Tropical Update - Tropical Storm Marco/Laura - Sun, Aug 23, 2020 4 am

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Here is an update concerning mostly Tropical Storm Marco. 

Changes from previous update: 

• A Hurricane Warning has been issued along the Louisiana coast from Morgan City to the Mouth of the Pearl River including Lake Borgne, but not the city of New Orleans.

• A Storm Surge Warning has been issued along the Gulf coast from Morgan City to Ocean Springs.

• A Tropical Storm Warning has been issued for the parishes surrounding Lake Pontchartrain and Lake Maurepas including metropolitan New Orleans.

• The Hurricane Watch for the Mississippi coastal counties has been changed to a Tropical Storm Warning.

• Track of Marco is about the same, however the track of Laura has been shifted west.

Overview:

• Tropical Storm Marco is forecast to move generally north-northwestward across the central to northwest Gulf and is expected to bring tropical storm to hurricane conditions along with storm surge to southeast Louisiana and south Mississippi Monday.

• Tropical Storm Laura is forecast to move generally west-northwestward along the Greater Antilles chain, then enter the Gulf of Mexico by Monday night. Thereafter, Laura is likely to intensify into a hurricane while approaching the north-central to northwest Gulf coast region Wednesday and Wednesday night.

Confidence:

• We are confident both storms will bring impacts to the local area.

• We are less confident in the impacts from Laura than Marco

Impacts from Marco:

• Storm Surge

  • 4 to 6 ft of inundation will be possible along immediate coastal areas from Morgan City to Ocean Springs

  • 2 to 4 ft of inundation will be possible along the shores of Lakes Pontchartrain and Maurepas 

• Rainfall

  • Rainfall of 2 to 4 inches is currently forecast. Locally higher amounts of double or more 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. This watch may be expanded, depending on future track adjustments.

• Wind

  • Sustained hurricane force winds will be possible, mainly across a small area near Marco's core.

  • Tropical storm force winds will be more widespread.

  • 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 stronger winds, higher inundation and additional heavy rainfall to portions of the area, however this is low confidence at this point given the westward shift in the track.

  • 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/