NOUS41 KWBC 251514

PNSWSH

 

Service Change Notice 16-18

National Weather Service Headquarters Washington DC

1114 AM EDT Wed May 25 2016

 

To:      Subscribers:

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network

         -NOAAPORT

         Other NWS Partners and NWS Employees

 

From:    Eli Jacks

         Chief, Forecast Services Division

 

Subject: Experimental Potential Storm Surge Flooding Map

         Transitioning to Operational Status June 1, 2016

 

Effective June 1, 2016, the Potential Storm Surge Flooding Map

issued by the National Hurricane Center (NHC) will transition

from experimental to operational status. If necessary before June

1, the map can be released as an operational product.

 

The map will show:

 

- Geographical areas where inundation from storm surge could

occur

 

- How high above ground the water could reach in those areas

 

Areas of possible storm surge flooding for a given storm will be

represented in different colors on the map based on water level:

 

- Blue: greater than 1 foot above ground

- Yellow: greater than 3 feet above ground

- Orange: greater than 6 feet above ground

- Red: greater than 9 feet above ground

 

The Potential Storm Surge Flooding map takes into account:

 

- Flooding due to storm surge from the ocean, including adjoining

tidal rivers, sounds, and bays

- Normal astronomical tides

- Land elevation

- Uncertainties in the track, landfall location, intensity,

forward speed, and size of the cyclone

 

The map does not take into account wave action, freshwater

flooding from rainfall, riverine discharge, and flooding inside

and overtopping of certain levees.

 

The intertidal zone, the area that is above water at low tide and

under water at high tide, will be displayed with a user-

selectable mask layer on the Potential Storm Surge Flooding Map.

This mask layer will allow users to differentiate between areas

that could experience consequential flooding of normally dry

ground and areas that routinely flood during typical high tides.

The intertidal mask will be depicted as gray on the Potential

Storm Surge Flooding Map.

 

The potential storm surge hazard is not depicted within certain

levee areas, such as the Hurricane and Storm Damage Risk

Reduction System in Louisiana. These areas are highly complex and

water levels resulting from overtopping are difficult to predict.

Users are asked to consult local officials for flood risk inside

these leveed areas.

 

NHC will release the initial map for any storm that is expected

to affect the Gulf or East Coast when it issues a hurricane (or

optionally with a tropical storm) watch or warning.

 

The map is subject to change every 6 hours with each new NHC full

advisory package. Due to the processing time required to generate

the storm surge guidance and produce the map, it will be

available about 60 to 90 minutes after the NHC advisory.

 

The map provides a reasonable worst-case scenario for flooding at

particular locations due to storm surge, and therefore conveys

the flooding that a person should be prepared for. Specifically,

the map depicts the amount of flooding over normally dry land

that has a 1-in-10 (10 percent) chance of being exceeded. The map

is created from multiple runs of the Sea, Lake, and Overland

Surges from Hurricanes (SLOSH) model.

 

Additional information and map examples are online at:

 

http://www.nhc.noaa.gov/surge/inundation

 

The map will be available on the NHC website at:

 

http://www.nhc.noaa.gov

 

GIS data will be available for each advisory this graphic is

active and can be found via the NHC GIS webpage at:

 

http://www.nhc.noaa.gov/gis

 

For technical questions regarding this notice, contact:

 

Jamie Rhome

National Hurricane Center

Storm Surge Team Lead

Miami, FL 33165

305-229-4444

Jamie.R.Rhome@noaa.gov

 

For policy questions regarding this notice, contact:

 

Wayne Presnell

NWS Marine, Tropical and Tsunami Services Branch

Silver Spring, MD 20910

301-427-9390

wayne.presnell@noaa.gov

 

National Service Change Notices are online at:

 

    http://www.weather.gov/os/notif.htm

 

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