Authors– Sanjeev Kumar Singh, Yogesh Kant and D. Mitra

Cyclone Shakhti, the first cyclonic storm of 2025 over the Arabian Sea, formed from a low-pressure area in early October after the monsoon season. It intensified into a Severe Cyclonic Storm by October 4, reaching peak wind speeds of approximately 110-120 km/h and a central pressure of around 990 hPa (India Meteorological Department, 2025). Named by Sri Lanka, “Shakhti” means “power” or “strength.” The storm moved generally westward, remaining mostly offshore and avoiding direct impact on the Indian coast. It later weakened as it approached the coastal waters of Oman. It did not make landfall in India. Cyclone Shakhti lasted from around 1 October 2025 to 7 October 2025.

During Cyclone Shakhti, INSAT-3DS satellite-derived brightness temperature (BT) played a crucial role in monitoring the storm. Thermal Infrared satellite BT imagery revealed extremely cold brightness temperatures (below–190 K) near the cyclone’s center at its peak (Figure 1), indicating strong deep convection, high cloud tops, and a well-organised core. These cold BT regions corresponded to vigorous thunderstorms within the eyewall and spiral bands, signifying rapid intensification over the warm Arabian Sea.

Figure 1: Brightness temperature observed by INSAT-3DS TIR1 on 04 October 2025 at 08:00 UTC. (Data Source: MOSDAC, SAC, ISRO

On October 4, 2025, at 08:00 UTC, the INSAT-3DS TIR1 image captured a dense cloud formation associated with Cyclone Shakhti, showcasing the storm’s organised structure. Overlaying this image are the surface wind data from the EOS-06 scatterometer, collected on the same date at 07:52 UTC (Figure 2). This scatterometer data reveals high wind speeds (> 20 m/s) around the storm’s center. Together, the imagery and wind data provide a comprehensive analysis of the cyclone’s cloud structure and surface wind patterns, offering valuable insights into its dynamics and intensity.

Figure 2: INSAT-3DS TIR1 image on 04 October 2025 at 08:00 UTC with superimposed EOS-06 scatterometer surface winds from 04 October 2025 at 07:52 UTC. (Data Source: MOSDAC, SAC, ISRO)

Cyclone Shakhti has dissipated over the coastal waters of Oman. On October 4, 2025, the National Oceanic and Atmospheric Administration (NOAA) daily OISST (Optimum Interpolation Sea Surface Temperature) at a spatial resolution of 0.25°×0.25° (Huang et al., 2020) showed warm sea surface temperatures ranging from 29 to 30°C fueled the system’s conversion into a severe cyclonic storm (Figure 3). However, upon entering cooler waters below 27°C on October 6, 2025, Shakhti began to lose intensity. Tropical cyclones rely on warm ocean waters for their energy, so the decrease in heat limited further convection and caused the system to weaken.

Figure 3: NOAA daily SST on 04 October 2025 with superimposed IMD observed track for Cyclone Shakhti.  (Data Source: NOAA OISST v2.1 (0.25° daily SST) and IMD, 2025)

References:

India Meteorological Department. (2025). Tropical Cyclone Advisory Bulletin: Cyclone Shakhti (04 October 2025). RSMC, New Delhi. https://www.rsmcnewdelhi.imd.gov.in

Huang, Boyin, Chunying Liu, Viva F. Banzon, Eric Freeman, Garrett Graham, William Hankins, Thomas M. Smith, and Huai-Min Zhang. (2020). NOAA 0.25-degree Daily Optimum Interpolation Sea Surface Temperature (OISST), Version 2.1. NOAA National Centers for Environmental Information. https://doi.org/10.25921/RE9P-PT57