Several aspects of the interaction between midlatitude and subtropical systems are investigated using a case study and a potential vorticity (PV) framework. Our case study occurred on 25 November 2009; Jeddah and other regions in Western Saudi Arabia were hit by heavy rainstorms. The analysis of absolute, relative, and potential vorticity implies the significance of the lower level dynamics in the initiation of this case of cyclogenesis. The impact of the severe convective weather process caused more than 90 millimeters of rain to fall in Jeddah in just four hours. The analysis indicates that the heavy rainfall was due to the existence of an upper level cold trough in the Eastern Mediterranean and a warm blocking high situated over southeasternSaudi Arabiaand theArabian Sea. In addition, an evident low level shear line set up in the northwest of Jeddah, and the southeast movement of the shear line caused dynamic lifting and unstable energy release over Jeddah. The water vapor transport occurred primarily below 700 hPa, and a low level jet transported the water vapor from the Red Sea to centralSaudi Arabia. Furthermore, the blocking high in southernSaudi Arabiawas favorable for maintaining water vapor passage for a long time. The topography of Jeddah also played a role in the enhancement of convection.
Cite this paper
A. ALKhalaf and H. Abdel Basset, "Diagnostic Study of a Severe Thunderstorm over Jeddah," Atmospheric and Climate Sciences, Vol. 3 No. 1, 2013, pp. 150-164. doi: 10.4236/acs.2013.31017.
 B. J. Hoskins, M. E. McIntyre and A. W. Robertson, “On the Use and Significance of Isentropic Potential Vorticity Maps,” Quarter Journal of Meteorological Society, Vol. 111, No. 470, 1985, pp. 877-946.
 C. A. Davis and K. A. Emanuel, “Potential Vorticity Diagnostics of Cyclogenesis,” Monthely Weather Review, Vol. 119, No. 8, 1991, pp.1929-1953.
 M. T. Stoelinga, “A Potential Vorticity-Based Study of the Role of Diabatic Heating and Friction in a Numerically Simulated Baroclinic Cyclone,” Monthely Weather Review, Vol. 121, No. 5, 1996, pp. 849-874.
 Z. Huo, D. L. Zhang and J. R. Gyakum, “Interaction of Potential Vorticity Anomalies in Extratropical Cyclogenesis Part I: Static Piecewise Inversion,” Monthely Weather Review, Vol. 127, No. 11, 1999, pp. 2546-2561.
 R. S. Plant, G. C. Craig and S. L. Gray, “On a Threefold Classification of Extratropical Cyclogenesis,” Quarter Journal of Meteorological Society, Vol. 129, No. 594, 2003, pp. 2989-3012. doi:10.1256/qj.02.174
 A. Agusti-Panareda, C. D. Thorncroft, G. C. Craig and S. L. Gray, “The Extratropical Transition of Hurricane Irene (1999): A Potential Vorticity,” Quarter Journal of Meteorological Society, Vol. 130, No. 598, 2004, pp. 1047-1074. doi:10.1256/qj.02.140
 F. Ahmadi-Givi, G. C. Craig and R. S. Plant, “The Dynamics of a Midlatitude Cyclone with Very Strong Latent Heat Release,” Quarter Journal of Meteorological Society, Vol. 130, No. 596, 2004, pp. 295-323.
 H. A. Basset and A. Gahein, “Diagnostic Study on the Relation between Ozone and Potential Vorticity,” Atmosfera, Vol. 16, 2003, pp. 67-82.
 H. Abdel Basset and A. M. Ali, “Diagnostics of Cyclogenesis Using Potential Vorticity, Atmosfera,” Vol. 19, No. 4, 2006, pp. 213-234.
 N. G. Prezerakos, “Formation of Sub-Synoptic-Scale Waves on the Eastern Flank of a Large Anticyclone at 500 Hpa Leading to Surface Cyclogenesis in the Greek Area on 5th October 1989,” Report on the Fourth Session of the Steering Group on Mediterranean Cyclones Study Project, WMO, Geneva, 1992, pp. 99-110.
 N. G. Prezerakos, H. A. Flocas and S. C. Michaelides, “Absolute Vorticity Advection and Potential Vorticity of the Free Troposphere as a Synthetic Tool for the Diagnosis and Forecasting Of Cyclogenesis,” Atmosphere-Ocean, Vol. 35, No. 1, 1997, pp. 65-91.
 N. G. Prezerakos, A. H. Flocas and S. C. Michaelides, “Upper-Tropospheric Downstream Development Leading to Surface Cyclogenesis in the Central Mediterranean,” Applied Meteorology, Vol. 6, No. 4, 1999, pp. 313-322. doi:10.1017/S1350482799001218
 T. S. Karacostas and A. A. Flocas, “The Development of the Bomb over the Mediterranean Area,” La Meteorologie, Vol. 34, 1983, pp. 351-358.
 A. A. Flocas and T. S. Karacostas, “Cyclogenesis over the Aegean Sea: Identification and Synoptic Categories,” Applied Meteorology, Vol. 33, 1996, pp. 53-61.
 H. R. Pomroy and A. J. Thorpe, “The Evolution and Dynamical Role of Reduced Upper-Tropospheric Potential Vorticity in Intensive Observing Period One of FASTEX,” Monthely Weather Review, Vol. 128, No. 6, 2000, pp. 1817-1834.
 WMO, “Atmospheric Ozone”, Vol. I, No. 16, WMO, Geneva, 1986.
 T. N. Krishnamurti and L. Bounoua, “An Introduction to Numerical Weather Prediction Techniques,” Academic Press, Waltham, 1996.
 A. D. Karein, “The Forecasting of Cyclogenesis in the Mediterranean Region,” Ph.D. Thesis, University of Edinburgh, Scotland, 1979.
 E. Palmen and C. Newton, “Atmospheric Circulation Systems: Their Structure and Physical Interpretation,” Academic Press, New York and London, 1969.
 S. Petterssen, “Weather Analysis and Forecasting,” 2nd Edition, Mc Graw-Hill Book Company, New York, 1956.
 M. Kurz, “The Role of Diagnostic Tools in Modern Weather Forecasting,” Applied Meteorology, Vol. 1, 1994, pp. 45-46.