The One-Two Punch: here comes LAURA!

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’.

Image of the Indian Ocean as it appeared of 30 July 2020, populated by numerous storms, rain, and disturbed weather cells, which often generate weather impulses that cross the ‘horn of Africa’ and become tropical waves that in time may generate tropical cyclones in the Atlantic basin.

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.

Satellite image of LAURA in the central Gulf of Mexico on Tuesday 25 August 2020, already showing an eye as a Cat 1 hurricane as it continues to strengthen and move northwestward for potential landfall somewhere around Texas and Louisiana within the next 24-36 hours or so.

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.

Remote-sensing map showing the temperature of sea-surface waters. Notice the large area of rather warm waters, warmer than 31 C, extending from the northern Caribbean into most of the Gulf of Mexico. This image is based on data from Saturday 22 August as MARCO was on its final approach toward Louisiana.
Sea surface temperature map of the same region shown above, but based on data from 24 August. Notice how there is a large swath of cooler surface waters (around 26 to 28 C) where tropical cyclone MARCO tracked. This condition may be one of the factors influencing the westward shift in LAURA’s track.

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.

LAURA’s track (after NOAA) as forecasted on 08/25/2020 already showing the westward shift influenced at least partially by the pool of rather warm sea surface waters in that region of the Gulf.

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.

On 25 August 2020 the 9000 kilometer-long region from the ‘horn of Africa’ to the Cape Verde Islands was populated by at least five large tropical waves making their trek westward toward the gate to ‘hurricane alley’ and beyond just as the 2020 Atlantic Hurricane season had already began what historically has been the period of peak activity. There are plenty of seeds for potential cyclogenesis in this picture indeed!

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!

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