• Agustí-Panareda, A., S. L. Gray, G. C. Craig, and C. Thorncroft, 2005: The extratropical transition of Tropical Cyclone Lili (1996) and its crucial contribution to a moderate extratropical development. Mon. Wea. Rev., 133, 15621573, https://doi.org/10.1175/MWR2935.1.

    • Search Google Scholar
    • Export Citation
  • Archambault, H. M., L. F. Bosart, D. Keyser, and J. M. Cordeira, 2013: A climatological analysis of the extratropical flow response to recurving western North Pacific tropical cyclones. Mon. Wea. Rev., 141, 23252346, https://doi.org/10.1175/MWR-D-12-00257.1.

    • Search Google Scholar
    • Export Citation
  • Archambault, H. M., D. Keyser, L. F. Bosart, C. A. Davis, and J. M. Cordeira, 2015: A composite perspective of the extratropical flow response to recurving western North Pacific tropical cyclones. Mon. Wea. Rev., 143, 11221141, https://doi.org/10.1175/MWR-D-14-00270.1.

    • Search Google Scholar
    • Export Citation
  • Benjamini, Y., and Y. Hochberg, 1995: Controlling the false discovery rate: A practical and powerful approach to multiple testing. J. Roy. Stat. Soc., 57B, 289300, https://doi.org/10.1111/j.2517-6161.1995.tb02031.x.

    • Search Google Scholar
    • Export Citation
  • Bian, G.-F., G.-Z. Nie, and X. Qiu, 2021: How well is outer tropical cyclone size represented in the ERA5 reanalysis dataset? Atmos. Res., 249, 105339, https://doi.org/10.1016/j.atmosres.2020.105339.

    • Search Google Scholar
    • Export Citation
  • Bieli, M., S. J. Camargo, A. H. Sobel, J. L. Evans, and T. Hall, 2019a: A global climatology of extratropical transition. Part I: Characteristics across basins. J. Climate, 32, 35573582, https://doi.org/10.1175/JCLI-D-17-0518.1.

    • Search Google Scholar
    • Export Citation
  • Bieli, M., S. J. Camargo, A. H. Sobel, J. L. Evans, and T. Hall, 2019b: A global climatology of extratropical transition. Part II: Statistical performance of the cyclone phase space. J. Climate, 32, 35833597, https://doi.org/10.1175/JCLI-D-18-0052.1.

    • Search Google Scholar
    • Export Citation
  • Bister, M., and K. A. Emanuel, 2002: Low frequency variability of tropical cyclone potential intensity. Part I: Interannual to interdecadal variability. J. Geophys. Res., 107, 4801, https://doi.org/10.1029/2001JD000776.

    • Search Google Scholar
    • Export Citation
  • Bluestein, H., 1993: Synoptic-Dynamic Meteorology in Midlatitudes. Vol. II: Observations and Theory of Weather Systems. Oxford University Press, 594 pp.

    • Search Google Scholar
    • Export Citation
  • Bosart, L. F., C. S. Velden, W. E. Bracken, J. Molinari, and P. G. Black, 2000: Environmental influences on the rapid intensification of Hurricane Opal (1995) over the Gulf of Mexico. Mon. Wea. Rev., 128, 322352, https://doi.org/10.1175/1520-0493(2000)128<0322:EIOTRI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Bracken, W. E., and L. F. Bosart, 1998: Multiple development aspects of Hurricane Opal (1995). Preprints, Symp. on Tropical Cyclone Intensity Change, Phoenix, AZ, Amer. Meteor. Soc., 99104.

    • Search Google Scholar
    • Export Citation
  • Browning, K. A., G. Vaughan, and P. Panagi, 1998: Analysis of an ex-tropical cyclone after its reintensification as a warm-core extratropical cyclone. Quart. J. Roy. Meteor. Soc., 124, 23292356, https://doi.org/10.1002/qj.49712455108.

    • Search Google Scholar
    • Export Citation
  • Dawson, A., 2016: Windspharm: A high-level library for global wind field computations using spherical harmonics. J. Open Res. Software, 4, e31, https://doi.org/10.5334/jors.129.

    • Search Google Scholar
    • Export Citation
  • Dee, D. P., and Coauthors, 2011: The ERA‐Interim reanalysis: Configuration and performance of the data assimilation system. Quart. J. Roy. Meteor. Soc., 137, 553597, https://doi.org/10.1002/qj.828.

    • Search Google Scholar
    • Export Citation
  • Dullaart, J. C. M., S. Muis, N. Bloemendaal, and J. C. J. H. Aerts, 2019: Advancing global storm surge modelling using the new ERA5 climate reanalysis. Climate Dyn., 54, 10071021, https://doi.org/10.1007/s00382-019-05044-0.

    • Search Google Scholar
    • Export Citation
  • Efron, B., 1979: Bootstrap methods: Another look at the jackknife. Ann. Stat., 7, 126, https://doi.org/10.1214/aos/1176344552.

  • European Centre for Medium-Range Weather Forecasts, 2019: ERA5 Reanalysis (0.25 Degree Latitude-Longitude Grid). Research Data Archive at the National Center for Atmospheric Research, Computational and Information Systems Laboratory, accessed 11 October 2022, https://doi.org/10.5065/BH6N-5N20.

    • Search Google Scholar
    • Export Citation
  • Evans, C., and Coauthors, 2017: The extratropical transition of tropical cyclones. Part I: Cyclone evolution and direct impacts. Mon. Wea. Rev., 145, 43174344, https://doi.org/10.1175/MWR-D-17-0027.1.

    • Search Google Scholar
    • Export Citation
  • Evans, J. L., and R. E. Hart, 2003: Objective indicators of the life cycle evolution of extratropical transition for Atlantic tropical cyclones. Mon. Wea. Rev., 131, 909925, https://doi.org/10.1175/1520-0493(2003)131<0909:OIOTLC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Evans, J. L., and B. E. Prater-Mayes, 2004: Factors affecting the post-transition intensification of Hurricane Irene (1999). Mon. Wea. Rev., 132, 13551368, https://doi.org/10.1175/1520-0493(2004)132<1355:FATPIO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Galarneau, T. J., C. A. Davis, and M. A. Shapiro, 2013: Intensification of Hurricane Sandy (2012) through extratropical warm core seclusion. Mon. Wea. Rev., 141, 42964321, https://doi.org/10.1175/MWR-D-13-00181.1.

    • Search Google Scholar
    • Export Citation
  • Gilford, D. M., 2021: pyPI (v1.3): Tropical cyclone potential intensity calculations in Python. Geosci. Model Dev., 14, 23512369, https://doi.org/10.5194/gmd-14-2351-2021.

    • Search Google Scholar
    • Export Citation
  • Goerss, J. S., and R. A. Jeffries, 1994: Assimilation of synthetic tropical cyclone observations into the Navy Operational Global Atmospheric Prediction System. Wea. Forecasting, 9, 557576, https://doi.org/10.1175/1520-0434(1994)009<0557:AOSTCO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Harr, P. A., and R. L. Elsberry, 2000: Extratropical transition of tropical cyclones over the western North Pacific. Part I: Evolution of structural characteristics during the transition process. Mon. Wea. Rev., 128, 26132633, https://doi.org/10.1175/1520-0493(2000)128<2613:ETOTCO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Harr, P. A., R. L. Elsberry, and T. F. Hogan, 2000: Extratropical transition of tropical cyclones over the western North Pacific. Part II: The impact of midlatitude circulation characteristics. Mon. Wea. Rev., 128, 26342653, https://doi.org/10.1175/1520-0493(2000)128<2634:ETOTCO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hart, R. E., 2003: A cyclone phase space derived from thermal wind and thermal asymmetry. Mon. Wea. Rev., 131, 585616, https://doi.org/10.1175/1520-0493(2003)131<0585:ACPSDF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hart, R. E., and J. L. Evans, 2001: A climatology of the extratropical transition of Atlantic tropical cyclones. J. Climate, 14, 546564, https://doi.org/10.1175/1520-0442(2001)014<0546:ACOTET>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hart, R. E., J. L. Evans, and C. Evans, 2006: Synoptic composites of the extratropical transition life cycle of North Atlantic tropical cyclones: Factors determining post-transition evolution. Mon. Wea. Rev., 134, 553578, https://doi.org/10.1175/MWR3082.1.

    • Search Google Scholar
    • Export Citation
  • Hersbach, H., 2019: ECMWF’s ERA5 reanalysis extends back to 1979. ECMWF Newsletter, No. 158, ECMWF, Reading, United Kingdom, 1, https://www.ecmwf.int/en/newsletter/158/news/ecmwfs-era5-reanalysis-extends-back-1979.

  • Hersbach, H., and Coauthors, 2020: The ERA5 global reanalysis. Quart. J. Roy. Meteor. Soc., 146, 19992049, https://doi.org/10.1002/qj.3803.

    • Search Google Scholar
    • Export Citation
  • Hines, K. M., and C. R. Mechoso, 1993: Influence of surface drag on the evolution of fronts. Mon. Wea. Rev., 121, 11521176, https://doi.org/10.1175/1520-0493(1993)121<1152:IOSDOT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hogan, T. F., and T. E. Rosmond, 1991: The description of the Navy Operational Global Atmospheric Prediction System’s spectral forecast model. Mon. Wea. Rev., 119, 17861815, https://doi.org/10.1175/1520-0493(1991)119<1786:TDOTNO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., and P. J. Valdes, 1990: On the existence of storm-tracks. J. Atmos. Sci., 47, 18541864, https://doi.org/10.1175/1520-0469(1990)047<1854:OTEOST>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Jones, S. C., and Coauthors, 2003: The extratropical transition of tropical cyclones: Forecast challenges, current understanding, and future directions. Wea. Forecasting, 18, 10521092, https://doi.org/10.1175/1520-0434(2003)018<1052:TETOTC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Keller, J. H., and Coauthors, 2019: The extratropical transition of tropical cyclones. Part II: Interaction with the midlatitude flow, downstream impacts, and implications for predictability. Mon. Wea. Rev., 147, 10771106, https://doi.org/10.1175/MWR-D-17-0329.1.

    • Search Google Scholar
    • Export Citation
  • Kitabatake, N., 2008: Extratropical transition of tropical cyclones in the western North Pacific: Their frontal evolution. Mon. Wea. Rev., 136, 20662090, https://doi.org/10.1175/2007MWR1958.1.

    • Search Google Scholar
    • Export Citation
  • Kitabatake, N., 2011: Climatology of extratropical transition of tropical cyclones in the western North Pacific defined by using cyclone phase space. J. Meteor. Soc. Japan, 89, 309325, https://doi.org/10.2151/jmsj.2011-402.

    • Search Google Scholar
    • Export Citation
  • Klein, P. M., P. A. Harr, and R. Elsberry, 2000: Extratropical transition of western North Pacific tropical cyclones: An overview and conceptual model of the transformation stage. Wea. Forecasting, 15, 373395, https://doi.org/10.1175/1520-0434(2000)015<0373:ETOWNP>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Klein, P. M., P. A. Harr, and R. L. Elsberry, 2002: Extratropical transition of western North Pacific tropical cyclones: Midlatitude and tropical cyclone contributions to reintensification. Mon. Wea. Rev., 130, 22402259, https://doi.org/10.1175/1520-0493(2002)130<2240:ETOWNP>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Knapp, K. R., and Coauthors, 2011: Globally gridded satellite (GridSat) observations for climate studies. Bull. Amer. Meteor. Soc., 92, 893907, https://doi.org/10.1175/2011BAMS3039.1.

    • Search Google Scholar
    • Export Citation
  • Kuo, Y., R. J. Reed, and S. Low-Nam, 1992: Thermal structure and airflow in a model simulation of an occluded marine cyclone. Mon. Wea. Rev., 120, 22802297, https://doi.org/10.1175/1520-0493(1992)120<2280:TSAAIA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Landsea, C. W., and J. L. Franklin, 2013: Atlantic hurricane database uncertainty and presentation of a new database format. Mon. Wea. Rev., 141, 35763592, https://doi.org/10.1175/MWR-D-12-00254.1.

    • Search Google Scholar
    • Export Citation
  • Malakar, P., A. P. Kesarkar, J. N. Bhate, V. Singh, and A. Deshamukhya, 2020: Comparison of reanalysis datasets to comprehend the evolution of tropical cyclones over North Indian Ocean. Earth Space Sci., 7, e2019EA000978, https://doi.org/10.1029/2019EA000978.

  • Mass, C. F., and D. M. Schultz, 1993: The structure and evolution of a simulated midlatitude cyclone over land. Mon. Wea. Rev., 121, 889917, https://doi.org/10.1175/1520-0493(1993)121<0889:TSAEOA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Masson, A., 2014: The extratropical transition of Hurricane Igor and the impacts on Newfoundland. Nat. Hazards, 72, 617632, https://doi.org/10.1007/s11069-013-1027-x.

    • Search Google Scholar
    • Export Citation
  • May, R. M., and Coauthors, 2022: MetPy: A Python package for meteorological data. Unidata, accessed 11 October 2022, https://doi.org/10.5065/D6WW7G29.

  • McTaggart-Cowan, R., J. R. Gyakum, and M. K. Yau, 2001: Sensitivity testing of extratropical transitions using potential vorticity inversions to modify initial conditions: Hurricane Earl case study. Mon. Wea. Rev., 129, 16171636, https://doi.org/10.1175/1520-0493(2001)129<1617:STOETU>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • McTaggart-Cowan, R., J. R. Gyakum, and M. K. Yau, 2003: The influence of the downstream state on extratropical transition: Hurricane Earl (1998) case study. Mon. Wea. Rev., 131, 19101929, https://doi.org/10.1175//2589.1.

    • Search Google Scholar
    • Export Citation
  • McTaggart-Cowan, R., J. R. Gyakum, and M. K. Yau, 2004: The impact of tropical remnants on extratropical cyclogenesis: Case study of Hurricanes Danielle and Earl (1998). Mon. Wea. Rev., 132, 19331951, https://doi.org/10.1175/1520-0493(2004)132<1933:TIOTRO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., S. Skubis, and D. Vollaro, 1995: External influences on hurricane intensity. Part III: Potential vorticity structure. J. Atmos. Sci., 52, 35933606, https://doi.org/10.1175/1520-0469(1995)052<3593:EIOHIP>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., S. Skubis, D. Vollaro, F. Alsheimer, and H. E. Willoughby, 1998: Potential vorticity analysis of tropical cyclone intensification. J. Atmos. Sci., 55, 26322644, https://doi.org/10.1175/1520-0469(1998)055<2632:PVAOTC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Neu, U., and Coauthors, 2013: IMILAST: A community effort to intercompare extratropical cyclone detection and tracking algorithms. Bull. Amer. Meteor. Soc., 94, 529547, https://doi.org/10.1175/BAMS-D-11-00154.1.

    • Search Google Scholar
    • Export Citation
  • Pantillon, F., J.-P. Chaboureau, C. Lac, and P. Mascart, 2013: On the role of a Rossby wave train during the extratropical transition of Hurricane Helene (2006). Quart. J. Roy. Meteor. Soc., 139, 370386, https://doi.org/10.1002/qj.1974.

    • Search Google Scholar
    • Export Citation
  • Petterssen, S., 1955: A general survey of factors influencing development at sea level. J. Meteor., 12, 3642, https://doi.org/10.1175/1520-0469(1955)012<0036:AGSOFI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Polvani, L. M., and R. A. Plumb, 1992: Rossby wave breaking, filamentation, and secondary vortex formation: The dynamics of a perturbed vortex. J. Atmos. Sci., 49, 462476, https://doi.org/10.1175/1520-0469(1992)049<0462:RWBMFA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Polvani, L. M., G. R. Flierl, and N. J. Zabusky, 1989: Filamentation of unstable vortex structures via separatrix crossing: A quantitative estimate of onset time. Phys. Fluids A Fluid Dyn., 1, 181184, https://doi.org/10.1063/1.857485.

    • Search Google Scholar
    • Export Citation
  • Rantanen, M., J. Räisänen, V. A. Sinclair, J. Lento, and H. Järvinen, 2020: The extratropical transition of Hurricane Ophelia (2017) as diagnosed with a generalized omega equation and vorticity equation. Tellus, 72A, 1721215, https://doi.org/10.1080/16000870.2020.1721215.

    • Search Google Scholar
    • Export Citation
  • Reynolds, R. W., T. M. Smith, C. Liu, D. B. Chelton, K. S. Casey, and M. G. Schlax, 2007: Daily high-resolution-blended analyses for sea surface temperature. J. Climate, 20, 54735496, https://doi.org/10.1175/2007JCLI1824.1.

    • Search Google Scholar
    • Export Citation
  • Ritchie, E. A., and R. L. Elsberry, 2003: Simulations of the extratropical transition of tropical cyclones: Contributions by the midlatitude upper-level trough to reintensification. Mon. Wea. Rev., 131, 21122128, https://doi.org/10.1175/1520-0493(2003)131<2112:SOTETO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Ritchie, E. A., and R. L. Elsberry, 2007: Simulations of the extratropical transition of tropical cyclones: Phasing between the upper-level trough and tropical cyclones. Mon. Wea. Rev., 135, 862876, https://doi.org/10.1175/MWR3303.1.

    • Search Google Scholar
    • Export Citation
  • Sainsbury, E. M., R. K. H. Schiemann, K. I. Hodges, L. C. Shaffery, A. J. Baker, and K. T. Bhatia, 2020: How important are post-tropical cyclones for European windstorm risk? Geophys. Res. Lett., 47, e2020GL089853, https://doi.org/10.1029/2020GL089853.

  • Schultz, D. M., and F. Zhang, 2007: Baroclinic development within zonally-varying flows. Quart. J. Roy. Meteor. Soc., 133, 11011112, https://doi.org/10.1002/qj.87.

    • Search Google Scholar
    • Export Citation
  • Schultz, D. M., D. Keyser, and L. F. Bosart, 1998: The effect of large-scale flow on low-level frontal structure and evolution in midlatitude cyclones. Mon. Wea. Rev., 126, 17671791, https://doi.org/10.1175/1520-0493(1998)126<1767:TEOLSF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Schultz, D. M., and Coauthors, 2019: Extratropical cyclones: A century of research on meteorology’s centerpiece. A Century of Progress in Atmospheric and Related Sciences: Celebrating the American Meteorological Society Centennial, Meteor. Monogr., No. 59, Amer. Meteor. Soc., https://doi.org/10.1175/AMSMONOGRAPHS-D-18-0015.1.

  • Shapiro, L. J., and D. Keyser, 1990: Fronts, jet streams, and the tropopause. Extratropical Cyclones: The Erik Palmen Memorial Volume, C. W. Newton and E. O. Holopainen, Eds., Amer. Meteor. Soc., 167191.

    • Search Google Scholar
    • Export Citation
  • Studholme, J., K. I. Hodges, and C. M. Brierly, 2015: Objective determination of the extratropical transition of tropical cyclones in the Northern Hemisphere. Tellus, 67A, 24474, https://doi.org/10.3402/tellusa.v67.24474.

    • Search Google Scholar
    • Export Citation
  • Sun, Y., Z. Zhong, and Y. Wang, 2012: Kinetic energy budget of Typhoon Yagi (2006) during its extratropical transition. Meteor. Atmos. Phys., 118, 6578, https://doi.org/10.1007/s00703-012-0200-1.

    • Search Google Scholar
    • Export Citation
  • Sutcliffe, R. C., and A. G. Forsdyke, 1950: The theory and use of upper air thickness patterns in forecasting. Quart. J. Roy. Meteor. Soc., 76, 189217, https://doi.org/10.1002/qj.49707632809.

    • Search Google Scholar
    • Export Citation
  • Swanson, K. L., P. J. Kushner, and I. M. Held, 1997: Dynamics of barotropic storm tracks. J. Atmos. Sci., 54, 791810, https://doi.org/10.1175/1520-0469(1997)054<0791:DOBST>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C. D., and S. C. Jones, 2000: The extratropical transitions of Hurricanes Felix and Iris in 1995. Mon. Wea. Rev., 128, 947972, https://doi.org/10.1175/1520-0493(2000)128<0947:TETOHF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C. D., B. J. Hoskins, and M. E. McIntyre, 1993: Two paradigms of baroclinic‐wave life‐cycle behaviour. Quart. J. Roy. Meteor. Soc., 119, 1755, https://doi.org/10.1002/qj.49711950903.

    • Search Google Scholar
    • Export Citation
  • Wilks, D. S., 2006: Statistical Methods in the Atmospheric Sciences. 2nd ed. International Geophysics Series, Vol. 100, Academic Press, 648 pp.

  • Wilks, D. S., 2016: “The stippling shows statistically significant grid points”: How research results are routinely overstated and overinterpreted, and what to do about it. Bull. Amer. Meteor. Soc., 97, 22632273, https://doi.org/10.1175/BAMS-D-15-00267.1.

    • Search Google Scholar
    • Export Citation
  • Wood, K. M., and E. A. Ritchie, 2014: A 40-year climatology of extratropical transition in the eastern North Pacific. J. Climate, 27, 59996015, https://doi.org/10.1175/JCLI-D-13-00645.1.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 935 935 26
Full Text Views 237 237 10
PDF Downloads 239 239 13

An Updated Investigation of Post-Transformation Intensity, Structural, and Duration Extremes for Extratropically Transitioning North Atlantic Tropical Cyclones

Giorgio SarroaAtmospheric Science Program, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin
bDepartment of Geophysical Sciences, University of Chicago, Chicago, Illinois

Search for other papers by Giorgio Sarro in
Current site
Google Scholar
PubMed
Close
and
Clark EvansaAtmospheric Science Program, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin

Search for other papers by Clark Evans in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The transformation stage of extratropical transition characterizes the process by which a tropical cyclone transforms into an extratropical cyclone at higher latitudes in a cooler, more baroclinic environment. A 2006 study connects extremes in transformation-stage duration, post-transformation intensity change, and post-transformation thermal structure for North Atlantic basin tropical cyclones to synoptic-scale environmental variability. However, the 2006 study’s findings are derived from coarse atmospheric analyses that include fictitious tropical cyclone vortices applied to small samples with substantial variability between cases. This study updates the 2006 study’s findings using larger sample sizes, improvements in atmospheric reanalysis resolution and fidelity, and advances in scientific understanding over the last two decades. Transformation-stage duration is primarily a function of the duration that a transforming cyclone remains in an environment supportive of tropical development after entering a region supportive of baroclinic development. Post-transformation intensity-change composites are distinguished primarily by whether proper phasing is achieved between the transforming cyclone and upstream trough following the transformation stage. Finally, post-transformation thermal structure is distinguished primarily by whether the transforming cyclone moves into a strongly confluent synoptic-scale environment following the transformation stage. This study also presents the first composite analyses of North Atlantic tropical cyclones that maintain a lower-tropospheric warm-core structure post-transformation, termed instant warm-seclusion cyclones, which have previously only been diagnosed in case studies of individual North Atlantic tropical cyclones and for a limited climatology of western North Pacific tropical cyclones. These cyclones, comprising approximately one-third of all cases, are characterized by the transforming TC becoming negatively tilted with respect to the upstream trough and undergoing cyclonic Rossby wave breaking.

© 2022 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Clark Evans, evans36@uwm.edu

Abstract

The transformation stage of extratropical transition characterizes the process by which a tropical cyclone transforms into an extratropical cyclone at higher latitudes in a cooler, more baroclinic environment. A 2006 study connects extremes in transformation-stage duration, post-transformation intensity change, and post-transformation thermal structure for North Atlantic basin tropical cyclones to synoptic-scale environmental variability. However, the 2006 study’s findings are derived from coarse atmospheric analyses that include fictitious tropical cyclone vortices applied to small samples with substantial variability between cases. This study updates the 2006 study’s findings using larger sample sizes, improvements in atmospheric reanalysis resolution and fidelity, and advances in scientific understanding over the last two decades. Transformation-stage duration is primarily a function of the duration that a transforming cyclone remains in an environment supportive of tropical development after entering a region supportive of baroclinic development. Post-transformation intensity-change composites are distinguished primarily by whether proper phasing is achieved between the transforming cyclone and upstream trough following the transformation stage. Finally, post-transformation thermal structure is distinguished primarily by whether the transforming cyclone moves into a strongly confluent synoptic-scale environment following the transformation stage. This study also presents the first composite analyses of North Atlantic tropical cyclones that maintain a lower-tropospheric warm-core structure post-transformation, termed instant warm-seclusion cyclones, which have previously only been diagnosed in case studies of individual North Atlantic tropical cyclones and for a limited climatology of western North Pacific tropical cyclones. These cyclones, comprising approximately one-third of all cases, are characterized by the transforming TC becoming negatively tilted with respect to the upstream trough and undergoing cyclonic Rossby wave breaking.

© 2022 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Clark Evans, evans36@uwm.edu
Save