A low pressure area centered over the Mozambique Channel has organized into Tropical Cyclone (TC) 21S Friday afternoon, EDT, as it drifts slowly southeastward paralleling the coast of Mozambique.
TC 21S started as a disorganized area of showers and thunderstorms over the eastern third of Mozambique earlier this week, but recently entered an environment favorable for tropical development once it formed a low-level center of circulation and progressed over open water.
TC 21S has sustained winds of 40 mph with gusts as high as 50 mph with a slow forward speed of 6 mph.
The cyclone is expected to strengthen over the Mozambique Channel as it continues slowly southeastward through the next 24-48 hours, progressing just south of the islands of Comorros and Mayotte before clipping the west coast of Madagascar late Saturday night or early Sunday morning EDT. The storm is currently expected to reach maximum strength of 60 mph, equivalent to tropical storm strength in the Western Hemisphere, over open water late Saturday night EDT.
The center of the storm is expected to stay over water, as a ridge of high pressure building over Madagascar forces most of the storm to stay over the Mozambique Channel. This ridge will force TC21S in a more westerly direction starting Sunday night or Monday. The interaction with land and the drier air associated with the high pressure area should act to weaken the system before it reaches the coast of Mozambique toward the middle of next week.
Even if TC21S does not make landfall, it may still bring heavy rain and gusty winds to the northwest portion of Madagascar Saturday night and Sunday that can result in flooding and mudslides, along with downed trees and power lines.