Interpretation of single-Doppler radar signatures in a V-shaped hailstorm: Part I—evolution of reflectivity-based features

Abstract

Part I of this two-part descriptive research documents the evolution of updrafts, hail, and cloud-to-ground lightning within a North Dakota multicell hailstorm that had a V-shaped radar reflectivity pattern. Details of storm evolution were inferred from single-Doppler velocity and radar reflectivity signatures using a single-Doppler radar analysis technique. Utilizing the analysis technique, fresh updrafts were deduced to form at the upstream extremity of the storm at the point of the V shape. After an updraft died, the V shape was maintained as the associated hydrometeors mov down either the right or left storm flank as they droped The V-shaped storm structure was the follow of interactions between individual updrafts and ambient flow

Evolution of hail within the storm was presum from the nearness of flare echo reflectivity signatures that reach forthed beyond the far side of the storm relative to the radar. When flare repercussion of sound length was at its greatest, large hailstones the sizes of golf balls to baseballs were reported. The alone positive cloud-to-ground lightning strikes in the storm coincided with the accident of large hail.

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1 Introduction

Weather forecasters who monitor and interpret radar data for issuance of strict thunderstorm warnings frequently observe that an reverberation develops a U- or V-shape when it is in the proces of splitting. A storm splits into a rightmoving storm and a leftmoving storm because novel updrafts develop on the storm's right and left lateral flanks (eg Charba and Sasaki 1971; Brown and Meitin 1994) Then, end a process of discrete propagation, the sum of two units updraft regions move away from each other as single or both storms become unrelenting However, on less frequent occasions, a storm is observ to maintain a V-shape (open in downstream direction) without splitting, similar as the German hailstorm studied by means of Holler et al. (1994). by the agency of tracking reflectivity maxima, they noted that the wings of the V-shape generally corresponded to the tracks of the maxima. The reasons wherefore reflectivity maxima would have divergent tracks within a given storm are not entirely understood.

It is fortuitous that, during the 1989 North Dakota Thunderstorm throw (Boe et al. 1992), detailed single-Doppler radar data were assembleed in two non-splitting multicell storms that had V-shaped echoe Brown et al. (2002) discuss cloud-to-ground lightning activity in relation to evolution of the V-shaped Elgin, North Dakota storm. In this two-part research radar reflectivity and Doppler velocity signatures are used to investigate the constitution and evolution of the companion Carson, North Dakota storm. In Part I of the application of mind updraft and hail evolution are deduc from Doppler radar measurements and the reason for the V-shape is revealed. In Part II, the midaltitude wake stream downstream of the updraft region will be investigated using Doppler velocity signatures.

An informative approach for depicting evolution of an individual radar confined apartment within a convective storm is to piece of ground a time-height profile of maximum reflectivity within observ confined apartments (e.g., Renick 1971; Heymsfield 1981; Knight et al. 1983; coloring liquor et al. 1986; Tuttle et al. 1989; Hondl and Eilts 1994; Brown et al. 2002) as well as within numerically protoplasted cells (e.g., Danielsen et al. 1972; English 1973) These profiles typically exhibit radar-detectable particles initially forming at midaltitudes. With time, radar reflectivity increases in vertical expansion reaching the rising updraft summit and coincident vapor top. During the same time period, reflectivity intensity increases at midaltitudes as hydrometeors (typically graupel and/or hail) increase in size and concentration within the developing updraft. When midaltitude particles within the small room attain a sufficient size, of that kind that the local updraft can no longer suspend them, they start to come down As the reflectivity maximum reaches the turf heavy rain, graupel and/or hail, and able-bodied outflow winds may be observ at the surface. Meanwhile, following updraft demise, hydrometeors that had reached upper portions of the updraft within the small room take tens of minutes to fall without at their respective terminal velocities as they impel downstream with the environmental run This updraft/downdraft cell evolution come [i]or[/i] go after [i]or[/i] behinds the general model proposed by means of Byers and Braham (1948) based upon data collected during the Thunderstorm throw out of 1946-47.

As pointed on the outside by Brown et al. (2002) the bourn "cell" has been misapplied in novel years. Instead of being applied to an individual updraft/downdraft period the term is being applied to a cluster of confined apartments in various stages of updraft disentanglement which is found in the middle- and upper-altitude maximum reflectivity region of a thunderstorm. It is easier to identify the overall confined apartment cluster (maximum reflectivity region) than to identify the individual confined apartments (localized reflectivity maxima and protrusions). For example, algorithms, like as the WSR-88D Storm confined apartment Identification and Tracking Algorithm (eg Johnson et al. 1998) identify the entire maximum reflectivity region as a cell