4.5 Using Ensembles to Diagnose Environmental Influences on Tropical Cyclone Predictability

Wednesday, 25 January 2017: 5:15 PM
Conference Center: Skagit 5 (Washington State Convention Center )
Sharanya J. Majumdar, Univ. of Miami/RSMAS, Miami, FL; and W. A. Komaromi, J. R. Moskaitis, J. D. Doyle, and C. S. Velden

The broad research goal of the Office of Naval Research Tropical Cyclone Intensity (TCI) program is to enhance our understanding of the dynamics of the upper-level outflow of tropical cyclones and its connection to the larger-scale environment, and its ultimate influence on intensity change.  
The variability and predictability of tropical cyclone structural changes is investigated using ensemble predictions from the global European Centre for Medium-Range Weather Forecasts (ECMWF) and regional Coupled Ocean/Atmosphere Mesoscale Prediction System for Tropical Cyclones (COAMPS-TC) ensembles for selected tropical cyclones.  A particularly interesting case is Hurricane Joaquin (2015), which underwent two separate phases of intensification during its life cycle and also included a low-predictability track scenario.  The ECMWF ensemble indicated that the predictability of the track and first intensification phase was largely dependent on the vortex structure.  The COAMPS-TC ensemble indicated that in addition to the vortex structure, the synoptic-scale environment and in particular a mid-latitude trough west of Joaquin may have influenced the predictability of the track.  During the second interaction phase, both the ECMWF and COAMPS-TC ensembles suggested that the predictability was associated with the interaction with the approaching trough, which strengthened the outflow in the north-western quadrant and weakened the outflow in the southward and eastward directions.  Work is ongoing to investigate the causality on multiple temporal and spatial scales, and further insights into how these multi-scale interactions govern the predictability of the TC track and structure will be presented.
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