Tropical Storm Karen is poised to become the first named storm to hit the United States this season. Karen, as of 2PM Eastern Daylight Time, was 240 miles south-southwest of the mouth of the Mississippi River and 275 miles south-southeast of Morgan City, Louisiana. The storm is moving north-northwest at ten miles per hour. According to the NHC, a turn toward the north and a decrease in forward speed are expected by early Saturday, with a turn toward the northeast on Sunday.
The National Hurricane Center (NHC) predicts the storm will make landfall as a tropical storm, with the center near the central Gulf Coast on Saturday. Landfall scenarios from Eastern Louisiana to the Central Florida Panhandle are possible sometime late Saturday into Sunday. The forecast carries considerable uncertainty due to timing of interaction with a frontal system leaving the mainland. Expected hazards include heavy rainfall, tropical storm conditions and possible hurricane conditions, with a storm surge on the order of three to five feet.
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Meteorological Discussion and Forecast Reasoning
Karen has weakened slightly in the last 12 hours, but has surprisingly maintained a strong circulation in a hostile environment of dry air and 20-25 kt wind shear. As a frontal boundary leaves the mainland, Karen should turn to the northeast into the frontal boundary. During this interaction, conditions should better enable development with relaxed shear, and some strengthening is possible as a result. The timing of the frontal boundary has slowed considerably, resulting in a high degree of uncertainty for where and when Karen will phase with frontal system. Track and intensity scenarios show great variability as a result.
Model guidance gives landfall scenarios from Eastern Louisiana to near Apalachicola Florida. Landfall intensity scenarios range from weaker in the Louisiana scenario to stronger in the Florida scenario. Landfall is expected late Saturday into Sunday as a tropical storm.
Hazards, Watches, Warnings
A tropical storm warning is in effect for Morgan City, Louisiana to the mouth of the Pearl River, according to the NHC. The NHC has also issued tropical storm watches for the city of New Orleans, as well as areas near Lake Maurepas and Lake Pontchartrain, and from the mouth of the Pearl River to Indian Pass, Florida.
Areas in the tropical storm warning are expected to experience tropical storm conditions on Saturday, while tropical storm conditions are possible for portions of the watch area Saturday night into Sunday morning, according to the NHC. A combination of storm surge and high tide will cause flooding in normally dry areas near the coast. If peak storm surge occurs during high tide, some parts of the coast could see up to five feet of surge, particularly in the area near the mouth of the Mississippi River to Mobile Bay, Alabama. The surge will also be accompanied by dangerous waves. Karen is expected to produce three to six inches of rainfall over the central and eastern Gulf Coast through Sunday night, with some isolated areas receiving up to ten inches of rain.
The governors of Louisiana, Mississippi and Florida declared states of emergency in order to expedite storm preparations. Mayor David Camardelle of Grand Isle, Louisiana, a tourist town about 60 miles south of New Orleans, has called for voluntary evacuations ahead of the storm. The Inner Harbor Navigation Canal is also being closed in Louisiana in order to keep storm surge out. Workers have been evacuated from offshore platforms and oil production has been halted in the Gulf due to the storm, accounting for nearly a fifth of the daily U.S. oil output.
Sources: National Hurricane Center (NOAA), Storm Prediction Center (NOAA), National Weather Service (NOAA), Associated Press, Reuters, CNN.
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