Toward the end of July, as it tends to happen during the summer months in the northern hemisphere, the northern Indian Ocean was boiling with numerous storms, disturbed weather cells and rather warm surface waters. This cauldron of bad weather generates pulses of storms toward the ‘horn of Africa’ which then feed into the “tropical wave assembly line” over Equatorial Africa. Typically these tropical waves move west and emerge over the waters of the East Atlantic, south of the Cape Verde Islands. Many of these Cape Verde waves, but not all, continue traveling west along a corridor leading to the Caribbean and the Antilles known as ‘hurricane alley’.
In my opinion, two of such weather impulses crossed into Equatorial Africa in late July – early August, traversed Equatorial Africa, in the process morphing into Cape Verde tropical waves that eventually were the genesis of tropical cyclones LAURA and MARCO. Quite a journey indeed, roughly 22000 kilometers from where they started to were they ended up in about four weeks. Ah, the powers of Mother Nature on display!
MARCO was an interesting tropical cyclone as it rapidly intensified once it had entered the Gulf of Mexico, fueled by rather warm surface water and plenty of accumulated heat content, but on the other hand battling against moderate to strong wind shear and various features of the ocean-atmosphere environment that caused much of its convection to shift to the northeast of the center of circulation and its rapid decay as it approached the Louisiana coastline. Eventually MARCO did a disappearing act under pressure from the forces of Nature, and it appears it may not have even made landfall before it became just the remnants of a cyclone and moved west along the Louisiana and Texas coastline. Not really a spectacular ending after such a remarkable journey from half a way around the world.
Now we have LAURA, in the Gulf of Mexico this Tuesday 25 August 2020, rapidly strengthening to hurricane strength and already showing an eye in satellite imagery. It is interesting to note that when LAURA approached the northern Leeward Islands the model consensus had it tracking north of the big islands of the Antilles toward southern Florida and possibly the eastern Gulf of Mexico. Over time, under the influence of features in the ocean-atmosphere environment and, in my opinion, and the influence of the track of MARCOS cutting across the Gulf, LAURA began shifting its own track southward and then westward until arriving at its current position in the central Gulf. LAURA is tending to move toward the northwestern Gulf where the warmest surface waters remain after MARCO cut a swath through the central Gulf, which caused an upwelling of cooler waters.
LAURA and MARCO have provided a rich field to study how two tropical cyclones in relatively close proximity, traveling in tandem over thousands of kilometers, may have influenced each others tracks and intensities over time. We will have top wait until full complete reports on both cyclones are available to determine what or how much of a mutual influence was actually present, but in my opinion and only empirically speaking it is had not to conclude there has been some degree of influencing between the two storms.
All that remain is for LAURA to continue its approach to land in the northwestern Gulf and see if it may become a major hurricane as it draws energy from the heat content of the ocean and travels to a generally favorable ocean-atmosphere environment. We will soon find out.
While we continue monitoring LAURA’s progress toward its eventual landfall, and pose questions about the rather interesting interaction among LAURA and MARCO, we would do well to keep our eyes on hurricane alley, the Cape Verde Island region and equatorial Africa where the tropical wave assembly line is already populated by menacing cells of disturbed weather making their way west.
There is no question in my mind that we have already learned quite a bit from witnessing the tandem performance of the one-two punch of LAURA and MARCO. While we mull these initial lessons and ponder the myriad questions that remain, let us consider the 55% that remains of the 2020 Atlantic Hurricane season still ahead. Let us remain alert. Be prepared. MITIGATE!