Severe Tropical Storm Chido over the Indian Ocean, headed for Madagascar.
View of Tropical Storm Chido as of December 10, 2024. Image via NASA Worldview
Chido moving generally toward Madagascar, due Friday
The 3rd named tropical storm this season in the Southwest Indian Ocean Basin – called Chido – formed Tuesday, December 10. The storm has quickly intensified as of today into a Severe Tropical Storm (wind speeds 88-117 kilometers per hour). It currently has sustained winds of 95 kilometers per hour (59 miles per hour) and is approximately 500 kilometers east-southeast of Agalega, Mauritius. This would also put Chido approximately 985 kilometers east of Sambava on the northeast coast of Madagascar.
According to the Meteo-France, the weather agency that forecasts tropical cyclones for the Southwest Indian Ocean Basin, Chido maintains a general westerly track at about 11 mph (18 km/h), toward Madagascar, which is the world’s 4th largest island nation, off the southeastern coast of Africa.
Chido is expected to continue strengthening over the coming days. Warm ocean water and weakening upper levels winds will allow Chido to gain strength as it moves west. It is expected to reach Tropical Cyclone strength by Thursday, December 12 with estimated wind speeds up to 138 km per hour (86 miles per hour).
Landfall by Friday?
Chido is forecast to move very near the northern end of Madagascar by Friday, December 13, bringing strong wind and rain. Whether or not Chido makes direct landfall on Madagascar or just moves close by, depends on the strength of the storm. Since there is uncertainty in the models, the exact strength on approach to Madagascar is still being fine-tuned; however, Meteo-France says, while a low probability, gale force winds are possible Friday, with wave heights of 4 meters.
Tropical Storm Chido’s forecast path. Image via Meteo-France
Models disagree on strength
Meteo-France defines the strength of tropical cyclones in the Southwest Indian Ocean using these classifications:
A Moderate Tropical Storm has max wind speeds from 63-87 kilometers per hour (at this point, the storm is strong enough to get a name).
Severe Tropical Storm (wind speeds 88-117 kilometers per hour).
Tropical Cyclone (118-165 kilometers per hour).
Intense Tropical Cyclone (166-212 kilometers per hour).
Very Intense Tropical Cyclone (wind speeds greater than 212 kilometers per hour).
It’s important to note – that while Meteo-France is forecasting Chido to become a Tropical Cyclone – another forecasting agency, the Joint Typhoon Warning Center (or JTWC) keeps Chido slightly weaker with maximum sustained winds at 111 kilometers per hour. JTWC’s reasoning is discrepancy between forecast model solutions and the strength of wind shear. Wind shear, or strong upper-level winds that change speed and/or direction with height, actively work against developing tropical cyclones.
Tropical cyclones need to be “stacked” vertically, and wind shear can tear apart developing tropical cyclones, or weaken stronger ones. The JTWC’s forecast calls for this wind shear to keep Chido slightly weaker, while Meteo-France acknowledges the possibility of higher wind shear, which may keep Chido weaker, and also a disagreement across weather model forecast solutions.
The Forecast Track from the Joint Typhoon Warning Center. Image Via: Joint Typhoon Warning Center
Southern Hemisphere summer hasn’t peaked yet
While Chido is this season’s 3rd named storm, it is in fact the fourth tropical system of the 2024-25 season. In August, a tropical depression formed, but never became strong enough to get a name. The first named storm of the season wouldn’t come until more than a month later, September 29, when Moderate Tropical Storm Ancha developed. Ancha would stay in the open ocean, not impacting land with its strongest winds reaching 83 kilometers per hour October 2.
The second named storm, Intense Tropical Cyclone Bheki, formed November 8 and later dissipated November 25. At its strongest point on November 17, Bheki had maximum sustained winds of 194 kilometers per hour.
The first three storms of the season (the unnamed tropical depression, Ancha and Bheki) developed before the official start of the Southwest Indian Ocean Cyclone Season. The season runs from November 15 to April 30 with 80% of storms developing from December through March. Ocean water in the Southwest Indian Ocean tends to be warmest during the first few months of the year, which leads to the potential for more tropical cyclone development as tropical cyclones get their strength from warm ocean water.
This also means the cyclone season for the Southwest Indian Ocean is just beginning. The warmest part of the summer in the Southern Hemisphere has yet to occur, but once it does, it’s normally a few weeks to a month for the ocean water to be at its warmest, which is fuel for tropical cyclones.
There are 23 names left to go on the list for Cyclone season in the Southwest Indian Ocean. With Ancha, Bheki and Chido already crossed off less than a month into the season, we may be monitoring this area for a while.
Bottom line: Chido – now a Severe Tropical Storm and still intensifying – is forecast to move near northern Madagascar, off southeast Africa, by Friday, December 13, bringing strong wind and rain.
Via Meteo-France
Via WMO Severe Weather Information Center
Via WMO Classification of Tropical Cyclones
Via Joint Typhoon Warming Center
Rachel Duensing
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About the Author:
Rachel Duensing is a Certified Broadcast Meteorologist by the American Meteorological Society and is currently a meteorologist and climate reporter at CBS17 in Raleigh, North Carolina. Rachel has previously worked in Fort Myers, Florida and Carterville, Illinois. In addition to daily weather, she has covered tornado outbreaks, hurricanes, and extreme heat and cold. Rachel received her Bachelor of Science degree in Meteorology and Digital Media from Valparaiso University in Valparaiso, Indiana. While at Valpo, she was a member of the Valparaiso University Storm Intercept Team, and along with professors and classmates, chased tornadoes and severe weather across the United State's Great Plains and Midwest. Rachel grew up outside Chester, Illinois, a small town in the southern end of the state (nowhere near Chicago!). When she was only 10 years old, Rachel learned about weather in science class, and when those lessons were followed up by a tornado outbreak outside her town, she took it as a sign and has been in love with weather ever since! When not forecasting the weather or reporting on weather and climate, Rachel spends her time volunteering at a local cat shelter and watching hockey with her husband.