Synoptic–Thermodynamic Controls of Thunderstorm Activity over Eastern Iraq: A 30-Year Analysis of Instability Indices and Jet Stream Dynamics

This work aims to analyze the climatic and physical characteristics of thunderstorms over the city of Khanaqin in eastern Iraq by integrating surface observational data with global reanalysis data from 1990 to 2019. Recordings from the Khanaqin meteorological station were used to identify thunderstorm days, along with ERA-5 and MERRA-2 data to analyze the thermal, humidistic, and dynamic properties of the atmosphere, particularly in the upper atmosphere associated with jet streams. Time-based statistical analysis of thunderstorm oscillations was performed, and indices of atmospheric instability (K-index, Total Totals index, and CAPE) were calculated. Their relationship to the vertical structure of thunderstorms was investigated, including the updraft level, equilibrium level, and cloud thickness. MERRA-2 data were also employed in synoptic analysis to characterize the role of jet streams and upper divergence in driving deep convection. The results showed that thunderstorm activity in the study area exhibited clear annual and seasonal oscillations without a statistically significant long-term trend. The majority of storms occurred during the spring season, in an atmospheric environment characterized by moderate thermal instability, with CAPE values generally below 1000 J/kg. Despite this, deep thunderstorms with significant vertical extent were observed, indicating the crucial role of large-scale dynamic factors, particularly upper-level troughs and jet stream coupling, in enhancing storm intensity. The study reveals that thunderstorms in eastern Iraq are primarily regulated by upper-level synoptic influences rather than solely by convection energy, highlighting the limitations of using CAPE as a sole indicator for estimating storm intensity in semi-arid environments. These findings contribute to a better understanding of convection mechanisms in areas with limited observational data and provide an important scientific basis for developing weather forecasting and severe storm early warning systems in Iraq and neighboring regions.