Wednesday, September 5, 2018

Gordon's Storm Surge Ranged from 2-3 Feet

Tropical Storm Gordon made landfall near the Mississippi/ Alabama border last night. Highest storm surge levels ranged from 2-3 feet along the stretch of coast from Shell Beach, Louisiana through Apalachicola, Florida.

Gordon's track, lopsided nature and relatively fast forward speed kept storm surge levels modest through the region.

Map of Gordon's peak storm surge along the Gulf Coast and Southeast Atlantic

Gordon generally maintained a forward speed of 14-15 mph as it tracked across the Gulf of Mexico. This is slightly higher-than-normal for the region and did not allow enough time for Gordon to generate substantial storm surge.

As Gordon approached landfall, the heavier convection was clearly located on the northern and eastern areas around the eye, with much less activity to the west and south. This kept storm surge levels relatively low to the west of the storm's track.

This radar image from Weather Underground shows the lopsided nature of Gordon's convection as it approached landfall. Most of the activity was located to the north and west of the eye, with less activity found on the south and west sides.

Had Gordon tracked farther west, making landfall in southwest Mississippi or southeast Louisiana, the stronger side of the storm would have pushed higher storm surge levels into Mississippi that would have likely reached the 3-5 foot range. However, Gordon's strongest winds impacted Alabama and the western Florida panhandle, which are less efficient than Mississippi and southeast Louisiana for generating storm surge.

Here are selected storm surge observations, measured in maximum difference between observed and predicted tide levels:

Apalachicola, Florida:               2.19 ft
Panama City Beach, Florida:     2.0 ft
Pensacola, Florida:                    2.5 ft
Dauphin Island, Alabama:         2.88 ft
Mobile State Docks, Alabama:  2.53 ft
Pascagoula, Mississippi:            1.87 ft
Bay Waveland Yacht Club
(Bay St Louis, Mississippi:)       2.0 ft
Shell Beach, Louisiana:              2.88 ft

The next concern is inland flood potential, as Gordon's track is forecast to slow down. Even after Gordon is downgraded to a tropical depression, flood potential remains high from the Lower Mississippi Valley through much of Arkansas.

From a storm surge perspective, all eyes now turn to Florence, well offshore in the Atlantic. Both American and European models suggest it could approach the Eastern Seaboard as a powerful hurricane next week.

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