Thursday, October 3, 2013

Surge Maps from Tropical Storms along the Northern U.S. Gulf Coast

Wind shear and some dry air entrainment have been making it difficult for TS Karen to get better organized today. Satellite imagery this afternoon is less impressive than this morning.

Nonetheless, the National Hurricane Center's 1PM CDT advisory still places the maximum sustained winds of TS Karen at 65 MPH and forecasts that the storm may reach hurricane intensity while tracking towards the central U.S. Gulf Coast.

I've reached  into the storm surge archive today to find some storm surge/ storm tide maps from tropical storms that have generally tracked north and made landfall along the central U.S. Gulf Coast. Actually, the events I've pulled all occurred within the past 20 years. I've run a computer script today that plots the storm track and coastal flooding observations for the following storms:
Tropical Storm Alberto (1994)
Hurricane Isidore (2002)
Tropical Storm Bill (2003)
Tropical Storm Arlene (2005)

These maps make use of the SURGEDAT database, which has identified the location and height of more than 7,600 storm surge/ storm tide observations since 1880. The database pulls data from more than 70 sources, including government documents, books and academic publications, as well as historic newspapers.

The maps are pasted below. But before we get to the maps, I wanted to provide a bit of clarification because this is the first time I've posted maps this season.

1. These maps are in no way a forecast or an indication of surge potential related to TS Karen. If you're interested in surge forecasts, please see the National Hurricane Center website. This resource provides surge forecasts in the latest advisory, as well as some great storm surge probability and surge exceedance products.

2. The purpose of these maps is to provide historical context. In some cases, we've seen geographic patterns in the high water history, which may indicate where high water tends to pile up in a given region. That was the case last year with Hurricane Sandy. Many people were surprised to find some of the highest water levels in the New York Metro area occurring in SW Long Island Sound, but this was a very similar pattern to the 1938 Long Island Express Hurricane. Along the central Gulf Coast, some favorite locations where water likes to pile up include SE Louisiana, east of the Mississippi River, and also along the Mississippi Coast.


All four of these storms crossed the Gulf of Mexico from south to north as tropical storms. Isidore reached hurricane status when the center of circulation was near Cuba and the Yucatan Peninsula, but then moved across the Gulf of Mexico as a tropical storm.

The highest water level in three of these four storms was 4-8 feet above various datums, or vertical reference lines. (Note: These water levels do not refer to height above ground level, like some of the latest NHC products.) Hurricane Isidore was the exception, which produced storm surge heights exceeding 8 feet along portions of the Mississippi and Louisiana coasts. The highest storm surge level produced by Isidore was 8.3 feet at the Rigolets in extreme E Louisiana (near the Mississippi border), while a storm surge of 8.26 feet was recorded at Gulfport, Mississippi.

Although all of these events were tropical storms, it should be noted that Isidore was a fairly intense tropical storm with a relatively large wind field. At about 8 hours before landfall in SE Louisiana, Isidore produced max wind speeds of 55 knots (~ 63MPH), with a radius of tropical storm force winds extended 300 nm (345 miles) from the center of circulation (Demuth et al. 2006).

By comparison, at the latest advisory, TS Karen's tropical storm force wind field only extended about 105 miles from the center of circulation. Generally speaking, tropical cyclones with larger wind fields tend to produce more coastal flooding, so it's important to consider the size of such storms and not just the maximum sustained wind speed.

Stay tuned to this blog for more historical storm surge information and/or updates on observed water levels along the U.S. Gulf Coast. There is also a slight chance I may be able to get field observations/ photos from the impacted surge area Fri or Sat. If you want to contact me, the best way is through email at:

-Hurricane Hal

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