The warning covers the MS and Alabama coast, from the mouth of the Pearl River to the Florida-Alabama border, the National Hurricane Center said.
At Lowdermilk Park, the beach was almost empty despite there being no signs of red tide.
Schools in parts of coastal Louisiana, Alabama, Florida and MS were closed Tuesday, and others announced they would open for only part of their normal day.
Police advised beach-goers to stay indoors. This will mean some flooding possibilities for Gulf Shores, Orange Beach, and the Mobile area. It is possible these totals need to be increased further north into parts of Alabama, Mississippi, and Arkansas-this is heavily dependent upon the track of Gordon.
Pat Landry, who owns the Landry House bed and breakfast on Louisiana's Grand Isle, said late Monday night that he was trying to pick up everything low in the yard in preparation for the storm surge expected with Gordon's arrival.
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Strong winds brought down one company's storage facility in Shiga Prefecture, killing one man, according to local media. Television footage showed high waves crashing into breakers and flying debris in areas where the storm made landfall.
Gordon was located about 450km east-southeast of the mouth of the Mississippi River and was packing maximum sustained winds of 100km/h, the Miami-based weather forecaster said.
A hurricane watch - meaning that hurricane conditions are possible - was put into effect for the area stretching from the mouth of the Pearl River in MS to the Alabama-Florida border.
Tropical storm warnings extend to the west to around New Orleans and Lake Pontchartrain and to the east over the western Florida panhandle. Many replies to various National Weather Service accounts or other outlets with their pleas that the storm veer spontaneously away, as the Gulf coast is still dealing with the aftermath of Hurricane Harvey.
The storm left many businesses on Florida's Gulf Coast feeling shortchanged by the holiday weekend.
Flooding was also a high risk for the areas affected by the storm, including portions of southeast Louisiana north of Interstate 10 and southwest MS west of Interstate 55.
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"It looks like for the next three or four days we're going to be having to really watch close", National Hurricane Center Director Ken Graham said in a video briefing on Facebook, according to Reuters.
There is a Storm Surge Watch in effect for the Mississippi-Alabama border westward to the Mouth of the Mississippi River.
Right now, the storm is moving steadily northwest at a speed of about 16 miles per hour.
At 5 p.m. ET, Gordon, with top sustained winds of 50 mph, was about 50 miles west-southwest of Fort Myers, Florida, and was moving west-northwest at 17 mph.
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