The authors wish to thank the Kenya and Tanzania Meteorological Departments for provision of part of the rainfall data used in the study. Very constructive comments from two anonymous reviewers are also gratefully acknowledged.
Anantakrishnan, R., , and M. K. Soman, 1988: The onset of the south-west monsoon over Kerala: 1901–1980. J. Climatol., 8 , 283–296.
Boos, W. R., , and K. A. Emanuel, 2009: Annual intensification of the Somali jet in a quasi-equilibrium framework: Observational composites. Quart. J. Roy. Meteor. Soc., 135 , 319–335.
Cadet, D. L., , and M. Desbois, 1980: The burst of the 1978 Indian summer monsoon as seen from METEOSAT. Mon. Wea. Rev., 108 , 1697–1701.
Camberlin, P., , and R. E. Okoola, 2003: The onset and cessation of the “long rains” in eastern Africa and their interannual variability. Theor. Appl. Climatol., 75 , 43–54.
Chakraborty, A., , R. S. Nanjundiah, , and J. Srinivasan, 2008: Impact of African orography and the Indian summer monsoon on the low-level Somali jet. Int. J. Climatol., 29 , 983–992. doi:10.1002/joc.1720.
Fasullo, J., , and P. J. Webster, 2003: A hydrological definition of Indian monsoon onset and withdrawal. J. Climate, 16 , 3200–3211.
Findlater, J., 1969: A major low-level air current near the Indian Ocean during the northern summer. Quart. J. Roy. Meteor. Soc., 95 , 362–380.
Findlater, J., 1974: The low-level cross-equatorial air current of the western Indian Ocean during the northern summer. Weather, 29 , 411–416.
Findlater, J., 1978: Observational aspects of the low-level cross-equatorial jet stream. Monsoon Dynamics, T. N. Krishnamurti, Ed., Birkhäuser Verlag, 1251–1262.
Fontaine, B., , and S. Louvet, 2006: Sudan-Sahel rainfall onset: Definition of an objective index, types of years, and experimental hindcasts. J. Geophys. Res., 111 , D20103. doi:10.1029/2005JD007019.
Fontaine, B., , S. Louvet, , and P. Roucou, 2008: Definition and predictability of an OLR-based West African monsoon onset. Int. J. Climatol., 28 , 1787–1798. doi:10.1002/joc.1674.
Hahn, D. G., , and S. Manabe, 1975: The role of mountains in the South Asian monsoonal circulation. J. Atmos. Sci., 32 , 1515–1541.
He, H., , J. W. McGinnis, , Z. Song, , and M. Yanai, 1987: Onset of the Asian monsoon in 1979 and the effect of the Tibetan Plateau. Mon. Wea. Rev., 115 , 1966–1995.
Janicot, S., 2009: A comparison of Indian and African monsoon variability at different time scales. C. R. Geosci., 351 , 575–590. doi:10.1016/j.crte.2009.02.002.
Janicot, S., , F. Mounier, , N. M. J. Hall, , S. Leroux, , B. Sultan, , and G. N. Kiladis, 2009: Dynamics of the West African monsoon. Part IV: Analysis of 25–90-day variability of convection and the role of the Indian monsoon. J. Climate, 22 , 1541–1565.
Joseph, P. V., , J. K. Eischeid, , and P. J. Pyle, 1994: Interannual variability of the onset of the Indian summer monsoon and its association with atmospheric features, El Niño, and sea surface temperatures. J. Climate, 7 , 81–105.
Joseph, P. V., , K. P. Sooraj, , and C. K. Rajan, 2006: The summer monsoon onset over process over south Asia and an objective method for the date of monsoon onset over Kerala. Int. J. Climatol., 26 , 1871–1893.
Kanamitsu, M., , W. Ebisuzaki, , J. Woollen, , S. K. Yang, , J. J. Hnilo, , M. Fiorion, , and G. L. Potter, 2002: NCEP-DOE AMIP-II Reanalysis (R-2). Bull. Amer. Meteor. Soc., 83 , 1631–1643.
Knutson, T. R., , and K. M. Weickmann, 1987: 30–60-day atmospheric oscillations: Composite life cycles of convection and circulation anomalies. Mon. Wea. Rev., 115 , 1407–1436.
Krishnamurti, T. N., , V. Wong, , H. L. Pan, , R. Pasch, , J. Molinari, , and P. Ardanuy, 1983: A three-dimensional planetary boundary layer model for the Somali jet. J. Atmos. Sci., 40 , 894–908.
Lavender, S. L., , and A. J. Matthews, 2009: Response of the West African monsoon to the Madden–Julian oscillation. J. Climate, 22 , 4097–4116.
Lawrence, D. M., , and P. J. Webster, 2002: The boreal summer intraseasonal oscillation: Relationship between northward and eastward movement of convection. J. Atmos. Sci., 59 , 1593–1606.
Le Barbé, L., , T. Lebel, , and D. Tapsoba, 2002: Rainfall variability in West Africa during the years 1950–1990. J. Climate, 15 , 187–202.
Li, C., , and M. Yanai, 1996: The onset and interannual variability of the Asian summer monsoon in relation to land–sea thermal contrast. J. Climate, 9 , 358–375.
LinHo, L. H., , X. Huang, , and N. Lau, 2008: Winter-to-spring transition in East Asia: A planetary-scale perspective of the South China spring rain onset. J. Climate, 21 , 3081–3096.
Louvet, S., , B. Fontaine, , and P. Roucou, 2003: Active phases and pauses during the installation of the West African monsoon through 5-day CMAP rainfall data (1979–2001). Geophys. Res. Lett., 30 , 2271–2275.
Maloney, E. D., , and J. Shaman, 2008: Intraseasonal variability of the West African monsoon and Atlantic ITCZ. J. Climate, 21 , 2898–2918.
Murakami, T., 1987: Effects of the Tibetan Plateau. Monsoon Meteorology, C.-P. Chang and T. N. Krishnamurti, Eds., Oxford University Press, 235–270.
Murakami, T., , L-X. Chen, , A. Xie, , and M. L. Shresha, 1986: Eastward propagation of 30–60-day perturbations as revealed from outgoing longwave radiation data. J. Atmos. Sci., 43 , 961–971.
Nicholson, S. E., 1996: A review of climate dynamics and climate variability in Eastern Africa. The Limnology, Climatology and Paleoclimatology of the East African Lakes, T. C. Johnson and E. O. Odada, Eds. Gordon and Breach, 25–56.
Ogallo, L. J., 1985: Climatology of rainfall in East Africa. WMO Conf. on GATE, WAMEX and Tropical Meteorology, Dakar, Senegal, WMO, 96–102.
Okoola, R. E., , P. Camberlin, , and J. M. Ininda, 2008: Wet periods along the East Africa coast and the extreme wet spell event of October 1997. J. Kenya Meteor. Soc., 2 , 67–83.
Pai, D. S., , and R. M. Nair, 2009: Summer monsoon onset over Kerala: New definition and prediction. J. Earth Syst. Sci., 118 , 123–135.
Pohl, B., , S. Janicot, , B. Fontaine, , and R. Marteau, 2009: Implication of the Madden–Julian oscillation in the 40-day variability of the West African monsoon. J. Climate, 22 , 3769–3785.
Raju, P. V. S., , U. C. Mohanty, , and R. Bhatla, 2005: Onset characteristics of the southwest monsoon over India. Int. J. Climatol., 25 , 167–182.
Raju, P. V. S., , U. C. Mohanty, , and R. Bhatla, 2007: Interannual variability of onset of the summer monsoon over India and its prediction. Nat. Hazards, 42 , 287–300.
Rao, V. B., , J. P. Reyes Fernandez, , and S. H. Franchito, 2000: Monsoonlike circulations in a zonally averaged numerical model with topography. Mon. Wea. Rev., 128 , 779–794.
Riddle, E. E., , and K. H. Cook, 2008: Abrupt rainfall transitions over the Greater Horn of Africa: Observations and regional model simulations. J. Geophys. Res., 113 , D15109. doi:10.1029/2007JD009202.
Rodwell, M. J., 1997: Breaks in the Asian monsoon: The influence of Southern Hemisphere weather systems. J. Atmos. Sci., 54 , 2597–2611.
Rodwell, M. J., , and B. J. Hoskins, 1995: A model of the Asian summer monsoon. Part II: Cross-equatorial flow and PV behavior. J. Atmos. Sci., 52 , 1341–1356.
Slingo, J., , H. Spencer, , B. Hoskins, , P. Berrisford, , and E. Black, 2004: The meteorology of the western Indian Ocean and the influence of the East African highlands. Philos. Trans. Roy. Soc. London, 363A , 25–42.
Sultan, B., , and S. Janicot, 2000: Abrupt shift of the ITCZ over West Africa and intra-seasonal variability. Geophys. Res. Lett., 27 , 3353–3356.
Sultan, B., , and S. Janicot, 2003: The West African monsoon dynamics. Part II: The “pre-onset” and the “onset” of the summer monsoon. J. Climate, 16 , 3407–3427.
Wang, B., , Q. Ding, , and P. V. Joseph, 2009: Objective definition of the Indian summer monsoon onset. J. Climate, 22 , 3303–3316.
Webster, P. J., , T. Palmer, , M. Yanai, , R. Tomas, , V. Magana, , J. Shukla, , and A. Yasunari, 1998: Monsoons: Processes, predictability and the prospects for prediction. J. Geophys. Res., 103 , 14451–14510.
Wheeler, M. C., , and H. H. Hendon, 2004: An all-season real-time multivariate MJO index: Development of an index for monitoring and prediction. Mon. Wea. Rev., 132 , 1917–1932.
Wu, M. L. C., , S. Schubert, , and N. E. Huang, 1999: The development of the South Asian summer monsoon and the intraseasonal oscillation. J. Climate, 12 , 2054–2075.
Xavier, P. K., , C. Marzin, , and B. N. Goswami, 2007: An objective definition of the Indian summer monsoon season and a new perspective of the ENSO-monsoon relationship. Quart. J. Roy. Meteor. Soc., 133 , 749–764. doi:10.1002/qj.45.
Xie, P., , and P. A. Arkin, 1997: Global precipitation: A 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78 , 2539–2558.
Yin, X., , A. Gruber, , and P. Arkin, 2004: Comparison of the GPCP and CMAP merged gauge–satellite monthly precipitation products for the period 1979–2001. J. Hydrometeor., 5 , 1207–1222.
Zorita, E., , and F. F. Tilya, 2002: Rainfall variability in northern Tanzania in the March–May season (long rains) and its links to large-scale climate forcing. Climate Res., 20 , 31–40.