Sunday 25 October, 2020

Dangerous storm surge expected as Delta moves over the Gulf Coast

Hurricane Delta continues to move northwestward over the Gulf of Mexico.

The National Hurricane Centre said life-threatening storm surge is expected to begin along portions of the northern Gulf Coast on Friday.

 A Storm Surge Warning is in effect for:
* Sabine Pass to Ocean Springs, Mississippi including Calcasieu Lake, Vermilion Bay, Lake Pontchartrain, Lake Maurepas, and Lake Borgne.

A Storm Surge Watch is in effect for:

  • High Island, Texas to Sabine Pass
  • East of Ocean Springs, Mississippi to the Mississippi/Alabama state line

A Hurricane Warning is in effect for:

  • East of Sabine Pass to Morgan City, Louisiana

A Tropical Storm Warning is in effect for:

  • San Luis Pass, Texas to Sabine Pass
  •  East of Morgan City, Louisiana to the mouth of the Pearl River, including New Orleans, Lake Pontchartrain and Lake Maurepas.

A Tropical Storm Watch is in effect for...

  • East of the mouth of the Pearl River to Bay St. Louis Mississippi

 A few tornadoes are possible late tonight through Friday over southern parts of Louisiana and Mississippi. 

At 4am CDT, the centre of Hurricane Delta was located over the southern Gulf of Mexico about 450 miles (725 km) south-southeast of Cameron, Louisiana. Delta is moving toward the northwest near 15 mph (24 km/h), and this motion with a reduction in forwarding speed is expected today. 

A turn to the north is forecast to occur by late tonight, followed by a north-northeastward motion by Friday night. On the forecast track, the centre of Delta will move over the central Gulf of Mexico today and move inland within the hurricane warning area Friday afternoon or Friday night.

Maximum sustained winds are near 100 mph (155 km/h) with higher gusts - a category 2 hurricane on the Saffir-Simpson Hurricane Wind Scale. Hurricane-force winds extend outward up to 35 miles (55 km) from the centre and tropical-storm-force winds extend outward up to 125 miles (205 km). 

Strengthening is forecast to occur and Delta is expected to become a major hurricane again by tonight.  Some weakening is forecast when Delta approaches the northern Gulf coast on Friday.

The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. 

The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide...

  • Pecan Island to Port Fourchon, LA including Vermilion Bay, 7-11 ft
  • Cameron, LA to Pecan Island, LA, 4-7 ft
  • Port Fourchon, LA to the Mouth of the Mississippi River, 4-6 ft
  • Mouth of the Mississippi River to Ocean Springs, MS, 3-5 ft
  • Lake Borgne, Lake Pontchartrain, & Lake Maurepas, 3-5 ft
  • Ocean Springs, MS to MS/AL state line, 2-4 ft
  • High Island, Texas to Cameron, LA including Calcasieu Lake, 2-4 ft
  • MS/AL state line to the AL/FL state line including Mobile Bay, 1-3 ft
  • Sabine Lake, 1-3 ft
  • Port O'Connor, Texas to High Island, TX incl. Galveston Bay, 1-3 ft.

Friday through Saturday, Delta is expected to produce 5 to 10 inches of rain, with isolated maximum totals of 15 inches, for southwest into south-central Louisiana. 

This rainfall will lead to significant flash, urban, small stream flooding, along with minor to isolated moderate river flooding. 

For extreme east Texas into northern Louisiana, southern Arkansas and western Mississippi, Delta is expected to produce 3 to 6 inches of rain, with isolated maximum totals of 10 inches. Flash, urban, small stream and isolated minor river flooding are expected.

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