Marco became a hurricane Sunday afternoon in the Gulf of Mexico, while Tropical Storm Laura continued to produce heavy rainfall and life-threatening flash flooding over the Dominican Republic and Haiti. Both storms are expected to graze the Sunshine State with their outer bands Monday, when heavy rain, gusty winds, and rough seas are possible in the Florida Keys and across the Florida Panhandle.
Tropical Storm Laura strengthened a bit Sunday morning, and as of 2 pm Sunday, was located 55 miles south of the eastern tip of Cuba and had winds up to 50 mph. Land interaction from the Greater Antilles is still expected to hinder any significant strengthening of the tropical storm through Monday, but thereafter Laura is likely to become a hurricane in the Gulf of Mexico on Tuesday.
While the center of circulation is expected to remain to the south of the Sunshine State, periods of heavy rainfall and gusty winds are possible across the Florida Keys and extreme South Florida Monday, where a Tropical Storm Watch remains in effect. Isolated tornadoes or waterspouts will also be possible with some of the rain bands, beginning early Monday near Key West, then spreading into much of Southwest Florida Monday afternoon.
How widespread and strong the rain bands become will depend on the how close Tropical Storm Laura tracks, in addition to which side of the storm most of the thunderstorm activity will be weighted on. As of Sunday afternoon, the strongest activity was favoring the southern half of Laura's circulation, but this could change as it interacts with the mountains over Cuba. Regardless, residents and visitors to the Florida Keys are encouraged to bring in loose outdoor items and avoiding coastal areas due to rough seas and strong rip currents from Tropical Storm Laura.
Before Tropical Storm Laura enters the Gulf of Mexico Monday night, Hurricane Marco will likely be approaching Louisiana. As of midday Sunday, Hurricane Hunters found the season's third hurricane to be located 280 miles south of the mouth of the Mississippi River. Maximum sustained wind speeds were near 75 mph with a forward movement to the northwest at 14 mph. The hurricane is anticipated to make landfall along the Louisiana coastline early Monday afternoon. A Hurricane Warning and Storm Surge Warning are in effect for coastal portions of Louisiana and Mississippi.
Marco does not pose an immediate threat to the state of Florida, but strong upper-level southwesterly winds are likely to pull some related hazards far enough to the northeast of its track to influence the weather over much of the Florida Panhandle. A Coastal Flood Advisory is in effect for Escambia, Santa Rosa, and Okaloosa Counties, and a High Surf Advisory extends east to include the rest of the beaches along the Emerald Coast to Panama City and Apalachicola. In these areas, minor beach erosion and flooding will be possible - especially at times of high tide - from a potential water inundation of 1 to 3 feet.
Periods of rain from the outer bands of Hurricane Marco will also be possible across the Florida Panhandle and the Gulf Coast of the peninsula on Monday. However, the extent, duration and intensity of these bands remains uncertain due to some lingering uncertainty of Marco's forecast track and the interaction it may have with Tropical Storm Laura to its southeast. Similar to Laura's potential risks for minor wind damage near the Florida Keys, the strongest cells associated with Hurricane Marco might also produce wind gusts up to 50 mph and pose an isolated tornado risk on Monday.
Neither Laura or Marco are expected to bring significant impacts to Florida this week, but the peak of hurricane season is just beginning for the North Atlantic basin. Mid-August through late October is generally when the Atlantic experiences a dramatic increase in tropical cyclone frequency and strength. Thirteen named tropical systems have already developed in the Atlantic this year, compared to the yearly average which is twelve. Normally the twelfth named storm forms at the end of hurricane season in November, and there is no average date for the thirteenth named storm since a normal hurricane season does not typically see more than twelve named systems.