**6. Prevailing patterns of precipitation in Jeddah**

To deduce the characteristic patterns of rainfall in the Jeddah area, we need a large number of reordering storms which are not available in the whole KSA. However, in the current work depending on the storms collected in the Jeddah area from the new installed automated rainfall stations, some suggestions can be made to understand the behavior of storms in the Jeddah area. To achieve this, the data available for each storm were converted to dimensionless data (**Figure 10**). The behavior of all possible storms was compared with the SCS-type II distribution curve. It is noticed that these storms can be divided into two groups. The first group represents the storms, which exceeded 50 mm of precipitation (**Figure 11a**). This group is represented by the storms recorded at the headquarters of the SGS station on November 21, 2017; January 26, 2011; and November 17, 2011, in both the Wadi Qaws and J134 stations. The second group represents short-term storms which recorded precipitation quantities less than 50 mm (**Figure 11b**). This group includes the storms registered at the headquarters of the SGS station on November 22, 2014, and December 2, 2016. For both groups, the average curves of each storm set were derived. To verify that these two storm groups are different from each other and have different behaviors, a distribution histogram of the average curve for each storm group was extracted and simplified as shown in **Figure 12**.

**Figure 11.**

*Cumulative dimensionless hyetographs: (a) for storms above 50 mm and (b) for storms below 50 mm.*

**Figure 12.**

*(a) Dimensionless histogram for storms above 50 mm. (b) Dimensionless histogram for storms below 50 mm.*
