Monday, September 3, 2018

Tropical Storm Gordon Eyes the Northern Gulf Coast and May Threaten Inland Areas Later in the Week

Tropical Storm Gordon forms over South Florida and is forecast to approach the Northern Gulf Coast...



Key Messages:

1) Gordon may produce some localized flooding in South Florida on Labor Day;

2) Gordon will track northwest and impact Southeast Louisiana, Southern Mississippi and Southern Alabama late Tue/ early Wed;

3) Gordon's movement is faster than average and its fast pace is forecast to continue. Faster moving storms do not have time to generate substantial storm surges, so expect coastal flooding to be minor from Southeast Louisiana through Mississippi and Alabama;

4) Gordon is forecast to slowly strengthen over the Gulf and will likely bring tropical storm force winds near and east of the landfall location;

5) After Gordon is well inland it is forecast to become a tropical depression but slow down considerably. This may pose a threat for life-threatening flooding to inland locations later this week...




Gordon's rain bands were pushing into South Florida this morning...my location is shown as the blue dot on the map- we experienced some decent squalls this morning

In Detail:

Tropical Storm Gordon formed this morning near where the southern tip of the Florida Peninsula meets the Florida Keys. I live in Southwest Miami, about 45 miles northeast of the center of circulation. We awoke to squally weather this morning, with periods of strong winds and heavy rain.

As expected, some banding of the squalls is occurring in South Florida, from Key Largo to Palm Beach, and persistent squalls training over the same locations could quickly bring several inches of rain to locations in South Florida today. Expect street flooding in low-lying areas.



Gordon is moving towards the west-northwest at 17 mph, and is forecast to make a turn towards the northwest, enabling the storm to approach the Northern Gulf Coast by Tuesday night. This forward speed is faster than average, which is beneficial for several reasons. Fast-moving hurricanes and tropical storms do not have as much time to build storm surge, so expect coastal flooding to be minor near and to the east of landfall.

Gordon's persistent squalls have generated some street flooding in South Florida this morning. I took this picture in the Kendall area of Miami. Photo: Hal Needham


Also, in recent years we have experienced several hurricanes/ tropical storms stalling out near the coastline, enabling these storms to dump massive amounts of rain just inland and produce compound flooding from rain and storm surge. Hurricane Harvey was a classic example of this.



Gordon is forecast to move quickly across the Gulf of Mexico and maintain a fast pace through the time of landfall. This is great news for minimizing flood impacts from both storm surge and heavy rain.



Unfortunately, Gordon is forecast to slow down considerably later this week. Although Gordon will likely be downgraded to a tropical depression and be centered well inland by the time this happens, life-threatening flooding is a potential threat across a swath from eastern Oklahoma through Arkansas and Northern Louisiana later in the week.

The National Hurricane Center 11AM Eastern advisory on Mon Sep 3 forecasts Gordon to track near the Northern Gulf Coast at a rapid pace and then slow down considerably after being downgraded to a tropical depression later this week

If Gordon does indeed stall once it is inland, the greatest threat to life and property would likely be from inland flooding hundreds of miles from the Gulf Coast.

We should note that Gordon comes on the heels of substantial rainfall in portions of Southeast Texas and Southwest Louisiana. Some locations in Southeast Texas have picked up 3-5 inches of rain in the past 24 hours, from Galveston Bay through the Louisiana border.


Even before Gordon's approach to the Northern Gulf Coast, portions of SE Texas and SW Louisiana have observed big-time rains, with some areas observing 3-5" over the past 24 hours. It appears that Gordon's heaviest rain will pass east and north of this area. Source: National Weather Service Radar.

It appears that Gordon will stay far enough east that torrential rains will hopefully not be repeated for SW Louisiana and SE Texas. However, later in the week, as Gordon slows down, things could get interesting for Northeast Texas, Northern Louisiana, Arkansas and Oklahoma.




NOAA's Quantitative Precipitation Forecast (QPF) rainfall map (above) shows rain potential for the next 7 days (Mon Sep 3- Mon Sep 10). Notice that the heaviest rain bypasses Arkansas. However, if Gordon slows down and tracks through SW Arkansas as a tropical depression, we have to wonder if the updated forecast will dramatically increase the rainfall in that state. We will see how things play out through the week.

Gordon will likely bring tropical storm force winds to locations near and east of the landfall location on Tuesday night. While this is better news than hurricane-force winds, tropical storm force winds can still cause some problems. Expect downed trees, loss of power and even minor structural damage on items like sheds, car ports and other structural features that are not secured.

Gordon threatens to produce flood and wind impacts from Florida through the Northern Gulf Coast and even the Mississippi River Valley/ Southern Plains later in the week



Last year during Hurricane Harvey I stayed on Galveston Island. Galveston's peak sustained (10-min) winds were 39 mph, which is the minimum threshold for tropical storm force winds. The highest wind gust (2-min) was 49 mph. While these winds don't sound extraordinary, they caused a loud whistling sound through the power lines and brought down a car port on some cars in a nearby apartment complex.



Tropical storm force winds tore down a carport on Galveston Island during Hurricane Harvey on August 27, 2018. While not as destructive as hurricane-force winds, tropical storm force winds can still cause some structural damage, bring down trees and cause power outages. Photos: Hal Needham

I have been receiving messages from dear friends in Louisiana and Texas over the past day. Given the forecast track, I expect minimal storm impacts for Baton Rouge and points west along the Gulf Coast, but inland flooding could spread as far west as Oklahoma later this week.

I will post some maps soon on Gordon's storm surge potential, and, like other storms, I will create a map that enables us to get a birds-eye-view of Gordon's storm surge as it approaches the coast.

Feel free to comment on this blog or email me at hal@marineweatherandclimate.com if you would like to reach out.

Stay safe everyone!
Hurricane Hal

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