A Diagnostic Study of Three Heavy Precipitation Episodes in the Western Mediterranean Region

Charles A. Doswell III NOAA/Environmental Research Laboratories, National Severe Storms Laboratory, Norman, Oklahoma

Search for other papers by Charles A. Doswell III in
Current site
Google Scholar
PubMed
Close
,
Clemente Ramis Geophysical Fluid Dynamics Group, University of the Balearic Isles, Palma de Mallorca, Spain

Search for other papers by Clemente Ramis in
Current site
Google Scholar
PubMed
Close
,
Romualdo Romero Geophysical Fluid Dynamics Group, University of the Balearic Isles, Palma de Mallorca, Spain

Search for other papers by Romualdo Romero in
Current site
Google Scholar
PubMed
Close
, and
Sergio Alonso Geophysical Fluid Dynamics Group, University of the Balearic Isles, Palma de Mallorca, Spain

Search for other papers by Sergio Alonso in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

A diagnostic evaluation of three project ANOMALIA case studies involving heavy precipitation in the western Mediterranean region has been carried out. The evaluation shows the unique characteristics of each event, as well as some limited similarities. Heavy precipitation events in the western Mediterranean region typically occur downstream of a significant cyclone aloft (often, but not always, exhibiting “cutoff” cyclone characteristics), but important structural and evolutionary differences are found among these cases. At low levels, a long fetch of flow over the Mediterranean Sea frequently interacts with terrain features to produce persistent heavy precipitation. Although most heavy precipitation events occur during the fall season, they can develop at other times. In the first case, the synoptic-scale environment produced low static stability and substantial storm-relative environmental helicity, thereby supporting both heavy rain in the vicinity of Valencia on mainland Spain and on Ibiza in the Balearic Islands, as well as a tornado at Menorca in the Balearic Islands on 7–9 October 1992. The second case involved a slow-moving cyclone that destabilized the stratification and produced several days of heavy precipitation over the period 31 January–6 February 1993. In the third case, in the Italian Piedmont region on 5–6 November 1994, the heavy precipitation included a nonconvective component, with moist but relatively stable air impinging on steep terrain gradients.

A set of basic diagnostic tools is applied to the cases, and it is shown that anything but a superficial diagnosis of each case requires flexibility in selecting diagnostic tools. The ways by which heavy precipitation is created can vary substantially from case to case and in different parts of the world; however, there is a common thread. Heavy precipitation is the result of moist, low-level air ascending rapidly, so any diagnosis aimed at forecasting heavy precipitation needs to address the following: vertical motion, static stability, moisture supply, and orographic effects (when appropriate). Forecasting implications of the cases are discussed, with the emphasis on considering these physically relevant processes.

Corresponding author address: Dr. Charles A. Doswell III, National Severe Storms Laboratory, 1313 Halley Circle, Norman, OK 73069.

Email: doswell@nssl.noaa.gov

Abstract

A diagnostic evaluation of three project ANOMALIA case studies involving heavy precipitation in the western Mediterranean region has been carried out. The evaluation shows the unique characteristics of each event, as well as some limited similarities. Heavy precipitation events in the western Mediterranean region typically occur downstream of a significant cyclone aloft (often, but not always, exhibiting “cutoff” cyclone characteristics), but important structural and evolutionary differences are found among these cases. At low levels, a long fetch of flow over the Mediterranean Sea frequently interacts with terrain features to produce persistent heavy precipitation. Although most heavy precipitation events occur during the fall season, they can develop at other times. In the first case, the synoptic-scale environment produced low static stability and substantial storm-relative environmental helicity, thereby supporting both heavy rain in the vicinity of Valencia on mainland Spain and on Ibiza in the Balearic Islands, as well as a tornado at Menorca in the Balearic Islands on 7–9 October 1992. The second case involved a slow-moving cyclone that destabilized the stratification and produced several days of heavy precipitation over the period 31 January–6 February 1993. In the third case, in the Italian Piedmont region on 5–6 November 1994, the heavy precipitation included a nonconvective component, with moist but relatively stable air impinging on steep terrain gradients.

A set of basic diagnostic tools is applied to the cases, and it is shown that anything but a superficial diagnosis of each case requires flexibility in selecting diagnostic tools. The ways by which heavy precipitation is created can vary substantially from case to case and in different parts of the world; however, there is a common thread. Heavy precipitation is the result of moist, low-level air ascending rapidly, so any diagnosis aimed at forecasting heavy precipitation needs to address the following: vertical motion, static stability, moisture supply, and orographic effects (when appropriate). Forecasting implications of the cases are discussed, with the emphasis on considering these physically relevant processes.

Corresponding author address: Dr. Charles A. Doswell III, National Severe Storms Laboratory, 1313 Halley Circle, Norman, OK 73069.

Email: doswell@nssl.noaa.gov

Save
  • Barnes, S. L., 1985: Omega diagnosis as a supplement to LFM/MOS guidance in weakly forced convective situations. Mon. Wea. Rev.,113, 2122–2141.

    • Crossref
    • Export Citation
  • ——, and C. W. Newton, 1986: Thunderstorms in the synoptic setting. Thunderstorm Morphology and Dynamics, 2d ed., E. Kessler, Ed., University of Oklahoma Press, 75–112.

  • Benet, C., 1986: Meteorological data in Sabadell 1897–1979 (in Catalan). 42 pp. [Available from Ajuntament de Sabadell, Pl. Sant Roc 2, 08021 Sabadell, Spain.].

  • Bolton, D., 1980: The computation of equivalent potential temperature. Mon. Wea. Rev.,108, 1046–1053.

    • Crossref
    • Export Citation
  • Buzzi, A., D. Gomis, M. A. Pedder, and S. Alonso, 1991: A method to reduce the adverse impact that inhomogeneous station distributions have on spatial interpolation. Mon. Wea. Rev.,119, 2465–2491.

    • Crossref
    • Export Citation
  • Caracena, F., and J. M. Fritsch., 1983: Focusing mechanisms in the Texas hill country flash floods of 1978. Mon. Wea. Rev.,111, 2319–2332.

    • Crossref
    • Export Citation
  • Davies-Jones, R., D. Burgess, and M. Foster, 1990: Test of helicity as a tornado forecast parameter. Preprints, 16th Conf. on Severe Local Storms, Kananaskis Park, AB, Canada, Amer. Meteor. Soc., 588–592.

  • Doswell, C. A., III, 1987: The distinction between large-scale and mesoscale contribution to severe convection: A case study example. Wea. Forecasting,2, 3–16.

    • Crossref
    • Export Citation
  • ——, 1994: Flash flood-producing convective storms: Current understanding and research. Proc. U.S.–Spain Workshop on Natural Hazards, Barcelona, Spain, National Science Foundation, 97–107.

  • ——, and F. Caracena, 1988: Derivative estimation from marginally sampled vector point functions. J. Atmos. Sci.,45, 242–253.

    • Crossref
    • Export Citation
  • ——, H. E. Brooks, and R. A. Maddox, 1996: Flash flood forecasting:An ingredients-based methodology. Wea. Forecasting,11, 560–581.

    • Crossref
    • Export Citation
  • Durran, D. R., and L. W. Snellman, 1987: The diagnosis of synoptic-scale vertical motion in an operational environment. Wea. Forecasting,2, 17–31.

    • Crossref
    • Export Citation
  • Emanuel, K. A., 1991: A scheme for representing cumulus convection in large-scale models. J. Atmos. Sci.,48, 2313–2335.

    • Crossref
    • Export Citation
  • Fernández, C., M. A. Gaertner, C. Gallardo, and M. Castro, 1995: Simulation of a long-lived meso-β scale convective system over the Mediterranean coast of Spain. Part I: Numerical predictability. Meteor. Atmos. Phys.,56, 157–179.

    • Crossref
    • Export Citation
  • Font, I., 1983: Climatology of Spain and Portugal (in Spanish). Instituto Nacional de Meteorologia, 296 pp.

  • García-Dana, F., R. Font, and A. Rivera, 1982: Situación Meteorológica durante el Episodio de Lluvia Intensa en el Levante Español durante Octubre de 1982 (in Spanish). Instituto Nacional de Meteorologia, 68 pp.

  • Hollingsworth, A., D. B. Shaw, P. Lönnberr, L. Illari, K. Arpe, and A. J. Simmons, 1986: Monitoring of observation and analysis quality by a data assimilation system. Mon. Wea. Rev.,114, 861–879.

    • Crossref
    • Export Citation
  • Hoskins, B. J., and M. A. Pedder, 1980: The diagnosis of middle latitude synoptic development. Quart. J. Roy. Meteor. Soc.,106, 707–719.

    • Crossref
    • Export Citation
  • Lionetti, M., 1996: The Italian floods of 4–6 November 1994. Weather,51, 18–27.

    • Crossref
    • Export Citation
  • Llasat, M. C., 1987: Precipitaciones intensas en Cataluña: Génesis, evolución y mecanismo (in Spanish). Universitat de Barcelona No. 40, 543 pp. [Available from Departament de Publicacions, Universitat de Barcelona, Avda. Diadonal 647, 08028 Barcelona, Spain.].

  • Maddox, R., 1980: Mesoscale convective complexes. Bull. Amer. Meteor. Soc.,61, 1374–1387.

    • Crossref
    • Export Citation
  • ——, and C. A. Doswell III, 1982: An examination of jet stream configurations, 500 hPa vorticity advection and low-level thermal advection patterns during extended periods of intense convection. Mon. Wea. Rev.,110, 184–197.

    • Crossref
    • Export Citation
  • Meteorological Office, 1962: Weather in the Mediterranean. Vol. I. Meteorological Office, 362 pp.

  • Nickerson, E. C., E. Richard, R. Rosset, and D. R. Smith, 1986: The numerical simulation of clouds, rain and airflow over the Vosges and Black Forest mountains: A meso-β model with parameterized microphysics. Mon. Wea. Rev.,114, 398–414.

    • Crossref
    • Export Citation
  • Pedder, M. A., 1993: Interpolation and filtering of spatial observations using successive corrections and Gaussian filters. Mon. Wea. Rev.,121, 2889–2902.

    • Crossref
    • Export Citation
  • Ramis, C., and R. Romero, 1995: A first numerical simulation of the development and structure of the sea breeze in the island of Mallorca. Ann. Geophys.,13, 981–994.

    • Crossref
    • Export Citation
  • ——, M. C. Llasat, A. Genovés, and A. Jansá, 1994: The October 1987 floods in Catalonia: Synoptic and mesoscale mechanisms. Meteor. Appls.,1, 337–350.

    • Crossref
    • Export Citation
  • ——, S. Alonso, and M. C. Llasat, 1995: A comparative study of two cases of heavy rain in Catalonia: Synoptic and mesoscale mechanisms, Surv. Geophys.,16, 141–161.

    • Crossref
    • Export Citation
  • Riosalido, R., 1990: Characterization of mesoscale convective systems by satellite pictures during PREVIMET MEDITERRANEO-89 (in Spanish). Proc. Segundo Simposio Nacional de Predicción, Madrid, Spain, Instituto Nacional de Meteorología, 135–148.

  • Romero, R., C. Ramis, and S. Alonso, 1997: Numerical simulation of an extreme rainfall event in Catalonia: Role of orography and evaporation from the sea. Quart. J. Roy. Meteor. Soc.,123, 537–559.

    • Crossref
    • Export Citation
  • ——, ——, ——, C. A. Doswell III, and D. J. Stensrud, 1998: Mesoscale model simulations of three heavy precipitation events in the western Mediterranean. Mon. Wea. Rev., in press.

  • Trenberth, K. E., and J. G. Olson, 1988: An evaluation and intercomparison of global analyses from the National Meteorological Center and the European Centre for Medium-Range Weather Forecasts. Bull. Amer. Meteor. Soc.,69, 1047–1057.

    • Crossref
    • Export Citation
  • Tudurí, E., and C. Ramis, 1997: On the environments of significant convective events in the western Mediterranean. Wea. Forecasting,12, 294–306.

    • Crossref
    • Export Citation
  • Weisman, M. L., and J. B. Klemp, 1986: Characteristics of isolated convective storms. Mesoscale Meteorology and Forecasting, P. S. Ray, Ed., Amer. Meteor. Soc., 331–358.

    • Crossref
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 675 242 15
PDF Downloads 547 110 9