Tropical Storm Laura formed on Friday morning just northeast of the Lesser Antilles, one of two tropical cyclones forecast to slowly intensify into hurricanes by early next week and swirl in the unusually warm waters of the Gulf of Mexico.

Forecast guidance from computer models and other sources suggest two hurricane landfalls are possible along the Gulf Coast beginning on Tuesday, with the possibility that the storms could interact in some way, depending on their size.

These are the latest developments in what’s already been one of the busiest Atlantic hurricane seasons to date.

Tropical Storm Laura marks the earliest-forming L storm on record, beating out Tropical Storm Luis, which formed on Aug. 29, 1995. The season has also featured the earliest-forming C, E, F, G, H, I, J and K storms on record.

Tropical Storm Laura is forecast to meander west-northwest during the next few days, toward the Bahamas and Florida.

Tropical storm warnings have been issued in Puerto Rico, the U.S. Virgin Islands, the northern Leeward Islands and the southeast Bahamas, where tropical storm conditions could arrive as early as Friday night.

A second disturbance, Tropical Depression 14, may eventually earn the name Marco. It is located just offshore of northeastern Honduras and will drift northwestward and bring heavy rain and possible flooding to the Yucatán Peninsula before reemerging over the Gulf of Mexico. It then could intensify into a hurricane, but there is considerable forecast uncertainty.

If both systems reach or maintain hurricane strength in the Gulf of Mexico simultaneously, it would be the first time this has happened in the satellite era. While there is precedent for a hurricane and a tropical storm or two tropical storms to have occupied the basin contemporaneously, there have never been two hurricanes there at the same time.

It is not out of the question that Laura becomes a more significant hurricane, given more favorable conditions in the bathtub-like waters of the eastern Gulf, compared with Marco’s path that may run into strong winds in the upper atmosphere. The pair of cyclones could end up in close enough proximity to affect one another, interacting in ways that will complicate both path and intensity forecasts.

Tropical Storm Laura

The leading edge of Laura’s mass of thunderstorms began moving into the northern Leeward Islands at midday on Friday, and rains could arrive in eastern Puerto Rico during evening. A tropical storm warning has been issued for the island, as has a flash flood watch, where a widespread 3 to 6 inches of rain could lead to pockets of flooding and isolated mudslides.

“There is a high risk for flash flooding across the local islands, as well as mudslides in areas of steep terrain,” wrote the National Weather Service in San Juan. “Some main rivers may overflow their banks.”

Present data indicate Laura’s center is slightly farther south than originally believed, making the system more likely to have a direct impact on Puerto Rico through Saturday evening.

Tropical storm warnings are also up for the northern Leeward Islands, southeast Bahamas, the Virgin Islands and Turks and Caicos.

Over the weekend, Laura will lash Puerto Rico before continuing west-northwest and sweeping through many of the Bahama islands. It is forecast to thread the needle between Cuba and the Florida Keys early Monday, emerging into the Gulf and reaching hurricane strength.

However, its strength will depend heavily on the extent to which it interacts with land. More time spent over land will weaken the system.

Its southward tendency could increase the likelihood of it being weakened or even partially shredded by the high terrain of Hispaniola.

“For now, we will assume that the northern part of the circulation will remain over water so that the system will not be too disrupted by Hispaniola and Cuba,” the Hurricane Center said in an online forecast discussion.

Gulf of Mexico water temperatures are extremely warm, particularly in the eastern Gulf, and upper-level winds are likely to be favorable for strengthening. Storm intensity forecasts are highly uncertain, especially this far in advance, and it is not outside the realm of possibility that Tropical Storm Laura becomes a major hurricane of Category 3 or above by Tuesday.

The approximate timing of then-Hurricane Laura’s eventual landfall somewhere in the central or eastern Gulf would be late Tuesday or Wednesday morning, according to current forecasts.

Similarly, it is also possible the storm remains relatively weak.

Tropical Depression 14, soon-to-be Tropical Storm Marco

Tropical Storm Laura is one of two disturbances to watch. The second, Tropical Depression 14, was located off the northeast tip of Honduras. It could bring heavy rain and potential flooding to portions of Honduras, northern Nicaragua, Belize, and the Yucatán Peninsula of Mexico during the next two days before drifting northwestward over the Gulf early Sunday.

On satellite, Tropical Depression 14 lacks extensive shower and thunderstorm activity, indicating a relatively weak system. The storm had, however, acquired a more well-defined center, which is a prerequisite for intensification.

The National Hurricane Center found more than one low level center in the storm during a Friday morning reconnaissance flight, which indicates a relatively disorganized storm. “There are likely multiple low-level swirls rotating around a common center,” forecasters said.

The lack of this storm’s organization makes it tricky for computer models to reliably simulate what will happen in the future, since it is hard for them to capture the initial center of the storm.

By Sunday evening, the center of Tropical Depression 14, likely to be named Tropical Storm Marco by then, is forecast to pass over the Gulf again and resume strengthening.

“After some weakening while over the Yucatán Peninsula, re-intensification is likely to occur over the central Gulf of Mexico,” the NHC wrote.

A hurricane watch has been issued from Punta Herrero to Cancun, Mexico, while a tropical storm warning is also up for there and the Bay Islands of Honduras. Tropical storm watches stretch from north and west of Cancun to Dzilam de Bravo, Mexico.

Marco is then forecast to approach the northwestern Gulf Coast near hurricane strength on Monday or Tuesday, but it is highly uncertain how strong eventual Marco will be at that point. While water temperatures could support quick strengthening, increasingly disruptive upper-level winds will be acting to weaken the storm.

“This forecast remains highly uncertain,” notes the Hurricane Center, “and users are urged to continue monitoring changes to this forecast.”

Two storms in the Gulf: here’s what that means.

Having two tropical cyclones in the Gulf of Mexico is rare. And for two hurricanes to be there at once is unheard of. There have been instances of multiple tropical storms or a combination of a tropical storm and a hurricane in the Gulf together, but never twin hurricanes.

Having two systems in the Gulf of Mexico simultaneously would open up a meteorological can of worms for forecasters, since when tropical cyclones near one another they can start to interact in ways that are hard to anticipate:

  • If they draw close enough, for example, they could dance around a common center. That is known as the Fujiwhara Effect.
  • It is even possible that the circulation around one storm would delay the arrival of the other, possibly allowing a storm like Marco to have more of an opportunity to intensify over the warm Gulf waters before moving inland.
  • There is also a chance that the United States could hurricane see landfalls on three consecutive days if Laura moves over the Florida Keys, soon-to-be Marco arrives in the Northwest Gulf, and then Laura makes a second landfall in the northeastern Gulf.

Suffice to say, it is going to be a very busy and perilous week ahead. Coastal residents are being advised to make preparations to shelter in place from wind impacts, and evacuate from vulnerable coastal locations should such steps be necessary.