Tropical Updates

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Tropical Update - Marco and Laura, Mon August 24, 2020 4am

Click HERE to see a 4 AM updated slides from the NWS.Here is an update concerning Tropical Storm Marco and Tropical Storm Laura. 

Changes from previous update: 

  • Marco has considerably weakened below hurricane strength and is not expected to regain intensity. All Hurricane Warnings in coastal areas have been replaced with Tropical Storm Warnings, and all Hurricane Watches surrounding Lake Pontchartrain and Maurepas have been cancelled.

  • All Tropical Storm Watches for inland areas have been cancelled. Some other inland parishes of southeast Louisiana have been removed from the Tropical Storm Warning.

  • Storm Surge Watches for coastal areas east of Ocean Springs (Jackson County) and for the parishes surrounding Lakes Pontchartrain and Maurepas have been replaced with Coastal Flood Advisories.

  • Storm Surge Warnings remain in effect for the open coast from Morgan City to Ocean Springs, however inundation values have been lowered.

  • The Flash Flood Watch is no longer in effect for inland areas from metro Baton Rouge to near Hammond. This is consistent with the Weather Prediction Center's Excessive Rainfall and precipitation forecast through tonight.

  • TS Laura's forecast track has not changed substantially, so expected impacts have not changed across southeast Louisiana and coastal Mississippi. Confidence in the track is rising slightly with each advisory cycle.

Overview:

  • Marco is forecast to approach the coast and turn westward today, bringing coastal flooding, bands of heavy rainfall and gusty winds to SE LA and S MS

  • Tropical Storm Laura is forecast to be at least a category two as it approaches the Northwest Gulf coast on Wednesday.

Confidence:

  • We are confident Marco will bring impacts to the local area, however these impacts are less than earlier forecast.

  • We are confident Laura will bring impacts (mainly potential for coastal flooding and heavy rain) to the local area, but less confident in the magnitude of impacts

Impacts from Marco:

  • Storm Surge Inundation Potential:

    • Open coast from Morgan City to Ocean Springs: 2 to 4 ft

    • Lakes Pontchartrain and Maurepas: 2 to 3 ft

    • Open coast Ocean Springs to AL Border: 2 to 3 ft

  • Rainfall

    • Rainfall of 3 to 5 inches with locally higher amounts will be possible

    • Expect ponding of water in low lying areas and some potential for localized flash flooding

    • A Flash Flood Watch is in effect for the lower parishes of southeast Louisiana and coastal Mississippi.

  • Wind

    • Sustained tropical storm force winds are expected in coastal areas and some inland areas near tidal lakes, mainly with heavier rain bands

    • These winds could result in minor damage mainly to trees, powerlines, and weaker structures. 

  • Tornadoes

    • Short-lived and fast-moving tornadoes can occur in Marco's outer bands as it moves ashore and inland.

  • Other Considerations:

    • TS Laura could bring additional coastal flooding and heavy rainfall, as well as gusty winds to portions of the area mainly west of the MS River

    • Keep in mind that preparation for TS Laura may be made more difficult by lingering impacts from TS Marco.

Additional Information and Resources:

NWS New Orleans Website: www.weather.gov/neworleans

NWS New Orleans DSS Website: http://www.weather.gov/lix/embrief

NWS New Orleans Tropical Page: https://www.weather.gov/srh/tropical?office=lix

River Gauges and Forecasts: http://water.weather.gov/ahps2/index.php?wfo=lix

NWS New Orleans Facebook: www.facebook.com/NWSNewOrleans

NWS New Orleans Twitter: https://twitter.com/NWSNewOrleans

Online Severe Weather Reporting: https://www.weather.gov/lix/submit_storm_report

National Hurricane Center Website: https://www.nhc.noaa.gov/

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