Hurricane Marco (2020)

Hurricane Marco was the first of two tropical cyclones to threaten the Gulf Coast of the United States within a three-day period, with the other being Hurricane Laura. The thirteenth named storm and third hurricane of the record-breaking 2020 Atlantic hurricane season, Marco developed from a fast-moving tropical wave west of the Windward Islands and south of Jamaica on August 20. The fast motion of the wave inhibited intensification initially, but as the wave slowed down and entered a more favorable environment, the system developed into a tropical depression, which in turn rapidly intensified into a strong tropical storm. Due to strong wind shear, Marco's intensification temporarily halted; however, after entering the warm waters of the Gulf of Mexico on August 23, Marco briefly intensified into a hurricane, only to quickly weaken later that evening due to another rapid increase in wind shear. Marco subsequently weakened to a tropical depression before degenerating into a remnant low early on the next morning. Marco's remnants subsequently dissipated on August 26.

Heavy rains across the Yucatán Peninsula caused river rises and flooding throughout the region. One person was indirectly killed in Comitán, Mexico, due to the storm, although this was not included in the official toll. Impacts in the United States were generally minor, as the storm was quite weak when it impacted the Gulf Coast.

Meteorological history

At 00:00 UTC on August 16, the National Hurricane Center (NHC) began monitoring a westward-moving tropical wave over the Central Atlantic that had the potential for development. The disturbance quickly moved westward at a speed over , which initially limited its development as it passed through the Windward Islands and into the Caribbean Sea. The system slowed down and gradually organized south of the Greater Antilles on August 19. By 15:00 UTC on August 20, satellite imagery revealed that the wave had developed a well defined low-level center, prompting the NHC to designate it ''Tropical Depression Fourteen''. Post-storm analysis found that the system formed nine hours earlier at 06:00 UTC. At the time the system was located east of the Nicaragua–Honduras border. The storm continued westward toward Honduras, before making a sharp turn northward. Despite favorable conditions, the storm initially failed to intensify, with pulsing convection around a poorly defined center. Eventually, the storm's center became better defined and a small but persistent cluster of convection formed over it. This allowed the depression to intensify, and the NHC upgraded the system to ''Tropical Storm Marco'' in the northwest Caribbean at 03:00 UTC on August 22. This was the earliest 13th named storm ever recorded in the Atlantic basin, breaking the record set by Maria of 2005 by 11 days.

Shortly after being named, Marco continued to contradict the forecasts and followed a more northerly course. As it was a small system, Marco was able to strengthen quickly, reaching its initial peak intensity of and just 12 hours after being named, with an almost closed eyewall being observed by Hurricane Hunters. Contrary to prior predictions, Marco's track was shifted eastward at the 21:00 EDT advisory on August 22, as the system moved north-northeastward instead of north-northwestward, introducing the possibility of successive landfalls around Louisiana from both Laura and Marco. An increase of southwesterly wind shear brought an abrupt end to the strengthening trend, as Marco moved through the Yucatán Channel, with the storm's minimum central pressure rising slightly and the eyewall mostly dissipating as the storm took on a sheared appearance. This weakening period proved to be short-lived, as the shear relaxed somewhat when Marco moved into the warm waters of the Gulf of Mexico on August 23. Slow but steady strengthening resumed and data from another Hurricane Hunter reconnaissance aircraft discovered sustained winds at hurricane strength in the northeastern eyewall. Subsequently, an update from the NHC confirmed that Marco had intensified into a Category 1 hurricane at 16:30 UTC on August 23. It then reached its peak intensity at 21:00 UTC, with 1-minute sustained winds of and a minimum central pressure of .

This strengthening proved to be short-lived, however, as upper-level wind shear increased again over the storm. This caused Marco to weaken back to a tropical storm by 03:00 UTC on August 24, and the center of circulation became displaced from the storm's convection. Relentless wind shear continued to plague the system as it turned westward near the Louisiana coastline, and Marco rapidly weakened to minimal tropical storm strength by 18:00 UTC. At 23:00 UTC on August 24, Marco passed just south of the mouth of the Mississippi River, with 1-minute sustained winds at and a central pressure of , although the strongest winds were displaced in convection that was over waters well northeast of the storm's center. Operationally, the NHC said that the storm made landfall here, but that was changed in post-storm analysis. Afterward, Marco weakened further and fell to tropical depression intensity just offshore of Louisiana, near Grand Isle, at 03:00 UTC on August 25, before degenerating into a remnant low three hours later. The remnant low continued to spin down as it slowly moved westward along the Louisiana coastline, ahead of the approaching Hurricane Laura, before opening up into a trough at 00:00 UTC on the next day.

Preparations

Honduras issued tropical storm watches along its coastline when ''Tropical Depression Fourteen'' was designated, before quickly upgrading to warnings just hours later. Tropical Storm Watches, and later Tropical Storm Warnings and Hurricane Watches, were also issued for the eastern side of the Yucatán Peninsula, as the storm was first predicted to move over the peninsula as a strong tropical storm. When Marco moved to the north instead of northwest, a Tropical Storm Warning was issued by the Government of Cuba for the Pinar del Río Province and the Isle of Youth.

Tropical Storm, Hurricane, and Storm Surge Watches were issued in Louisiana, Mississippi and Alabama when Marco's forecast track shifted significantly eastward on August 22. Many of these watches were upgraded to warnings as the storm continued its approach. In Mississippi, mandatory evacuation orders were in place on August 23 at the Gulfport and Biloxi marinas and the harbor in Long Beach. All boats were ordered to be moved by sundown that same day. In Gulfport, the fuel dock was closed. However, all the warnings were eventually downgraded and cancelled when the storm rapidly weakened as it approached the coast. A tornado watch was issued for Far Southeast Alabama, the Florida Panhandle, Southwest Georgia, and the Coastal Waters at 20:40 UTC on August 24.

Impacts

Latin America and Cayman Islands

The Instituto Meteorológico Nacional

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