Tropical Storm Melissa has not strengthened in its first two days over the central Caribbean, but this lopsided, ungainly storm is still expected to evolve into a dangerous major hurricane by early next week. As of midday Thursday, the National Hurricane Center was predicting that Melissa would reach hurricane strength by Friday night, becoming a major hurricane by Sunday and a Category 4 storm by Monday.
Stranded by weak steering currents, Melissa now appears likely to drift west to northwest over exceptionally warm water just south of Jamaica, eastern Cuba, and Haiti, likely dumping torrential rain for days on end and posing an increasingly serious flood and mudslide threat.
As of 11 a.m. EDT Thursday, Melissa’s low-level circulation was centered was about 220 miles (325 kilometers) southeast of Kingston, Jamaica, crawling north-northwest at a mere 2 mph (4 km/h). Melissa’s top sustained winds had actually decreased to 45 mph (75 km/h), focused mainly north and east of its center. Melissa’s disheveled, asymmetric structure is the result of high wind shear of 20-25 knots. Melissa is tilted with height, with its upper-level center visible as an area of spin just south of Haiti, well northeast of the surface center.
Showers and thunderstorms have been scattered in intense clumps, focused mainly toward the eastern side of Melissa’s broad, tilted circulation. Thus far, Melissa’s heavy rains have been mostly confined to the ocean. A personal weather station in southwestern Haiti recorded 0.79 inches of rain over the 3-day period ending at 11 a.m. EDT Thursday; a personal weather station in northeastern Jamaica recorded 1.82 inches during the same time span.
A critical forecast challenge: Melissa’s long-term track
Melissa and its precursor disturbance (Invest 98L) have been an unusually tough challenge for forecasters as well as the models they rely on. At first, when Melissa was still Invest 98L, the lack of a defined center was the main problem. Yet even with Melissa now established, the storm’s quirky structure and the weak steering flow has made its future devilishly tough to pin down. The biggest forecast fail has been with the GFS model, often a leading performer among longer-range track models. For days, the GFS has insisted on a sharp northeastward turn that’s never materialized, since the model expected wind shear to be lower, allowing the storm to organize and feel the steering currents attached to a trough of low pressure over the Bahamas.
In contrast, the European model has relentlessly predicted Melissa to stay weak and move slowly west across the central Caribbean, delaying any big northward turn till early next week. Many of the ensemble members from the Google DeepMind model, and even a substantial number of GFS ensemble members, have come around to this idea as well.
There’s still high uncertainty over whether the eventual projected turn would bring Melissa onshore in eastern Cuba, Jamaica, or Haiti. However, there’s now growing confidence that Melissa will inch northward through Friday and then westward, likely moving near or just south of Jamaica through the weekend before cutting north, as depicted in the five-day track forecast issued Thursday morning by the National Hurricane Center.
An increasingly ominous setup for widespread flooding
Unfortunately, the consensus track outlined above would bring several days of relentless torrential rains across the area north of Melissa. The three-day rainfall forecast issued Thursday by the National Weather Service already depicts widespread amounts of 4 to 12 inches (100-300 millimeters) across eastern Jamaica and southern Hispaniola. Heavy rains could easily extend beyond that period til at least Tuesday – particularly across Jamaica, where precipitation totals from multiple models suggest that storm totals exceeding 24 in (610 mm) and localized amounts above 30 in (762 mm) are quite possible. Depending on Melissa’s exact track and strength, catastrophic flooding will be a very real possibility in one or more of these areas. Although the Cayman Islands lie to the west of Melissa’s expected path, they may experience significant flooding rains early next week as well.
Satellite imagery midday on Thursday hinted that the wind shear preventing Melissa from aligning vertically and intensifying was lessening, as heavy thunderstorms were beginning to form more symmetrically around the center. Wind shear is predicted to be in the moderate range, 10-15 knots, through early next week. Such a trend would allow for more rapid strengthening and organization of Melissa’s core of showers and thunderstorms (convection) and the surrounding rainbands.
Apart from wind shear and any direct interaction with the rugged landscape of Jamaica, Cuba, and Haiti, Melissa has the potential to intensify dramatically given the near-record warm waters it will be traversing.
The Caribbean’s average sea surface temperature of around 30 degrees Celsius (86 degrees Fahrenheit) is the third warmest on record for late October, just barely beaten by slightly warmer readings in 2023 and 2024. Moreover, oceanic heat extends to great depths across the central and northwest Caribbean, which allows a slow-moving storm to strengthen without pulling up chillier water.
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