Morphology and evolution of cold‐frontal misocyclones

Smart, David; Browning, K. A.

doi:10.1002/qj.399

Cited by 31 publications

(31 citation statements)

References 39 publications

(47 reference statements)

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“…The association of tornadoes to frontal waves has been considered in recent studies (Clark, 2008;Smart and Browning, 2009;Groenemeijer et al, 2010). Markowski et al (1998) found that nearly 70 % of tornadoes during the Verification of the Origins of Rotation in Tornadoes EXperiment (VORTEX) occurred near a pre-existing baroclinic boundary, most of them within 30 km distance on its cold side.…”

Section: Seasonal Composite Anomalies Of Synoptic Conditions and Liftmentioning

confidence: 99%

Analysis of synoptic conditions for tornadic days over western Greece

Nastos

2014

Nat. Hazards Earth Syst. Sci.

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Abstract.Tornadoes have been reported in Greece during the last few decades and recent studies have given evidence that western Greece is an area vulnerable to tornadoes, waterspouts and funnel clouds In this study, the composite means and anomalies of synoptic conditions for tornadic events (tornadoes, waterspouts and funnel clouds) over western Greece are analyzed and discussed.The daily composite means of synoptic conditions were based on the National Centers for Environmental PredictionNational Center for Atmospheric Research (NCEP-NCAR) reanalysis data sets, for the period 12 August 1953 to 31 December 2012. The daily composite anomalies were calculated with respect to 30 years of climatological study of the synoptic conditions. The analysis was carried out in terms of seasonal and monthly variability of composite means and anomalies of synoptic conditions for specific isobaric levels of 500, 700, 850, 925 hPa and the sea level pressure (SLP). In addition, an analysis and discussion about the dynamic lifted index from NCEP-NCAR reanalysis data sets is presented.The daily composite mean analysis of 500 hPa revealed a trough line across the northern Adriatic Sea and central Italy, associated with a SW upper-air stream over western Greece. The maximum composite anomalies were depicted at the isobaric level of 500 hPa during autumn, spring and summer, against winter when the anomaly appeared at 925 hPa isobaric level. In addition, 48 % of tornado events during the autumn season occurred in pre-frontal weather conditions (cold fronts) and 27 % developed after the passage of the cold front. Furthermore, the main difference in synoptic patterns between tornado and waterspout days along western Greece during the autumn season is the maximum daily composite anomaly over the Gulf of Taranto.

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Section: Seasonal Composite Anomalies Of Synoptic Conditions and Liftmentioning

confidence: 99%

Analysis of synoptic conditions for tornadic days over western Greece

Nastos

2014

Nat. Hazards Earth Syst. Sci.

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“…Microscale studies of fronts have revealed numerous features that are not observed at mesoscales; for example, Doswell and Haugland (2007) found that the temperature increased after the passage of a nocturnal cold front because of the destruction of an inversion, which permitted warm air from aloft to be mixed to the surface by turbulence behind the leading edge of the front. Many other investigators have also noted the visual similarity between certain synoptic-scale cold fronts and laboratory density currents (e.g., Young and Johnson 1984;Friedrich et al 2008;Smart and Browning 2009), and a summary of the relationship between cold fronts and density currents is given by Smith and Reeder (1988). Shapiro (1984) presented instrumented mast observations of a dry cold front passage in Colorado that showed that the temperature decrease of 138C was confined within a 200-m-wide zone.…”

Section: Introductionmentioning

confidence: 99%

Structure of a Narrow Cold Front in the Boundary Layer: Observations versus Model Simulation

Sinclair

Niemelä

Leskinen

2012

Monthly Weather Review

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A narrow and shallow cold front that passed over Finland during the night 30-31 October 2007 is analyzed using model output and observations primarily from the Helsinki Testbed. The aim is to describe the structure of the front, especially within the planetary boundary layer, identify how this structure evolved, and determine the ability of a numerical model to correctly predict this structure. The front was shallow with a small (2.5-3 K) temperature decrease associated with it, which is attributed to the synoptic evolution of the cold front from a frontal wave on a mature, trailing cold front in a region of weak upper-level forcing and where the midtroposphere was strongly stratified. Within the boundary layer, the frontal surface was vertical and the frontal zone was narrow (,8 km). The small cross-front scale was probably a consequence of the weak frontolytical turbulent mixing occurring at night, at high latitudes, combined with strong, localized frontogenetic forcing driven by convergence. The model simulated the mesoscale evolution of the front well, but overestimated the width of the frontal zone. Within the boundary layer, the model adequately predicted the stratification and near-surface temperatures ahead of, and within, the frontal zone, but failed to correctly predict the thermal inversion that developed in the stably stratified postfrontal air mass. This case study highlights the complex structure of fronts both within the nocturnal boundary layer, and in a location far from regions of cyclogenesis, and hence the challenges that both forecasters and operational models face.

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“…The PCs are typically aligned at a clockwise angle with respect to the synoptic-scale cold front (e.g., Hobbs and Persson 1982;Parsons and Hobbs 1983a;Wakimoto and Bosart 2000). Horizontal shear instabilities (HSIs) along the leading edge of a cold front or their coupling with a convective instability have frequently been proposed as mechanisms that lead to the alongfront variability (AFV) of NCFRs (e.g., Matejka 1980;Hobbs and Persson 1982;Moore 1985, Carbone 1982Parsons and Hobbs 1983b;Wakimoto and Bosart 2000;Smart and Browning 2009).…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Horizontal Shear Instability Waves along Narrow Cold Frontal Rainbands

Kawashima

2011

Journal of the Atmospheric Sciences

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The effects of variations in low-level ambient vertical shear and horizontal shear on the alongfront variability of narrow cold frontal rainbands (NCFRs) that propagate into neutral and slightly unstable environments are investigated through a series of idealized cloud-resolving simulations.In cases initialized with slightly unstable sounding and weak ambient cross-frontal vertical shears, core-gap structures of precipitation along NCFRs occur that are associated with wavelike disturbances that derive their kinetic energy mainly from the mean local vertical shear and buoyancy. However, over a wide range of environmental conditions, core-gap structures of precipitation occur because of the development of a horizontal shear instability (HSI) wave along the NCFRs.The growth rate and amplitude of the HSI wave decrease significantly as the vertical shear of the ambient cross-front wind is reduced. These decreases are a consequence of the enhancement of the low-level local vertical shear immediately behind the leading edge. The strong local vertical shear acts to damp the vorticity edge wave on the cold air side of the shear zone, thereby suppressing the growth of the HSI wave through the interaction of the two vorticity edge waves. It is also noted that the initial wavelength of the HSI wave increases markedly with increasing horizontal shear. The local vertical shear around the leading edge is shown to damp long HSI waves more strongly than short waves, and the horizontal shear dependency of the wavelength is explained by the decrease in the magnitude of the vertical shear relative to that of the horizontal shear.

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Morphology and evolution of cold‐frontal misocyclones

Cited by 31 publications

References 39 publications

Analysis of synoptic conditions for tornadic days over western Greece

Analysis of synoptic conditions for tornadic days over western Greece

Structure of a Narrow Cold Front in the Boundary Layer: Observations versus Model Simulation

Numerical Study of Horizontal Shear Instability Waves along Narrow Cold Frontal Rainbands

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