Hérincs et al. (2025) Synoptic analysis of cyclone Ianos based on surface and satellite observations and high-resolution reanalysis data

Identification

• Journal: Theoretical and Applied Climatology
• Year: 2025
• Date: 2025-12-01
• Authors: Dávid Hérincs, Zsuzsanna Dezső
• DOI: 10.1007/s00704-025-05930-0

Research Groups

• Department of Meteorology, Institute of Geography and Earth Sciences, ELTE Eötvös Loránd University, Budapest, Hungary
• HungaroMet Hungarian Meteorological Service, Budapest, Hungary

Short Summary

This study provides a comprehensive synoptic analysis of Medicane Ianos, the strongest medicane in recent years, using multi-source observations and high-resolution reanalysis data. It confirms Ianos's tropical cyclone characteristics, including a deep warm core and hurricane-force winds, and details its tropical transition process.

Objective

• To conduct a comprehensive synoptic analysis of Medicane Ianos's life cycle using surface and satellite observations, and high-resolution reanalysis data.
• To determine the cyclone's classification based on parameters that differentiate tropical from non-tropical cyclones.
• To present a possible analysis method for medicanes that can distinguish between their extratropical, subtropical, and tropical phases.

Study Configuration

• Spatial Scale: Central Mediterranean Sea, Ionian Sea, Greece (especially Kefalonia, Zakynthos, Thessaly), southern Italy.
• Temporal Scale: Mid-September 2020 (specifically 14-20 September 2020), covering the cyclone's entire life cycle.

Methodology and Data

• Models used: None (reanalysis data analyzed).
• Data sources:
  • Reanalysis: ECMWF ERA5 (European Centre for Medium-Range Weather Forecasts Reanalysis v5) data with 0.25° × 0.25° resolution (for divergence, potential and relative vorticity, relative humidity, vertical velocity, equivalent potential temperature, and thickness).
  • Satellite Observations:
    • Passive Microwave: GPM GMI (Global Precipitation Measurement’s Microwave Imager), GCOM-W1 AMSR-2 (Global Change Observation Mission Water Satellite’s Advanced Microwave Scanning Radiometer 2) (brightness temperature data at 19 GHz, 37 GHz, and 89 GHz).
    • Active Microwave (Radar): GPM’s Dual-frequency Precipitation Radar (DPR) (high-resolution reflectivity, rain rate, storm top height).
    • Sea Surface Temperature (SST): CNR-GOS (Consiglio Nazionale delle Ricerche - Gruppo di Oceanografia da Satellite) analysis, including data from Sentinel-3A/3B SLSTR, NOAA/Suomi NPP VIIRS, Metop-B/C AVHRR, and SEVIRI sensors.
    • Wind: Metop-A/-B/-C ASCAT (Advanced Scatterometer), NASA SMAP (Soil Moisture Active Passive), CIMSS ATMS (Cooperative Institute for Meteorological Satellite Studies Advanced Technology Microwave Sounder) (wind speed and direction).
  • Surface Observations: Land-based weather stations (e.g., Palliki, Skinari, Kefalhnia Airport, Neochori), ship reports (for wind, pressure, and precipitation).
  • Lightning Data: LINET lightning detecting system (mentioned in related work, but not explicitly stated as a primary data source for this study's analysis, though it is referenced in the context of deep convection).

Main Results

• Cyclone Ianos reached at least Category 1 on the Saffir-Simpson scale, with estimated maximal sustained winds of approximately 33 m/s (64 kt) at its first peak and 44 m/s (85 kt) with gusts up to 54 m/s (105 kt) at landfall on Kefalonia Island. The minimum central pressure recorded was 984.3 hPa.
• Ianos exhibited well-defined tropical characteristics, including a deep, symmetrical warm core, persistent and organized deep convection, a concentrated and symmetrical wind field, well-defined upper-level outflow, and low-level maxima in relative and potential vorticity.
• Unlike most medicanes, Ianos's precursor was not a frontal extratropical cyclone; it developed from a weak surface low-pressure area associated with an upper-level low.
• The cyclone underwent a tropical transition process within two to three days, with convective processes gradually becoming more dominant than baroclinicity.
• Heavy rainfall was recorded, with 4-day accumulated precipitation reaching 317.4 mm at Pertouli and a daily maximum of 644.7 mm at Antipata (Kefalonia), significantly influenced by topography.
• Sea surface temperature decreased by approximately 5-6 °C (from 27-28 °C to 21-23 °C) along the cyclone's path due to wind-induced mixing and precipitation.
• ERA5 reanalysis showed strong upper-level divergence (up to 3–4 × 10⁻⁴ s⁻¹) contributing to intensification and low-level relative vorticity reaching 8–9 × 10⁻⁴ s⁻¹ during the storm's peak.

Contributions

• Provides a comprehensive, multi-source synoptic analysis of Medicane Ianos, confirming its tropical characteristics and tropical transition process, making it the strongest medicane in recent years.
• Details the structural and dynamic evolution of a medicane from its formation to landfall and regeneration, highlighting the interplay of baroclinic and diabatic processes.
• Proposes an analysis method for categorizing medicanes based on their structural organization and intensity, distinguishing between extratropical, subtropical, and tropical phases using various satellite products and reanalysis fields.
• Emphasizes the importance of combining in-situ measurements, high-resolution satellite data, and reanalysis for accurate medicane analysis, especially given the underestimation of intensity by larger-scale models.

Funding

• Hungarian National Research, Development and Innovation Fund (grant K-129162)
• National Multidisciplinary Laboratory for Climate Change (grant RRF-2.3.1-21-2022-00014)

Citation

@article{Hérincs2025Synoptic,
  author = {Hérincs, Dávid and Dezső, Zsuzsanna},
  title = {Synoptic analysis of cyclone Ianos based on surface and satellite observations and high-resolution reanalysis data},
  journal = {Theoretical and Applied Climatology},
  year = {2025},
  doi = {10.1007/s00704-025-05930-0},
  url = {https://doi.org/10.1007/s00704-025-05930-0}
}