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there is any such pattern, does it exhibit regional variability? Similarly, at larger scales, high correlation is observed between the morphological parameters of the systems (maximum cluster size and MCS duration). It indicates that the largest cloud shields are associated with long-lasting mesoscale convection that injects enough water condensate in the upper levels during enough time to allow the growth of the shield to its largest value [ Houze (2004) and references therein]. This relationship
there is any such pattern, does it exhibit regional variability? Similarly, at larger scales, high correlation is observed between the morphological parameters of the systems (maximum cluster size and MCS duration). It indicates that the largest cloud shields are associated with long-lasting mesoscale convection that injects enough water condensate in the upper levels during enough time to allow the growth of the shield to its largest value [ Houze (2004) and references therein]. This relationship
1. Introduction Organized clusters of thunderstorms meeting particular spatial and temporal requirements have been termed mesoscale convective systems (MCSs; e.g., Zipser 1982 ; Hilgendorf and Johnson 1998 ; Parker and Johnson 2000 ). Knowledge of the environments that support the intensity of MCSs is essential in operational meteorology. This is especially true of MCSs that are long lived and produce damaging surface winds. The most intense end of this spectrum includes a class of systems
1. Introduction Organized clusters of thunderstorms meeting particular spatial and temporal requirements have been termed mesoscale convective systems (MCSs; e.g., Zipser 1982 ; Hilgendorf and Johnson 1998 ; Parker and Johnson 2000 ). Knowledge of the environments that support the intensity of MCSs is essential in operational meteorology. This is especially true of MCSs that are long lived and produce damaging surface winds. The most intense end of this spectrum includes a class of systems
1. Introduction In the central United States, mesoscale convective systems (MCSs) are one of the dominant convective features in the warm season and are responsible for a substantial fraction of warm season rainfall ( Fritsch et al. 1986 ). Schumacher and Johnson (2006) find that 74% of all warm season extreme rain events over the eastern two-thirds of the United States during the period 1999–2003 were associated with an MCS. Consequently, excessive or meager MCS activity can contribute to
1. Introduction In the central United States, mesoscale convective systems (MCSs) are one of the dominant convective features in the warm season and are responsible for a substantial fraction of warm season rainfall ( Fritsch et al. 1986 ). Schumacher and Johnson (2006) find that 74% of all warm season extreme rain events over the eastern two-thirds of the United States during the period 1999–2003 were associated with an MCS. Consequently, excessive or meager MCS activity can contribute to
1. Introduction Bands of anvil cirrus extending radially outward from regions of deep convection ( Fig. 1 ) are a common cloud characteristic near the outer edge of divergent upper-level outflows of mesoscale convective systems (MCSs). Lenz et al. (2009 , hereafter L09) document such banding events, lasting an average of 9 h, in approximately ½ of a sample of 136 large MCSs over the central United States during the 2006 warm season. L09 suggest the practical importance of these bands by
1. Introduction Bands of anvil cirrus extending radially outward from regions of deep convection ( Fig. 1 ) are a common cloud characteristic near the outer edge of divergent upper-level outflows of mesoscale convective systems (MCSs). Lenz et al. (2009 , hereafter L09) document such banding events, lasting an average of 9 h, in approximately ½ of a sample of 136 large MCSs over the central United States during the 2006 warm season. L09 suggest the practical importance of these bands by
1. Introduction An important unresolved issue in severe weather research is the relationship between quasi-linear convective systems (QLCSs) such as squall lines and bow echoes and the complex mesoscale environments within which they evolve. Some observational results (e.g., Klimowski et al. 2000 ; Przybylinski et al. 2000 ; Schmocker et al. 2000 ) suggest that mesoscale variability in the wind and thermodynamic fields due, for example, to convective outflows can significantly affect the
1. Introduction An important unresolved issue in severe weather research is the relationship between quasi-linear convective systems (QLCSs) such as squall lines and bow echoes and the complex mesoscale environments within which they evolve. Some observational results (e.g., Klimowski et al. 2000 ; Przybylinski et al. 2000 ; Schmocker et al. 2000 ) suggest that mesoscale variability in the wind and thermodynamic fields due, for example, to convective outflows can significantly affect the
1. Introduction Our understanding of mesoscale convective system (MCS) structure has developed in part through numerical modeling ( Rotunno et al. 1988 ; Pandya and Durran 1996 ; Parker and Johnson 2004 ; among many others), through radar-based climatologies such as the one developed by Parker and Johnson (2000) , and through case study events ( Houze 1977 ; Gamache and Houze 1982 ; Smull and Houze 1985 ). Parker and Johnson (2004) have shown that reproducible structures in MCSs include
1. Introduction Our understanding of mesoscale convective system (MCS) structure has developed in part through numerical modeling ( Rotunno et al. 1988 ; Pandya and Durran 1996 ; Parker and Johnson 2004 ; among many others), through radar-based climatologies such as the one developed by Parker and Johnson (2000) , and through case study events ( Houze 1977 ; Gamache and Houze 1982 ; Smull and Houze 1985 ). Parker and Johnson (2004) have shown that reproducible structures in MCSs include
lines were the leading edges of mesoscale storms. The early paper by Hamilton and Archbold (1945) also captured the essential character of the storm-scale overturning air motions within these mesoscale systems. Figure 17-1a shows the wind pattern at the ground as they deduced it from surface meteorological stations in West Africa, while Fig. 17-1b is an accompanying vertical section showing the cloud outline and system-relative air motions in a plane normal to the line. Hamilton and Archbold
lines were the leading edges of mesoscale storms. The early paper by Hamilton and Archbold (1945) also captured the essential character of the storm-scale overturning air motions within these mesoscale systems. Figure 17-1a shows the wind pattern at the ground as they deduced it from surface meteorological stations in West Africa, while Fig. 17-1b is an accompanying vertical section showing the cloud outline and system-relative air motions in a plane normal to the line. Hamilton and Archbold
weak in time-mean real-data forecasts with the WRF model based on precipitation climatologies compared to observations. They speculated that cold pools produced by CPSs were insufficiently cold to permit propagation. However, Anderson et al. (2007) have shown that a modified version of the KF scheme can produce propagating, nocturnal mesoscale convective systems (MCSs). Many authors ( Zhang and Fritsch 1986 , 1988 ; Zhang et al. 1994 ; Kain and Fritsch 1998 ) have shown that successful
weak in time-mean real-data forecasts with the WRF model based on precipitation climatologies compared to observations. They speculated that cold pools produced by CPSs were insufficiently cold to permit propagation. However, Anderson et al. (2007) have shown that a modified version of the KF scheme can produce propagating, nocturnal mesoscale convective systems (MCSs). Many authors ( Zhang and Fritsch 1986 , 1988 ; Zhang et al. 1994 ; Kain and Fritsch 1998 ) have shown that successful
1. Introduction Mesoscale convective systems (MCSs) have been the object of much study because of their importance for severe weather and rainfall production ( Cotton and Anthes 1989 ; Houze 2004 ). One common tool in studying these systems has been to examine clusters of connected pixels for radar, microwave, or infrared indicators of cloud. Working definitions of MCSs are phrased in terms of such clusters—for example, an area of brightness temperature below 250 K of at least 2000 km 2
1. Introduction Mesoscale convective systems (MCSs) have been the object of much study because of their importance for severe weather and rainfall production ( Cotton and Anthes 1989 ; Houze 2004 ). One common tool in studying these systems has been to examine clusters of connected pixels for radar, microwave, or infrared indicators of cloud. Working definitions of MCSs are phrased in terms of such clusters—for example, an area of brightness temperature below 250 K of at least 2000 km 2
1. Introduction Satellite-based cloud climatologies of mesoscale convective systems (MCSs) have been constructed using infrared (IR) observations from geostationary satellites ( Williams and Houze 1987 ; Miller and Fritsch 1991 ; Zuidema 2003 ; Machado and Laurent 2004 ; Kondo et al. 2006 ; Pope et al. 2008 ) and used to study various aspects of convection in the tropics. For instance, studies such as these have examined the seasonal and diurnal cycles of tropical convection and the
1. Introduction Satellite-based cloud climatologies of mesoscale convective systems (MCSs) have been constructed using infrared (IR) observations from geostationary satellites ( Williams and Houze 1987 ; Miller and Fritsch 1991 ; Zuidema 2003 ; Machado and Laurent 2004 ; Kondo et al. 2006 ; Pope et al. 2008 ) and used to study various aspects of convection in the tropics. For instance, studies such as these have examined the seasonal and diurnal cycles of tropical convection and the
