Cyclone Mocha intensifies ahead of landfall in Myanmar and Bangladesh

Mocha is expected to reach the coast during midday or afternoon Sunday in the local region. The anticipated landfall is presently near or north of Sittwe, Myanmar, a city about 50 miles south of the Myanmar-Bangladesh border.

Evacuations of about half a million people are ongoing in the region, focused on northern Myanmar and southern Bangladesh. Locations near the landfall zone can expect disastrous winds, extreme surge and rainfall, as well as a freshwater flood threat that wanders farther inland with the storm.

The latest intensity estimate from the Joint Typhoon Warning Center (JTWC), as of Saturday evening local time in the region, pegged Cyclone Mocha at 150 mph (130 knots) sustained. This is less than 10 mph shy of Category 5.

Mocha exhibits a textbook presentation, with intense convection surrounding an open eye amid relative symmetry. It has so far become the fourth strongest storm on record in the region this year, and may end up the strongest storm to strike Myanmar since Nargis in 2008, which killed more than 100,000 in the country.

An atmospheric wave near China helping steer it northward, rather than weakening it markedly, appears to be enhancing Mocha’s outflow, which can keep intensification going despite what might often be disruptive wind shear.

“Conditions are favorable for further intensification, with low (5-10 kts) vertical wind shear, warm [sea surface temperatures] and strong poleward outflow,” wrote the JTWC in a Saturday update. “Additional near-term intensification is likely.”

Landfall is expected to be near or north of Sittwe, Myanmar. It could be as far north as the Bangladesh border, a few dozen miles past the city.

The JTWC forecast calls for Mocha to reach peak intensity about 12 hours before landfall, with some minor weakening as it reaches shore Sunday afternoon local time. Their official landfall intensity is 130 mph (115 knots) sustained.

There remains some disagreement as to its landfall intensity. The storm is likely to come ashore as a major hurricane equivalent of Category 3 or higher. It could reach shore as a Category 4 or higher. Mocha continues to be stronger than forecast in the short term, which may mean a stronger system as it reaches land.

Even if Mocha peaks before landfall, the impacts are largely set given the short time until it strikes, as well as the intensity of the storm.

Massive waves — up to 45 feet high near the center but subdued by about half at landfall — accompany a storm surge of (6.5 to 13 feet) 2 to 4 meters above normal water height, with locally higher possible. The worst surge will occur near and south of landfall as onshore winds pile up the water.

“Even if Mocha weakens to a Cat 3 at landfall, its surge will likely be Cat 4-level,” wrote hurricane expert Jeff Masters.

Near-shore winds sustained above 100 mph, gusting perhaps as high as twice that, will probably shred many things in their path, knocking over structures and stripping trees of vegetation. The most destructive winds are associated with the eyewall of the storm, a band around the center that largely impacts places within about 25 miles of the eye. Devastating wind threats wane as the storm heads inland, but some damaging gusts are likely to progress several hundred miles from shore.

Along with water surging in from the ocean, water falling from the sky will cause widespread flooding.

A large swath of at least 5 to 10 inches of rain is likely for much of the northern Myanmar coastal region and into Bangladesh. Potentially flooding rain then moves inland toward parts of India and ultimately toward Tibet. Some spots, especially higher elevations inland, could see as much as a foot or more of rain from the storm through early next week.

Concerns because of topography and ongoing war

Bay of Bengal storms are historically the deadliest on Earth. This can be attributed to the funneling effect of the bay as storms head north, typically scorching water temperatures that fuel rapid intensification, and socio-economic influences.

The likely landfall zone sits at the mouth of several rivers, meaning land in the area is particularly low lying and with minimal slope headed inland. As with many Bay of Bengal tropical cyclones, the ability of deep destructive surge to head well past the coastline is a major concern.

Ongoing war in Myanmar has also led to the creation of several large mega camps for the displaced. There is potential for hundreds of thousands of unhoused individuals to face the fury of surge, wind and rain from Mocha, including up to 1 million people in a camp just north of the border in Bangladesh.

The northernmost Myanmar state bordering Bangladesh, seemingly facing the brunt of the storm, is also home to many displaced people and has been a frequent location of violence in recent years.

“Of particular worry is the situation facing 232,100 people who are displaced across Rakhine,” wrote the U.N. Office for Coordination of Humanitarian Affairs on Friday.

While the storm will weaken rapidly after making landfall, heavy rain is likely to continue inland, leading to river flooding and the potential for landslides into early next week.