NOUS41 KWBC 121855



Service Change Notice 18-05

National Weather Service Headquarters Silver Spring MD

155 PM EDT Fri Jan 12 2018


To:      Subscribers:

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network


         Other NWS Partners and Employees


From:    Edward Myers

         Coast Survey Development Laboratory, National Ocean



Subject:  Implementation of New Extratropical Surge and Tide

          Operational Forecast System for Micronesia

          Effective February 13, 2018


Effective February 13 2018, beginning at 1200 Coordinated

Universal Time (UTC), the Extratropical Surge and Tide

Operational Forecast System for the Oceania sub-region of

Micronesia (ESTOFS Micronesia) will be implemented on NOAA's

Weather Climate Operational Supercomputing System (WCOSS)

operated by NCEP Central Operations (NCO). The ESTOFS Micronesia

model output provides coverage of the Western Tropical Pacific,

including the Federated States of Micronesia, Palau, Marianas

Islands, Marshall Islands, and Wake Island. The system will

provide users with nowcasts (analyses of near present

conditions) and forecast guidance of water level conditions. The

forecast outputs will extend out to 180 hours and will include

water levels caused by the combined effects of storm surge and

tides, by astronomical tides alone, and by sub-tidal water

levels (isolated storm surge).


The hydrodynamic model employed by ESTOFS is the Advanced

Circulation Model (ADCIRC) finite element model. ADCIRC was

developed to perform high resolution simulations of time-

dependent, free surface circulation and transport problems in

two and three dimensions. ESTOFS uses the Two-Dimensional Depth

Integrated (2DDI) version of ADCIRC, which computes the water

surface elevation and barotropic depth-averaged currents. ADCIRC

uses the finite element method in space, taking advantage of

highly flexible, irregularly spaced grids.


The unstructured grid used by ESTOFS Micronesia consists of

234,333 nodes and 462,967 triangular elements. Nearshore coastal

resolution is about 200m, and overland resolution extends to the

10m topographic height. The open-ocean boundary surrounds the

entire domain, where harmonic tidal constituents from the global

tidal model TPXO 7.2 are used to specify tidal water surface

fluctuations, while tidal potential forcing is applied within

the interior of the domain. The performance of this grid for

astronomical tides was verified using tidal elevation data from

observation stations located throughout the domain.


ESTOFS is designed to provide water surface elevations caused by

storm surge and astronomical tide to the NCEP WAVEWATCH III

(WW3) wave model for coupling wave and water level predictions.

ESTOFS set-up is designed to mimic the WW3 model. It uses the

same Global Forecast System (GFS) atmospheric forcing (ESTOFS

applies 10m wind speeds and sea level pressure from the GFS

Semi-Lagrangian T1534). It also has the same forecast cycle (4

times per day concurrent with GFS), length (6 hour nowcast

followed by a 180 hour forecast), and both will run



ESTOFS output files are provided in two formats, structured

GRIB2 files for the North Pacific (10.0 km resolution) and Guam

(2.5 km resolution) grids, and unstructured NetCDF files on the

native ESTOFS finite element grid. NetCDF output is also

provided at station locations and warning points located near

major populated islands.


Operational forecast guidance from ESTOFS Micronesia will be

available in the netCDF and GRIB2 files described below via NCEP

Web Services:

Where the directory is estofs_mic.YYYYMMDD (YYYYMMDD is year,

month and day)


GRIB2 files are created for each hourly prediction during a

forecast cycle, consisting of records of combined water level

(surge with tide), harmonic tidal prediction (astronomical

tides), and sub-tidal water levels (the isolated surge).


Where FFF is forecast hour (000-180)




Where CC is the cycle (00,06,12,18), AAAA is area (guam,



NetCDF files contain an entire nowcast/forecast cycle and

consist of the hourly combined water level over the native

ESTOFS grid, or six-minute water level records at station

locations and warning points.


ESTOFS provides SHEF E format output at station locations. SHEF

files contain 30-minute combined water level (surges with

tides), harmonic tidal prediction (astronomical tides), and sub-

tidal water levels (the isolated surges).





AWIPS Product Additions:

WMO Headers as follows

-SHEF Harmonic Tidal Prediction


-SHEF Combined Water Level


-SHEF Sub-tidal Water Levels



Users will also be able access maps of the ESTOFS Micronesia

guidance from the NOAA nowCOAST map service

(Where "guidance_model_coastalocean_estofs_time" is the

selectable target) using two different protocols:

- ArcGIS Representational State Transfer (REST) Map Service

- OGC Web Map Service (WMS) 


In addition, users will also be able to view the guidance via

the nowCOAST map viewer.


A consistent parallel feed of data is available on the NCEP HTTP

site at the following URL:


Any questions, comments, or requests regarding this

implementation should be directed to the contacts below.  We

will review any feedback and decide whether to proceed.


Dr. Edward P. Myers

Coastal Marine Modeling Branch

Coast Survey Development Laboratory

NOAA/NOS/Office of Coast Survey

Silver Spring, MD


For questions regarding the data aspects, please contact:


Carissa Klemmer

NCEP/NCO Dataflow Team Lead

College Park, MD


National Service Change Notices are online at: