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1. Introduction The topographically complex western United States is a region where mountains play a major role in frontal evolution (e.g., Braun et al. 1997 ; Colle et al. 1999 ; Steenburgh and Blazek 2001 ; Colle et al. 2002 ; Shafer et al. 2006 ; Shafer and Steenburgh 2008 ; Steenburgh et al. 2009 ). As cold fronts approach the Pacific coast, orographic blocking and friction produce enhanced prefrontal southerly flow, confluent deformation, frontogenesis, frontal deceleration, and, in
1. Introduction The topographically complex western United States is a region where mountains play a major role in frontal evolution (e.g., Braun et al. 1997 ; Colle et al. 1999 ; Steenburgh and Blazek 2001 ; Colle et al. 2002 ; Shafer et al. 2006 ; Shafer and Steenburgh 2008 ; Steenburgh et al. 2009 ). As cold fronts approach the Pacific coast, orographic blocking and friction produce enhanced prefrontal southerly flow, confluent deformation, frontogenesis, frontal deceleration, and, in
1. Introduction The midlatitudes, where most of the world’s population resides, are strongly affected by the passage of extratropical cyclones and their warm and cold fronts, and in particular by the amount of precipitation they might produce (e.g., Stewart et al. 1998 ; Kunkel et al. 2012 ). Insufficient precipitation affects crops and water supply, whereas precipitation extremes can result in havoc and severe loss of life and property. In the context of a warming world, it is still unclear
1. Introduction The midlatitudes, where most of the world’s population resides, are strongly affected by the passage of extratropical cyclones and their warm and cold fronts, and in particular by the amount of precipitation they might produce (e.g., Stewart et al. 1998 ; Kunkel et al. 2012 ). Insufficient precipitation affects crops and water supply, whereas precipitation extremes can result in havoc and severe loss of life and property. In the context of a warming world, it is still unclear
al. 1995 ; Fovell 2005 ), and drylines (e.g., Fujita 1970 ; Koch and McCarthy 1982 ; Schaefer 1986 ; Hane et al. 1997 ; Murphey et al. 2006 ) have received the largest amount of attention in terms of documenting their kinematic and moisture characteristics for convective weather forecasting applications. Precipitating cold fronts, particularly those associated with narrow cold frontal rainbands, have been examined in this context as well (e.g., James and Browning 1979 ; Hobbs and Persson
al. 1995 ; Fovell 2005 ), and drylines (e.g., Fujita 1970 ; Koch and McCarthy 1982 ; Schaefer 1986 ; Hane et al. 1997 ; Murphey et al. 2006 ) have received the largest amount of attention in terms of documenting their kinematic and moisture characteristics for convective weather forecasting applications. Precipitating cold fronts, particularly those associated with narrow cold frontal rainbands, have been examined in this context as well (e.g., James and Browning 1979 ; Hobbs and Persson
1. Introduction Naud et al. (2015) describe the cloud and precipitation structure of cold fronts over the global oceans from satellites using CloudSat radar data, CALIPSO lidar data, and MERRA reanalyses for temperature and wind. Using a set of automated approaches, more than 30 000 fronts over the global oceans within 30°–60°N and 30°–60°S over a 4-yr period were composited to produce cross sections of various properties across the fronts. In this comment, concerns are raised about the
1. Introduction Naud et al. (2015) describe the cloud and precipitation structure of cold fronts over the global oceans from satellites using CloudSat radar data, CALIPSO lidar data, and MERRA reanalyses for temperature and wind. Using a set of automated approaches, more than 30 000 fronts over the global oceans within 30°–60°N and 30°–60°S over a 4-yr period were composited to produce cross sections of various properties across the fronts. In this comment, concerns are raised about the
1. Introduction Intense, rapidly developing cold fronts threaten lives and property over the Intermountain West several times a year. High winds, which may occur in the pre- or postfrontal environment, can cause major wildfire runs, road closures because of blowing dust, power outages, and property damage. For example, 40 m s −1 wind gusts produced more than $15 million of damage as a cold front moved across northern Utah on 5 June 1995 ( NCDC 1995 , p. 356), while the cold front accompanying
1. Introduction Intense, rapidly developing cold fronts threaten lives and property over the Intermountain West several times a year. High winds, which may occur in the pre- or postfrontal environment, can cause major wildfire runs, road closures because of blowing dust, power outages, and property damage. For example, 40 m s −1 wind gusts produced more than $15 million of damage as a cold front moved across northern Utah on 5 June 1995 ( NCDC 1995 , p. 356), while the cold front accompanying
boundary. A surface cold front was located far to the south in Oklahoma (not shown in Fig. 2 , which depicts conditions just to the north of the front), to north of which there was a mesoscale convective system (MCS; Fig. 4 ). The funnel cloud formed well to the northwest of a stratiform area of precipitation ( Fig. 4 ) in a relatively cool surface environment ( Figs. 2 and 3 ) and also just to the northeast of small-scale, parallel bands of precipitation, that might have been triggered by gravity
boundary. A surface cold front was located far to the south in Oklahoma (not shown in Fig. 2 , which depicts conditions just to the north of the front), to north of which there was a mesoscale convective system (MCS; Fig. 4 ). The funnel cloud formed well to the northwest of a stratiform area of precipitation ( Fig. 4 ) in a relatively cool surface environment ( Figs. 2 and 3 ) and also just to the northeast of small-scale, parallel bands of precipitation, that might have been triggered by gravity
1. Introduction Precipitation patterns along cold fronts as observed by radar can exhibit a variety of morphologies. Sometimes the precipitation can fall within a single narrow line called a narrow cold-frontal rainband (e.g., Browning and Harrold 1970 ; Hobbs 1978 ; Houze and Hobbs 1982 ; Knight and Hobbs 1988 ). Other times, the precipitation can break up into regularly spaced cores of maximum precipitation rate separated by gaps of lighter or no precipitation in between, called core
1. Introduction Precipitation patterns along cold fronts as observed by radar can exhibit a variety of morphologies. Sometimes the precipitation can fall within a single narrow line called a narrow cold-frontal rainband (e.g., Browning and Harrold 1970 ; Hobbs 1978 ; Houze and Hobbs 1982 ; Knight and Hobbs 1988 ). Other times, the precipitation can break up into regularly spaced cores of maximum precipitation rate separated by gaps of lighter or no precipitation in between, called core
initiation near the intersection between a moving cold front and a dryline. They showed that no convection was initiated in this area, even though upward motions were relatively strong. Instead, cumulus cloud development was observed ∼50 km to the east in an area with enhanced moisture and large potential instability. With the high-resolution mobile instrumentation used during IHOP, horizontal and vertical shear instabilities and moisture variations across drylines and cold fronts and their role in
initiation near the intersection between a moving cold front and a dryline. They showed that no convection was initiated in this area, even though upward motions were relatively strong. Instead, cumulus cloud development was observed ∼50 km to the east in an area with enhanced moisture and large potential instability. With the high-resolution mobile instrumentation used during IHOP, horizontal and vertical shear instabilities and moisture variations across drylines and cold fronts and their role in
1. Introduction It is now well established that the regions of heavy precipitation in extratropical cyclones are often organized on the mesoscale in the form of rainbands (e.g., Houze et al. 1976 ; Hobbs 1978 ; Matejka et al. 1980 ). Among the various types of rainbands, the narrow cold-frontal rainbands (NCFRs) that straddle the surface cold front (SCF) are generally associated with the most intense precipitation and vertical motions ( Matejka et al. 1980 ). These features result from the
1. Introduction It is now well established that the regions of heavy precipitation in extratropical cyclones are often organized on the mesoscale in the form of rainbands (e.g., Houze et al. 1976 ; Hobbs 1978 ; Matejka et al. 1980 ). Among the various types of rainbands, the narrow cold-frontal rainbands (NCFRs) that straddle the surface cold front (SCF) are generally associated with the most intense precipitation and vertical motions ( Matejka et al. 1980 ). These features result from the
effects of surface anticyclones along the east (downstream) side of the Andes that lead to rapid incursions of cold air that may reach as far north as the Amazon basin ( Garreaud 2000 ; Lupo et al. 2001 ; Seluchi et al. 2006 ). The disruption of weather systems, particularly cold fronts, along the west ( upstream ) side of the extratropical Andes has been less studied, in part because of the lack of data over the adjacent Pacific Ocean. Orographic influences on frontal systems have been studied
effects of surface anticyclones along the east (downstream) side of the Andes that lead to rapid incursions of cold air that may reach as far north as the Amazon basin ( Garreaud 2000 ; Lupo et al. 2001 ; Seluchi et al. 2006 ). The disruption of weather systems, particularly cold fronts, along the west ( upstream ) side of the extratropical Andes has been less studied, in part because of the lack of data over the adjacent Pacific Ocean. Orographic influences on frontal systems have been studied
