@article{183ab0fdd18c4ba4bad8d38cc1d97a27,
title = "The extratropical transition of tropical cyclones. Part II: Interaction with the midlatitude flow, downstream impacts, and implications for predictability",
abstract = "The extratropical transition (ET) of tropical cyclones often has an important impact on the nature and predictability of the midlatitude flow. This review synthesizes the current understanding of the dynamical and physical processes that govern this impact and highlights the relationship of downstream development during ET to highimpact weather, with a focus on downstreamregions. It updates a previous review from2003 and identifies new and emerging challenges and future research needs. First, the mechanisms through which the transitioning cyclone impacts the midlatitude flow in its immediate vicinity are discussed. This ''direct impact''manifests in the formation of a jet streak and the amplification of a ridge directly downstream of the cyclone. This initial flow modification triggers or amplifies amidlatitude Rossby wave packet,which disperses the impact ofETinto downstream regions (downstream impact) and may contribute to the formation of high-impact weather. Details are provided concerning the impact of ET on forecast uncertainty in downstream regions and on the impact of observations on forecast skill. The sources and characteristics of the following key features and processes thatmay determine the manifestation of the impact of ET on the midlatitude flow are discussed: the upper-tropospheric divergent outflow, mainly associated with latent heat release in the troposphere below, and the phasing between the transitioning cyclone and the midlatitude wave pattern. Improving the representation of diabatic processes during ET in models and a climatological assessment of the ET's impact on downstream high-impact weather are examples for future research directions.",
keywords = "Diabatic heating, Dynamics, Extreme events, Numerical weather prediction/forecasting, Rossby waves, Tropical cyclones",
author = "Keller, {Julia H.} and Grams, {Christian M.} and Michael Riemer and Archambault, {Heather M.} and Lance Bosart and Doyle, {James D.} and Evans, {Jenni L.} and Galarneau, {Thomas J.} and Kyle Griffin and Harr, {Patrick A.} and Naoko Kitabatake and Ron McTaggart-Cowan and Florian Pantillon and Quinting, {Julian F.} and Reynolds, {Carolyn A.} and Ritchie, {Elizabeth A.} and Torn, {Ryan D.} and Fuqing Zhang",
note = "Funding Information: The paper was jointly written by Julia H. Keller, Christian M. Grams, and Michael Riemer, based on contributions from all coauthors. We thank John Gyakum for his support in initiating this work, as well as Clark Evans for comments that helped to improve the manuscript. Well-thought-out and thorough comments by five anonymous reviewers and the editor David Schultz on a previous version of the manuscript provided very helpful guidance for improving the content and tangibility of this review. CMG, JHK, and MR would like to thank Sarah Jones for sparking their interest in ET and for making parts of the work presented here happen. The contribution by CMG was made while he held a Swiss National Science Foundation (SNSF) Ambizione fellowship under Grant PZ00P2_148177/1 and finished under Grant VH-NG-1243 of the Helmholtz Association. MR acknowledges support from the subproject ''A4: Evolution and predictability of storm structure during extratropical transition of tropical cyclones'' of the Transregional Collaborative Research Center SFB/TRR 165 ''Waves to Weather'' program funded by the German Science Foundation (DFG). Parts of the results presented in this review have been produced within the German PANDOWAE (FOR896) project, funded by DFG as a contribution to the WMO World Weather Research Programme THORPEX. Coauthors acknowledge the following support: Bosart from NSF (AGS-1240502 and AGS-1355960); Doyle and Reynolds from the Chief of Naval Research through the NRL Base Program PE 0601153N and the ONR PE 0602435N; Quinting from the Australian Research Council Centre of Excellence for Climate System Science (CE110001028); Torn from NSF (ATM-1461753); and Zhang from ONR (Grant N000140910526). This review was partly initiated at the World Meteorological Organization's Eighth International Workshop on Tropical Cyclones in 2014. Funding Information: Acknowledgments. The paper was jointly written by Julia H. Keller, Christian M. Grams, and Michael Riemer, based on contributions from all coauthors. We thank John Gyakum for his support in initiating this work, as well as Clark Evans for comments that helped to improve the manuscript. Well-thought-out and thorough comments by five anonymous reviewers and the editor David Schultz on a previous version of the manuscript provided very helpful guidance for improving the content and tangibility of this review. CMG, JHK, and MR would like to thank Sarah Jones for sparking their interest in ET and for making parts of the work presented here happen. The contribution by CMG was made while he held a Swiss National Science Foundation (SNSF) Ambizione fellowship under Grant PZ00P2_148177/1 and finished under Grant VH-NG-1243 of the Helmholtz Association. MR acknowledges support from the subproject {\textquoteleft}{\textquoteleft}A4: Evolution and predictability of storm structure during extratropical transition of tropical cyclones{\textquoteright}{\textquoteright} of the Transregional Collaborative Research Center SFB/TRR 165 {\textquoteleft}{\textquoteleft}Waves to Weather{\textquoteright}{\textquoteright} program funded by the German Science Foundation (DFG). Parts of the results presented in this review have been produced within the German PANDOWAE (FOR896) project, funded by DFG as a contribution to the WMO World Weather Research Programme THORPEX. Coauthors acknowledge the following support: Bosart from NSF (AGS-1240502 and AGS-1355960); Doyle and Reynolds from the Chief of Naval Research through the NRL Base Program PE 0601153N and the ONR PE 0602435N; Quinting from the Australian Research Council Centre of Excellence for Climate System Science (CE110001028); Torn from NSF (ATM-1461753); and Zhang from ONR (Grant N000140910526). This review was partly initiated at the World Meteorological Organization{\textquoteright}s Eighth International Workshop on Tropical Cyclones in 2014. Publisher Copyright: {\textcopyright} 2019 American Meteorological Society.",
year = "2019",
month = apr,
day = "1",
doi = "10.1175/MWR-D-17-0329.1",
language = "English (US)",
volume = "147",
pages = "1077--1106",
journal = "Monthly Weather Review",
issn = "0027-0644",
publisher = "American Meteorological Society",
number = "4",
}