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, the influence of MARCOS’ track 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, causing 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 hard 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 between 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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The Gulf Waters are Hot!

Today is Saturday 23 August 2020 and there are two tropical cyclones, LAURA and MARCO in action basically chasing each other. These named-storms started their respective journeys around 4 August as tropical waves generated over equatorial Africa moving west toward the far east Atlantic, south of the Cape Verde Islands.

LAURA five-day track as of 08/23/2020
MARCO five-day track as of 08/23/2020

By 7 August one of these tropical waves had emerged over the waters of the east Atlantic to travel west along ‘Hurricane Alley’, followed three days later by another tropical wave taking the same route toward the Lesser Antilles and the Caribbean beyond.

On 11 August two tropical waves traveling west along ‘Hurricane Alley’, in the general direction of the Lesser Antilles and the Caribbean beyond, would eventually become the seeds for LAURA and MARCO the 12th and 13th named storms of the 2020 Atlantic Hurricane Season.

While the first of these two tropical waves brushed past Barbados and entered the Caribbean aiming toward Central America to eventually become Tropical Depression #14, the one following behind became Tropical Depression #13 mid-way along Hurricane Alley aiming toward the Leeward Islands.

On 21 August TD #13 became Tropical Storm LAURA near the northern Leeward Islands and the Virgin Islands on a track that would take it to the open Atlantic north of the major islands of the Antilles toward Florida and the Gulf of Mexico. Some twelve hours later, also on 21 August, TD #14 became Tropical Storm MARCO as it brushed near Cabo Gracias a Dios (“Cape Thanks God”) and the Nicaragua/Honduras border, the same cape that Columbus named in 1502 after outrunning and escaping another Caribbean tropical cyclone.

In the early morning of Sunday 23 August 2020 Tropical Storm LAURA is over the island of Hispaniola moving west-northwest toward Cuba and the Gulf of Mexico, while Tropical Storm MARCO is in southeastern Gulf moving north-northwest toward Louisiana and neighboring states. (Satellite image courtesy of NOAA GOES-East 08/23/2020 at 0500 DST)

It is of interest to note that the tracks of both these tropical cyclones had shifted over the previous day or so toward what could be characterized as a converging common line aiming at the central Gulf of Mexico where surface water temperatures are quite hot at close to 31 Celsius (~88 F), in the general direction of Louisiana. It is clear that these storms are influencing each other as they grapple with a complex ocean-atmosphere environment involving various features in addition to moderate to strong wind shear and surrounding dry air. It is also clear that the warm waters of the Gulf and the accumulated heat content are acting as a magnet for both LAURA and MARCO, and may eventually contribute to their potential strengthening into hurricanes before landfall in coming days.

Remote sensing map depicting sea surface water temperatures on 22 August 2020. Notice the colors of the water in the northern Caribbean and the Gulf of Mexico indicating temperatures ranging from 31 to near 34 Celsius (88 to 93 F).

We will soon have the initial reports of damage from the Leeward Islands, the Virgin Islands, Puerto Rico, Dominican Republic, Haiti, Cuba, Jamaica, Nicaragua, Honduras, Belize, the Yucatan Peninsula of Mexico, and eventually from the USA Gulf states affected by either or both LAURA and MARCO. It will be interesting to learn what effect the hot waters of the Gulf ended up having on the intensity and tracks of these tropical cyclones. While we anticipate those initial reports and the eventual after-action full reports, I believe it is remarkable to think that LAURA and MARCO have been active for almost three weeks already, and to imagine that they may have been in motion for much longer than that because it is quite possible that they started as weather impulses a week or two earlier over the Indian Ocean, which moved west over the horn of Africa to become rain storms or thunderstorms, and eventually morphed into the tropical waves that initiated their journeys as summarized here.

There is no question that the 2020 Atlantic Hurricane Season has been quite active so far. It started early, in mid-May, and has already generated 13 named tropical cyclones, five of these in the first three weeks in August as we come upon the 28th anniversary of Hurricane ANDREW (1992), which was the first named-storm of the 1992 Atlantic season. And to think that 55% of the 2020 season is still ahead. So there will be plenty of activity over the next three plus months. Let’s see what lessons Mother Nature has in store for us regarding cyclogenesis!

Elsewhere in the northern tropics, Typhoon BAVI is tracking some 250 kilometers northeast of Taiwan aiming for the Korean Peninsula. Closer to our neck-of-the-woods we are monitoring a cell of disturbed weather, in the northeaster Pacific, 275 kilometers south of Puerto Angel in the State of Oaxaca, Mexico, and another one approximately 1500 kilometers southeast of the Big Island of Hawaii in the central Pacific. Both of these disturbances show potential for further development.

Despite the rather active Atlantic Hurricane season, overall the rest of the northern tropical basins for cyclogenesis have been somewhat quieter than what has been usual over the past few years. In the Atlantic basin itself we have had a lot of activity, but very few hurricanes. I will venture the opinion that global warming and other climate factors or effects are raising the threshold for cyclogenesis to occur. We would need to conduct a comprehensive comparative analysis of past hurricane seasons to determine if this is indeed the case, but in my opinion it is something to consider.

For all of those that may be affected by what remains of the 2020 Atlantic Hurricane Season, please remain alert. Be prepared. MITIGATE!

Posted in Cyclogenesis, Flooding, Hazard Mitigation, Hazards, Hurricanes, Storm Surge, Tropical Cyclones, Tropical Depression, Tropical Storm, Tropical Wave, Typhoon, Weather | Leave a comment