• Arnault, J., , and F. Roux, 2010: Comparison between two case studies of developing and nondeveloping African easterly waves during NAMMA and AMMA/SOP-3: Absolute vertical vorticity budget. Mon. Wea. Rev., 138, 14201445, doi:10.1175/2009MWR3120.1.

    • Search Google Scholar
    • Export Citation
  • Arnault, J., , and F. Roux, 2011: Characteristics of African easterly waves associated with tropical cyclogenesis in the Cape Verde islands region in July–August–September of 2004–2008. Atmos. Res., 100, 6182, doi:10.1016/j.atmosres.2010.12.028.

    • Search Google Scholar
    • Export Citation
  • Berry, G., , and C. D. Thorncroft, 2005: Case study of an intense African easterly wave. Mon. Wea. Rev., 133, 752766, doi:10.1175/MWR2884.1.

    • Search Google Scholar
    • Export Citation
  • Bister, M., , and K. A. Emanuel, 1997: The genesis of Hurricane Guillermo: TEXMEX analyses and a modeling study. Mon. Wea. Rev., 125, 26622682, doi:10.1175/1520-0493(1997)125<2662:TGOHGT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Briegel, L. M., , and W. M. Frank, 1997: Large-scale influences on tropical cyclogenesis in the western North Pacific. Mon. Wea. Rev., 125, 13971413, doi:10.1175/1520-0493(1997)125<1397:LSIOTC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Cadet, D. L., , and N. O. Nnoli, 1987: Water vapour transport over Africa and the Atlantic Ocean during summer 1979. Quart. J. Roy. Meteor. Soc., 113, 581602, doi:10.1002/qj.49711347609.

    • Search Google Scholar
    • Export Citation
  • Carlson, T. N., 1969: Synoptic histories of three African disturbances that developed into Atlantic hurricanes. Mon. Wea. Rev., 97, 256276, doi:10.1175/1520-0493(1969)097<0256:SHOTAD>2.3.CO;2.

    • Search Google Scholar
    • Export Citation
  • Chiao, S., , and G. S. Jenkins, 2010: Numerical investigations on the formation of Tropical Storm Debby during NAMMA-06. Wea. Forecasting, 25, 866884, doi:10.1175/2010WAF2222313.1.

    • 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, doi:10.1002/qj.828.

    • 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, doi:10.1175/1520-0434(2001)016<0219:ATCGPF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Diedhiou, A., , S. Janicot, , A. Viltard, , P. de Felice, , and H. Laurent, 1999: Easterly wave regimes and associated convection over West Africa and tropical Atlantic: Results from the NCEP/NCAR and ECMWF reanalyses. Climate Dyn., 15, 795822, doi:10.1007/s003820050316.

    • Search Google Scholar
    • Export Citation
  • Diedhiou, A., , S. Janicot, , A. Viltard, , and P. de Felice, 2001: Composite patterns of easterly disturbances over West Africa and the tropical Atlantic: A climatology from the 1979–95 NCEP/NCAR reanalyses. Climate Dyn., 18, 241253, doi:10.1007/s003820100173.

    • 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, doi:10.1175/BAMS-85-3-353.

    • Search Google Scholar
    • Export Citation
  • Emanuel, K. A., 1986: An air–sea interaction theory for tropical cyclones. Part I: Steady-state maintenance. J. Atmos. Sci., 43, 585605, doi:10.1175/1520-0469(1986)043<0585:AASITF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Fink, A. H., , and A. Reiner, 2003: Spatiotemporal variability of the relation between African easterly jets and West African squall lines in 1998 and 1999. J. Geophys. Res., 108, 4332, doi:10.1029/2002JD002816.

    • Search Google Scholar
    • Export Citation
  • Goldenberg, S. B., , and L. J. Shapiro, 1996: Physical mechanisms for the association of El Niño and West African rainfall with Atlantic major hurricanes. J. Climate, 9, 11691187, doi:10.1175/1520-0442(1996)009<1169:PMFTAO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Goldenberg, S. B., , C. W. Landsea, , A. M. Mestas-Nuñez, , and W. M. Gray, 2001: The recent increase of Atlantic hurricane activity: Causes and implications. Science, 293, 474479, doi:10.1126/science.1060040.

    • Search Google Scholar
    • Export Citation
  • Gray, W. M., 1975: Tropical cyclone genesis. CSU Dept. of Atmospheric Science Paper 234, Colorado State University, 121 pp.

  • Gray, W. M., 1979: Hurricanes: Their formation, structure and likely role in the tropical circulation. Meteorology over the Tropical Oceans, D. B. Shaw, Ed., Royal Meteorological Society, 155–218.

  • Gray, W. M., 1998: The formation of tropical cyclones. Meteor. Atmos. Phys., 67, 3769, doi:10.1007/BF01277501.

  • Hodges, K. I., , D. W. Chappel, , G. J. Robinson, , and G. Yang, 2000: An improved algorithm for generating global window brightness temperatures from multiple satellite infrared imagery. J. Atmos. Oceanic Technol., 17, 12961312, doi:10.1175/1520-0426(2000)017<1296:AIAFGG>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Hopsch, S. B., , C. D. Thorncroft, , K. Hodges, , and A. Aiyyer, 2007: West African storm tracks and their relationship to Atlantic tropical cyclones. J. Climate, 20, 24682483, doi:10.1175/JCLI4139.1.

    • Search Google Scholar
    • Export Citation
  • Hopsch, S. B., , C. D. Thorncroft, , and K. R. Tyle, 2010: Analysis of African easterly wave structures and their role in influencing tropical cyclogenesis. Mon. Wea. Rev., 138, 13991419, doi:10.1175/2009MWR2760.1.

    • Search Google Scholar
    • Export Citation
  • Houze, R. A., Jr., 2004: Mesoscale convective systems. Rev. Geophys., 42, RG4003, doi:10.1029/2004RG000150.

  • 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
  • Jenkins, G. S., and Coauthors, 2010: Coastal observations of weather features in Senegal during the African Monsoon Multidisciplinary Analysis special observing period 3. J. Geophys. Res., 115, D18108, doi:10.1029/2009JD013022.

    • 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, doi:10.1175/1520-0469(1988)045<3102:AANSOT>2.0.CO;2.

    • 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, doi:10.1175/1520-0493(2002)130<3100:SSIOTS>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Kiladis, G. N., , C. D. Thorncroft, , and N. M. J. Hall, 2006: Three-dimensional structure and dynamics of African easterly waves. Part I: Observations. J. Atmos. Sci., 63, 22122230, doi:10.1175/JAS3741.1.

    • Search Google Scholar
    • Export Citation
  • Leduc-Leballeur, M., , G. de Coëtlogon, , and L. Eymard, 2013: Air–sea interaction in the Gulf of Guinea at intraseasonal time-scales: Wind bursts and coastal precipitation in boreal spring. Quart. J. Roy. Meteor. Soc., 139, 387–400, doi:10.1002/qj.1981.

    • Search Google Scholar
    • Export Citation
  • Leppert, K. D., , D. J. Cecil, , and W. A. Petersen, 2013: Relation between tropical easterly waves, convection, and tropical cyclogenesis: A Lagrangian perspective. Mon. Wea. Rev., 141, 26492668, doi:10.1175/MWR-D-12-00217.1.

    • Search Google Scholar
    • Export Citation
  • Maddox, R. A., 1980: Mesoscale convective complexes. Bull. Amer. Meteor. Soc., 61, 13741387, doi:10.1175/1520-0477(1980)061<1374:MCC>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Mapes, B. E., , and R. A. Houze, 1993: Cloud clusters and superclusters over the oceanic warm pool. Mon. Wea. Rev., 121, 13981416, doi:10.1175/1520-0493(1993)121<1398:CCASOT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Mathon, V., , and H. Laurent, 2001: Life cycle of Sahelian mesoscale convective cloud systems. Quart. J. Roy. Meteor. Soc., 127, 377406, doi:10.1002/qj.49712757208.

    • Search Google Scholar
    • Export Citation
  • McBride, J. L., , and R. Zehr, 1981: Observational analysis of tropical cyclone formation, Part II: Comparison of non-developing versus developing systems. J. Atmos. Sci., 38, 11321151, doi:10.1175/1520-0469(1981)038<1132:OAOTCF>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Menard, R. D., , and J. M. Fritsch, 1989: A mesoscale convective complex-generate inertially stable warm core vortex. Mon. Wea. Rev., 117, 12371261, doi:10.1175/1520-0493(1989)117<1237:AMCCGI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Meynadier R., , O. Bock, , S. Gervois, , F. Guichard, , J.-L. Redelsperger, , A. Agusti-Panareda, , and A. Beljaars, 2010: West African monsoon water cycle: 2. Assessment of numerical weather prediction water budgets. J. Geophys. Res.,115, D19107, doi:10.1029/2010JD013919.

  • Nzeukou, A., , and H. Sauvageot, 2002: Distribution of rainfall parameters near the coasts of France and Senegal. J. Appl. Meteor., 41, 6982, doi:10.1175/1520-0450(2002)041<0069:DORPNT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Pasch, R. J., , L. A. Avila, , and J. G. Jiing, 1998: Atlantic tropical systems of 1994 and 1995: A comparison of a quiet season to a near-record-breaking one. Mon. Wea. Rev., 126, 11061123, doi:10.1175/1520-0493(1998)126<1106:ATSOAA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Peng, M. S., , B. Fu, , T. Li, , and D. E. Stevens, 2012: Developing versus nondeveloping disturbances for tropical cyclone formation. Part I: North Atlantic. Mon. Wea. Rev., 140, 10471066, doi:10.1175/2011MWR3617.1.

    • Search Google Scholar
    • Export Citation
  • Pytharoulis, I., , and C. D. Thorncroft, 1999: The low-level structure of African easterly waves in 1995. Mon. Wea. Rev., 127, 22662280, doi:10.1175/1520-0493(1999)127<2266:TLLSOA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Raymond, D. J., , and H. Jiang, 1990: A theory for long-lived convective systems. J. Atmos. Sci., 47, 30673077, doi:10.1175/1520-0469(1990)047<3067:ATFLLM>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Reed, R., , D. Norquist, , and E. Recker, 1977: The structure and properties of African wave disturbances as observed during phase III of GATE. Mon. Wea. Rev., 105, 317333, doi:10.1175/1520-0493(1977)105<0317:TSAPOA>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Ritchie, E. A., , and G. J. Holland, 1997: Scale interactions during the formation of Typhoon Irving. Mon. Wea. Rev., 125, 13771396, doi:10.1175/1520-0493(1997)125<1377:SIDTFO>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Ritchie, E. A., , J. Simpson, , W. T. Liu, , J. Halverson, , C. Velden, , K. F. Brueske, , and H. Pierce, 2003: Present day satellite technology for hurricane research: A closer look at formation and intensification. Hurricane! Coping with Disaster, R. Simpson, Ed., Amer. Geophys. Union, 249–289.

  • Saha, S., and Coauthors, 2010: The NCEP Climate Forecast System Reanalysis. Bull. Amer. Meteor. Soc., 91, 10151057, doi:10.1175/2010BAMS3001.1.

    • Search Google Scholar
    • Export Citation
  • Sall, S. M., , and H. Sauvageot, 2005: Cyclogenesis off the African coast: The case of Cindy in August 1999. Mon. Wea. Rev., 133, 28032813, doi:10.1175/MWR3003.1.

    • Search Google Scholar
    • Export Citation
  • Sall, S. M., , H. Sauvageot, , A. Gaye, , A. Viltard, , and P. de Felice, 2006: A cyclogenesis index for tropical Atlantic off the African coasts. Atmos. Res., 79, 123147, doi:10.1016/j.atmosres.2005.05.004.

    • Search Google Scholar
    • Export Citation
  • Shapiro, L. J., , and S. B. Goldenberg, 1998: Atlantic sea surface temperatures and tropical cyclone formation. J. Climate, 11, 578590, doi:10.1175/1520-0442(1998)011<0578:ASSTAT>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Simpson, J., , E. Ritchie, , G. J. Holland, , J. Halverson, , and S. Stewart, 1997: Mesoscale interactions in tropical cyclone genesis. Mon. Wea. Rev., 125, 26432661, doi:10.1175/1520-0493(1997)125<2643:MIITCG>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Sippel, J. A., , S. A. Braun, , and C.-L. Shie, 2011: Environmental influences on the strength of Tropical Storm Debby (2006). J. Atmos. Sci., 68, 25572581, doi:10.1175/2011JAS3648.1.

    • Search Google Scholar
    • Export Citation
  • Small, R. J., and Coauthors, 2008: Air–sea interaction over ocean fronts and eddies. Dyn. Atmos. Oceans, 45, 274319, doi:10.1016/j.dynatmoce.2008.01.001.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C., , and K. Hodges, 2001: African easterly wave variability and its relationship to Atlantic tropical cyclone activity. J. Climate, 14, 11661179, doi:10.1175/1520-0442(2001)014<1166:AEWVAI>2.0.CO;2.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C., , J. Lafore, , G. Berry, , R. Roca, , F. Guichard, , M. Tomasini, , and N. Asencio, 2007: Overview of African weather systems during the summer 2006. CLIVAR Exchanges, No. 12, International CLIVAR Project Office, Southampton, United Kingdom, 18–20.

    • Search Google Scholar
    • Export Citation
  • Thorncroft, C., , H. Nguyen, , C. Zhang, , and P. Peyrille, 2011: Annual cycle of the West African monsoon: Regional circulations and associated water vapour transport. Quart. J. Roy. Meteor. Soc., 137, 129147, doi:10.1002/qj.728.

    • Search Google Scholar
    • Export Citation
  • 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, doi:10.1175/2009JAS3064.1.

    • Search Google Scholar
    • Export Citation
  • Zehr, R., 1992: Tropical cyclogenesis in the western North Pacific. NOAA Tech. Rep. NESDIS 16, 181 pp.

  • 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, doi:10.1175/2009BAMS2728.1.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 142 142 21
PDF Downloads 126 126 15

Analysis of Strengthening and Dissipating Mesoscale Convective Systems Propagating off the West African Coast

View More View Less
  • 1 Laboratoire de Physique de l’Atmosphère et de l’Océan Siméon Fongang, Cheikh Anta Diop University, Dakar, Senegal
  • 2 Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, Pierre et Marie Curie University, Paris, France
  • 3 Laboratoire de Physique de l’Atmosphère et de l’Océan Siméon Fongang, Cheikh Anta Diop University, Dakar, Senegal
  • 4 Laboratoire d'Océanographie et du Climat: Expérimentations et Approches Numériques, Pierre et Marie Curie University, Paris, France
  • 5 Laboratoire Atmosphères, Milieux, Observations Spatiales, Pierre et Marie Curie University, Paris, France
© Get Permissions
Restricted access

Abstract

A large number of Atlantic tropical depressions are generated in the eastern basin in relation to the African easterly wave (AEW) and embedded mesoscale convective systems (MCSs) coming from the African continent. In this paper, the structures of strengthening and dissipating MCSs evolving near the West African coast are analyzed, including the role of the ocean surface conditions in their evolution.

Satellite infrared brightness temperature and meteorological radar data over seven summer seasons between 1993 and 2006 are used to subjectively select 20 cases of strengthening and dissipating MCSs in the vicinity of the Senegal coast. With these observed MCSs, a lagged composite analysis is then performed using Interim ECMWF Re-Analysis (ERA-Interim) and Climate Forecast System Reanalysis (CFSR).

It is shown that the strengthening MCS is generally preceded by prior passage of an AEW near the West African coast. This previous wave trough is associated with a convective cyclonic circulation in the low and middle troposphere, which enhances the southwesterly flow and then provides humidity to the strengthening MCS, located in the vicinity of the subsequent AEW trough. This is favored by the contraction of the wavelength associated with the two troughs. The sea surface contributes to the MCS enhancement through surface evaporation flux. But this contribution is found to be less important than advection of humidity from the previous wave trough. These conditions are almost not found in the dissipating MCS cases, which dissipate in a dry environment dominated by a subsident and anticyclonic circulation, with generally no interaction with a previous wave trough.

Corresponding author address: Abdou Lahat Dieng, Laboratoire de Physique de l’Atmosphère et de l’Océan Siméon Fongang, Cheikh Anta Diop University, BP 5085 Dakar, Fann, Senegal. E-mail: aldlod@locean-ipsl.upmc.fr

Abstract

A large number of Atlantic tropical depressions are generated in the eastern basin in relation to the African easterly wave (AEW) and embedded mesoscale convective systems (MCSs) coming from the African continent. In this paper, the structures of strengthening and dissipating MCSs evolving near the West African coast are analyzed, including the role of the ocean surface conditions in their evolution.

Satellite infrared brightness temperature and meteorological radar data over seven summer seasons between 1993 and 2006 are used to subjectively select 20 cases of strengthening and dissipating MCSs in the vicinity of the Senegal coast. With these observed MCSs, a lagged composite analysis is then performed using Interim ECMWF Re-Analysis (ERA-Interim) and Climate Forecast System Reanalysis (CFSR).

It is shown that the strengthening MCS is generally preceded by prior passage of an AEW near the West African coast. This previous wave trough is associated with a convective cyclonic circulation in the low and middle troposphere, which enhances the southwesterly flow and then provides humidity to the strengthening MCS, located in the vicinity of the subsequent AEW trough. This is favored by the contraction of the wavelength associated with the two troughs. The sea surface contributes to the MCS enhancement through surface evaporation flux. But this contribution is found to be less important than advection of humidity from the previous wave trough. These conditions are almost not found in the dissipating MCS cases, which dissipate in a dry environment dominated by a subsident and anticyclonic circulation, with generally no interaction with a previous wave trough.

Corresponding author address: Abdou Lahat Dieng, Laboratoire de Physique de l’Atmosphère et de l’Océan Siméon Fongang, Cheikh Anta Diop University, BP 5085 Dakar, Fann, Senegal. E-mail: aldlod@locean-ipsl.upmc.fr
Save