Part I: Storm Structure and Evolution from Radar Data

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1980

This is a four part Technical Note that reports on aircraft, radar, and surface observations made on 25 July during the 1976 field season of the National Hail Research Experiment. This case study of precipitation development in a convective storm will also be the subject matter of a three part formal publication; however, a more extensive presentation of data is included in the Technical Note than will be presented in the formal publication.

2014

Using the cell tracker TITAN (Thunderstorm Identification, Tracking, Analysis, and Nowcasting) and a manual synoptic classification scheme, individual storms are obtained and classified for the period 2006 to 2010 for Thessaly into seven distinct synoptic patterns. Following a strict storm-tracking procedure, 2875 single cell storms are identified during the months April to September for the five-year period. The aim of this study is to identify differences in formation, structure, intensity and behavior of the storms among the recognized storm producing synoptic patterns over the area. Storms are characterized through their initiation time, duration, speed, direction, maximum top, maximum reflectivity, rain rate, volume, area and precipitation area. Results indicate that certain differences exist in storm characteristics among different synoptic patterns such as speed, direction, maximum top, maximum reflectivity and area. Storms following NW to SE movement are well organized exhibiting higher intensities and lifetime. Storms following SW to NE movement exhibit more complex structure, move faster, cover wider area and form in bigger numbers. In both cases orographic forced lifting is the dominant storm producing mechanism.

Meteorological Monographs

s The history of severe thunderstorm research and forecasting over the past century has been a remarkable story involving interactions between technological development of observational and modeling capabilities, research into physical processes, and the forecasting of phenomena with the goal of reducing loss of life and property. Perhaps more so than any other field of meteorology, the relationship between researchers and forecasters has been particularly close in the severe thunderstorm domain, with both groups depending on improved observational capabilities. The advances that have been made have depended on observing systems that did not exist 100 years ago, particularly radar and upper-air systems. They have allowed scientists to observe storm behavior and structure and the environmental setting in which storms occur. This has led to improved understanding of processes, which in turn has allowed forecasters to use those same observational systems to improve forecasts. Because o...

Monthly Weather Review, 2002

Convective cell identification methods, besides their operational utility, are useful to identify cells, to understand cell interactions within multicell thunderstorms, and to distinguish between convective and stratiform regions within mesoscale convective systems. The method developed in this note was utilized for research on cell interactions within the 9 August 1991 Convection and Precipitation/Electrification (CaPE) multicell thunderstorm. A critical component of such research is an objective method to accurately depict all significant convective cells within an evolving multicell thunderstorm. While conventional methods based upon radar reflectivity can be successfully used in identifying cells, especially when the cells are in their growth stage, the methods are not as useful during the later stages of cell growth. This is because updraft and precipitation cores are not collocated at these advanced stages, and thus the reflectivity (precipitation) core may not be a good indicator of convectively active regions. The method presented in this note uses four objective criteria to define and identify convective cells within multicell thunderstorms. These criteria are chosen from a prestorm proximity sounding using the air parcel theory. The four objective criteria and their threshold values for the CaPE storm included in parentheses are 1) a threshold updraft W d (ϳ8 m s Ϫ1), 2) a threshold cloud-layer depth D d (ϳ4.9 km), 3) a threshold updraft area A d (ϳ1 km 2), and 4) cell origin within the planetary boundary layer indicated by the W pbl (ϳ3 m s Ϫ1) contour. Since the method is based upon upward motion and not reflectivity factor, multiple Doppler radar data are required to utilize this method.

Monthly Weather Review, 2000

The characteristics of radar echoes for 12 thunderstorm days in the vicinity of Sydney, Australia, in the summer of 1995/96 have been examined using an objective methodology for storm identification and tracking. The spatial distribution of identified storms shows a maximum in frequency and intensity along the east side of the mountains that lie inland from the coast. Characteristics such as storm volume, area, and height are shown to have a lognormal frequency distribution. Reflectivity also has a skewed frequency distribution with a prevalence of lower reflectivity storms. Both the maximum reflectivity and storm height are shown to be correlated with the logarithm of storm volume. Although small storms predominate, the bulk of precipitation flux comes from the relatively few large-scale storms. It is also shown that storms generally move or propagate in a direction slightly to the left of the mass-weighted mean wind for the surface-to-300-hPa layer at a speed slightly less than the mean speed. Furthermore the deviation of the storm to the left of the mean layer wind increases and the standard deviation decreases as the storm size increases.

Monthly Weather Review, 1997

The relationships among kinematic, microphysical, and electric field properties within a multicell Florida thunderstorm are investigated using observations from three Doppler radars (one with multiple wavelength and polarization diversity capabilities), four instrumented penetrating aircraft, a surface-based electric field mill network, and other observation facilities. The storm was convectively active for about 1 h and at least five primary cells developed within the storm during this time, one of which went through three consecutive development cycles. The updrafts in this storm were 2-4 km wide, exhibited bubble-like evolution, and had lifetimes of 10-20 min. The maximum updraft determined by the multiple Doppler analysis was about 20 m s Ϫ1 . A differential reflectivity (Z DR ) ''column,'' indicating regions containing millimeter-size raindrops, extending above the freezing level, was associated with each cell during its developing stages. This column reached altitudes exceeding 6 km (Ϫ8ЊC) in the stronger updrafts. As the Z DR columns reached maximum altitude, a ''cap'' of enhanced linear depolarization ratio (LDR) and enhanced 3-cm wavelength attenuation (A 3 ) formed, overlapping the upper regions of the Z DR column. These parameters indicate rapid development of mixed-phase conditions initiated by freezing of supercooled raindrops.

Monitoring thunderstorms activity is an essential part of operational weather surveillance given their potential hazards, including lightning, hail, heavy rainfall, strong winds or even tornadoes. This study has two main objectives: firstly, the description of a methodology, based on radar and total lightning data to characterise thunderstorms in real-time; secondly, the application of this methodology to 66 thunderstorms that affected Catalonia (NE Spain) in the summer of 2006. An object-oriented tracking procedure is employed, where different observation data types generate four different types of objects (radar 1-km CAPPI reflectivity composites, radar reflectivity volumetric data, cloud-toground lightning data and intra-cloud lightning data). In the framework proposed, these objects are the building blocks of a higher level object, the thunderstorm.

Journal of Applied Meteorology, 1996

This paper presents an analysis of a unique radar and radiometer dataset from the National Aeronautics and Space Administration (NASA) ER-2 high-altitude aircraft overflying Florida thunderstorms on 5 October 1993 during the Convection and Moisture Experiment (CAMEX). The observations represent the first ER-2 Doppler radar (EDOP) measurements and perhaps the most comprehensive multispectral precipitation measurements collected from a single aircraft. The objectives of this paper are to 1) examine the relation of the vertical radar reflectivity structure to the radiometric responses over a wide range of remote sensing frequencies, 2) examine the limitations of rain estimation schemes over land and ocean backgrounds based on the observed vertical reflectivity structures and brightness temperatures, and 3) assess the usefulness of scattering-based microwave frequencies (86 GHz and above) to provide information on vertical structure in the ice region. Analysis focused on two types of convection: a small group of thunderstorms over the Florida Straits and sea-breeze-initiated convection along the Florida Atlantic coast.

Advances in Geosciences, 2006

The most important hail event recorded in the region of the Ebro Valley (NE Spain) in 2004 was the 11 September episode. Large hailstones (some of them with a diameter of over 30 mm) caused important damages in agriculture and properties. The hail event affected an area of 3848 ha and was caused by several multicellular systems. The aim of this paper is the analysis of the associated convective structures using the meteorological radar as well as the MM5 mesoscale model, thermodynamic data and a hailpad network. To achieve this end, the new hailstorm analysis tool RHAP (Rainfall events and Hailstorms Analysis Program) has been applied. It identifies tracks and characterises precipitation systems and convective cells, taking into account 2-D and 3-D structures. The event has also been studied with the TITAN software (Thunderstorm Identification, Tracking, Analysis and Nowcasting) in an attempt to compare both methods. Results show that the episode had a strong convective activity with CAPE values over 4000 J/kg and with hail-forming cells characterised by VIL (Vertical Integrated Liguid) exceeding 40 kg/m 2 , VILD (VIL density) over 4 g/m 3 , HP (Hail Probability) of 100% and SHP (Severe Hail Probability) of over 75%. The hail cells evolved into multicellular systems that lasted between 70 and 90 min. Finally, the comparison of RHAP and TITAN has shown significant correlations between methods.