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Article
Article Type:
Research Article

Genesis of Pre–Hurricane Felix (2007). Part I: The Role of the Easterly Wave Critical Layer

Zhuo Wang University of Illinois at Urbana–Champaign, Urbana, Illinois

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M. T. Montgomery Naval Postgraduate School, Monterey, California, and NOAA/Hurricane Research Division, Miami, Florida

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T. J. Dunkerton Naval Postgraduate School, Monterey, California, and NorthWest Research Associates, Bellevue, Washington

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Print Publication:
01 Jun 2010
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TCSP NAMMA
DOI:
https://doi.org/10.1175/2009JAS3420.1
Page(s):
1711–1729
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Abstract

The formation of pre–Hurricane Felix (2007) in a tropical easterly wave is examined in a two-part study using the Weather Research and Forecasting (WRF) model with a high-resolution nested grid configuration that permits the representation of cloud system processes. The simulation commences during the wave stage of the precursor African easterly-wave disturbance. Here the simulated and observed developments are compared, while in Part II of the study various large-scale analyses, physical parameterizations, and initialization times are explored to document model sensitivities.

In this first part the authors focus on the wave/vortex morphology, its interaction with the adjacent intertropical convergence zone complex, and the vorticity balance in the neighborhood of the developing storm. Analysis of the model simulation points to a bottom-up development process within the wave critical layer and supports the three new hypotheses of tropical cyclone formation proposed recently by Dunkerton, Montgomery, and Wang. It is shown also that low-level convergence associated with the ITCZ helps to enhance the wave signal and extend the “wave pouch” from the jet level to the top of the atmospheric boundary layer. The region of a quasi-closed Lagrangian circulation within the wave pouch provides a focal point for diabatic merger of convective vortices and their vortical remnants. The wave pouch serves also to protect the moist air inside from dry air intrusion, providing a favorable environment for sustained deep convection. Consistent with the authors’ earlier findings, the tropical storm forms near the center of the wave pouch via system-scale convergence in the lower troposphere and vorticity aggregation. Components of the vorticity balance are shown to be scale dependent, with the immediate effects of cloud processes confined more closely to the storm center than the overturning Eliassen circulation induced by diabatic heating, the influence of which extends to larger radii.

Corresponding author address: Zhuo Wang, Department of Atmospheric Sciences, University of Illinois, Urbana, IL 61801. Email: zhuowang@illinois.edu

This article included in the TCSP NAMMA special collection.

Abstract

The formation of pre–Hurricane Felix (2007) in a tropical easterly wave is examined in a two-part study using the Weather Research and Forecasting (WRF) model with a high-resolution nested grid configuration that permits the representation of cloud system processes. The simulation commences during the wave stage of the precursor African easterly-wave disturbance. Here the simulated and observed developments are compared, while in Part II of the study various large-scale analyses, physical parameterizations, and initialization times are explored to document model sensitivities.

In this first part the authors focus on the wave/vortex morphology, its interaction with the adjacent intertropical convergence zone complex, and the vorticity balance in the neighborhood of the developing storm. Analysis of the model simulation points to a bottom-up development process within the wave critical layer and supports the three new hypotheses of tropical cyclone formation proposed recently by Dunkerton, Montgomery, and Wang. It is shown also that low-level convergence associated with the ITCZ helps to enhance the wave signal and extend the “wave pouch” from the jet level to the top of the atmospheric boundary layer. The region of a quasi-closed Lagrangian circulation within the wave pouch provides a focal point for diabatic merger of convective vortices and their vortical remnants. The wave pouch serves also to protect the moist air inside from dry air intrusion, providing a favorable environment for sustained deep convection. Consistent with the authors’ earlier findings, the tropical storm forms near the center of the wave pouch via system-scale convergence in the lower troposphere and vorticity aggregation. Components of the vorticity balance are shown to be scale dependent, with the immediate effects of cloud processes confined more closely to the storm center than the overturning Eliassen circulation induced by diabatic heating, the influence of which extends to larger radii.

Corresponding author address: Zhuo Wang, Department of Atmospheric Sciences, University of Illinois, Urbana, IL 61801. Email: zhuowang@illinois.edu

This article included in the TCSP NAMMA special collection.

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  • Bolton, D., 1980: The computation of equivalent potential temperature. Mon. Wea. Rev., 108 , 1046–1053.

  • Dudhia, J., 1989: Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model. J. Atmos. Sci., 46 , 3077–3107.

    • Search Google Scholar
    • Export Citation

  • Dunkerton, T. J., 2006: A tale of two ITCZs—The Jim Holton perspective. Bull. Amer. Meteor. Soc., 87 , 1492–1495.

  • Dunkerton, T. J., M. T. Montgomery, and Z. Wang, 2009: Tropical cyclogenesis in a tropical wave critical layer: Easterly waves. Atmos. Chem. Phys., 9 , 5587–5646.

    • Search Google Scholar
    • Export Citation

  • Emanuel, K. A., 1994: Atmospheric Convection. Oxford University Press, 580 pp.

  • Gray, W. M., 1968: Global view of the origin of tropical disturbances and storms. Mon. Wea. Rev., 96 , 669–700.

  • Gray, W. M., 1998: The formation of tropical cyclones. Meteor. Atmos. Phys., 67 , 37–69.

  • Hack, J. J., W. H. Schubert, D. E. Stevens, and H-C. Kuo, 1989: Response of the Hadley circulation to convective forcing in the ITCZ. J. Atmos. Sci., 46 , 2957–2973.

    • Search Google Scholar
    • Export Citation

  • Halverson, J., and Coauthors, 2007: NASA’s Tropical Cloud Systems and Processes Experiment: Investigating tropical cyclogenesis and hurricane intensity change. Bull. Amer. Meteor. Soc., 88 , 867–882.

    • Search Google Scholar
    • Export Citation

  • Haynes, P. H., and M. E. McIntyre, 1987: On the evolution of vorticity and potential vorticity in the presence of diabatic heating and frictional or other forces. J. Atmos. Sci., 44 , 828–841.

    • Search Google Scholar
    • Export Citation

  • Hendricks, E. A., M. T. Montgomery, and C. A. Davis, 2004: The role of “vortical” hot towers in the formation of tropical cyclone Diana (1984). J. Atmos. Sci., 61 , 1209–1232.

    • Search Google Scholar
    • Export Citation

  • Hong, S-Y., and J-O. Lim, 2006: The WRF single-moment 6-class microphysics scheme (WSM6). J. Korean Meteor. Soc., 42 , 129–151.

  • Houze, R. A., W. C. Lee, and M. M. Bell, 2009: Convective contribution to the genesis of Hurricane Ophelia (2005). Mon. Wea. Rev., 137 , 2778–2800.

    • Search Google Scholar
    • Export Citation

  • Kain, J. S., and J. M. Fritsch, 1990: A one-dimensional entraining/detraining plume model and its application in convective parameterization. J. Atmos. Sci., 47 , 2784–2812.

    • Search Google Scholar
    • Export Citation

  • Karyampudi, V. M., and H. F. Pierce, 2002: Synoptic-scale influence of the Saharan air layer on tropical cyclogenesis over the eastern Atlantic. Mon. Wea. Rev., 130 , 3100–3128.

    • Search Google Scholar
    • Export Citation

  • Landsea, C. W., 1993: A climatology of intense (or major) Atlantic hurricanes. Mon. Wea. Rev., 121 , 1703–1713.

  • Mapes, B. E., and R. A. Houze, 1995: Diabatic divergence profiles in western Pacific mesoscale convective systems. J. Atmos. Sci., 52 , 1807–1828.

    • Search Google Scholar
    • Export Citation

  • McWilliams, J. C., 1984: The emergence of isolated coherent vortices in turbulent flow. J. Fluid Mech., 140 , 21–43.

  • Mlawer, E. J., S. J. Taubman, P. D. Brown, M. J. Iacono, and S. A. Clough, 1997: Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave. J. Geophys. Res., 102 , 16663–16682.

    • Search Google Scholar
    • Export Citation

  • Montgomery, M. T., and J. Enagonio, 1998: Tropical cyclogenesis via convectively forced vortex Rossby waves in a three-dimensional quasigeostrophic model. J. Atmos. Sci., 55 , 3176–3207.

    • Search Google Scholar
    • Export Citation

  • Montgomery, M. T., M. E. Nicholls, T. A. Cram, and A. B. Saunders, 2006: A vortical hot tower route to tropical cyclogenesis. J. Atmos. Sci., 63 , 355–386.

    • Search Google Scholar
    • Export Citation

  • Montgomery, M. T., Z. Wang, and T. J. Dunkerton, 2009: Intermediate and high resolution numerical simulations of the transition of a tropical wave critical layer to a tropical storm. Atmos. Chem. Phys. Discuss., 9 , 26143–26197.

    • Search Google Scholar
    • Export Citation

  • Noh, Y., W-G. Cheon, S-Y. Hong, and S. Raasch, 2003: Improvement of the K-profile model for the planetary boundary layer based on large eddy simulation data. Bound.-Layer Meteor., 107 , 401–427.

    • Search Google Scholar
    • Export Citation

  • Nolan, D. S., 2007: What is the trigger for tropical cyclogenesis? Aust. Meteor. Mag., 56 , 241–266.

  • Raymond, D. J., C. López-Carrillo, and L. López Cavazos, 1998: Case-studies of developing east Pacific easterly waves. Quart. J. Roy. Meteor. Soc., 124 , 2005–2034.

    • Search Google Scholar
    • Export Citation

  • Reasor, P. D., M. T. Montgomery, and L. F. Boast, 2005: Mesoscale observations of the genesis of Hurricane Dolly (1996). J. Atmos. Sci., 62 , 3151–3171.

    • Search Google Scholar
    • Export Citation

  • Riehl, H., and J. S. Malkus, 1958: On the heat balance in the equatorial trough zone. Geophysica, 6 , 503–538.

  • Riehl, H., and J. S. Simpson, 1979: On the heat balance in the equatorial trough zone, revisited. Contrib. Atmos. Phys., 52 , 287–305.

  • Ritchie, E. A., and G. J. Holland, 1997: Scale interactions during the formation of Typhoon Irving. Mon. Wea. Rev., 125 , 1377–1396.

  • Schecter, D. A., and D. H. E. Dubin, 1999: Vortex motion driven by a background vorticity gradient. Phys. Rev. Lett., 83 , 2191–2194.

  • Shapiro, L. J., and H. E. Willoughby, 1982: The response of balanced hurricanes to local sources of heat and momentum. J. Atmos. Sci., 39 , 378–394.

    • Search Google Scholar
    • Export Citation

  • Simpson, J., J. B. Halverson, B. S. Ferrier, W. A. Petersen, R. H. Simpson, R. Blakeslee, and S. L. Durden, 1998: On the role of “hot towers” in tropical cyclone formation. Meteor. Atmos. Phys., 67 , 15–35.

    • Search Google Scholar
    • Export Citation

  • Sippel, J. A., J. W. Nielsen-Gammon, and S. E. Allen, 2006: The multiple-vortex nature of tropical cyclogenesis. Mon. Wea. Rev., 134 , 1796–1814.

    • Search Google Scholar
    • Export Citation

  • Skamarock, W. C., J. B. Klemp, J. Dudhia, D. O. Gill, D. M. Barker, W. Wang, and J. G. Powers, 2005: A description of the Advanced Research WRF version 2. NCAR Tech. Note NCAR/TN-468+STR, 88 pp.

    • Search Google Scholar
    • Export Citation

  • Tory, K. J., and M. T. Montgomery, 2006: Internal influences on tropical cyclone formation. Proc. Sixth Int. Workshop on Tropical Cyclones, San Jose, Costa Rica, World Meteorological Organization, 2.2.

    • Search Google Scholar
    • Export Citation

  • Tory, K. J., and M. T. Montgomery, 2008: Tropical cyclone formation: A synopsis of the internal dynamics. Extended abstracts, 28th Conf. on Hurricanes and Tropical Meteorology, Orlando, FL, Amer. Meteor. Soc., 10A.1. [Available online at http://ams.confex.com/ams/28Hurricanes/techprogram/paper_138062.htm].

    • Search Google Scholar
    • Export Citation

  • Tory, K. J., M. T. Montgomery, and N. E. Davidson, 2006: Prediction and diagnosis of tropical cyclone formation in an NWP system. Part I: The critical role of vortex enhancement in deep convection. J. Atmos. Sci., 63 , 3077–3090.

    • Search Google Scholar
    • Export Citation

  • Wang, C-C., and G. Magnusdottir, 2005: ITCZ breakdown in three-dimensional flows. J. Atmos. Sci., 62 , 1497–1512.

  • Wang, Z., M. T. Montgomery, and T. J. Dunkerton, 2009: A dynamically based method for forecasting tropical cyclogenesis location in the Atlantic sector using global model products. Geophys. Res. Lett., 36 , L03801. doi:10.1029/2008GL035586.

    • Search Google Scholar
    • Export Citation

  • Wang, Z., M. T. Montgomery, and T. J. Dunkerton, 2010: Genesis of pre–Hurricane Felix (2007). Part II: Warm core formation, precipitation evolution, and predictability. J. Atmos. Sci., 67 , 1730–1744.

    • Search Google Scholar
    • Export Citation
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