page_title: Cyclone Belna
section_title: Meteorological history
hierarchical_section_title: Cyclone Belna / Meteorological history
caption_attribution_description: English: Track map of Tropical Cyclone Belna of the 2019-20 South-West Indian Ocean cyclone season. The points show the location of the storm at 6-hour intervals. The colour represents the storm's maximum sustained wind speeds as classified in the Saffir–Simpson scale (see below), and the shape of the data points represent the nature of the storm, according to the legend below. Saffir–Simpson scale Tropical depression≤38 mph≤62 km/h Category 3111–129 mph178–208 km/h Tropical storm39–73 mph63–118 km/h Category 4130–156 mph209–251 km/h Category 174–95 mph119–153 km/h Category 5≥157 mph≥252 km/h Category 296–110 mph154–177 km/h Unknown Storm type Tropical cyclone Subtropical cyclone Extratropical cyclone / Remnant low / Tropical disturbance / Monsoon depression
context_page_description: Cyclone Belna was a strong tropical cyclone that made landfall over northwestern Madagascar in December 2019, becoming the first to do so since Hellen in 2014. Belna's precursor—an initially broad trough of low pressure west of Seychelles—was formally designated as a zone of disturbed weather on 2 December during a favourable period for tropical cyclogenesis in the Indian Ocean. The disturbance gradually developed over the course of several days, tracking slowly westward. Météo-France upgraded the system to a tropical depression on 5 December and then to a tropical storm later that day. Belna reached tropical cyclone strength on 7 December as it began to turn towards the southwest, peaking with maximum sustained winds of 155 km/h before fluctuating in intensity over the following day as it passed just east of Mayotte. On 9 December, Belna restrengthened and reattained its peak winds upon making landfall near Soalala along the northwestern coast of Madagascar. The cyclone weakened before ultimately dissipating over southern Madagascar on 11 December.
  In the French overseas department of Mayotte, up to 15,000 people relocated to shelters in advance of the storm.
context_section_description: MFR began highlighting the potential for tropical cyclone development in their daily bulletins on 25 November, noting an increase in shower activity west of Seychelles. Aided by the passage of a Kelvin wave and a favourable window in the Madden–Julian oscillation, a broad trough of low pressure began to take shape within the storm activity, extending across the equator. Projections from computer models remained in disagreement over the system's future, complicated by the concurrent development of a tropical disturbance in the northwestern Indian Ocean along the same trough. A loosely-defined wind circulation was detected 263 km (163 mi) south of Mahe, Seychelles on 29 November, offset from convection. Over the following days, this circulation tightened within an environment moderately conducive for tropical development. Météo-France declared the system as a zone of disturbed weather on 2 December; at the time the system had drifted west from its point of origin. Although the storm was better organised and the environment conducive for intensification, the storm's wind field initially remained elongated and rainfall remained north of the storm's centre. The disturbance became a tropical depression on 5 December, attended by an increase in rainbands and the return of convection at the centre of circulation; at 18:00 UTC that day, the system was upgraded to Moderate Tropical Storm Belna.
  Belna was upgraded to severe tropical storm status early on 6 December. Around the same time, a cloud-obscured eye briefly became apparent in microwave satellite imagery. Due to a strengthening area of high pressure to its east, Belna began to curve from its initial westward drift to a more directed southwestward trajectory. After a brief period of strengthening, Belna's central dense overcast remained largely unchanged throughout 6 December before signs of resumed intensification emerged by the day's end, followed by the development of another eye 9–19 km (5.6–11.8 mi) across. With the storm's eye becoming better defined, MFR upgraded Belna to a tropical cyclone early on 7 December. Hot towers were detected atop and within the storm's radius of maximum winds, suggesting the onset of a more accelerated rate of intensification. However, the presence of dry air in the mid-levels of the troposphere towards the storm's southeastern quadrant prevented Belna from developing considerably. At 18:00 UTC on 7 December, Belna's winds topped out at 155 km/h (100 mph) before fluctuating at a slightly lower strength over the ensuing day. The system's structure disorganised significantly in a short period, caused by both the dry air and northerly wind shear.
  The cyclone's structure varied considerably throughout 8 December, at times featuring a small eye surrounded by intense lightning activity and at other times degrading in response to an intrusion of dry air into the Belna's circulation. Belna's strength was highly variable in part due to its small size, making it susceptible to changes in the local atmospheric environment and complicating forecasts. On 9 December, a new phase of intensification began as Belna approached the Madagascar coast near Soalala, with an eye becoming apparent on visible satellite imagery. In its advisories, the MFR noted a "spectacular intensification spell" in the hours leading up to Belna's landfall on Madagascar, assessing the cyclone's winds at 155 km/h (100 mph) and the pressure at 955 mbar (hPa; 28.35 inHg)–the lowest analysed over the course of the storm's existence—as Belna moved ashore at 15:30 UTC on 9 December. The storm then began to weaken as it tracked farther inland, parallelling the western coast of Madagascar. By 12:00 UTC the next day, Belna's winds had tapered below tropical depression thresholds, though the storm retained a well-defined wind circulation with tightly packed rainbands. Belna curved towards the southeast over Madagascar, and deep convection associated with the cyclone dissipated on 11 December. MFR issued their last update on the system later that day while the centre was over Haute Matsiatra,
caption: Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale
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