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Variations of summer temperature over Egypt have been studied using the data of 19 stations. The analysis of these data shows that the surface temperature is a stable climate element where its coefficient of variation (COV) is found to be low during summer. The time sequence of cumulative seasonal mean (CSM) is shown to exhibit bounded, oscillatory, nonperiodic behavior. The boundedness of the oscillation supports the notion of climate compensation; i.e. that spells of cold must eventually follow spells of warm. The trend analysis of the time series of our stations shows striking positive trend values during the last 20 years; this could be attributed not only to human activities but also to atmospheric circulation changes. Spectral analyses of the monthly values of the 19 stations were made. It was found that the first harmonic plays a dominant role in the regional climatological variations in Egypt; it explains more than 38% of the amplitude variations and may be related to the sunspot cycle, which affects summer temperature over Egypt. Other harmonics may be related to El Nino southern oscillation (ENSO) cycle, quasi-biennial oscillation (QBO) cycle, and solar inertial motion cycle. Each of them contribute approximately 9% to summer temperature in Egypt and so their influence on summer temperatures in the area is not so much.

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.

In this study monthly, seasonal and annual values of temperature have been analyzed over Egypt during the period 1960-2016. It is found that the temperature is a function of latitudes where the values of temperature increase gradually from north to south. The trend analysis illustrates that there is a significant increase in seasonal and annual values of temperature over Egypt. The annual wave dominates at all stations; its amplitude for the northern stations is smaller than those for the southern stations. The analysis of the spatial distribution of the monthly average of temperature (1960 -2016) for each month of the year has been made. It is found that Latitudinal gradients in temperature are strong in winter and spring seasons with particular increase over the north of Egypt due to the effect of mid-latitude travelling depressions from west to east over Egypt. The climatological distribution of temperature throughout the months of the year reflects the effect of meteorological factors and pressure systems affecting the weather and climate in the study area. The warmest areas in summer are the middle and the south eastern parts of Egypt.