questions such as:

Does the simulated storm produce greater graupel/hail volume mass fluxes at low levels during landfall? If so, is the latter more pronounced within the rainbands or within the inner core region?

How does the net charge density structure differ within the inner core and inside the rainbands? Does the middle level charge region experience a downslope/upslope trend as a TC makes landfall?

Which of intra-cloud or cloud to ground lightning flash rates experience the most drastic changes and how is this related to changes observed in the hydrometeor field and intensity of the storm?

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