• Barker, D. M., , W. Huang, , Y.-R. Guo, , A. J. Bourgeois, , and Q. N. Xiao, 2004: A three-dimensional variational data assimilation system for MM5: Implementation and initial results. Mon. Wea. Rev., 132, 897914.

    • Search Google Scholar
    • Export Citation
  • Bender, M. A., , and I. Ginis, 2000: Real-case simulations of hurricane–ocean interaction using a high-resolution coupled model: Effects on hurricane intensity. Mon. Wea. Rev., 128, 917946.

    • Search Google Scholar
    • Export Citation
  • Bender, M. A., , I. Ginis, , and Y. Kurihara, 1993: Numerical simulations of tropical cylone–ocean interaction with a high-resolution coupled model. J. Geophys. Res., 98, 23 24523 263.

    • Search Google Scholar
    • Export Citation
  • Black, P. G., 1983: Ocean temperature changes induced by tropical cyclones. Ph.D. dissertation, The Pennsylvania State University, 278 pp.

    • Search Google Scholar
    • Export Citation
  • Braun, S. A., 2010a: Reevaluating the role of the Saharan air layer in Atlantic tropical cyclogenesis and evolution. Mon. Wea. Rev., 138, 20072037.

    • Search Google Scholar
    • Export Citation
  • Braun, S. A., 2010b: Comments on “Atlantic tropical cyclogenesis processes during SOP-3 NAMMA in the GEOS-5 global data assimilation and forecast system.” J. Atmos. Sci., 67, 24022410.

    • Search Google Scholar
    • Export Citation
  • Braun, S. A., , J. A. Sippel, , and D. Nolan, 2011: The impact of dry midlevel air on hurricane intensity in idealized simulations with no mean flow. J. Atmos. Sci., in press.

    • Search Google Scholar
    • Export Citation
  • Carlson, T. N., , and J. M. Prospero, 1972: The large-scale movement of Saharan air outbreaks over the northern equatorial Atlantic. J. Appl. Meteor., 11, 283297.

    • Search Google Scholar
    • Export Citation
  • Davis, C., , and L. F. Bosart, 2002: Numerical simulations of the genesis of Hurricane Diana (1984). Part II: Sensitivity of track and intensity prediction. Mon. Wea. Rev., 130, 11001124.

    • Search Google Scholar
    • Export Citation
  • Davis, C., and Coauthors, 2008: Prediction of landfalling hurricanes with the Advanced Hurricane WRF model. Mon. Wea. Rev., 136, 19902005.

    • Search Google Scholar
    • Export Citation
  • DeMaria, M., , J. A. Knaff, , and B. H. Connell, 2001: A tropical cyclone genesis parameter for the tropical Atlantic. Wea. Forecasting, 16, 219233.

    • Search Google Scholar
    • Export Citation
  • Doswell, C. A., III, , and E. N. Rasmussen, 1994: The effect of neglecting the virtual temperature correction on CAPE calculations. Wea. Forecasting, 9, 625629.

    • Search Google Scholar
    • Export Citation
  • Dudhia, J., 1989: Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model. J. Atmos. Sci., 46, 30773107.

    • Search Google Scholar
    • Export Citation
  • Dunion, J. P., , and C. S. Velden, 2004: The impact of the Saharan air layer on Atlantic tropical cyclone activity. Bull. Amer. Meteor. Soc., 85, 353365.

    • Search Google Scholar
    • Export Citation
  • Gray, W. M., 1968: Global view of the origin of tropical disturbances and storms. Mon. Wea. Rev., 96, 669700.

  • Hakim, G. J., , and R. D. Torn, 2008: Ensemble synoptic analysis. Synoptic–Dynamic Meteorology and Weather Analysis and Forecasting: A Tribute to Fred Sanders, Meteor. Monogr., No. 55, Amer. Meteor. Soc., 147–162.

    • Search Google Scholar
    • Export Citation
  • Hawblitzel, D. P., , F. Zhang, , Z. Meng, , and C. A. Davis, 2007: Probabilistic evaluation of the dynamics and predictability of the mesoscale convective vortex of 10–13 June 2003. Mon. Wea. Rev., 135, 15441563.

    • 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, 828841.

    • Search Google Scholar
    • Export Citation
  • Hong, S.-Y., , J. Dudhia, , and S.-H. Chen, 2004: A revised approach to ice-microphysical processes for the bulk parameterization of cloud and precipitation. Mon. Wea. Rev., 132, 103120.

    • Search Google Scholar
    • Export Citation
  • Huffman, G. J., , R. F. Adler, , D. T. Bolvin, , G. Gu, , E. J. Nelkin, , K. P. Bowman, , E. F. Stocker, , and D. B. Wolff, 2007: The TRMM multisatellite precipitation analysis: Quasi-global, multiyear, combined-sensor precipitation estimates at fine scale. J. Hydrometeor., 8, 3855.

    • Search Google Scholar
    • Export Citation
  • Jenkins, G. S., , and A. Pratt, 2008: Saharan dust, lightning and tropical cyclones in the eastern tropical Atlantic during NAMMA-06. Geophys. Res. Lett., 35, L12804, doi:10.1029/2008GL033979.

    • Search Google Scholar
    • Export Citation
  • Jenkins, G. S., , A. Pratt, , and A. Heymsfield, 2008: Possible linkages between Saharan dust and tropical cyclone rain band invigoration in the eastern Atlantic during NAMMA-06. Geophys. Res. Lett., 35, L08815, doi:10.1029/2008GL034072.

    • Search Google Scholar
    • Export Citation
  • Jones, T. A., , D. J. Cecil, , and J. Dunion, 2007: The environmental and inner-core conditions governing the intensity of Hurricane Erin (2007). Wea. Forecasting, 22, 708725.

    • 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., 23, 27842802.

    • Search Google Scholar
    • Export Citation
  • Kain, J. S., , and J. M. Fritsch, 1993: Convective parameterization for mesoscale models: The Kain–Fritsch scheme. The Representation of Cumulus Convection in Numerical Models. Meteor. Monogr., No. 46, Amer. Meteor. Soc., 165–170.

    • Search Google Scholar
    • Export Citation
  • Karyampudi, V. M., , and T. N. Carlson, 1988: Analysis and numerical simulations of the Saharan air layer and its effect on easterly wave disturbances. J. Atmos. Sci., 45, 31023136.

    • 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, 31003128.

    • Search Google Scholar
    • Export Citation
  • Lau, K. M., , and J. M. Kim, 2007a: How nature foiled the 2006 hurricane forecasts. Eos, Trans. Amer. Geophys. Union, 88, 105107.

  • Lau, K. M., , and J. M. Kim, 2007b: Cooling of the Atlantic by Saharan dust. Geophys. Res. Lett., 34, L23811, doi:10.1029/2007GL031538.

  • Mlawer, E. J., , S. J. Taubman, , P. D. Brown, , M. J. Iacono, , and S. A. Clough, 1997: Radiative transfer for inhomogeneous atmosphere: RRTM, a validated correlated-k model for the longwave. J. Geophys. Res., 102, 16 66316 682.

    • 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, 401427.

    • Search Google Scholar
    • Export Citation
  • Pratt, A. S., , and J. L. Evans, 2009: Potential impacts of the Saharan air layer on numerical model forecasts of North Atlantic tropical cyclogenesis. Wea. Forecasting, 24, 420435.

    • Search Google Scholar
    • Export Citation
  • Prospero, J. M., , and T. N. Carlson, 1981: Saharan air outbreaks over the tropical North Atlantic. Pure Appl. Geophys., 119, 677691.

  • Raymond, D. J., , and H. Jiang, 1990: A theory for long-lived mesoscale convective systems. J. Atmos. Sci., 47, 30673077.

  • Reale, O., , and W. K. Lau, 2010: Reply. J. Atmos. Sci., 67, 24112415.

  • Reale, O., , W. K. Lau, , K.-M. Kim, , and E. Brin, 2009: Atlantic tropical cyclogenetic processes during SOP-3 NAMMA in the GEOS-5 global data assimilation and forecast system. J. Atmos. Sci., 66, 35633578.

    • Search Google Scholar
    • Export Citation
  • Reimer, M., , and M. T. Montgomery, 2010: Simple kinematic models for the environmental interaction of tropical cyclones in vertical wind shear. Atmos. Chem. Phys. Discuss., 10, 28 05728 107.

    • Search Google Scholar
    • Export Citation
  • Shu, S., , and L. Wu, 2009: Analysis of the influence of the Saharan air layer on tropical cyclone intensity using AIRS/Aqua data. Geophys. Res. Lett., 36, L09809, doi:10.1029/2009GL037634.

    • Search Google Scholar
    • Export Citation
  • Sippel, J. A., , and F. Zhang, 2008: A probabilistic analysis of the dynamics and predictability of tropical cyclogenesis. J. Atmos. Sci., 65, 34403459.

    • Search Google Scholar
    • Export Citation
  • Sippel, J. A., , and F. Zhang, 2010: Factors affecting the predictability of Hurricane Humberto (2007). J. Atmos. Sci., 67, 17591778.

  • 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
  • Sun, D., , K. M. Lau, , and M. Kafatos, 2008: Contrasting the 2007 and 2005 hurricane seasons: Evidence of possible impacts of Saharan dry air and dust on tropical cyclone activity in the Atlantic basin. Geophys. Res. Lett., 35, L15405, doi:10.1029/2008GL034529.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C. D., , and B. J. Hoskins, 1994: An idealized study of African easterly waves. Part I: A linear view. Quart. J. Roy. Meteor. Soc., 120, 953982.

    • Search Google Scholar
    • Export Citation
  • Torn, R. D., 2010: Ensemble-based sensitivity analysis applied to African easterly waves. Wea. Forecasting, 25, 6178.

  • Vizy, E. K., , and K. H. Cook, 2009: Tropical storm development from African easterly waves in the eastern Atlantic: A comparison of two successive waves using a regional model as part of NASA AMMA 2006. J. Atmos. Sci., 66, 33133334.

    • Search Google Scholar
    • Export Citation
  • Wu, L., 2007: Impact of Saharan air layer on hurricane peak intensity. Geophys. Res. Lett., 34, L09802, doi:10.1029/2007GL029564.

  • Wu, L., , S. A. Braun, , J. J. Qu, , and X. Hao, 2006: Simulating the formation of Hurricane Isabel (2003) with AIRS data. Geophys. Res. Lett., 33, L04804, doi:10.1029/2005GL024665.

    • Search Google Scholar
    • Export Citation
  • Zhang, F., 2005: Dynamics and structure of mesoscale error covariance of a winter cyclone estimated through short-range ensemble forecasts. Mon. Wea. Rev., 133, 28762893.

    • Search Google Scholar
    • Export Citation
  • Zhang, F., , and J. A. Sippel, 2009: Effects of moist convection on Hurricane predictability. J. Atmos. Sci., 66, 19441961.

  • Zipser, E. J., and Coauthors, 2009: The Saharan air layer and the fate of African easterly waves—NASA’s AMMA field study of tropical cyclogenesis. Bull. Amer. Meteor. Soc., 90, 11371156.

    • Search Google Scholar
    • Export Citation
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Environmental Influences on the Strength of Tropical Storm Debby (2006)

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  • 1 Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, Maryland
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Abstract

This study uses mesoscale ensemble forecasts to compare the magnitude of nonaerosol effects of the Saharan air layer (SAL) with other environmental influences on the intensity of Tropical Storm Debby. Debby was a weak Cape Verde storm that dissipated over the tropical North Atlantic a few days after forming in August 2006. The system has received considerable attention because of its vicinity to the SAL as it struggled to intensify, which has led to speculation that the SAL helped lead to the storm’s demise. Statistical correlation is used to better understand why some ensemble members strengthen the pre-Debby wave into a hurricane and others develop only a weak vortex.

Although the results here suggest that the SAL slowed intensification during the predepression to depression stages, it was not likely responsible for Debby’s dissipation. The most obvious SAL-related factor to affect long-term intensity in the ensembles is dry air above 2 km, which delays organization of the low-level vortex. Warm temperatures within the SAL and shear associated with the African easterly jet (AEJ) exhibit a weak, secondary relationship with forecast intensity variability. An important result here is that sensitivity to the dry environmental air depends considerably on cyclone strength, and it becomes insignificant once a tropical storm forms. Furthermore, Debby’s most rapid period of intensification coincided with its track over somewhat higher sea surface temperatures, and intensification ended when the storm moved over cooler waters. The results herein suggest that this factor might have affected the storm’s intensity more strongly than did any effect of the SAL. Even later, subsequent to the period examined by these ensembles, Debby dissipated under the influence of stronger vertical wind shear from an upper-level trough.

These results show that the relationship among the SAL, AEJ, and developing tropical cyclones is not as straightforward as has been hypothesized by some recent studies. Ultimately, the nuanced relationship between storm intensity and the SAL shows that much care needs to be taken before drawing conclusions about the effect of the SAL on any particular cyclone. The authors therefore advocate more rigorous future analysis through both idealized and ensemble studies to more fully quantify the effect of the SAL on tropical cyclones in general.

Additional affiliation: Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Baltimore, Maryland.

Corresponding author address: Dr. Jason A. Sippel, NASA GSFC, Code 613.1, Greenbelt, MD 20771. E-mail: jason.sippel@nasa.gov

Abstract

This study uses mesoscale ensemble forecasts to compare the magnitude of nonaerosol effects of the Saharan air layer (SAL) with other environmental influences on the intensity of Tropical Storm Debby. Debby was a weak Cape Verde storm that dissipated over the tropical North Atlantic a few days after forming in August 2006. The system has received considerable attention because of its vicinity to the SAL as it struggled to intensify, which has led to speculation that the SAL helped lead to the storm’s demise. Statistical correlation is used to better understand why some ensemble members strengthen the pre-Debby wave into a hurricane and others develop only a weak vortex.

Although the results here suggest that the SAL slowed intensification during the predepression to depression stages, it was not likely responsible for Debby’s dissipation. The most obvious SAL-related factor to affect long-term intensity in the ensembles is dry air above 2 km, which delays organization of the low-level vortex. Warm temperatures within the SAL and shear associated with the African easterly jet (AEJ) exhibit a weak, secondary relationship with forecast intensity variability. An important result here is that sensitivity to the dry environmental air depends considerably on cyclone strength, and it becomes insignificant once a tropical storm forms. Furthermore, Debby’s most rapid period of intensification coincided with its track over somewhat higher sea surface temperatures, and intensification ended when the storm moved over cooler waters. The results herein suggest that this factor might have affected the storm’s intensity more strongly than did any effect of the SAL. Even later, subsequent to the period examined by these ensembles, Debby dissipated under the influence of stronger vertical wind shear from an upper-level trough.

These results show that the relationship among the SAL, AEJ, and developing tropical cyclones is not as straightforward as has been hypothesized by some recent studies. Ultimately, the nuanced relationship between storm intensity and the SAL shows that much care needs to be taken before drawing conclusions about the effect of the SAL on any particular cyclone. The authors therefore advocate more rigorous future analysis through both idealized and ensemble studies to more fully quantify the effect of the SAL on tropical cyclones in general.

Additional affiliation: Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Baltimore, Maryland.

Corresponding author address: Dr. Jason A. Sippel, NASA GSFC, Code 613.1, Greenbelt, MD 20771. E-mail: jason.sippel@nasa.gov
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