NOUS41 KWBC 251514
Service Change Notice 16-18
National Weather Service Headquarters Washington DC
1114 AM EDT Wed May 25 2016
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
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
- 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:
The map will be available on the NHC website at:
GIS data will be available for each advisory this graphic is
active and can be found via the NHC GIS webpage at:
For technical questions regarding this notice, contact:
National Hurricane Center
Storm Surge Team Lead
Miami, FL 33165
For policy questions regarding this notice, contact:
NWS Marine, Tropical and Tsunami Services Branch
Silver Spring, MD 20910
National Service Change Notices are online at: