NHESS Natural Hazards and Earth System Sciences NHESS Nat. Hazards Earth Syst. Sci. 1684-9981 Copernicus Publications Göttingen, Germany 10.5194/nhess-9-551-2009 Numerical forecast and analysis of a tropical-like cyclone in the Ionian Sea Davolio S. 1 Miglietta M. M. 2 Moscatello A. 2 Pacifico F. 1 4 Buzzi A. 1 Rotunno R. 3 Institute of Atmospheric Sciences and Climate, ISAC – CNR, Bologna, Italy Institute of Atmospheric Sciences and Climate, ISAC – CNR, Lecce, Italy National Center for Atmospheric Research (NCAR is sponsored by the National Science Foundation), Boulder, Colorado, USA now at: School of Geographical Science, University of Bristol, Bristol, UK; Met Office Hadley Centre, Exeter, UK 03 04 2009 9 2 551 562 Copyright: © 2009 S. Davolio et al. 2009 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://nhess.copernicus.org/articles/9/551/2009/nhess-9-551-2009.html The full text article is available as a PDF file from https://nhess.copernicus.org/articles/9/551/2009/nhess-9-551-2009.pdf

A forecasting system has been implemented for operational weather prediction over southern Italy in the framework of the RISKMED (INTERREG IIIB) project, which aims at weather-risk reduction in the central and eastern Mediterranean area. The system comprises two different regional forecasting chains, one based on BOLAM and MOLOCH models, the second based on the Weather Research and Forecasting (WRF) model. <br><br> On 26 September 2006, a subsynoptic-scale vortex developed over the Mediterranean Sea and affected south-eastern Italy. The cyclone was documented by radar reflectivity maps, Meteosat Second Generation satellite images and surface stations data. The observational analysis showed that the cyclone possessed the typical characteristics of a Mediterranean tropical-like cyclone. <br><br> All the limited-area models employed in RISKMED were able to properly forecast the formation of the small-scale vortex, although with differences in intensity, trajectory and evolution. The predictability of the event has been evaluated employing a multi-model, multi-analysis approach. The simulation results show strong sensitivity to the specification of the initial and boundary conditions. <br><br> Sensitivity experiments were performed in order to analyse the mechanisms responsible for the development and the maintenance of the cyclone over the sea. The life cycle of the vortex turned out to be characterized by different phases: the orographic cyclogenesis on the lee side of the Atlas Mountains; the initial phase of development, characterised by the critical role played by the surface heat fluxes; the transition to a tropical-like cyclone mainly as a consequence of the latent-heat release associated with strong convective activity over the Ionian Sea; finally, the maintenance of the vortex strength due to both the surface fluxes and the release of latent heat.

 References Billing, H., Haupt, I., and Tonn, W.: Evolution of a hurricane-like cyclone in the Mediterranean Sea, Beitr. Phys. Atmos., 56, 508–510, 1983. Davolio, S., Buzzi, A., and Malguzzi, P.: High resolution simulations of an intense convective precipitation event, Meteorol. Atmos. Phys., 95, 139–154, 2007. Emanuel, K.: Genesis and maintenance of "Mediterranean hurricanes", Adv. Geosci., 2, 217–220, 2005. Fita, L., Romero, R., Luque, A., Emanuel, K., and Ramis, C.: Analysis of the environments of seven Mediterranean tropical-like storms using an axisymmetric, nonhydrostatic, cloud resolving model, Nat. Hazards Earth Syst. Sci., 7, 41–56, 2007. Homar, V., Romero, R., Stensrud, D. J., Ramis, C., and Alonso, S.: Numerical diagnosis of a small, quasi-tropical cyclone over the western Mediterranean: dynamical vs. boundary factors, Q. J. Roy. Meteor. Soc., 129, 1469–1490, 2003. Lagouvardos, K., Kotroni, V., Nickovic, S., Jovic, D., and Kallos, G.: Observations and model simulations of a winter sub-synoptic vortex over the Central Mediterranean, Meteorol. Appl., 6, 371–383, 1999. McTaggart-Cowan, R., Bosart, L. F., Gyakum, J. R., and Atallah, E. H.: Hurricane Katrina (2005). Part I: Complex life cycle of an intense tropical cyclone, Mon. Weather Rev., 135, 3905–3926, 2007. Miglietta, M. M., Davolio, S., Moscatello, A., Pacifico, F., and Rotunno, R. R.: The role of surface fluxes in the development of a tropical-like cyclone in southern Italy, Adv. Sci. Res., 2, 35–39, 2008. Montgomery, M. T., Nicholls, M. E.,~Cram, T. A., and~Saunders, A. B.: A vortical hot tower route to tropical cyclogenesis, J. Atmos. Sci., 63, 355–386, 2006. Moscatello, A., Miglietta, M. M., and Rotunno, R.: Numerical analysis of a Mediterranean "Hurricane" over south-eastern Italy, Mon. Weather Rev., 136, 4373–4397, 2008a. Moscatello, A., Miglietta, M. M., and Rotunno, R.: Observational analysis of a Mediterranean "hurricane" over south-eastern Italy, Weather, 63, 306–311, 2008b. Pytharoulis, I., Craig, C. G., and Ballard, S. P.: The hurricane-like Mediterranean cyclone of January 1995, Meteorol. Appl., 7, 261–279, 2000. Rasmussen, E. and Zick, C.: A subsynoptic vortex over the Mediterranean with some resemblance to polar lows, Tellus, 39A, 408–425, 1987. Reale, O. and Atlas, R.: Tropical cyclone-like vortices in the extratropics: observational evidence and synoptic analysis, Weather Forecasting, 16, 7–34, 2001. Rotunno, R. and Emanuel, K.: An air-sea interaction theory for tropical cyclones. Part II: Evolutionary study using a nonhydrostatic axysimmetric numerical model, J. Atmos. Sci., 44, 542–561, 1987. Skamarock, W. C., Klemp, J. B., Dudhia, J., Gill, D. O., Barker, D. M., Wang, W., and Powers, J. G.: A description of the Advanced Research WRF Version 2, NCAR Technical Note, 468STR, 88 pp., 2005. Tibaldi, S., Buzzi, A., and Speranza, A.: Orographic cyclogenesis, in: Extratropical Cyclones, edited by: Newton, C., and Holopainen, E. O., Amer. Meteor. Soc., 107–128, 1990.