Tropical Storm Melissa puts Caribbean’s most flood-vulnerable places at risk
A hurricane watch is in place for the southern coast of Haiti and a tropical storm watch for Jamaica as new tropical storm Melissa tracks westward across the central Caribbean. Melissa assembles forces on near-record, untouched Caribbean waters. hurricane or tropical storm so far this year, and from 2 p.m. EDT Tuesdaywas located in the central Caribbean, approximately 490 kilometers south of Port-au-Prince, Haiti. Melissa’s highest sustained winds were already 50 mph (85 kph), and the National Hurricane Center predicted the storm would reach hurricane strength by Saturday. Melissa was moving just north, due west, at about 14 mph.
The many possibilities for Melissa’s future over the next few days include several days of torrential rain over some of the Caribbean’s most flood-vulnerable locations. Catastrophic flooding and mudslides pose a growing threat to Haiti, as well as the southern Dominican Republic. Due to strong wind shear from the location of Florida’s subtropical jet stream eastward across the Bahamas, Melissa is not expected to pose a threat to the continental United States for at least the next week, and ensemble models indicate only a small chance that the storm will end up far enough northwest to affect Florida.
Melissa is the 13th named storm of the 2025 Atlantic season, forming just four days before the average arrival of the 13th named storm of the season on October 25 (over the period 1991-2020).
Near-record Caribbean waters will fuel Melissa’s growth
Although we are near the end of the Atlantic hurricane season, the Caribbean is where we would most expect to see a named storm develop between mid-to-late October, as wind shear further north has generally become too strong for tropical cyclones. At this point in the year, Caribbean waters have generally not cooled too much from their seasonal peak, while the wind shear that so often makes the Caribbean a “graveyard” for nascent tropical systems has generally subsided.
This week, Melissa will pass through some of the warmest waters ever recorded this late in the season in the Atlantic basin. On average across the Caribbean, the sea surface temperature was at least 0.5 degrees Celsius (0.9°F) warmer on Sunday, October 19, than in any year on that date except 2023 and 2024. as analyzed by Kim Wood of the University of Arizona.
Of human origin climate change has made current heat in the central Caribbean 500 to 800 times more likely, according to Climate Central’s Climate Change Index (see Fig. 2).
Where will Melissa go?
If Melissa followed the initial forecast According to the National Hurricane Center released Tuesday at 11 a.m. EDT, it would slow to move just south of Haiti over the weekend (and possibly beyond) while continuing to strengthen – a recipe for potentially devastating flooding and mudslides on southern Hispaniola. Poverty, government instability and deforestation have made Haiti extremely vulnerable to the kind of disaster Melissa could inflict.
That said, forecasting models are far from unanimous on Melissa’s future (see Fig. 3 below). Part of the problem is that the storm didn’t have a clear center until Tuesday. Now that Melissa is a true tropical storm, we may well see an increasing number of model agreements. However, it appears that steering currents will be weak and slow-moving storms can be a problem for even the best forecast models.
Until Tuesday morning, the European model continued to favor a slow westward trajectory, with most members of the European model ensemble keeping the system in the Caribbean at least until next Monday, October 27 (left side of Figure 3), although a substantial minority takes Melissa westward from Haiti. The (American) GFS model (right side of Figure 3) equally emphasizes that Melissa will turn north and leave the Caribbean, but its ensemble members differ sharply on when and where this turn will take place. THE Google DeepMind AI-powered modelwho has been one of the best on track this year, is also moving towards a possible turn north, but again with strong variations among ensemble members in terms of timing and location.
Intensity forecast for Melissa
Constant reinforcement seems to be a safe bet for Melissa over the next few days. The storm is engulfed in an unusually humid atmosphere: average relative humidity will rise from 70 to 75 percent Tuesday to 80 percent by Wednesday. Wind shear was moderate at 10 to 20 knots Tuesday afternoon and is expected to remain moderate to high for a few days. High pressures aloft are expected to develop over the Caribbean around this weekend, which would encourage them to strengthen.
In addition to unusually warm surface waters, the Caribbean currently has abundant ocean heat that extends to substantial depth, so even a slow-moving Melissa is unlikely to be greatly hampered by the churning of colder groundwater. NHC did not predict that Melissa would rapidly intensify over the next five days, but the 18Z Tuesday SHIPS model forecast predicted a 12% chance of a rapid intensification of 35 mph in 24 hours, and a 25% chance of a rapid intensification of 75 mph in 72 hours. That would put Melissa at Category 3 strength Friday afternoon, with winds of 125 mph.
If the predicted scenario of an “M” storm in October crossing the Caribbean, stopping, and turning north as a major hurricane sounds familiar, it should: This outcome would be remarkably similar to what we saw with Matthew in 2016. bmcnoldy.blogspot.com/2025/10/meli… #Melissa
– @bmcnoldy.bsky.social (@bmcnoldy.bsky.social.bsky.social) 2025-10-23T12:03:13.447Z
The dangers of late-season hurricanes in the Caribbean
Slow-moving, late-season systems gaining strength in the Caribbean can cause immense problems. In early October 2016, Hurricane Matthew moved north over far western Haiti as a Category 4 hurricane, dumping more than 20 inches (500 mm) of rain over much of far eastern Cuba and southwestern Haiti and striking the Bahamas and several other islands. Matthew claimed the lives of 731 people and caused more than $16 billion in damage (2016 USD).
A little over 20 years ago, Hurricane Wilma strengthened with astonishing speed to become a Category 5 monster in the northwest Caribbean. On October 18 and 19, 2005, Wilma carried out two all-time records for the Atlantic basin for rapid intensification, as the storm deepened from 975 to 892 millibars (hPa) in 12 hours and from 979 to 882 mb in 24 hours – the latter making Wilma the most powerful hurricane in terms of central pressure in Atlantic history. Wilma also set a record for the largest 24-hour increase in maximum sustained winds, from 75 to 175 mph. Wilma struck Mexico’s Yucatan Peninsula as a strong Category 4 storm and raced northeast to strike southwest Florida on October 24 with Category 3 strength. Wilma caused 52 deaths and caused $26.5 billion in damage (2005 USD).
Towards the end of October 1998, the old categories 5 Hurricane Mitch dumped gigantic amounts of rain on Guatemala, Nicaragua, and Honduras (30 to 40 inches, or 750 to 1,000 millimeters, in many areas) even as it decelerated and weakened, coming ashore at Category 1 strength. The floods and landslides caused damage of approximately $6 billion (1998 USD) and caused more than 11,000 confirmed deaths, with another 11,000 people missing. Mitch was the deadliest Atlantic hurricane in the era of satellite monitoring (i.e. since the 1960s), and perhaps since the Great hurricane of 1780.
This article was originally published by Yale Climate Connections.
