|Above: Fearsome Kenneth was bearing down on the coast of Mozambique on Thursday, as seen in this infrared satellite image from 11Z (7 am EDT) Thursday, April 25, 2019. Image credit: Scott Bachmeier and @CIMSS_Satellite.|
Tropical Cyclone Kenneth slammed onto the coast of far northern Mozambique around 4 pm Thursday afternoon local time (10:15 am EDT) as a potentially catastrophic Category 4 storm. Just before landfall, at 12Z (8 am EDT), Kenneth’s top sustained winds were pegged at 120 knots (140 mph)—solidly in the Cat 4 range—by the Joint Typhoon Warning Center. The agency issuing the official forecasts for the South Indian Ocean, RSMC-La Reunion, put Kenneth’s top winds at 12Z at 110 knots (125 mph), but this is a 10-minute average, a value tends to run slightly lower than the 1-minute average used by JTWC and by the U.S. National Hurricane Center. At its peak, Kenneth was classified as an intense tropical cyclone, the second highest rating on the seven-point scale used in the Southwest Indian Ocean.
Update: As of 18Z (2 pm EDT) Thursday, Kenneth had moved inland and weakened dramatically, with top sustained winds down to 75 knots (85 mph) as rated by JTWC.
The cyclone made landfall at the northern end of Mozambique’s Quirimbas National Park, a thinly populated area but with a number of villages with no experience of a storm of this magnitude. The stronger southern side of Kenneth’s eyewall was focused in this region. The Quisanga Islands, which includes several resorts, were likely quite hard hit by Kenneth’s winds and by a storm surge that could have been as high as 3 -5 meters (10 – 16 feet), according to RSMC-La Reunion.
Kenneth has been a very compact cyclone, which facilitated its rapid growth from tropical storm to Category 4 strength in just 36 hours. As Kenneth approached the coast, its hurricane-force winds extended only about 40-45 miles to the south and 30-35 miles to the north. At the city of Pemba, about 60 miles south of where Kenneth made landfall, top sustained winds at the time were only about 27 mph, with gusts to 39 mph.
NOAA’s HWRF model did an especially impressive job of predicting Kenneth’s rapid intensification. More than two days in advance, HWRF was consistently calling for Kenneth to hit Category 4 strength in the 24 hours before landfall.
On Wednesday, Kenneth swept past the northern end of the Comoros Islands, with its southern eyewall passing over Grande Comore, the largest of the islands. Trees and power lines were downed, and several shacks destroyed, according to AFP. At least three deaths have been attributed to the storm, according to Reuters.
See the weather.com article for frequent updates on Kenneth's impacts.
An unprecedented event for northern Mozambique
In records going back 50 years, far northern Mozambique has no record of storms of even minimal hurricane strength, much less a system as powerful as Kenneth. The landfall location (12°S) is quite close to the equator, in a latitude range where it becomes more difficult for cyclones to gather enough atmospheric spin to develop. Only a couple of tropical depressions and tropical storms have made landfall this far north in Mozambique or in Tanzania in the several decades of satellite coverage.
Kenneth ranks among the strongest landfalls on record for the entire African mainland. Cyclone Leon-Eline struck Mozambique on Feb. 26, 2000, with top one-minute sustained winds of 134 mph as assessed by JTWC. Off the mainland, Cyclones Hary (2000) and Gafilo (2004) both struck Madagascar at Category 5 strength, with top sustained winds of 160 mph, according to JTWC.
Kenneth is smaller but more intense than Tropical Cyclone Idai, which made a catastrophic landfall in central Mozambique near the city of Beira on March 15. Idai peaked offshore as a Category 3 storm—with top sustained winds of 120 mph, according to JWTC—and made landfall as a Category 2 with top winds of 105 mph. In modern satellite-era records, Mozambique has never recorded two Cat 2 or stronger landfalls in the same year. The closest analog to this year would be in 2000, when Cyclone Eline (Leon-Eline) struck south of Beira as a Category 4 on February 22 (see below), followed by Cyclone Hudah, which struck further north, near Pebane, as a Category 1 storm on April 8.
Next up: Massive rainfall and a serious flood threat
Kenneth will be rapidly weakening while onshore, but the circulation will also broaden and slow down, leading to a formidable multi-day rainfall event. From Friday into Saturday, Kenneth is expected to stall out less than 100 miles inland, perhaps making a turn toward the south and east that could bring it back offshore early next week in a much-weakened state.
As it drifts across far northern Mozambique, Kenneth will dump massive amounts of rain onto lowlands and swampy coastal areas. Forecasts from multiple models indicate that much or most of the province of Cabo Delgado—roughly the size of Maine—will receive 10” to 20” of rain, with localized amounts potentially topping 30”. An increasing amount of runoff could be flowing into the Messalo and Lurio rivers, depending on Kenneth’s exact track and where the heaviest rains set up.
|Figure 1. Rainfall forecast for Kenneth from weather.com through Sunday, April 27, 2019.|
Kenneth and the influence of climate change
Kenneth’s landfall in Mozambique as a Category 4 storm with 140 mph winds makes it the strongest landfalling tropical cyclone ever observed in mainland southeast Africa. Just last month, Mozambique had its fifth strongest landfalling cyclone on record, Idai, which was a Category 2 storm with 110 mph winds when it hit. It’s pretty remarkable that two of the top five strongest cyclones in the region’s history have occurred this year, which raises the question of whether human-produced climate change may have played a role.
We can say that climate change probably made the odds of such an unusual occurrence more likely, but we have to remember that regular satellite imagery of the Southwest Indian Ocean only began in 1998. Since climate change is best studied using datasets of 30 years or longer, the mere 21-year-long satellite data record for the basin makes it difficult to say specifically how climate change is affecting Southwest Indian Ocean tropical cyclones.
We should expect that Kenneth’s heavy rains are being increased due to climate change, though, since one of the more confident predictions hurricane scientists can make on the future of tropical cyclones in a warmer climate is that they will dump heavier rains due to increased moisture in the atmosphere. A study done for Hurricane Harvey of 2017--Wang et al. (2018), Quantitative attribution of climate effects on Hurricane Harvey's extreme rainfall in Texas--found that warming of the atmosphere and ocean since 1980 could have increased Hurricane Harvey’s extreme precipitation by 13% - 37%.
As detailed in our June 2018 post, Observed Slowdown in Tropical Cyclone Motion May Portend More Harvey-Like Rainstorms, a 4% slowdown in the forward speed of tropical cyclones in the Southwest Indian Ocean has been observed in recent decades. Cyclone Idai’s very slow motion at landfall—les than 10 mph—greatly contributed to it highly destructive rains, and Kenneth will also dump a huge amount of rain due to it very slow motion at landfall. It is uncertain if this trend is due to human-caused global warming, but there are good reasons to believe that this could be the case.
Tropical cyclone storm surges worldwide are definitely worse because of climate change. Global sea levels are about 8” higher than they were a century ago, and this extra rise allows the storm surge of all tropical cyclones to cause increased destruction.
Probably the most sophisticated study done yet on what the future may hold for tropical cyclones on the Southwest Indian Ocean was a 2018 paper, Projected Response of Tropical Cyclone Intensity and Intensification in a Global Climate Model, which used a high-resolution global climate model (HiFLOR). The 2018 study predicted a dramatic increase in the global incidence of rapid intensification due to global warming, and a 20% increase in the number of major hurricanes globally in the climate of the late 21st century. For the Southwest Indian Ocean, the model did not predict a significant increase in the number of days Category 3 and stronger cyclones would affect Mozambique, but did for nearby Madagascar and Mauritius.
Mozambique’s tropical cyclone history
NOAA’s historical hurricanes database lists twelve tropical cyclones of hurricane strength (if we include Idai and Kenneth) and ten tropical storms that have hit Mozambique since 1934. Many storms that hit before the advent of reliable satellite imagery in the Indian Ocean in 1998 were likely missed, though. Prior to Kenneth, the strongest landfalling storm was Tropical Cyclone Leon-Eline, which hit southern Mozambique as a Category 4 storm with 130 mph winds on February 22, 2000. The only other major tropical cyclones to hit were Favio of 2007 (Category 3, 115 mph winds) and Jokwe of 2008 (Category 3, 115 mph winds).
A record-active South Indian Ocean tropical cyclone season for major storms
According to the CSU Tropical Meteorology Project, the South Indian Ocean has seen 17 named storms, 12 hurricanes, and 11 major hurricanes during the 2018 – 2019 tropical cyclone season. An average season has 16 named storms, 9 hurricanes, and 4.5 major hurricanes by this point in the season. The most major hurricanes on record in one season was 9, set in 1980.
Northern Indian Ocean heating up
The northern Indian Ocean, which has two tropical cyclone seasons—in May, before the onset of the annual monsoon, and in November, after the monsoon has waned—may see its first tropical cyclone of 2019 by Sunday. Both the GFS and European models have been predicting in recent runs that a tropical disturbance (Invest 91B) in the waters a few hundred miles east-southeast of Sri Lanka could become a tropical cyclone by Sunday. The system could potentially threaten Sri Lanka and southeastern India by Monday or Tuesday.
Jeff Masters co-wrote this post.