The flash flood event of June 2000 in Catalonia: monitoring and nowcasting using the meteorological radar and an automatic raingauge network

MARA DEL CARMEN LLASAT TOMEU RIGOMeteorological Hazards Analysis Team Department of Astronomy & MeteorologyUniversity of Barcelona, Spaincarmell@am.ub.es http://www.am.ub.es/~carmell

INTERREG IIIC: HYDROPTIMET MEETING. GRENOBLE 2-3 FEBRUARY 2004

During the early morning of 10 June 2000 there occurred a heavy rainfall event over Catalonia (NE of Spain) that caused material damages estimated at over 65,000,000 euros and there were 5 fatalities.A short diagnosis of the event

Location of the eventThe affected region is placed at NE of the Spain. It is named Internal Basins of Catalonia and it consists of 4 larger basins (Ter, Besos, Llobregat and Francoli) and other smaller ones.

DataRaingauge data in surfaceRadar imageryRadiosoundings of Barcelona and Palma MallorcaSynoptic analysisMesoscale analysisAcknowledgements for the data: Agencia Catalana de lAigua, Instituto Nacional de Meteorologa, Servei de Meteorologia de Catalunya Our special acknowledgement to E. Velasco (ACA) and P. Martn (INM) for their collaboration

The raingauge networkThe SAIH system of the IBC covers an area of 16000 km2. The rainfall network is composed by 126 tipping-bucket automatic rain gauges.The precipitation is cumulated and recorded every 5 minutes. Rainfall overturning of 0.1 mm.

The meteorological radar

Placed over the Puig de les Agulles (20 km at SW of Barcelona) at 612 m asl.It belongs to the INM radar network and operates in the C-band.

Range

240 km (normal mode)

120 km (Doppler mode)

First elevation altitude (degrees)

0.5

0.5

Number of levels

20

8

PRF

250Hz

900/1200 Hz

Frequency

5600-5650 MHz

Polarization

Horizontal

Total Cumulated RainfallThe 94% of the rainfall gauges of the IBC registered a cumulated rainfall above 15 mm in 24 hours. A lot of 24 hours maximum rainfall values exceeding the 100 mm were recorded in many gauges of the Llobregat Basin and other minor basins.Some examples of maximum values registered are: 223 mm in 24 hours 158 mm in 3 hours 13.2 mm in 5 minutes21:00 UTC 9 June- 21:00 UTC 10 June

The maximum 5-minutal rainfall value (13.2 mm) is equivalent to 154.8 mm in only one hour. Rainfall Rate and Time EvolutionThe rainfall event started at the Southern Basins at 21:30 UTC as a consequence of the pass of a quasi-stationary rainfall band, that remained over the same place for about 2 hours.

Flow evolution

Synoptic EvolutionOn 10 June at 0000 UTC: Previously: anticyclonic situation, warm and very wet advection in low levels, great potential instabilitythe cold front was situated around the west of Catalonia. in the previous few hours to the event, a surface depression (1008 hPa) had been forming, centred on the Balearic Islands. the flow from the west that dominated most of the Peninsula at 850 hPa had been veering, so that by that time it was coming mainly from the north and had advected very cold air that extended right to the upper troposphere

BarcelonaPalmaMadridMurciaThe day of the floods:10 June(00 UTC)

Cross sections 10/06/0000 UTC12 UTCLISBOA- MADRID- MURCIA-BARCELONA-PALMA-CAGLIARIpep

Mesoscale analysisLIt showed a conjunction of the following factors:1. Mesoscalar depression at surface. It led to the convergence of water vapour at low levels and played a direct role in triggering the potential instability cumulated previously2. the existence of a line of convergence, which advance over Catalonia along a SW-NE axis, with the slow movement of the depression. The squall lines were formed near of it.

The radar toolInteraction between the 2 procedures (2D&3D), adapting, improving and combining different algorithms

2D: rainfall structures (separating convective & stratiform precipitation)

3D: convective cells

Use of the wind profile over the meteorological radar for tracking and nowcasting 2D&3D structures

Warnings production

To classify convective structures in 2D

To identify convective structures in 3D

To integrate cells and convective structures

The method (Johnson et al., 1998) uses the centroid position and other features (size, shape and intensity) of 3D cells of the 6 previous images.For each actual cell identifiyed, the algorithm has tried to detect past cells which distance was less than 10 km. The other features help to describe the state and the life-cycle of the cell.However, for cases where two cells could be associated to the same previous 3D structure, those features, combined with distance, can help to determine which is the selected.Tracking and nowcasting of cellsApplication to rainfall nowcasting

Application to rainfall nowcastingTracking and nowcasting of cellsCells can move throughout the convective system or in the same direction that the 2D structure. First case is the most dangerous: slow or null cells movement can gives strong rainfall values over the same zone

Previous positions have not been used. Reason: in general, positions of 2D structures changes extraordinarily in 10 minutes.The displacement vector has been obtained by combining two different vectors: mean wind vector at mid-levels (HIRLAM data) mean movement vector of convective cells associated to that structureTracking and nowcasting of convective structures 2D+3DApplication to rainfall nowcasting

Example of tracking and nowcasting

Example of tracking and nowcastingApplication to rainfall nowcasting

Past: t-60-t0Future: t0-t+60Tracking & WarningApplication to rainfall nowcastingApplication to rainfall nowcasting

Radar image at 22:40 UTCZ = 800 R1.6

The next stepsTo apply this methodology to other eventsTo improve the analysis using lightning dataTo apply objective mesoscale models (see contribution UIB) To obtain the nowcasted rainfall chart by applying the suitable algorithms (convective and stratiform relationships) in order to improve the flood warning system To integrate with hydrological models

Thanks for your attention