From tropical depression to hurricane or dissipation: environmental conditions shaping early-stage evolution
Brianna J. Poirier1, Xubin Zeng2, Kimberly M. Wood3
Department of Hydrology and Atmospheric Sciences
1The University of Arizona, Tucson, AZ
2,3The University of Arizona, Tucson, AZ
Environmental conditions associated with tropical cyclone genesis in the North Atlantic Ocean Basin were examined to identify variables that may distinguish systems that dissipate from those that intensify. ERA5 reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) were collocated with tropical cyclone best-track positions from the International Best Track Archive for Climate Stewardship (IBTrACS). An initial analysis was conducted using 20 cases from 2002-2022, evenly divided between systems that remained tropical depressions (≤ 33 kts or 38 mph) and systems that later intensified into hurricanes. To isolate pre-intensification signals, only the tropical depression phase was analyzed for each case. Environmental statistics were computed using grid boxes centered on the storm location as provided by IBTrACS, with a 2°x2° box representing the storm environment and a 4°x4° box excluding the inner 2°x2° region representing the background environment. For each variable, the 10th, 50th, and 90th percentiles were calculated to characterize the distribution of environmental conditions and identify potential thresholds distinguishing intensity outcomes. Preliminary results suggest that saturation deficit (400-900 hPa), differential divergence (200-925 hPa), and convective inhibition may modulate subsequent storm evolution. Ongoing work will expand the dataset to 1998-2025, incorporate additional cases with refined selection criteria, and evaluate variables at more dynamically appropriate levels to strengthen statistical robustness. These efforts aim to improve understanding of environmental favorability during early-stage cyclone development.