As of Sunday evening, two named storms were gaining strength as they swept across the Gulf of Mexico and toward the coastal states of Louisiana, Mississippi, and east Texas. Upgraded from a tropical storm to a Category 1 hurricane on Sunday afternoon, Hurricane Marco is expected to make landfall along the Mississippi River delta at some point on Monday. Tropical Storm Laura, which has already battered Haiti and the Dominican Republic with heavy rainfall and high winds, is expected to intensify as it moves further into the Gulf. It is expected to reach Category 1 level — with winds ranging from 74 mph to 94 mph — late on Tuesday, and is expected to reach Category 2 by the time it makes landfall between east Texas and Mississippi on Wednesday or early Thursday.
With some of the largest groups of wildfires to ever hit California still largely uncontrolled in the West and a pandemic still killing over 1,000 Americans on many days this month, below is everything we know about the storms and how they will affect the crises already at hand in the Gulf.
Where are the storms and where are they going?
The weather system over the Gulf is already creating some alarming conditions:
Both storms are expected to make landfall somewhere between Louisiana and east Texas within a 48-hour period this week, and both Mississippi and Louisiana have declared states of emergency. Compared with predictions on Saturday, the track forecast for Laura has shifted west, increasing the threat for western Louisiana and eastern Texas, and decreasing but not eliminating the threat for New Orleans. Houston should pay particular attention to Laura.
Long sections on the coasts of both states are expected to experience significant storms urges, which may be as high as four to six feet in the 180-mile range between Morgan City, Louisiana, and Ocean Springs, Mississippi — a coastal region that includes New Orleans. Storm surges, which often cause the greatest damage in severe weather events, could be particularly dangerous if Laura and Marco hit the same place on the map, as water levels may spike back up just as the first wave is subsiding.
Is it common to have two storms at the same time?
No. As the Washington Post notes, if both storms maintain the windspeed to qualify as hurricanes at the same time, “it would be a first in more than a century and a half of record-keeping.”
Due to the warming of the oceans, climate change is already making hurricanes, cyclones, and typhoons — which are all the same category of storm, just in different parts of the world — both more frequent and more dangerous. Laura and Marco are the earliest occurring “L” and “M” storms in the Atlantic on record, in a hurricane season that has been twice as active as the average year.
Is it possible for two hurricanes to form into one?
If Laura and Marco were to collide — though the timing suggests it would be unlikely — it would decrease the power of both storms. Such interactions are governed by the Fujiwhara Effect, explained in a recent post by meteorologist Jack Sillin:
Thankfully, any worries about the two storms merging into a “super-hurricane” are unfounded. When tropical cyclones arrive in close proximity to another tropical cyclone, the interaction is detrimental for both storms. The reasons for this are twofold: destructive interference of low-level circulations and increase in upper-level wind shear. This is particularly true when one storm is much stronger than the other …
In the lower levels of the atmosphere, two circulations spinning in the same direction near each other will “cancel each other out” where they meet. In this case, over the Gulf of Mexico south of central Louisiana, [Marco’s] circulation wants to produce southerly winds and [Laura’s] circulation wants to produce northerly winds. The net result is almost no wind. If there’s no wind, the cyclones can’t access heat and moisture from that part of their circulation.
How could the storms affect the economic and public-health crises in the Gulf?
“It should not be lost on any Louisianan that in addition to twin tropical weather threats, we still have to deal with the COVID-19 pandemic,” Governor John Bel Edwards said on Saturday. “COVID-19 does not become less of a threat because of tropical weather.” Indeed, there is the danger that the exposure of weather events like hurricanes in the East and fires in the West could increase the spread of COVID-19, if large groups of people are forced to gather without proper distance or personal protective equipment.
Thankfully, in the past few weeks, Louisiana’s summer surge of cases has slowed down. In early August, infections grew to over 3,000 per day, while last Friday marked the fifth consecutive day in which the state counted fewer than 1,000 new cases. Mass sheltering is not normally required in Louisiana for hurricanes weaker than a Category 3, though state officials have said that if it is required, families will stay together within large shelters and PPE will be provided. While daily caseloads are down, evictions are expected to go up, with the 30-day extension of the CARES Act’s eviction moratorium expiring on Tuesday.
As for the unprecedented challenge of the back-to-back storms, “the first 72 hours is on you,” Governor Edwards said on Saturday. “That is because the second storm comes in so close that there may not be much of a window when we can fly search-and-rescue helicopters, when we can get out with high-water vehicles, and those sorts of things.”