Use of data from Meteosat water vapour channel and surface observations for studying pre-convective environment of a tornado-producing storm
ABSTRACT An alternative to the upper air sounding approach is used for assessing potential instability in the environment of a tornado-producing storm on 15 May 1999. The storm developed over a mountain area of the most southern part of Bulgaria located close to the Mediterranean coast. Hourly High Resolution Image (HRI) data in water vapour (WV) channel of Meteosat are used to identify the continuously decreasing of mid- and upper level humidity over the upstream area of the tornado location within 9 h prior to the severe weather event. During the same period, three hourly data from six synoptic stations (altitude range: 140–1920 m) showed increasing of temperature and humidity of the low-level air mass around the area of subsequent development of the convective storm.A new quantity referred to as Potential Instability WV Index (IWV) is proposed as a measure of potential for destabilisation of the air mass. The IWV uses a combination of two different data sources: thermodynamic parameters calculated from surface observations at synoptic stations; HRI Meteosat WV data (representative for water content in the middle and upper troposphere) averaged in an area of 7×7 pixels around the synoptic stations.Nine hours prior to the tornadic event, high and continuously increasing values of IWV are observed at the upstream area of the tornado release point where the pronounced ‘C’-shaped dark zone appeared in the imagery. The proposed WV Index is used in this study to reflect the potential instability in the pre-thunderstorm environment having moist surface air capped by a deep mid- to upper-tropospheric dry layer.
- Monthly Weather Review - MON WEATHER REV. 01/1989; 117(9).
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ABSTRACT: On 24 May 1993, part of the Iberian Peninsula was affected by convective activity concentrated on the eastern side of a low-level thermal boundary which was orientated north–south. A series of storms evolved into a squall line striking at the province of Guadalajara (Central Spain). The southernmost cell of this mesoscale convective system generated a tornado that hit the city of Sigüenza between 1930 and 1940 UTC. This paper has two objectives. The first aim is to investigate the ingredients (buoyancy, wind shear, vertical distribution of moisture content, and synoptic and mesoscale lifting mechanisms) and the atmospheric agents (mid-upper level trough, low level-boundary, convergence zones, etc.) which favour the production of severe storms. The second one is to analyse information provided by operational remote-sensing systems (satellite, radar and lightning) in order to test and evaluate some conceptual models of severe storms in an operational environment. For the first objective, the ingredient-based methodology will be shown to be a valuable operational approach allowing forecasters to focus on the possibility of a severe event using the appropriate diagnostic or prognosis tools. For the second objective, special attention is given to the suitability of conceptual models associated with convective phenomena and the potential value of such models (lightning charge related to wind shear and radar-based multicell conceptual models) for understanding the observed processes. From an operational viewpoint some problems may arise because of the technical characteristics of the equipment, particularly related to radars (e.g. scanning strategy, distance between radar and targets, and radar signal processing and displaying). Possible guidelines for using volumetric radar data (non Doppler) for deep convection monitoring are suggested for rugged and complex topographical regions. Copyright © 1997 Royal Meteorological SocietyMeteorological Applications 12/2006; 4(3):191 - 206.
- Weather and Forecasting - WEATHER FORECAST. 01/1994; 9(4):606-618.