Alshamsi et al. (2025) Synoptic-Scale Forcing and Its Role in a Rare Severe Rainfall Event over the UAE: A Case Study of 15–16 April 2024

Identification

• Journal: Atmosphere
• Year: 2025
• Date: 2025-11-07
• Authors: Noor Alshamsi, Ahmed Al Kaabi, Abdulla Al Mandous, Omar Al Yazeedi, Alya Al Mazrouei, Michael Weston, Andrew VanderMerwe, Mahmoud A. Hussein, Esra AlNaqbi, Amir Hossein Kamali, Sufian Farah, Mahra Al Ghafli, Brandt Maxwell
• DOI: 10.3390/atmos16111267

Research Groups

• Research and Weather Enhancement Department, National Center of Meteorology, Abu Dhabi, United Arab Emirates
• Technical Services Department, National Center of Meteorology, Abu Dhabi, United Arab Emirates
• Meteorology Department, National Center of Meteorology, Abu Dhabi, United Arab Emirates
• Independent Researcher, San Diego, CA, USA

Short Summary

This study investigates the atmospheric conditions responsible for a rare severe rainfall event over the United Arab Emirates (UAE) on 15–16 April 2024, identifying a deep, negatively tilted cut-off low-pressure system (COL) as the primary driver, supported by subtropical jet (STJ) divergence and pre-monsoonal moisture influx.

Objective

• To examine the synoptic-scale evolution, dynamics, and interactions between the Subtropical Jet (STJ), Cut-Off Lows (COLs), and the Indian monsoon that contributed to the severe unstable weather and heavy rainfall in the UAE from 15 to 16 April 2024.
• To reconstruct the large-scale evolution and placement of the COL-STJ-monsoon system (timing, position, and intensity) during the event.
• To quantify moisture transport/convergence, thermodynamic profiles, and vertical motion indicators associated with convection and rainfall.
• To assess the relative roles of the COL (primary), STJ support, and monsoon moisture as dominant versus secondary drivers of the event.

Study Configuration

• Spatial Scale: United Arab Emirates (approximately 71,024 km²), Arabian Peninsula, focusing on specific locations like Abu Dhabi International Airport, Rowdah, and Owtaid.
• Temporal Scale: The severe rainfall event occurred from 15 to 16 April 2024. Data analysis covered 12–17 April 2024, with long-term rainfall data from 1974 to 2024 used for extreme event definition.

Methodology and Data

• Models used: European Centre for Medium-Range Weather Forecasts (ECMWF) "Atmospheric Model high resolution 10-day forecast (Set I—HRES)".
• Data sources:
  • ECMWF-HRES atmospheric model data (wind, geopotential height, temperature, mean sea-level pressure, relative humidity) on standard pressure levels (1000–200 hPa).
  • National Aeronautics and Space Administration (NASA) Landsat-9 satellite imagery (Operational Land Imager 2).
  • Spinning Enhanced Visible and Infrared Imager (SEVIRI) Meteosat Second Generation (MSG3) infrared 13.4 µm satellite data.
  • Automatic Weather Stations (AWS) network (133 stations) from the National Center of Meteorology (NCM) providing 15-minute measurements of temperature, humidity, wind speed and direction, and rainfall.
  • National radar network (seven dual-polarimetric C-band radars) from NCM, processed using the Lidar Radar Open Software Environment system (LROSE-Colette) and Thunderstorm Identification Tracking Analysis and Nowcasting (TITAN) algorithm.
  • Upper-air soundings (radiosonde launches) from Abu Dhabi International Airport (Vaisala RS41-SG system) twice daily.
  • Radar Wind and Thermodynamic Profiling System (RWTPS) at Abu Dhabi International Airport (Radiometrics Corporation MP-3000A Microwave Profiling Radiometer and RAPTOR XBS-BL Radar Wind Profiler) providing 5-minute data up to 4876.8 meters.

Main Results

• The severe rainfall event on 15–16 April 2024 was primarily driven by a deep, initially negatively tilted Cut-Off Low (COL) pressure system over the Arabian Peninsula.
• The COL's formation and intensification were facilitated by a southward displacement of the Subtropical Jet (STJ) at 250 hPa, leading to jet-induced divergence and upper-level forcing.
• A prolonged moisture influx from the Indian monsoon system (Arabian Sea) preconditioned the atmosphere, providing warm, moist air that interacted with the upper-level trough.
• Thermodynamic profiles showed periods of high Convective Available Potential Energy (CAPE) (e.g., >1000 J kg⁻¹ on 16 April 2024) and low lifted-condensation levels (approximately 945 m), indicating atmospheric instability conducive to deep convection.
• Radar data revealed storm tops reaching approximately 19 kilometers and maximum reflectivity exceeding 75 dBZ during the peak phase (1800–2300 UTC on 15 April 2024).
• Precipitation rates peaked near 75 mm h⁻¹ during the mature phase of bow echo systems on 16 April 2024.
• Some regions recorded over 200 mm of precipitation within this period, with accumulated rainfall reaching up to 259.5 mm, resulting in widespread flash floods.
• As the COL evolved towards a neutral or positive tilt, precipitation broadened, and rates declined, indicating a weakening of the system's intensity.

Contributions

• Provides an observationally anchored attribution of the 15–16 April 2024 UAE severe rainfall event, integrating multi-source radar, satellite, and surface observations with ECMWF HRES analyses.
• Offers process-level insight into the evolution of extreme convection in a hyperarid environment, addressing a knowledge gap in understanding the full spectrum of dynamic and thermodynamic factors driving such rare events in the Arabian Peninsula.
• Quantifies the relative roles of COL geometry, STJ quadrants, and integrated vapor transport/thermodynamics, concluding that the COL was the primary driver with STJ support and monsoon moisture as secondary contributors.
• Highlights practical implications for operational forecasting in hyperarid regions, emphasizing the importance of monitoring COL geometry (depth and tilt), jet-quadrant analysis, and low-level humidity.

Funding

This research received no external funding.

Citation

@article{Alshamsi2025SynopticScale,
  author = {Alshamsi, Noor and Kaabi, Ahmed Al and Mandous, Abdulla Al and Yazeedi, Omar Al and Mazrouei, Alya Al and Weston, Michael and VanderMerwe, Andrew and Hussein, Mahmoud A. and AlNaqbi, Esra and Kamali, Amir Hossein and Farah, Sufian and Ghafli, Mahra Al and Maxwell, Brandt},
  title = {Synoptic-Scale Forcing and Its Role in a Rare Severe Rainfall Event over the UAE: A Case Study of 15–16 April 2024},
  journal = {Atmosphere},
  year = {2025},
  doi = {10.3390/atmos16111267},
  url = {https://doi.org/10.3390/atmos16111267}
}