Comment on this storyComment
Cyclone Mocha, dubbed an extremely severe cyclonic storm by the India Meteorological Department, has been rapidly intensifying over the past day and is now in its final stages before hurtling towards Asia.
With sustained winds of about 150 miles per hour, Mocha equates to a strong Category 4 hurricane on a scale of 1 to 5. It will continue to gain strength for a while before slowly weakening in the final hours before landfall.
Mocha in the region is expected to reach the coast by Sunday noon or afternoon. The expected landfall is currently near or north of Sittwe, Myanmar, a town about 50 miles south of the Myanmar-Bangladesh border.
About half a million people are currently being evacuated in the region, with a focus on northern Myanmar and southern Bangladesh. Locations near the landfall zone face catastrophic winds, extreme storm surges and rainfall, and a risk of freshwater flooding moving inland with the storm.
The latest intensity estimate from the Joint Typhoon Warning Center (JTWC) as of Saturday evening local time in the region put a sustained velocity of 150 miles per hour (130 knots) for Cyclone Mocha. This is less than 10 mph below Category 5.
Very healthy inner core #CycloneMocha this morning, with a strong primary band transitioning into a robust and increasingly symmetrical eyewall. Unfortunately, it seems to intensify even more on the way to Southeast Bangladesh and Northwest Myanmar. pic.twitter.com/av2xFNxp3i
— Andy Hazelton (@AndyHazelton) May 13, 2023
Mocha shows a textbook presentation with intense convection surrounding an open eye amid relative symmetry. So far it has been fourth strongest storm of all time This year, the region is hit by a severe storm that has ravaged Myanmar since Nargis in 2008, which killed more than 100,000 people in the country.
An atmospheric wave near China is helping push the Mocha north rather than significantly weakening it. Instead, it appears to increase Mocha runoff, allowing intensification to be sustained despite often disruptive wind shear.
“Conditions are favorable for further intensification, with low vertical wind shear (5-10 knots) and warm [sea surface temperatures] and strong poleward flow,” the JTWC wrote in an update on Saturday. “Additional short-term tightening is likely.”
Landfall is expected to occur near or north of Sittwe, Myanmar. It could reach as far north as the Bangladesh border, a few dozen miles beyond the city.
The JTWC forecast expects Mocha to reach its maximum intensity about 12 hours before landfall, with a slight attenuation when it reaches shore on Sunday afternoon local time. Her official landing speed is 130 miles per hour (115 knots) at all times.
There remains disagreement about the intensity of the landing. The storm is likely to make landfall as a Category 3 or higher severe hurricane. It could make landfall as Category 4 or higher. Mocha continues to be stronger than forecast in the near term, which could mean the system will strengthen when it reaches the country.
Even if Mocha peaks before it makes landfall, the impact is largely limited given the short time to arrival and the intensity of the storm.
Massive waves — up to 45 feet tall near center, but dampened by about half upon landing — accompany a storm surge (6.5 to 13 feet) 2 to 4 meters above normal water level, with locally higher waves possible. The worst rise will occur near and south of the landfall as onshore winds pile up the water.
Current IMD #CycloneMocha The climb prediction is 2.5-3m, 0.5m higher than yesterday but probably too low considering the JTWC intensity estimate for 12Z on Saturday is at 150mph – just 10mph below Category 5. Even if Mocha mitigates to Category 3 on landfall, its increase will likely correspond to Category 4. pic.twitter.com/2xTsOj7kaX
— Jeff Masters (@DrJeffMasters) May 13, 2023
“Even if Mocha weakens to Category 3 upon landing, its rise will likely reach Category 4 levels.” wrote hurricane expert Jeff Masters.
Inshore winds with speeds in excess of 100 miles per hour and gusts up to twice that are likely to shred many things in their path, knocking over buildings and stripping trees of their vegetation. The most destructive winds are associated with the storm’s eyewall, a band around the center that mostly affects locations within about 25 miles of the eye. The threat of devastating winds is easing as the storm moves inland, but some damaging gusts are likely to spread several hundred miles offshore.
Along with water entering from the sea, water falling from the sky will also cause widespread flooding.
A heavy rainfall of at least 5 to 10 inches is expected for much of Myanmar’s northern coastal region and as far north as Bangladesh. Potentially inundating rains then move inland to parts of India and eventually towards Tibet. In some places, particularly at higher elevations inland, there could be up to 30cm or more of rain from the storm through early next week.
Concerns due to topography and the ongoing war
Bay of Bengal storms are historically the deadliest on Earth. This is due to the bay’s funneling effect as storms move northward, typically searing water temperatures that favor rapid intensification, and socioeconomic influences.
The likely landfall zone is at the confluence of several rivers, which means that the land in the area is particularly low-lying and has minimal inland gradient. As with many tropical cyclones in the Bay of Bengal, the ability of a deep, destructive wave to travel far beyond shore is a major concern.
The ongoing war in Myanmar has also led to the establishment of several large mega-camps for displaced people. There is a possibility hundreds of thousands of homeless people will face the violence of Mocha’s storm surge, wind and rain, including up to 1 million people in a camp north of the border in Bangladesh.
WFP prepares for arrival #CycloneMocha. The food supply is enough for 400,000 people in Rakhine and the surrounding areas for one month. WFP is also establishing transportation and telecommunications systems for the wider humanitarian community. https://t.co/CLTRsT1Iha
— United Nations in Myanmar (@UNinMyanmar) May 13, 2023
The northernmost Myanmar state bordering Bangladesh, which appears to be bearing the brunt of the storm, is also home to many displaced people and has been a frequent scene of violence in recent years.
“Particularly worrying is the situation of the 232,100 displaced people across Rakhine,” the UN Office for the Coordination of Humanitarian Affairs wrote on Friday.
While the storm will weaken quickly once it makes landfall, heavy rains are expected to continue inland, causing river flooding and possibly landslides by early next week.