Storm Surge

[Cookiely]

BAY NEWS 9 -- When people think of the danger inherent in hurricanes, they often think of wind.

But in reality, storm surge is the greatest killer in a hurricane. The Tampa Bay area is particularly vulnerable to storm surge because of shallow waters off the west coast of Florida.

Traditionally, storm surge predictions have been included in the Saffir-Simpson scale, the scale the National Hurricane Center uses to rank hurricane strength.

For example, according to the scale, a category 1 storm has winds of 74 miles per hour with four feet of storm surge. A category 5 has winds of 155 miles per hour with an 18-foot storm surge.

But Tom Iovino from Pinellas County Emergency Management said sometimes the storm surge can differ from a storm's winds as measured by the Saffir-Simpson scale.

Last year, Ike was a category 2 storm at landfall in Galveston. That would have meant an expected 6 to 8 feet of storm surge.

But Ike brought with it 15 to 20 feet of storm surge.

In 2004, Charlie was a category 4 storm. According to the Saffir-Simpson scale that would have meant a storm surge of 13 to 18 feet. The surge turned out to only be about 2 feet.

For these reasons, Bay News 9's meteorologists don't rely solely on the Saffir-Simpson scale and the National Hurricane Center is considering tweaking the Saffir-Simpson scale to take storm surge out of the equation.

"What they're trying to do now is just basically say the Saffir-Simpson from now on will be about wind speed," said Bay News 9 meteorologist Julie Marquez. "Then they're going to use other products to help people understand what the impact might be of storm surge."

Bay News 9 chief meteorolgist Mike Clay said the Bay area can get a damaging storm surge even from a tropical storm. In 1996, Tropical Storm Josephine produced a 6-foot storm surge in Pinellas County, even though it made landfall in the panhandle.
http://www.baynews9.com

[jinftl]

Good article but it is important to note that in the case of Ike, the high surge that took place was forecast well advance. As horrific as it was, the surge that actually took place was somewhat less than the forecast called for. Heighest Ike surge per NHC was 17.8 feet on the Bolivar Peninsula.
http://www.nhc.noaa.gov/pdf/TCR-AL092008_Ike.pdf

As early as 9/11, the NHC was releasing surge forecasts in the advisories that read:
COASTAL STORM SURGE FLOODING OF UP TO 20 FEET ABOVE NORMAL TIDE
LEVELS...ALONG WITH LARGE AND DANGEROUS BATTERING WAVES...CAN BE
EXPECTED NEAR AND TO THE EAST OF WHERE THE CENTER OF IKE MAKES
LANDFALL...EXCEPT AT THE HEADS OF BAYS...WHERE SURGE FLOODING OF UP
TO 25 FEET COULD OCCUR. COASTAL STORM SURGE FLOODING OF 6 TO 8 FEET
ABOVE NORMAL TIDE LEVELS...ALONG WITH LARGE AND DANGEROUS
WAVES...CAN BE EXPECTED WITHIN THE TROPICAL STORM WARNING AREA
ALONG THE NORTHERN GULF COAST.



Also, with Charley, there were areas of higher surge than 2' but the small size of the system was a factor in a large surge not developing...of course Charley was a storm where wind did most of the damage.

From NHC report on Charley:
A storm surge of 4.2 feet was measured by a tide gauge in Estero Bay, near Horseshoe Key. This is near Fort Myers Beach. Storm surges of 3.4 and 3.6 feet were measured on tide gauges on the Caloosahatchee River, near Fort Myers. There were also visual estimates of storm surges of 6 to 7 feet on Sanibel and Estero Islands
http://www.nhc.noaa.gov/2004charley.shtml


I do agree that the news media and the public need to focus on the NHC forecasts and what officials are telling them as far as evacuations from surge zones. If people are told to leave, there is a legitimate basis as determined from surge models and elevation maps that require leaving for safety.

Hopefully some of the changes the NHC is implementing, esp in regard to surge forecasts for 2009 will resonate with the media and public.

STARTING IN 2009...IN AN EFFORT TO ENSURE STORM SURGE FORECASTS
ARE FULLY UNDERSTOOD BY THE WIDEST POSSIBLE AUDIENCE...THE
NATIONAL HURRICANE CENTER /NHC/ WILL CHANGE THE WORDING IN THE
PUBLIC ADVISORY TEXT PRODUCTS TO REFERENCE STORM SURGE OR STORM
TIDE IN TERMS OF HEIGHT ABOVE GROUND LEVEL.

STORM SURGE REFERS TO THE ABNORMAL RISE IN SEA LEVEL
ACCOMPANYING A HURRICANE...THE DIFFERENCE BETWEEN THE OBSERVED
LEVEL OF THE SEA SURFACE AND THE LEVEL THAT WOULD HAVE OCCURRED
IN THE ABSENCE OF THE CYCLONE.

STORM TIDE IS THE ACTUAL LEVEL OF SEA WATER RESULTING FROM THE
ASTRONOMIC TIDE COMBINED WITH THE STORM SURGE. STORM TIDE IS OF
PARTICULAR IMPORTANCE IN THE NORTHERN LATITUDES...WHERE
THERE IS A GREATER DIFFERENCE IN HEIGHTS BETWEEN HIGH AND LOW
TIDE LEVELS...AND WHEN A STORM IS EXPECTED TO LANDFALL NEAR THE
TIMES OF ASTRONOMICAL HIGH TIDE.

BEGINNNING IN 2009...NHC PUBLIC ADVISORY PRODUCTS /TCP/S WILL
PROVIDE THE FOLLOWING POSSIBLE STATEMENTS ON COASTAL FLOODING
ASSOCIATED WITH TROPICAL CYCLONES:

EXAMPLE 1
STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS NN /FOR
EXAMPLE 15/ FEET ABOVE GROUND LEVEL ALONG THE COAST...WITH LARGE
AND DANGEROUS BATTERING WAVES...NEAR AND TO THE ZZZZ /DIRECTION
FOR EXAMPLE EAST/ OF WHERE THE CENTER MAKES LANDFALL. THE SURGE
COULD PENETRATE AS FAR INLAND AS ABOUT NN /FOR EXAMPLE 30/ MILES
FROM THE SHORE WITH DEPTH GENERALLY DECREASING AS THE WATER
MOVES INLAND.

EXAMPLE 2
STORM TIDE WILL RAISE WATER LEVELS BY AS MUCH AS NN /FOR EXAMPLE
18/ FEET ABOVE GROUND LEVEL ALONG THE COAST...WITH LARGE AND
DANGEROUS BATTERING WAVES...NEAR AND TO THE ZZZZ /DIRECTION FOR
EXAMPLE EAST/ OF WHERE THE CENTER MAKES LANDFALL. STORM TIDE
COULD PENETRATE AS FAR INLAND AS ABOUT NN /FOR EXAMPLE 30/ MILES
FROM THE SHORE WITH DEPTH GENERALLY DECREASING AS THE WATER
MOVES INLAND.

PLEASE SEE SERVICE CHANGE NOTICE 09-14...ISSUED ON FEB 24
2009...FOR FORMAT CHANGES TO TROPICAL CYCLONE PUBLIC ADVISORY
PRODUCTS FOR THE ATLANTIC...EAST PACIFIC...AND CENTRAL PACIFIC
HURRICANE BASINS: EFFECTIVE MAY 15 2009.

AN EXAMPLE OF THE TCP PRODUCT FOR 2009 IS PROVIDED ONLINE AT
/USE LOWER CASE LETTERS/:

HTTP://WWW.NHC.NOAA.GOV/TCP_EXAMPLE.SHTML

http://www.nhc.noaa.gov/pns8_2009.shtml