Mediterranean Storms (Proceedings of the 4th EGS Plinius Conference held at Mallorca, Spain, October 2002)  2003 by Universitat de les Illes Balears (Spain)

INTENSE PRECIPITATION OVER DURING MEDEX CASE OF 25-31 DECEMBER 2000

A.M.S. Delitala1, M. Casula1, G. Ficca1 (1) Servizio Agrometeorologico Regionale per la Sardegna, Viale 119, , I-07100, - e-mail: [email protected]

1 CONTENT

A set of four mid-latitude cyclones traversed the whole of Western Mediterranean, from the 25th to the 31st of December 2000, causing intense precipitation over Italy (Sardinia) and Spain (Cataluña), and causing strong wind over Tunisia. In figure 1 and 2 tracks of the four cyclones are plotted. Cyclones 1 (fig. 1) originated off the coast of Cataluña and Valencia (Spain) and moved to NE. Cyclones 3 and 4 (fig. 1) were both Atlantic features entering the Mediterranean through France; the former, after having crossed Italy, moved NE Eastern Europe, le latter traversed the whole of the Mediterranean down to Israel. Cyclone 2 (fig. 2) is the most interesting, as it was an Atlantic cyclone slowly crossing Europe; during its lifespan it triggered two secondary Mediterranean cyclones (2A and 2B in figure 2). An automatic check of cyclon tracks (by means of the automatic method described in Jansà et al., 2001) confirms those of cyclons 2, 2c, 3 and 4. Fig. 3 shows precipitation totals (over the whole period). Values are high (in certain area they are equal to mean monthly totals). The most intense precipitation always took place when each cyclone was NW of Sardinia, so that rain insisted over the same part of the Island (the basin of river Temo). Hazards were caused by that river, since precipitation mostly fell over Southern-eastern and western branches of Temo, which are not regimented. The river grew beyond safety high-water mark and the area near the foce was flooded. Near the hystorical town of Bosa the river overflowed twice, but fortunately only minor damages were caused. Figure 4 shows hourly totals of the three stations in the basin: Macomer, Giave and Modolo Figures 5 to 11 show the evolution of cyclones at synoptic-scale, as observed at surface and at 500hPa level. 2 FIGURES

Figure 1. Tracks at surface of cyclones 1, 3 and 4; figures next to symbols indicate day and hour (GMT) they refer to (e.g. 25 12 means 12GMT of the 25th dec. 2002).

Figure 2. Tracks at surface of cyclones 2 (primary), 2A (secondary) and 2B (secondary); figures next to symbols indicate day and hour (GMT) they refer to (e.g. 25 12 means 12GMT of the 25th dec. 2002).

Figure 3. Total precipitation over NW Sardinia between 25th and 31st of December 2000. 20

15 cyclone 2 cyclone 4 Modolo Macomer Giave Modolo Macomer Giave mm 45.6mm 38.8mm 65.8mm 18.2mm 32.4mm 22.0mm

10 Modolo cyclone 1 cyclone 3 Macomer Modolo Macomer Giave Modolo Macomer Giave 14.8mm 18.2mm 14.0mm 33.0mm 35.0mm 23.6mm Giave 5

0

day and time

Figure 4. Hourly totals of three stations in the basin of river Temo; dotted vertical lines separate the spells affected by each cyclone (cyclone 2 is together 2A and 2B).

Figure 5. Synoptic-scale analysis at 00GMT of 25th December: a) geopotential height at 500hPa and temperature at 850hPa; b) mean sea level pressure and surface wind.

Figure 6. Synoptic-scale analysis at 00GMT of 26th December: a) geopotential height at 500hPa and temperature at 850hPa; b) mean sea level pressure and surface wind.

Figure 7. Synoptic-scale analysis at 00GMT of 27th December: a) geopotential height at 500hPa and temperature at 850hPa; b) mean sea level pressure and surface wind.

Figure 8. Synoptic-scale analysis at 00GMT of 28th December: a) geopotential height at 500hPa and temperature at 850hPa; b) mean sea level pressure and surface wind.

Figure 9. Synoptic-scale analysis at 00GMT of 29th December: a) geopotential height at 500hPa and temperature at 850hPa; b) mean sea level pressure and surface wind.

Figure 10. Synoptic-scale analysis at 00GMT of 30th December: a) geopotential height at 500hPa and temperature at 850hPa; b) mean sea level pressure and surface wind.

Figure 11. Synoptic-scale analysis at 00GMT of 31st December: a) geopotential height at 500hPa and temperature at 850hPa; b) mean sea level pressure and surface wind.

Acknowledgements. Authors wish to thank Dina Sechi and Simona Canu for graphical work. They would also like to thank Juan Campins of INM/Balearic Islands for running the automatic method of cyclon track detection.

REFERENCES

Chessa, P.A., Cesari, D., Delitala, A.M.S. Regimes of Precipitation and Temperature in Sardinia (Italy) and the related synoptic situations. Theoretical and Applied Climatology, 1999, 63, 195-222. Jansà, A., Genoves, A., Picornel, M.A., Campins, J., Riosalindo, R., Carrettero, O. Western Mediterranean cyclones and heavy rain. Part 2: Statistical Approach. Meteorological Application. 2002, 8, 43-56.