Hurricane season: Tropical waves being watched as lull may be ending

The Atlantic Hurricane Basin has been remarkably quiet for weeks now, in what was widely considered to be an extremely hyper-active season. In fact, 2024 marks the first time since 1997 that not a single tropical system was named from August 21st to September 2nd, which is the start of peak hurricane season. So far, five storms have been named this season, with Beryl becoming the earliest category five hurricane on record in the Atlantic Basin.

Several factors have led to this downturn in activity including high levels of Saharan dust moving off the African coast, an unexpectedly high and persistent level of wind shear and potential tropical waves moving over cooler waters near the African coast. Cooling near the African coast has been stronger than usual in July and August and may have contributed to the lull. This cooling has weakened, however, heading into September. Tropical waves have moved off the African coast north of the Cape Verde islands, over generally cooler waters.

North Atlantic sea surface temperatures as of September 1st. Note the cooler waters off the northern African coast as opposed to farther south, near the Cape Verde islands:

Photo byUniversity of Maine

With that said, conditions are turning more favorable for gradual development of tropical systems. Saharan dust clouds usually begin to wane late in the summer, and that appears to be the case for this year as well. Wind shear, however, remains on the stronger side, but is expected to weaken as September continues along.

This gradual reactivation in the hurricane season can be seen as the National Hurricane Center is currently tracking three disturbances, both with the potential for gradual development over the next week. None of these disturbances have an immediate threat of developing as all have a 0-10% chance of development within the next 48 hours as of Tuesday morning.

National Hurricane Center 7 day tropical outlook as of Tuesday morning:

Photo byNational Hurricane Center

1. The system to the south of the Antilles Islands is expected to move over the Yucatan Peninsula late this week or this weekend. Enough development may occur by that time for a tropical depression to form by the weekend. The National Hurricane Center currently gives this storm a 40% chance of development in the next week. Any storm that forms could impact the Eastern Mexican coast and/or the western Gulf Coast.

Satellite image of the disturbance near Hispaniola as of Tuesday morning:

Photo byWindy.com

2. This disorganized system may be able to become a bit better organized over the next couple days. This storm is expected to encounter conditions that become less favorable for additional development quickly. This storm has only a 10% chance of development and will not impact land. 

3. This tropical wave off the African coast will be entering an area more favorable for gradual development in the coming days. A tropical depression could form late this week while the storm moves west-northwestward or northwestward. This system currently has a 40% chance of developing within the next week.

Early indications favor this system remaining out to sea, as is the case with many tropical disturbances in this position. Notice that this disturbance is south of the Cape Verde islands, which is where the warmer sea surface temperatures are located. If this trend continues with tropical waves moving farther south, it would favor more storm development nearing the peak of hurricane season.

Satellite image of the disturbance off the African coast as of Tuesday morning:

Photo byNational Hurricane Center

Heading into the late summer is when Cape Verde systems become likely to form. These storms are ones that begin to develop near the Cape Verde islands off the African coast. These storms typically slowly move over the open Atlantic in a west-northwest direction.

These storms are often steered north and west due to a large semi-permanent area of high pressure over the Atlantic. Though the exact track of specific storms depend on various other factors as well. To be clear, this is not a specific forecast for the current wave off the African coast, it’s a general idea of a kind of system that can form later in the season, near the season’s peak.

Photo byNew England Storm Center

While these systems often turn to the north, they can continue southward into the Caribbean. Hurricane Beryl in July is an example of a Cape Verde hurricane that eventually dove into the Gulf of Mexico.