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 Hurricane 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