An Investigation of Post-Transition Extremes for Extratropically Transitioning Tropical Cyclones

Giorgio Sarro, “An Investigation of Post-Transition Extremes for Extratropically Transitioning Tropical Cyclones”
Mentor: Clark Evans, Mathematical Sciences

Extratropical transition (ET) is the process by which a tropical cyclone (i.e., hurricane) transforms into a non-tropical, or extratropical, cyclone after it encounters frontal systems and reduced sea-surface temperature at higher latitudes. In this study, we focus on improving understanding of the atmospheric conditions associated with different ET outcomes, looking at the cyclone intensity post-ET, cyclone thermal structure post-ET, and the time to complete ET. The only previous study that focused on this topic (Hart et al., 2006, Mon. Wea. Rev.) examined a limited number of cyclones using coarse atmospheric analysis data that included a fake tropical cyclone vortex. The primary goal of this research is to quantify the reliability of their results over larger samples using state-of-the-art high-resolution atmospheric reanalysis data. Herein, we focus on the North Atlantic basin and analyze all National Hurricane Center-classified tropical cyclones that complete ET since 1995. Atmospheric fields are derived from ERA5 reanalysis data. A cyclone phase space (CPS) is used to objectively identify ET timing and diagnose post-transition cyclone structure. Cyclones are divided into three categories: (1) cyclones that become stronger, weaker, or do not change intensity after ET, (2) cyclones that have a cold-core versus warm-seclusion structure post-ET, and (3) cyclones with fast versus slow time to complete ET. ERA5 reanalysis is used to generate composites of atmospheric fields at selected milestones along an ET-timing-relative timeline, which allows for direct comparisons between individual cyclones. Moreover, limitations of the CPS are highlighted when transitioning tropical cyclones instantly become warm-core extratropical cyclones.


  1. Hello!

    My name is Giorgio Sarro and I am a senior in the Atmospheric Science program here at UWM working with Prof. Clark Evans.
    Feel free to comment any question or request further info!

    Thank you.

  2. Hello Giorgio, nicely done project. You taught me about a topic I knew nothing about! I appreciated not only the clarity of your explanation, but also how engaging you made the video. You managed to approximate the kind of engagement one might experience in a face-to-face poster session. Best wishes in your work.

Leave a Reply

Your email address will not be published. Required fields are marked *