After a flurry of intense activity in early October, the tropical Atlantic has calmed and we are monitoring two tropical disturbances with little chance of developing into a named storm. There’s a good chance Hurricane Milton will be the last named storm of October. However, with a pulse of the Madden-Julian Oscillation (MJO) set to arrive in the Atlantic in early November, encouraging rising air and increasing the likelihood of tropical cyclone formation, it is still too early to close the book on the Atlantic hurricane season from 2024.

94L near the Leeward Islands

A Kabanian disturbance in the central Atlantic called Invest 94L approached the northern Leeward Islands on Thursday, racing west at a speed of about 20 miles per hour. Although the disturbance brings light wind shear and record-warm ocean temperatures of 30 degrees Celsius (86°F) favoring development, 94L is embedded in a very dry air mass that keeps strong thunderstorm activity limited, as seen on satellite loops. Development is also hampered by its rapid forward speed, which makes it difficult for 94L to align its upper center with its surface center. In addition, 94L is battling an unfavorable Madden-Julian Oscillation (MJO) configuration that favors sinking air over the Atlantic.

By Saturday, 94L will face two major obstacles to development: a wall of hostile wind shear as it attempts to move west-northwest toward Florida, or the imposing mountains of Hispaniola as it moves more west-southwest over the Dominican Republic. Models are less than enthusiastic about the 94L’s development and are generally predicting its demise on Sunday. The disturbance may bring heavy showers with a rainfall of 25 to 50 mm across the Leeward Islands, Virgin Islands, Puerto Rico and the Dominican Republic from Friday to Saturday.

In its tropical weather outlook for Thursday at 8 a.m. EDT, the National Hurricane Center gave 94L a 20% and 30% chance of development over the two- and seven-day periods, respectively. The next name on the Atlantic list is Nadine.

Torrential rains are heading toward parts of Belize and extreme southeastern Mexico

A disturbance centered around a Central American vortex has little chance of becoming a tropical cyclone before it makes landfall this weekend, but it will still dump dangerous amounts of rain. This disturbance was centered about 50 miles off the northeast coast of Honduras on Thursday morning, moving northwest with a central pressure of 1,007 millibars and surrounded by a disorganized line of showers and thunderstorms. Ensemble models widely agreed that the disturbance would gradually move west or west-northwest and come ashore along the coast of Belize or perhaps the coast of Quintana Roo, Mexico, around Saturday.

This system is embedded in a relatively humid middle atmosphere and will pass through sea surface temperatures of around 29 to 30 degrees Celsius (84 to 86 °F), but the aforementioned wall of strong upper-level winds will lurk just to the northwest and has a limited time to develop before migrating inland. Only a few members of the GFS ensemble and even fewer of the European ensemble develop this system into a tropical depression or, at best, a weak tropical storm.

As of 8 a.m. EDT Thursday, the National Hurricane System estimated a 20% chance of the disturbance developing over the 2- and 7-day periods, with those odds primarily in effect through Saturday before the system moved inland . Whatever its status, this disturbance promises to dump torrential rains from the far south and east of Mexico to parts of Belize, Guatemala and Honduras, perhaps exceeding 15 to 20 inches in some places, increasing the risk of mudslides and flash floods.

It is cyclone season in the North Indian Ocean

There are two tropical cyclone seasons in the North Indian Ocean – one centered in May, before the monsoon sets in, and one centered in October/November, after the monsoon subsides. During the peak of the monsoon in June and September, tropical cyclones are rare due to disruption from the monsoon circulation. With the monsoon now easing, the region’s autumn cyclone season is likely to blossom next week, supported by a favorable phase of the Madden-Julian Oscillation (MJO) for the region. Several models predict that a tropical cyclone will form in the eastern Bay of Bengal on Monday and then move northwest or north. The MJO will also endorse the development of a typhoon in the Western Pacific next week (see tweet below).

The most recent major cyclone of Category 3 or stronger to hit the Bay of Bengal coast was Cyclone Mocha, which hit Myanmar on May 14, 2023 as a Category 4 storm with winds of 250 km/h, according to the Joint Typhoon Warning Center . Eight hours before landfall, at 0 UTC on May 14, the Joint Typhoon Warning Center classified Mocha as a Category 5 storm with winds of 175 mph, tying it with May 2019’s Cyclone Fani as the strongest tropical cyclone to emerge ever recorded in the North Indian Ocean. Mocha killed 151 people and caused $2.3 billion in damage. Unfortunately, since the ousting of the elected government in a military coup in 2021, Myanmar has been fighting a devastating civil war that has killed tens of thousands of people and displaced over a million. Due to the war, Mocha’s death toll should be considered unreliable.