NOAA Technical Memorandum NOS CS 20

EVALUATION OF NATIONAL WEATHER SERVICE AND 

EXTRAMURAL WATER LEVEL FORECAST GUIDANCE 

FROM REAL TIME OCEAN FORECAST SYSTEMS 

Silver Spring, Maryland 

October 2010 

noaa National Oceanic and Atmospheric Administration 

U.S. DEPARTMENT OF COMMERCE 

National Ocean Service 

Coast Survey Development Laboratory 
Office of Coast Survey 

National Ocean Service 

National Oceanic and Atmospheric Administration 

U.S. Department of Commerce

The Office of Coast Survey (OCS) is the Nation’s only official chartmaker. As the 

oldest United States scientific organization, dating from 1807, this office has a 

long history. Today it promotes safe navigation by managing the National 

Oceanic and Atmospheric Administration’s (NOAA) nautical chart and 

oceanographic data collection and information programs. 

There are four components of OCS: 

The Coast Survey Development Laboratory develops new and efficient 

techniques to accomplish Coast Survey missions and to produce new and 

improved products and services for the maritime community and other 

coastal users. 

The Marine Chart Division acquires marine navigational data to construct 

and maintain nautical charts, Coast Pilots, and related marine products for 

the United States. 

The Hydrographic Surveys Division directs programs for ship and shorebased hydrographic survey units and conducts general hydrographic 

survey operations. 

The Navigational Services Division is the focal point for Coast Survey 

customer service activities, concentrating predominately on charting 

issues, fast-response hydrographic surveys, and Coast Pilot updates. 
NOAA Technical Memorandum NOS CS 20 

EVALUATION OF NATIONAL WEATHER SERVICE AND 

EXTRAMURAL WATER LEVEL FORECAST GUIDANCE 

FROM REAL TIME OCEAN FORECAST SYSTEMS 

Philip H. Richardson and Richard A. Schmalz, Jr. 

Office of Coast Survey, Coast Survey Development Laboratory, 

Silver Spring, MD 

October 2010

noaa National Oceanic and Atmospheric Administration 

U. S. DEPARTMENT National Oceanic and National Ocean Service 

OF COMMERCE Atmospheric Administration David Kennedy 

Gary Locke, Dr. Jane Lubchenco Acting Assistant 

Secretary Under Secretary Administrator 

 

Office of Coast Survey Coast Survey Development Laboratory 

Captain John Lowell, NOAA Mary Erickson 
ii 

NOTICE 

Mention of a commercial company or product does not constitute an 

endorsement by NOAA. Use for publicity or advertising purposes of 

information from this publication concerning proprietary products or 

the tests of such products is not authorized.
iii

TABLE OF CONTENTS

LIST OF FIGURES ....................................................................................................................... iv 

LIST OF TABLES ........................................................................................................................ vii 

1. ABSTRACT .................................................................................................................................x 

1. INTRODUCTION .......................................................................................................................1 

2. CASE DESCRIPTIONS AND ANALYSIS PROCEDURES .....................................................7 

3. RTOFS WATER LEVEL ANALYSIS RESULTS ...................................................................15 

4. ADCIRC WATER LEVEL ANALYSIS RESULTS .................................................................27 

5. MODEL COMPARISON WATER LEVEL ANALYSIS RESULTS ......................................51 

6. CONCLUSIONS ........................................................................................................................59 

REFERENCES ..............................................................................................................................60 

APPENDIX A: SOFTWARE OVERVIEW AND PROGRAM DESCRIPTIONS ......................63 

APPENDIX B: SCRIPT AND CONTROL FILES .......................................................................69 
iv

LIST OF FIGURES 

Figure 1.1. RTOFS Grid with spacing from 5 to 17 km ............................................................. 3 

Figure 1.2. ADCIRC Western North Atlantic Grid along the East Coast with resolution 

ranging from 5.6 to 44.5 km with resolution ranging from 5.6 to 44.5 km .............. 3 

Figure 1.3. ETSS East Coast Grid with order 10 km coastal resolution ..................................... 4 

Figure 1.4. High Resolution ~6 km ETSS East Coast Grid in the Vicinity of Chesapeake and 

Delaware Bays .......................................................................................................... 4 

Figure 1.5. ETSS Gulf of Mexico Grid with order 10 km coastal resolution. ............................ 5 

Figure 1.6. G-NCOM Grid in the Atlantic Region 1/8 degree ~ 10km ...................................... 5 

Figure 3.1. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water 

Level Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf 

of Mexico Stations (b) for January 2006 ................................................................ 17 

Figure 3.2. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water 

Level Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf 

of Mexico Stations (b) for February 2006 .............................................................. 18 

Figure 3.3. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water 

Level Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf 

of Mexico Stations (b) for March 2006 .................................................................. 19 

Figure 3.4. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water 

Level Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf 

of Mexico Stations (b) for April 2006 .................................................................... 20 

Figure 3.5. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level 

Forecast Guidance against NOS Water Level Observations at Sandy Hook, NJ for 

January 2006 ........................................................................................................... 21 

Figure 3.6. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level 

Forecast Guidance against NOS Water Level Observations at Cape May, NJ for 

January 2006 ........................................................................................................... 22 

Figure 3.7. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level 

Forecast Guidance against NOS Water Level Observations at Charleston, SC for 

January 2006 ........................................................................................................... 23 
v

Figure 3.8. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level 

Forecast Guidance against NOS Water Level Observations at Mayport, FL for 

January 2006 ........................................................................................................... 24 

Figure 3.9. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level 

Forecast Guidance against NOS Water Level Observations at Naples, FL for 

January 2006 ........................................................................................................... 25 

Figure 3.10. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level 

Forecast Guidance against NOS Water Level Observations at Galveston Pleasure 

Pier, TX for January ................................................................................................ 26 

Figure 4.1. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for 

January 2006 ........................................................................................................... 28 

Figure 4.2. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) 

for February 2006 ................................................................................................... 29 

Figure 4.3. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) 

for March 2006 ....................................................................................................... 30 

Figure 4.4. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) 

for April 2006 ......................................................................................................... 31 

Figure 4.5. ADCIRC Nowcast vs. ADCIRC Total Water Level Forecast Guidance RMSE 

(meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for 

January 2006 ........................................................................................................... 33 

Figure 4.6. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Sandy Hook, NJ for February 2006 ........................................................................ 34 

Figure 4.7. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Mayport, FL for February 2006 .............................................................................. 35 

Figure 4.8. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Clearwater, FL for February 2006 .......................................................................... 36 

Figure 4.9. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Galveston Pleasure Pier, TX for February 2006 ..................................................... 37 
vi

Figure 5.1. G-NCOM vs. ADCIRC Total Water Level Forecast Guidance RMSE (meters) 

for East Coast Stations (a) and for Gulf of Mexico Stations (b) for November 

2008......................................................................................................................... 55 

Figure 5.2. G-NCOM Total Water Level vs. ETSS Subtidal Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for 

November 2008 ....................................................................................................... 56 

Figure 5.3. RTOFS vs. ADCIRC Total Water Level Forecast Guidance RMSE (meters) for 

East Coast Stations (a) and for Gulf of Mexico Stations (b) for November 2008 .. 57 
vii

LIST OF TABLES 

Table 2.1. Inventory of Evaluation Cases.....................................................................................7 

Table 2.2 Case 1: Operational RTOFS Total Water Level Comparison:Adjusted 

Forecast Guidance vs. Observations Hr 1-24 ........................................................... 8 

Table 2.3 Case 2: RTOFS Versions 1 and 2 Total Water Level Comparison: Adjusted 

Forecast Guidance vs. Observations Hr 1-24 .......................................................... 8 

Table 2.4. Case 3: ADCIRC Total Water Level Comparison: Adjusted Forecast 

Guidance vs. Observations Hr 6-36 .......................................................................... 9 

Table 2.5. Case 4: ADCIRC Total Water Level Comparison:Adjusted Nowcast vs. 

 Observations Hr 1-24 ................................................................................................ 9 

Table 2.6. Case 5: ADCIRC Total Water Level Comparison: Adjusted Forecast 

 Guidance vs. Observations Hr 1-24 .......................................................................... 9 

Table 2.7. Case 6: Operational RTOFS Total Water Level Comparison: Adjusted 

 Forecast Guidance vs. Observations Hr 6-36 ......................................................... 10 

Table 2.8. Case 7: ADCIRC Total Water Level Comparison: Adjusted Forecast 

 Guidance vs. Observations Hr 6-36 ........................................................................ 10 

Table 2.9. Case 8: G-NCOM Total Water Level Comparison: Adjusted Forecast 

 Guidance vs. Observations Hr 6-36 ........................................................................ 11 

Table 2.10. Case 9: ETSS Subtidal Water Level Comparison: Adjusted Forecast 

 Guidance vs. Filtered Observations Hr 6-36 ......................................................... 11 

Table 2.11. Case 10: ADCIRC Nowcast Processing and Harmonic Analysis..............................11 

Table 2.12. Case 11: ADCIRC Subtidal Water Level Comparison: Filtered and Adjusted 

 Nowcast vs. Filtered Observations ........................................................................ 13 

Table 2.13. Case 12: G-NCOM Subtidal Water Level Comparison: Detided and Adjusted 

Nowcast vs. Filtered Observations ........................................................................ 13 

Table 3.1. RTOFS Operational and Experimental Forecast Guidance Monthly Water Level 

Comparisons to NOS observations January – April 2006 (RMSE meters]) .......... 15 

Table 4.1. ADCIRC and RTOFS Operational Forecast Guidance Monthly Water Level 
viii

Comparisons to NOS Observations January – April 2006 (RMSE [meters]) ...... 27 

Table 4.2. ADCIRC Forecast Guidance and Nowcast Monthly Water Level Comparisons 

 to NOS Observations January – April 2006 (RMSE [meters]) ............................. 32 

Table 4.3. M2/S2 ADCIRC vs. NOS Harmonic Analysis Results at Nowcast/Forecast 

System Boundary Locations for January 2006 ....................................................... 38 

Table 4.4. ADCIRC vs. NOS Harmonic Analysis Results at Boston, MA for January 2006 ..... 

................................................................................................................................. 40 

Table 4.5. ADCIRC vs. NOS Harmonic Analysis Results at Sandy Hook, NJ for January 

2006......................................................................................................................... 41 

Table 4.6. ADCIRC vs. NOS Harmonic Analysis Results at Cape May, NJ for January 

2006......................................................................................................................... 42 

Table 4.7. ADCIRC vs. NOS Harmonic Analysis Results at Charleston, SC for January 

2006......................................................................................................................... 43 

Table 4.8. ADCIRC vs. NOS Harmonic Analysis Results at Mayport, FL for January 

 2006......................................................................................................................... 44 

Table 4.9. ADCIRC vs. NOS Harmonic Analysis Results at Naples, FL for January 

 2006......................................................................................................................... 45 

Table 4.10. ADCIRC vs. NOS Harmonic Analysis Results at Panama City, FL for January 

 2006 ....................................................................................................................... 46 

Table 4.11. ADCIRC vs. NOS Harmonic Analysis Results at Sabine Pass, TX for January 

 2006........................................................................................................................ 47 

Table 4.12. ADCIRC vs. NOS Harmonic Analysis Results at Galveston Pleasure Pier, 

TX for January 2006 .............................................................................................. 48 

Table 4.13. ADCIRC vs. NOS Harmonic Constituent Weighted Gain and Phase 

Results for January-April 2006 ............................................................................. 49 

Table 4.14. ADCIRC vs. NOS Harmonic Constituent Estimated RMS Error (meters) for 

January-April 2006 ................................................................................................ 50 

Table 5.1. ADCIRC, G-NCOM, and RTOFS Forecast Guidance Monthly Total Water 

 Level Comparisons to NOS Observations November 2008 (RMSE [meters]) ...... 52 
ix

Table 5.2. ETSS, ADCIRC, G-NCOM, and RTOFS Forecast Guidance Monthly 

Subtidal Water Level Comparisons to NOS Observations November 2008 

(RMSE [meters]) .................................................................................................... 53 

Table 5.3. ADCIRC Nowcast Subtidal Water Level Comparisons to NOS Observations 

January – April 2006 (RMSE [meters]) ................................................................. 54 
x

ABSTRACT 

The water level guidance, both subtidal and total, from National Weather Service (NWS) and 

extramural real-time oceanographic forecast modeling systems were compared to 24 National Ocean 

Service (NOS) water level stations on the U.S. East Coast and along the Gulf of Mexico shoreline. 

The National Weather Service (NWS) Real Time Ocean Forecast System (RTOFS), NWS ExtraTropical Storm Surge (ETSS) Model, United States Navy (USN) global Navy Coupled Ocean Model 

(G-NCOM), and University of North Carolina (UNC) Western North Atlantic Forecast System 

Advanced Circulation (ADCIRC) Model water level forecasts were compared with the observations 

during November 2008. Because the ETSS model is subtidal, the ETSS forecast water levels were 

compared with observed subtidal water levels. The observed subtidal water levels were obtained 

using a 30 hour low pass Fourier filter. Because the RTOFS, ADCIRC, and G-NCOM includes 

tides, their forecast water levels were compared with the total observed water level. Two new 

versions of RTOFS were considered and contrasted with the previous RTOFS results documented in 

Richardson and Schmalz (2007). Using the ADCIRC nowcast water levels, it was possible to 

perform a harmonic analysis as well as a subtidal comparison with subtidal observed water levels. 

Since G-NCOM included tides, subtidal results were obtained by subtraction of the NOS predicted 

astronomic tide from the total nowcast water level (detiding). 

The evaluation demonstrates that for total water level forecast guidance, the order of preference in 

terms of root mean square error (RMSE) is first ADCIRC, next G-NCOM, followed by RTOFS. For 

subtidal water level forecast guidance, again based on RMSE, the order of preference is ETSS, 

ADCIRC, RTOFS, and G-NCOM. 

An explanation of all cases which were run and a description of all processing steps are presented. 

Program descriptions are provided in Appendix A with script and program input files provided in 

Appendix B. 
1

1. INTRODUCTION 

Coastal ocean and estuarine nowcast/forecast systems require specification of the offshore boundary 

conditions for water level, density, and currents. These boundary conditions must be provided from 

basin scale numerical models, since observation density is insufficient in time and space to meet the 

necessary requirements. Here we evaluate the ability of both NWS and extramurally run ocean 

nowcast/forecast models to provide water level boundary conditions. 

The Real Time Ocean Forecast System (RTOFS) Atlantic application run at the National Centers 

for Environmental Prediction (NCEP) uses the Hybrid Coordinate Ocean Model (HYCOM) 

with1200 x 1684 points in the horizontal as shown in Figure 1.1 and 18 isopyncnal and 7 z-levels in 

the vertical. Surface forcings, in the form of 10-m winds and sea-level atmospheric pressure, are 

from the 3-hour NCEP Global Forecast System (GFS), a numerical weather prediction modeling 

system. The open boundaries are relaxed to NCEP climatology. Tides are included in terms of tidal 

potential and boundary tides, that are specified in terms of the M2, S2, N2, K2, K1, P1, O1, and Q1

tidal constituents. River inputs are specified in terms of US Geological Survey (USGS) daily 

streamflow data and climatology. In the previously analyzed operational version (Richardson and 

Schmalz, 2007), SST data from the GOES AVHRR are assimilated. In experimental version one, 

improvements to the tidal dynamics have been made, while in experimental version two, in addition 

to the tidal improvement SSH data assimilation has been incorporated. Refer to Bleck et al. (2002) 

for further details regarding the HYCOM model development and computational algorithms. 

The University of North Carolina(UNC) ADCIRC western North Atlantic Forecast model is a twodimensional vertically integrated finite element model. The domain covers the western Atlantic 

Ocean from 60 degrees West and contains the Gulf of Mexico and spans 7.9 to 45.8 degrees North 

latitudes as shown in Figure 1.2. Tidal forcings include the M2, S2, N2, K2, K1, 2N2, O1, and Q1 tidal 

constituents (Blain et al., 2003). See Leuttich et al. (1992) and Kolar et al. (1994) for computational 

details. The system is run 4 times daily forced by the NWS North American Mesoscale (NAM) 10-

meter winds. Each cycle produces a 24 hour nowcast, and an 84 hour forecast forced by the NWS 

NAM model for the AWIP32 (221) grid. 

NOS/Coast Survey Development Laboratory (CSDL) has utilized the subtidal water level forecast 

guidance produced by the NWS Meteorological Development Laboratory (MDL) Extra-Tropical 

Storm Surge (ETSS) Model for offshore water level boundary conditions for the NOS New York 

Harbor /Port of New Jersey, Chesapeake Bay, and Galveston Bay operational forecast systems. 

Separate domains are run for the East Coast as shown in Figures 1.3 and 1.4, West Coast, Alaskan 

Coast, and Gulf of Mexico as shown in Figure 1.5. The NWS GFS is used to provide the 

meteorological forcings at approximately 100 km resolution. The two-dimensional depth averaged 

shallow water equations are solved in complex variables via finite differences on an elliptical grid. 

See Chen et al. (1993) for additional model details. 

The U.S. Navy (USN) Global Coastal Ocean Model (G-NCOM) system in Region 1 contains the 

western North Atlantic and Gulf of Mexico and is run on a 1/8 by 1/8 degree grid as shown in Figure 

1.6 based on the Princeton Ocean Model (POM) using 41 layers. See Blumberg and Mellor (1987) 
2

and Blumberg and Herring (1987) for computational details and Martin (2000) for operational 

implementation. The daily 00Z forecast cycle has a horizon out 72 hours and is forced by U.S. Navy 

Operational Global Atmospheric Prediction System (NOGAPS) winds and Multi-Channel Sea 

Surface Temperature (MCSST). Barotropic tides are added from the Oregon State global 1⁄4 by 1⁄4 

degree TPXO6.2 tidal model (Egbert and Erofeeva, 2002) for the above eight RTOFS constituents as 

well as the two long period constituents (Mf, Mm). 

Initially, the two experimental RTOFS versions are contrasted with the operational version during 

January through April 2006 for hours 1-24. Next ADCIRC nowcast and forecast guidance are 

evaluated over this same time period and contrasted with the RTOFS results. 

For November 2008, we have compared daily forecast/nowcast results of both subtidal (ETSS) and 

total water level response (RTOFS, G-NCOM, and ADCIRC) along the East coast and throughout 

the Gulf of Mexico from hours 6-36 for all models. Results are compared and contrasted versus 

observations and some initial conclusions drawn. A set of programs has been developed to perform 

the comparisons. The software is outlined in Appendix A and is largely as previously reported by 

Richardson and Schmalz (2007). Also in Appendix A, a description of each program is provided 

while complete script and control file listings are given in Appendix B.

Chapter 2 presents a description of all “cases”, a total of twelve, one including the ADCIRC 

harmonic analysis. Instruction on how to run the analysis program set is also provided. In Chapter 3, 

the two experimental RTOFS versions are compared with the operational RTOFS for the months of 

January, February, March, and April 2006. In Chapter 4, ADCIRC nowcasts and forecast guidance 

are evaluated. In addition, water level harmonic analysis results are presented to enumerate the 

ADCIRC tidal error. Analysis results from the months of January, February, March, and April 2006, 

involving RTOFS and ETSS are presented in Chapter 4. In Chapter 5, all the forecast model water 

levels are compared and contrasted to observations in November 2008. Chapter 6 presents some 

conclusions drawn from the work already completed (see Richardson and Schmalz, 2007) as well as 

this study, as well as recommendations for future subjects of investigation. 
3

Figure 1.1 RTOFS Grid with spacing from 5 to 17 km 

Figure 1.2. ADCIRC Western North Atlantic Grid along the East Coast with resolution ranging 

from 5.6 to 44.5 km. 
4

Figure 1.3 ETSS East Coast Grid with order 10 km coastal resolution 

Figure1.4. High Resolution ~6 km ETSS East Coast Grid in the Vicinity of Chesapeake and 

Delaware Bays. 
5

Figure 1.5 ETSS Gulf of Mexico Grid with order 10 km coastal resolution 

Figure 1.6 G-NCOM Grid in the Mid-Atlantic Region 1/8 degree ~ 10km 
6

2. CASE DESCRIPTIONS 

Twelve cases, as shown in Table 2.1, were developed to facilitate the comparison of a subtidal 

forecast model (ETSS) with three total water level forecast models including RTOFS, ADCIRC, and 

G-NCOM. As a prerequisite, the observed water level data obtained with respect to MLLW and 

GMT must be processed. This is performed with the program reform_coops.f described by 

Richardson and Schmalz (2004). For the subtidal comparison, the observed water level data were 30 

hour low pass filtered using program 30hourlp.f, a version of the standard Fourier filter program. 

Cases 1 through 12 are described in this chapter. Note that all water level processing is in GMT. 

 Table 2.1. Inventory of Evaluation Cases 

Case 

No. 

Case 

Descriptions 

Period 

 

(Hours) 

Analysis 

Month 

( No, 

Year) 

1 RTOFS forecast guidance (operational, adjusted) vs. 

observations 

1-24 1-4, 2006 

2 RTOFS forecast guidance (versions 1 and 2, adjusted) vs. 

observations 

1-24 1-4, 2006 

3 ADCIRC forecast guidance (adjusted) vs. observations 6-36 1-4, 2006 

4 ADCIRC nowcast (adjusted) vs. observations 1-24 1-4, 2006 

5 ADCIRC forecast guidance (adjusted) vs. observations 1-24 1-4, 2006 

6 RTOFS forecast guidance (adjusted) vs. observations 6-36 11, 2008 

7 ADCIRC forecast guidance (adjusted) vs. observations 6-36 11, 2008 

 8 G-NCOM forecast guidance (adjusted) vs. observations 6-36 11, 2008 

 9 ETSS subtidal forecast guidance (adjusted) vs. 30 hr LPF 

observations 

6-36 11, 2008 

10 ADCIRC Nowcast Processing and Harmonic Analysis 1-24 1-4. 2006 

 11 ADCIRC nowcast 30hr LPF (adjusted) vs. 30hr LPF 

observations 

1-24 1-4, 2006 

 12 G-NCOM forecast guidance (detided, adjusted) vs. 30hr LPF 

observations 

6-36 11, 2008 

Case 1: Operational RTOFS Total Water Level Comparison: Adjusted Forecast Guidance vs. 

Observations Hr 1-24 

The processing steps for the RTOFS daily forecast files are given in Table 2.2 and are discussed 

below. Readhycom.f reads the forecast output for hours 1 through 24. The output format is the 

standard ETSS format, and the naming convention for output files is hycom.(mn)(dy)(year), where 

mn is the month, dy is the day, and the year is 2006. Adjust24.f reads these water level values and 

adds an offset. The offset is determined by subtracting the first forecast value from the first 

observed value. This offset is added to each forecast value for hours 1 through 24. The naming 
7

convention for output files is hycom.(mn)(dy)(year)_adj. The adjusted daily forecast files are fed 

into the analysis program, wl_sa.ph24.f, for comparison with the observed data. Wl_sa.ph24.f is a 

revision of wl_sa.ph. The comparison is performed over hours 1 through 24, instead of hours 6 

through 36 as had been done previously. 

Table 2.2. Case 1: Operational RTOFS Total Water Level Comparison: Adjusted Forecast Guidance 

vs. Observations Hr 1-24 

Script Source File Control File 

readhy.jcl readhycom.f readhy.jan06.n 

adjust.jcl adjust24.f adj_rtofs.jan06.n 

wl_sa.jcl wl_sa.ph24.f wl_rtofs.jan06.n 

Case 2: RTOFS Versions 1 and 2 Total Water Level Comparison: Adjusted Forecast Guidance vs. 

Observations Hr 1-24 

Read_monrtofs.f reads the (versions 1 and 2) RTOFS model output from netCDF files which were 

provided in the form of monthly concatenated files. These monthly concatenated files are converted 

into daily forecast files, for hours 1 through 24, just as we worked with before. Adjust24.f is a 

revision of adjust_blk.f. Adjust24.f adjusts model values for hours 1 through 24, instead of hours 6 

through 36, as had been done previously. The naming convention for output files is 

rtofs.(mn)(dy)(year)_adj. Wl_sa.ph24.f carries out the comparison with the observed values for 

hours 1 through 24. All processing steps are shown in Table 2.3. 

Table 2.3. Case 2: RTOFS Versions 1 and 2 Total Water Level Comparison: Adjusted Forecast 

Guidance vs. Observations Hr 1-24 

Script Source File Control File 

month.jcl read_monrtofs.f readhy.jan06.n 

adjust.jcl adjust24.f adj_rtofs.jan06mon.n 

wl_sa.jcl wl_sa.ph24.f wl_rtofs.jan06mon.n 

Case 3: ADCIRC Total Water Level Comparison: Adjusted Forecast Guidance vs. Observations Hr 

6-36 

Readadcirc.f reads ADCIRC forecast water level output. The naming convention for output files is 

adcirc.(year)(mn)(dy). The forecast output is adjusted to the observed in the standard way by 

adjust_blk.f. The naming convention for output files is adcirc.(year)(mn)(dy)_adj. The analysis is 

performed by wl_sa.ph.f for hours 6 through 36 of the Forecast Guidance cycle. All processing 

steps are shown in Table 2.4. 
8

Table 2.4. Case 3: ADCIRC Total Water Level Comparison: Adjusted Forecast Guidance vs. 

Observations Hr 6-36 

Script Source File Control File 

readadc.jcl read_adcirc.f adc_jan06.n 

adjust.jcl adjust_blk.f adj_adcirc.jan06.n 

wl_sa.jcl wl_sa.ph.f wl_adcirc.jan06.n 

Case 4: ADCIRC Total Water Level Comparison: Adjusted Nowcast vs. Observations Hr 1-24 

Readadcnew24.f reads ADCIRC nowcast water level values for hours 1 through 24. Adjust24.f 

reads these water level values and adds the appropriate offset, for hours 1 through 24. The naming 

convention for output files is rtofs.(mn)(dy)(year)_adj. The analysis is performed by wl_sa.ph24.f 

for hours 1 through 24 of the cycle. All processing steps are shown in Table 2.5. 

Table 2.5. Case 4: ADCIRC Total Water Level Comparison: Adjusted Nowcast vs. Observations Hr 

1-24 

Script Source File Control File 

readadcnew24.jcl read_adcnew24.f adcnew24_jan06.n 

adjust.jcl adjust24.f adj_adcnew.jan06.n 

wl_sa.jcl wl_sa.ph24.f wl_adcnew.jan06.n 

Case 5: ADCIRC Total Water level Comparison: Adjusted Forecast Guidance vs. Observations Hr 

1-24 

Readadcirc24.f reads ADCIRC forecast output for hours 1 through 24 of the forecast cycle. These 

forecast values are adjusted by adjust24.f. Analysis is performed by wl_sa.ph24.f. All processing 

steps are shown in Table 2.6. 

Table 2.6. Case 5: ADCIRC Total Water Level Comparison: Adjusted Forecast Guidance vs. 

Observations Hr 1-24 

Script Source File Control File 

readadcirc24.jcl read_adcirc24.f adc_jan06.n 

adjust.jcl adjust24.f adj_adcold.jan06.n 

wl_sa.jcl wl_sa.ph24.f wl_adcold.jan06.n 

Case 6: Operational RTOFS Total Water Level Comparison: Adjusted Forecast Guidance vs. 

Observations Hr 6-36 

Readrtofs.f reads daily RTOFS forecast output, hours 6 through 36, from netCDF. The output files 

are in standard ETSS block format, and the naming convention is rtofs.(mn)(dy)(year). Adjust_blk.f 

adjusts the model values in the standard way. The naming convention for output files is 

rtofs.(mn)(dy)(year)_adj. Wl_sa.ph.f carries out the comparison, hours 6 through 36, with the 

observed data. All processing steps are shown in Table 2.7. 
9

Table 2.7. Case 6: Operational RTOFS Total Water Level Comparison: Adjusted Forecast Guidance 

vs. Observations Hr 6-36 

Script Source File Control File 

rtofs.jcl readrtofs.f readhy.nov08.n 

adjust.jcl adjust_blk.f adj_rtofs.nov08.n 

wl_sa.jcl wl_sa.ph.f wl_rtofs.nov08.n 

Case 7: ADCIRC Total Water Level Comparison: Adjusted Forecast Guidance vs. Observations Hr 

6-36 

Readadcirc.f reads ADCIRC forecast water level output for hours 6 through 36 of each forecast 

cycle. The naming convention for output files is adcirc.(year)(mn)(dy). Adjust_blk.f adjusts the 

forecast output in the standard way by adding the appropriate offset. The naming convention for 

output files is adcirc(year)(mn)(dy)_adj. Wl_sa.ph.f carries out the comparison with observed 

values, hours 6 through 36, in the standard way. All processing steps are shown in Table 2.8. 

Table 2.8. Case 7: ADCIRC Total Water Level Comparison: Adjusted Forecast Guidance vs. 

Observations Hr 6-36 

Script Source File Control File 

readadc.jcl read_adcirc.f adc_nov08.n 

adjust.jcl adjust_blk.f adj_adcirc.nov08.n 

wl_sa.jcl wl_sa.ph.f wl_adcirc.nov08.n 

Case 8: G-NCOM Total Water Level Comparison: Adjusted Forecast Guidance vs. Observations Hr 

6-36 

Readncom.f reads G-NCOM forecast water level output from netCDF for hours 1 through 36. These 

daily netCDF files are converted to an output of daily forecast files in standard block format. 

However, the G-NCOM forecast output is at 3 hour intervals. Adjust_blk adds the offset (first 

observed value – the first forecast value) to the model values at 3 hour intervals. The naming 

convention for the adjusted output files is ncom.(mn)(dy)(year)_adj. Wl_sa.ph.f analyzes these 

adjusted forecast output vs. the observed water level values for hours 1 through 36 (at 3 hour 

intervals). All processing steps are shown in Table 2.9. 
10

Table 2.9. Case 8: G-NCOM Total Water Level Comparison: Adjusted Forecast Guidance vs. 

Observations Hr 6-36 

Script Source File Control File 

readncom.jcl readncom.f readncom.nov08.n 

adjust.jcl adjust_blk.f adj_ncom.nov08.n 

wl_sa.jcl wl_sa.ph.f wl_ncom.nov08.n 

Case 9: ETSS Subtidal Water Level Comparison: Adjusted Forecast Guidance vs. Filtered 

Observations Hr 6-36 

ETSS forecast files were copied to the analysis home directory. The directory structure is divided 

into ec (East Coast) and gm (Gulf of Mexico). The files are daily forecast files for all stations for 

that region. The water level forecast output is recorded in tenths of feet. The processing steps 

itemized in Table 2.10 are discussed in turn below. Read_tdl.f reads the water level data for each 

station, from hours 6 through 36, and converts the values from tenths of feet to meters. The naming 

convention of the output file is etss.(mn)(dy)(year) where mn is month, dy is day, and year is 2006. 

Adjust_blk.f reads these water level values (in meters) and adds an offset. The offset is determined 

by subtracting the first forecast value from the first observed value. This offset is then added to all 

of the forecast values through hour 36. The output format from this program is identical to the 

standard ETSS block format that it read the data from. The naming convention for the output files is 

etss.(nm)(dy)(year)_adj. Each daily adjusted forecast file is fed into the analysis program, 

wl_sa.ph.f, for comparison with the observed data. The comparison is performed over hours 6 

through 36 of each daily forecast cycle. All processing steps are shown in Table 2.10. Note since the 

ETTS forecast water levels are subtidal, the observed water levels are 30 hour low pass filtered. 

Table 2.10. Case 9: ETSS Subtidal Water Level Comparison: Adjusted Forecast Guidance vs. 

Filtered Observations Hr 6-36 

Script Source File Control File 

read_tdl.jcl read_tdl.f read_nov08.n 

adjust.jcl adjust_blk.f adj_etss.nov08.n 

wl_sa.jcl wl_sa.ph.f wl_tdl.nov08.n 

Case 10. ADCIRC Nowcast Processing and Harmonic Analysis 

The nowcast processing and harmonic analysis steps are given in Table 2.11 and described 

below. 

Table 2.11. Case 10: ADCIRC Nowcast Processing and Harmonic Analysis 

Script Source File Control File 

readadcnew24.jcl read_adcnew24.f adcnew24_jan06.n 

hycomha.jcl hycom29.f hycomha_jan06.n 

harm29d.jcl harm29d.f - 

const.jcl const2.f constt.jan06.n 
11

The ADCIRC nowcasts were extracted from the daily forecast files. The forecast output begins on 

hour 1 of that specified day. The 24 previous hourly values (-23 through 0, column 1), beginning at 

hour 1 of the previous day and continuing through hour 0 of the present day, are the nowcast data 

associated with the present nowcast/forecast cycle. Readhyc_nowc.f reads from the nowcast/forecast 

file, then reformats the nowcasts into the standard ETSS block format. The naming convention for 

the reformatted daily nowcast files is hycom.(mn)(dy)(year). Dy of the output file will always be 

one day prior to that of the original nowcast/forecast file. 

One purpose for working with the ADCIRC nowcasts was to perform harmonic analysis. 

Hycom29.f performs two functions necessary to run harm29. The nowcast data are read from the 

previously created nowcast daily files. The daily nowcast data is written to output files (by station) 

and concatenated. So for each station file, there is a continuous data string for the entire month (this 

is a necessary condition for the 30 hour low pass filter process). The naming convention for the 

output files is *_nowc.jan06. The program also creates the control files necessary to run harm29. 

The naming convention for these control files is control.*.001. The final step in the processing of 

nowcasts is to run program hyc_reform.f. This program will read the month long RTOFS nowcast 

data files (by station) and create from them the daily nowcast files in standard ETSS “block” format. 

The harmonic analysis was performed by running a script (harm29d.jcl) using NOS standard 

procedures as outlined by Zervas (1997). An output file for each station was created with the 

naming convention *_nowc.jan06.cons. 24 harmonic constituents, amplitude and phase, are written 

to output using the standard NOS format of 7(f5.3,f4.1). Const2.f was created to display the 

harmonic constants derived from harm29 along with the accepted harmonic constants from CO-OPS. 

 For each of the 24 constituents, the amplitude and phase (harm29 and accepted) are written to a 

table. The difference for both amplitude and phase are calculated and written to the table. Using 

these calculated values of difference for all 24 constituents, const2.f calculates an estimate of the 

RMS difference using a method discussed by Hess (1994). Also calculated is a NOS constituent 

weighted gain and phase difference in hours. 

Case 11: ADCIRC Subtidal Water Level Comparison: Nowcast vs. Filtered Observations 

Hr 1-24 

This comparison was done with the filtered and adjusted nowcast values vs. the filtered observed 

values. Processing steps are shown in Table 2.12. Note that it is necessary to first go from ETSS 

standard block format to single station file format to do the filtering and then to return to the ETSS 

block format for the adjustment and analysis steps. 
12

Table 2.12. Case 11. ADCIRC Subtidal Water Level Comparison: Filtered and Adjusted Nowcast 

vs. Filtered Observations Hr 1-24 

Script Source File Control File 

readadcnew24.jcl read_adcnew24.f adcnew24_jan06.n 

hycomha.jcl hycom29.f hycomha_jan06.n 

30hourlp.jcl 30hourlp.f interactive prompt 

hycref.jcl hyc_reform.f hycref30.jan06.n 

adjust.jcl adjust_blk.f adj_hyc.n30.jan06.n 

wl_sa.jcl wl_sa.ph.f wl_adc.nowc.jan06.n 

Case 12: G-NCOM Subtidal Water Level Comparison: Detided and Adjusted Forecast Guidance 

vs. Filtered Observations Hr 6-36 

NOS accepted harmonic constants for the ten tidal constituents used in the OSU tide model 

(TPXO6.2, Egbert and Erofeeva, 2002) were fed into the standard NOS prediction program 

(Program Pred) generating a month long prediction for each station (Zervas, 1997). These predicted 

values were subtracted from the forecast output, resulting in a de-tided series, which was adjusted 

and compared against the filtered observations as shown in Table 2.13. OSU tide model results at the 

G-NCOM water level station grid points were not used in the detiding. 

Table 2.13. Case 12: G-NCOM Subtidal Water Level Comparison: Detided and Adjusted Forecast 

Guidance vs. Filtered Observations Hr 6-36 

Script Source File Control File 

readncom.jcl readncom.f readncom.nov08.n 

readpred.jcl readpred.f read_nov08det.n 

adjust.jcl adjust_blk.f adj_ncomdet.nov08.n 

wl_sa.jcl wl_sa.ph.f wl_ncomdet.nov08.n 
13

3. RTOFS WATER LEVEL ANALYSIS RESULTS 

RTOFS experimental versions 1 and 2 water level forecasts were evaluated for each of the months 

January-April 2006 for hours 1-24. Next these forecasts were compared to the RTOFS operational 

water level forecast for each of the months January-April 2006 for hours 1 -24. It was necessary to 

use this time horizon, since the experimental version results were supplied in concatenated daily 

form. RMSEs with respect to NOS observations are given in Table 3.1 for each month. 

Table 3.1. RTOFS Operational and Experimental Forecast Guidance Monthly Water Level 

Comparisons to NOS Observations January – April 2006 (RMSE [meters]). Forecast hours 1-24 are 

used in the comparisons. Table entries are operational forecast guidance/experimental forecast 1 

guidance /experimental forecast 2 guidance. 

Station January February March April 

Eastport, ME 1.95/2.44/2.42 1.86/2.28/2.25 1.85/2.42/2.41 1.74/2.37/2.35 

Portland, ME 1.10/1.38/1.37 1.04/1.25/1.24 1.04/1.37/1.36 0.96/1.32/1.34 

Boston, MA 1.09/1.28/1.28 1.03/1.28/1.29 1.05/1.17/1.17 0.97/1.37/1.39 

Woods Hole, 

MA 

0.50/0.24/0.24 0.49/0.24/0.26 0.50/0.27/0.29 0.51/0.25/0.27 

Sandy Hook, NJ 0.96/0.44/0.45 0.95/0.43/0.44 0.94/0.45/0.48 0.95/0.49/0.50 

Atlantic City, NJ 0.68/0.34/0.34 0.68/0.33/0.34 0.66/0.40/0.40 0.67/0.39/0.41 

Cape May, NJ 0.83/0.39/0.39 0.81/0.36/0.36 0.76/0.40/0.41 0.80/0.40/0.42 

Lewes, DE 0.72/0.31/0.32 0.71/0.30/0.30 0.68/0.34/0.34 0.70/0.32/0.33 

Duck, NC 0.62/0.29/0.29 0.65/0.27/0.28 0.68/0.33/0.34 0.72/0.33/0.34 

Wilmington, NC 1.37/0.72/0.70 1.40/0.69/0.67 1.37/0.66/0.65 1.36/0.64/0.64 

Springmaid Pier, 

SC 

0.95/0.53/0.54 0.96/0.52/0.54 0.94/0.59/0.61 0.93/0.56/0.56 

Charleston, SC 1.19/0.61/0.60 1.20/0.58/0.59 1.21/0.65/0.67 1.21/0.63/0.64 

Fort Pulaski, GA 1.65/0.81/0.81 1.68/0.78/0.78 1.66/0.88/0.88 1.66/0.84/0.83 

Fernandina 

Beach, FL 

1.56/0.67/0.68 1.55/0.66/0.66 1.58/0.70/0.73 1.60/0.68/0.70 

Mayport, FL 1.31/0.48/0.49 1.31/0.49/0.47 1.35/0.51/0.52 1.36/0.48/0.49 

Naples, FL 0.78/0.27/0.28 0.80/0.32/0.34 0.78/0.23/0.25 0.76/0.26/0.31 

Clearwater, FL 0.58/0.45/0.46 0.55/0.31/0.31 0.59/0.32/0.32 0.55/0.36/0.31 

Apalachicola, FL 0.25/0.54/0.55 0.25/0.32/0.32 0.23/0.35/0.36 0.22/0.67/0.70 

Panama City, FL 0.13/0.27/0.27 0.12/0.16/0.15 0.13/0.18/0.19 0.14/0.28/0.31 

Pensacola, FL 0.18/0.22/0.22 0.18/0.23/0.22 0.18/0.24/0.25 0.21/0.28/0.30 

Sabine Pass, TX 0.61/0.28/0.28 0.63/0.45/0.45 0.64/0.50/0.51 0.63/0.31/0.32 

Galveston 

Pleasure Pier, 

TX 

0.43/0.40/0.40 0.48/0.35/0.35 0.49/0.39/0.40 0.49/0.47/0.48 

Freeport, TX 0.15/0.32/0.33 0.18/0.21/0.22 0.18/0.25/0.27 0.18/0.37/0.38 
14

 

Results for RTOFS experimental version 2, which includes the sea surface height (SSH) 

assimilation, are nearly the same as those in RTOFS experimental version 1 without SSH 

assimilation. This indicates that the SSH assimilation has a minor impact on coastal water levels. 

RTOFS Experimental versions 1 and 2 include improved tidal dynamics relative to the operational 

version. In Figure 3.1-3.4, the RMSEs for the operational version are plotted against the RMSEs for 

experimental version 1, along the Atlantic seaboard in Part (a) and along the Gulf Coast in Part (b), 

for the months January through April 2006, respectively. Note the consistency of the comparisons 

from month to month. In Figures 3.5-3.10, the RTOFS experimental version 1 forecast water levels 

are plotted versus water level observation over the first ten days during January 2006 (which are 

representative of conditions over the entire month) at Sandy Hook, NJ, Cape May, NJ, Charleston, 

SC, Mayport, FL, Naples, FL, and Galveston Pleasure Pier, TX, respectively. Note despite the 

adjustment applied at the start of each daily forecast, the forecast curves are nearly continuous at all 

stations. 
15

(a) 

(b) 

Figure 3.1. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water Level 

Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf of 

Mexico Stations (b) for January 2006.
16

 

(a) 

(b) 

Figure 3.2. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water Level 

Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf of 

Mexico Stations (b) for February 2006.
17

 

(a) 

(b) 

Figure 3.3. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water Level 

Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico 

Stations and (b) for March 2006. 
18

(a) 

(b) 

Figure 3.4. Experimental Version 1 RTOFS vs. Operational Version RTOFS Total Water Level 

Forecast Guidance RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico 

Stations and (b) for April 2006. 
19

(a) 

(b) 

Figure 3.5. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level Forecast 

Guidance against NOS Water Level Observations at Sandy Hook, NJ for January 2006. 

Operational RTOFS results are shown in (a), while Experimental Version 1 RTOFS 

results are shown in (b). Note (+,*,Δ, and ) are used to designate alternate 24 hour 

forecast values with the first symbol in the forecast series always on the observation 

curve due to the adjustment process. 
20

(a) 

(b) 

Figure 3.6. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level Forecast 

Guidance against NOS Water Level Observations at Cape May, NJ for January 2006. 

Operational RTOFS results are shown in (a), while Experimental Version 1 RTOFS 

results are shown in b). Note (+,*,Δ, and ) are used to designate alternate 24 hour 

forecast values with the first symbol in the forecast series always on the observation 

curve due to the adjustment process. 
21

(a) 

(b) 

Figure 3.7. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level Forecast 

Guidance against NOS Water Level Observations at Charleston, SC for January 2006. 

Operational RTOFS results are shown in (a), while Experimental Version 1 RTOFS 

results are shown in (b). Note (+,*,Δ, and ) are used to designate alternate 24 hour 

forecast values with the first symbol in the forecast series always on the observation 

curve due to the adjustment process. 
22

(a)

(b) 

Figure 3.8. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level Forecast 

Guidance against NOS Water Level Observations at Mayport, FL for January 2006. 

Operational RTOFS results are shown in (a), while Experimental Version 1 RTOFS 

results are shown in (b). Note (+,*,Δ, and ) are used to designate alternate 24 hour 

forecast values with the first symbol in the forecast series always on the observation 

curve due to the adjustment process 
23

(a) 

(b) 

Figure 3.9. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level Forecast 

Guidance against NOS Water Level Observations at Naples, FL for January 2006. 

Operational RTOFS results are shown in (a), while Experimental Version 1 RTOFS 

results are shown in (b). Note (+,*,Δ, and ) are used to designate alternate 24 hour 

forecast values with the first symbol in the forecast series always on the observation 

curve due to the adjustment process. 
24

(a)

(b) 

Figure 3.10. Operational RTOFS vs. Experimental Version 1 RTOFS Total Water Level Forecast 

Guidance against NOS Water Level Observations at Galveston Pleasure Pier, TX for 

January 2006. Operational RTOFS results are shown in (a), while Experimental 

Version 1 RTOFS results are shown in (b). Note (+,*,Δ, and ) are used to 

designate alternate 24 hour forecast values with the first symbol in the forecast series 

always on the observation curve due to the adjustment process. 
25

4. ADCIRC WATER LEVEL ANALYSIS RESULTS

ADCIRC vs. RTOFS 

ADCIRC total water level forecast guidance comparisons were made to the operational RTOFS 

version results previously reported by Richardson and Schmalz (2007) for forecast hours 6-36 for 

each of the four months January – April 2006 in Table 4.1. ADCIRC forecast guidance is shown 

versus the operational RTOFS version results in Figures 4.1 for January, in Figure 4.2 for February, 

in Figure 4.3 for March, and in Figure 4.4 for April, respectively. In each figure RMSE with respect 

to the NOS observations at the East Coast stations are shown in Part a, while the Gulf stations are 

given in Part b. 

Table 4.1. ADCIRC and RTOFS Operational Forecast Guidance Monthly Water Level Comparisons 

to NOS Observations January – April 2006 (RMSE [meters]). Forecast hours 6-36 are used in the 

comparisons. Table entries are ADCIRC forecast/ RTOFS forecast. 

Station January February March April 

Eastport, ME 0.67/1.84 0.68/1.80 0.68/1.73 0.66/1.71 

Portland, ME 0.34/1.01 0.33/0.97 0.30/0.95 0.28/0.91 

Boston, MA 0.35/1.01 0.33/0.97 0.31/0.94 0.30/0.90 

Woods Hole, MA 

 

0.22/0.47 0.19/0.47 0.19/0.50 0.19/0.51 

Sandy Hook, NJ 0.19/0.99 0.18/0.98 0.13/0.97 0.10/0.98 

Atlantic City, NJ 0.13/0.67 0.14/0.67 0.14/0.65 0.10/0.66 

Cape May, NJ 0.17/0.81 0.16/0.75 0.18/0.76 0.12/0.80 

Lewes, DE 0.16/0.70 0.17/0.66 0.14/0.70 0.10/0.71 

Duck, NC 0.11/0.69 0.11/0.65 0.12/0.70 0.12/0.69 

Wilmington, NC 0.73/1.38 0.70/1.35 0.73/1.44 0.71/1.37 

Springmaid Pier, 

SC 

0.14/1.00 0.12/0.98 0.14/1.01 0.13/1.01 

Charleston, SC 0.27/1.20 0.25/1.20 0.26/1.25 0.22/1.25 

Fort Pulaski, GA 0.31/1.66 0.29/1.60 0.29/1.71 0.25/1.70 

Fernandina Beach, 

FL 

0.40/1.51 0.36/1.41 0.37/1.54 0.35/1.52 

Mayport, FL 0.21/1.25 0.20/1.17 0.19/1.27 0.18/1.26 

Naples, FL 0.14/0.77 0.12/0.77 0.14/0.80 0.12/0.78 

Clearwater, FL 0.13/0.54 0.14/0.52 0.13/0.53 0.12/0.53 

Apalachicola, FL 0.12/0.24 0.12/0.22 0.12/0.21 0.10/0.19 

Panama City, FL 0.15/0.15 0.16/0.14 0.14/0.14 0.10/0.14 

Pensacola, FL 0.09/0.19 0.09/0.20 0.07/0.18 0.07/0.18 

Sabine Pass, TX 0.18/0.61 0.21/0.64 0.21/0.67 0.20/0.67 

Galveston Pleasure 

Pier, TX 

0.13/0.44 0.13/0.44 0.12/0.45 0.12/0.44 

Freeport, TX 0.12/0.19 0.12/0.16 0.11/0.15 0.11/0.14 
26

 

(a) 

(b) 

Figure 4.1. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for 

January 2006. 
27

(a) 

(b) 

Figure 4.2. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for 

February 2006. 
28

(a)

(b) 

Figure 4.3. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for 

March 2006.
29

(a)

(b) 

Figure 4.4. ADCIRC vs. RTOFS Operational Version Total Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf Stations (b) for April 2006.
30

The same procedures for adjustment of the initial forecast hour to the observations were followed 

for each forecast type. ADCIRC forecast guidance RMSEs are order 1/3 of the RTOFS RMSEs for 

the East Coast stations and order 1⁄2 the RTOFS RMSEs for the Gulf stations. 

ADCIRC Nowcast vs. Forecast 

ADCIRC nowcast RMSEs are contrasted with forecast guidance RMSEs for each month for hours 1-

24 of the forecast corresponding to the next nowcast period. Water levels were adjusted to match 

the NOS observations for the first hour with the adjustment used for the remaining 23 hours. 

Nowcast and forecast errors are nearly identical for all four months and are as shown for February 

2006 along the Atlantic coast in Figures 4.6-4.7 and along the Gulf coast in Figures 4.8-4.9. 

Nowcast and forecast guidance RMSEs are shown in Table 4.2 and in Figure 4.5 for January 2006. 

Table 4.2. ADCIRC Forecast Guidance and Nowcast Monthly Water Level Comparisons to NOS 

Observations January – April 2006 (RMSE [meters]). Nowcast hours 1-24 and corresponding 

forecast hours 1-24 are used in the comparisons. Table entries are forecast guidance/nowcast. 

Station January February March April 

Eastport, ME 0.76/0.77 0.77/0.76 0.71/0.70 0.66/0.66 

Portland, ME 0.36/0.36 0.35/0.35 0.32/0.31 0.31/0.31 

Boston, MA 0.39/0.39 0.37/0.37 0.32/0.32 0.32/0.32 

Woods Hole, MA 

 

0.24/0.25 0.22/0.22 0.21/0.21 0.20/0.20 

Sandy Hook, NJ 0.16/0.16 0.16/0.18 0.13/0.14 0.14/0.13 

Atlantic City, NJ 0.14/0.14 0.14/0.15 0.11/0.11 0.11/0.11 

Cape May, NJ 0.14/0.15 0.15/0.16 0.16/0.17 0.15/0.14 

Lewes, DE 0.16/0.16 0.14/0.15 0.13/0.14 0.12/0.11 

Duck, NC 0.10/0.09 0.11/0.12 0.11/0.10 0.10/0.10 

Wilmington, NC 0.74/0.74 0.72/0.73 0.69/0.69 0.70/0.70 

Springmaid Pier, 

SC 

0.12/0.12 0.14/0.15 0.16/0.15 0.15/0.15 

Charleston, SC 0.23/0.24 0.25/0.25 0.24/0.24 0.22/0.22 

Fort Pulaski, GA 0.29/0.30 0.32/0.31 0.28/0.28 0.25/0.25 

Fernandina Beach, 

FL 

0.39/0.38 0.38/0.38 0.36/0.36 0.36/0.36 

Mayport, FL 0.21/0.20 0.20/0.20 0.20/0.20 0.20/0.20 

Naples, FL 0.16/0.16 0.14/0.14 0.17/0.16 0.13/0.13 

Clearwater, FL 0.13/0.13 0.11/0.11 0.11/0.10 0.11/0.11 

Apalachicola, FL 0.13/0.13 0.12/0.12 0.13/0.12 0.10/0.10 

Panama City, FL 0.14/0.14 0.13/0.13 0.11/0.12 0.10/0.10 

Pensacola, FL 0.08/0.08 0.09/0.09 0.09/0.09 0.09/0.08 

Sabine Pass, TX 0.18/0.19 0.19/0.20 0.18/0.18 0.18/0.18 

Galveston Pleasure 

Pier, TX 

0.11/0.12 0.11/0.11 0.11/0.11 0.12/0.12 

Freeport, TX 0.09/0.10 0.10/0.10 0.10/0.10 0.10/0.10 
31

(a) 

(b) 

Figure 4.5. ADCIRC Nowcast vs. ADCIRC Total Water Level Forecast Guidance RMSE 

(meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for January 

2006.
32

 (a) 

(b) 

Figure 4.6. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Sandy Hook, NJ for February 2006. Note (+,*,Δ, and ) are used to designate 

alternate 24 hour forecast and nowcast series with the first symbol in the series 

always on the observation curve due to the adjustment process.
33

(a)

(b)

Figure 4.7. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Mayport, FL for February 2006. Note (+,*,Δ, and ) are used to designate alternate 

24 hour forecast and nowcast series with the first symbol in the series always on the 

observation curve due to the adjustment process.
34

(a)

(b)

Figure 4.8. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Clearwater, FL for February 2006. Note (+,*,Δ, and ) are used to designate alternate 

24 hour forecast and nowcast series with the first symbol in the series always on the 

observation curve due to the adjustment process.
35

(a)

(b)

Figure 4.9. ADCIRC Forecast Guidance (a) vs. ADCIRC Nowcast (b) Total Water Level for 

Galveston Pleasure Pier, TX for February 2006. Note (+,*,Δ, and ) are used to 

designate alternate 24 hour forecast and nowcast series with the first symbol in the 

series always on the observation curve due to the adjustment process.
36

ADCIRC Nowcast Harmonic Analysis 

To assess the error in the tidal portion of the ADCIRC water level forecast, it was necessary to use 

the following methodology. The daily water level forecasts could not be directly concatenated to 

produce the requisite monthly (29 day) series, since they may be discontinuous at the start and end 

of each 24 hour period. As a result, it was necessary to concatenate each 24 hour nowcast to avoid 

the discontinuities. Since the same tidal forcing is used during both the nowcast and forecast, this 

procedure should be valid. 29 day harmonic analyses were performed for each month, January 

through April, to produce 24 tidal constituents. NOS accepted harmonic constants are based on a 

least squares analysis of a minimum of one year record for the short term constituents, which are 

then increased by order 2-3% to enable a more favorable comparison to observations. For the long 

term constituents, Sa and Ssa, usually several year analyses are averaged. 

In Table 4.3, we consider the two major tidal constituents M2 and S2 and compare the ADCIRC 

harmonic analysis results with the NOS accepted harmonic constants. The amplitude and phase 

differences (ADCIRC – NOS) are given at selected locations where NOS nowcast/forecast systems 

have been developed or are planned in the near future. It is noted that ADCIRC under predicts the 

M2 and over predicts S2 tidal amplitudes at the majority of stations. ADCIRC leads in phase at most 

stations with respect to the NOS values for both constituents. 

 Table 4.3. M2/S2 ADCIRC vs. NOS Harmonic Analysis Results 

 at Nowcast/Forecast System Boundary Locations for January 2006 

NOS 

Station 

ADCIRC 

Amp(m) 

NOS 

Amp(m)

Difference

(m) 

ADCIRC 

Phase (o)

NOS 

Phase (o)

Difference 

(o) 

Sandy Hook, 

NJ 

NYOFS 

0.680 

0.154 

0.688 

0.134 

-0.008 

 0.020 

2.7 

6.2 

6.0 

32.6 

 -3.3 

-26.4 

Cape May, 

NJ 

DBOFS 

0.661 

0.123 

0.714 

0.125 

-0.053 

-0.002 

30.4 

37.1 

28.6 

55.3 

 1.8 

-18.2 

Charleston, 

SC 

CHOFS 

0.682 

0.137 

0.783 

0.119 

-0.101 

 0.018 

353.3 

351.2 

10.4 

36.1 

-17.1 

-44.9 

Mayport, 

FL 

SJOFS 

0.794 

0.154 

0.676 

0.105 

0.118 

0.049 

13.5 

13.8 

25.3 

48.3 

-11.8 

-34.5 

Naples, FL 

TBOFS 

0.250 

0.125 

0.286 

0.096 

-0.036 

 0.029 

126.4 

114.3 

144.2 

156.1 

-17.8 

-41.8 

Galveston, 

TX 

GBOFS 

0.128 

0.073 

0.139 

0.034 

-0.011 

 0.039 

272.0 

255.7 

276.1 

267.9 

 -4.10 

-12.2 
37

In Tables 4.4-4.8, detailed constituent comparisons are presented at Boston, MA, Sandy Hook, NJ, 

Cape May, NJ, Charleston, SC, and Mayport, FL, respectively, for the East Coast. In Tables 4.9-

4.12 results are presented in the same format at Naples, FL, Panama City, FL, Sabine Pass, TX, and 

Galveston Pleasure Pier, TX, for the Gulf Coast. As noted above for ADCIRC only 24 constituents 

are derived. The remainder of the 37 constituents not derived are indicated by ******. Note at the 

bottom of each table gain, phase, and an estimated RMS error are given. The gain of each 

constituent, ADCIRC/NOS, is first computed. The gain given is a weighted gain of each of the 24 

constituent gains, with the weights determined by the NOS accepted constituent amplitudes. A 

similar procedure is used to determine the phase, which is expressed in hours. An estimated RMS 

error is computed based on the individual constituent amplitude and phase differences following a 

method given by Hess (1994). Note a negative phase indicates that ADCIRC leads the NOS 

prediction. Best results along the East Coast are obtained at Duck, NC where the gain is 0.99, the 

phase difference is -0.16 hour, and the estimated RMS error is 4 cm, while along the Gulf Coast best 

results are achieved at Panama City, FL where the gain is 1.04, phase difference is -0.16 hour, and 

the estimated RMS error is 3 cm. 

To examine the consistency of the ADCIRC 29 day harmonic analysis, additional 29-day analyses 

were performed for February, March, and April 2006. The results at all 24 coastal stations are 

summarized in terms of NOS harmonic constituent weighted gain and phase in Table 4.13 and in 

terms of estimated RMS error in Table 4.14. In general, one notes very similar values of gain, 

phase, and estimated RMS error at each station for all four months. 
38

Table 4.4. ADCIRC vs. NOS Harmonic Analysis Results at Boston, MA for January 2006 

 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 1.5950 101.80 1.3980 109.40 0.1970 -7.60 

 S(2) 0.2840 131.30 0.2130 146.20 0.0710 -14.90 

 N(2) 0.3290 68.60 0.3090 78.90 0.0200 -10.30 

 K(1) 0.0960 200.70 0.1430 205.20 -.0470 -4.50 

 M(4) 0.0680 31.80 0.0230 25.90 0.0450 5.90 

 O(1) 0.1030 183.10 0.1190 186.70 -.0160 -3.60 

 M(6) 0.0220 86.80 0.0340 282.10 -.0120 164.70 

 MK(3) ****** ****** 0.0050 232.50 ****** ******* 

 S(4) 0.0010 204.00 0.0000 0.00 0.0010 -156.00 

 MN(4) ****** ****** 0.0110 14.60 ****** ******* 

 NU(2) 0.0640 73.10 0.0670 85.50 -.0030 -12.40 

 S(6) 0.0010 316.10 0.0000 0.00 0.0010 -43.90 

 MU(2) ****** ****** 0.0100 69.00 ****** ******* 

 2N(2) 0.0440 35.40 0.0390 55.00 0.0050 -19.60 

 OO(1) 0.0040 218.30 0.0050 227.00 -.0010 -8.70 

 LAMBD 0.0110 115.50 0.0220 143.20 -.0110 -27.70 

 S1 ****** ****** 0.0040 122.80 ****** ******* 

 M(1) 0.0070 191.90 0.0070 214.40 0.0000 -22.50 

 J(1) 0.0080 209.50 0.0100 213.50 -.0020 -4.00 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0180 89.80 ****** ******* 

 SA ****** ****** 0.0320 126.30 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0040 175.50 0.0030 152.80 0.0010 22.70 

 Q(1) 0.0200 174.40 0.0210 171.10 -.0010 3.30 

 T2 0.0170 130.10 0.0190 123.90 -.0020 6.20 

 R2 0.0020 132.50 0.0050 8.20 -.0030 124.30 

 2Q(1) 0.0030 165.60 0.0030 168.30 0.0000 -2.70 

 P(1) 0.0320 199.40 0.0470 202.10 -.0150 -2.70 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0000 0.00 ****** ******* 

 L(2) 0.0470 68.60 0.0550 156.20 -.0080 -87.60 

 2MK(3 ****** ****** 0.0070 207.90 ****** ******* 

 K(2) 0.0770 133.70 0.0590 144.50 0.0180 -10.80 

 M(8) 0.0050 262.80 0.0060 237.10 -.0010 25.70 

 MS(4) ****** ****** 0.0090 68.70 ****** ******* 

 GAIN (-): 1.09 

 PHASE (HR): -0.33 

 EST. RMS (M): 0.23 
39

Table 4.5. ADCIRC vs. NOS Harmonic Analysis Results at Sandy Hook, NJ for January 2006 

 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.6800 2.70 0.6880 6.00 -.0080 -3.30 

 S(2) 0.1540 6.20 0.1340 32.60 0.0200 -26.40 

 N(2) 0.1510 336.00 0.1580 348.60 -.0070 -12.60 

 K(1) 0.0790 170.40 0.1030 175.70 -.0240 -5.30 

 M(4) 0.0200 299.40 0.0160 269.70 0.0040 29.70 

 O(1) 0.0570 180.20 0.0540 172.50 0.0030 7.70 

 M(6) 0.0100 27.70 0.0170 83.80 -.0070 -56.10 

 MK(3) ****** ****** 0.0050 52.40 ****** ******* 

 S(4) 0.0010 228.70 0.0100 11.40 -.0090 -142.70 

 MN(4) ****** ****** 0.0080 275.80 ****** ******* 

 NU(2) 0.0290 339.60 0.0290 345.70 0.0000 -6.10 

 S(6) 0.0000 111.50 0.0000 0.00 0.0000 111.50 

 MU(2) ****** ****** 0.0240 14.50 ****** ******* 

 2N(2) 0.0200 309.30 0.0210 336.80 -.0010 -27.50 

 OO(1) 0.0020 160.60 0.0050 218.70 -.0030 -58.10 

 LAMBD 0.0050 4.30 0.0080 359.70 -.0030 4.60 

 S1 ****** ****** 0.0100 124.90 ****** ******* 

 M(1) 0.0040 175.30 0.0040 220.80 0.0000 -45.50 

 J(1) 0.0040 165.60 0.0050 209.20 -.0010 -43.60 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0280 42.90 ****** ******* 

 SA ****** ****** 0.0670 129.10 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0020 184.40 0.0020 171.10 0.0000 13.30 

 Q(1) 0.0110 185.10 0.0110 183.10 0.0000 2.00 

 T2 0.0090 6.00 0.0100 17.40 -.0010 -11.40 

 R2 0.0010 6.30 0.0010 33.80 0.0000 -27.50 

 2Q(1) 0.0010 189.90 0.0020 169.20 -.0010 20.70 

 P(1) 0.0260 171.20 0.0310 180.20 -.0050 -9.00 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0110 56.40 ****** ******* 

 L(2) 0.0220 336.00 0.0270 359.80 -.0050 -23.80 

 2MK(3 ****** ****** 0.0080 33.80 ****** ******* 

 K(2) 0.0420 6.50 0.0380 31.50 0.0040 -25.00 

 M(8) 0.0030 178.00 0.0000 0.00 0.0030 178.00 

 MS(4) ****** ****** 0.0120 224.30 ****** ******* 

 GAIN (-): 0.97 

 PHASE (HR): -0.32 

 EST. RMS (M): 0.07 

 
40

Table 4.6. ADCIRC vs. NOS Harmonic Analysis Results at Cape May, NJ for January 2006 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.6610 30.40 0.7140 28.60 -.0530 1.80 

 S(2) 0.1230 37.10 0.1250 55.30 -.0020 -18.20 

 N(2) 0.1370 4.00 0.1590 9.70 -.0220 -5.70 

 K(1) 0.0800 183.20 0.1050 200.40 -.0250 -17.20 

 M(4) 0.0250 202.30 0.0100 101.00 0.0150 101.30 

 O(1) 0.0650 200.10 0.0840 185.60 -.0190 14.50 

 M(6) 0.0080 338.90 0.0080 20.80 0.0000 -41.90 

 MK(3) ****** ****** 0.0000 0.00 ****** ******* 

 S(4) 0.0010 256.30 0.0000 0.00 0.0010 -103.70 

 MN(4) ****** ****** 0.0030 115.30 ****** ******* 

 NU(2) 0.0270 7.50 0.0320 7.40 -.0050 0.10 

 S(6) 0.0010 161.30 0.0000 0.00 0.0010 161.30 

 MU(2) ****** ****** 0.0120 40.50 ****** ******* 

 2N(2) 0.0180 337.50 0.0210 352.30 -.0030 -14.80 

 OO(1) 0.0030 166.30 0.0040 215.00 -.0010 -48.70 

 LAMBD 0.0050 33.50 0.0100 41.60 -.0050 -8.10 

 S1 ****** ****** 0.0090 134.70 ****** ******* 

 M(1) 0.0050 191.60 0.0040 243.40 0.0010 -51.80 

 J(1) 0.0050 174.80 0.0060 197.10 -.0010 -22.30 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0320 40.30 ****** ******* 

 SA ****** ****** 0.0580 147.70 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0020 207.30 0.0030 179.30 -.0010 28.00 

 Q(1) 0.0130 208.40 0.0130 184.10 0.0000 24.30 

 T2 0.0070 36.80 0.0120 33.70 -.0050 3.10 

 R2 0.0010 37.40 0.0010 56.50 0.0000 -19.10 

 2Q(1) 0.0020 216.80 0.0020 171.00 0.0000 45.80 

 P(1) 0.0260 184.50 0.0360 199.20 -.0100 -14.70 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0050 94.10 ****** ******* 

 L(2) 0.0200 4.00 0.0370 43.90 -.0170 -39.90 

 2MK(3 ****** ****** 0.0040 110.50 ****** ******* 

 K(2) 0.0330 37.60 0.0330 54.50 0.0000 -16.90 

 M(8) 0.0030 309.70 0.0000 0.00 0.0030 -50.30 

 MS(4) ****** ****** 0.0050 128.10 ****** ******* 

 GAIN (-): 0.89 

 PHASE (HR): -0.14 

 EST. RMS (M): 0.07 

 

 
41

Table 4.7. ADCIRC vs. NOS Harmonic Analysis Results at Charleston, SC for January 2006 

 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.6820 353.30 0.7830 10.40 -.1010 -17.10 

 S(2) 0.1370 351.20 0.1190 36.10 0.0180 -44.90 

 N(2) 0.1560 326.60 0.1720 354.90 -.0160 -28.30 

 K(1) 0.0730 178.70 0.1050 199.70 -.0320 -21.00 

 M(4) 0.0030 323.80 0.0330 209.60 -.0300 114.20 

 O(1) 0.0720 198.20 0.0790 203.40 -.0070 -5.20 

 M(6) 0.0060 31.00 0.0060 135.30 0.0000 -104.30 

 MK(3) ****** ****** 0.0080 4.40 ****** ******* 

 S(4) 0.0010 4.30 0.0000 0.00 0.0010 4.30 

 MN(4) ****** ****** 0.0140 201.40 ****** ******* 

 NU(2) 0.0300 330.20 0.0350 351.40 -.0050 -21.20 

 S(6) 0.0010 292.00 0.0000 0.00 0.0010 -68.00 

 MU(2) ****** ****** 0.0250 40.00 ****** ******* 

 2N(2) 0.0210 300.00 0.0220 343.30 -.0010 -43.30 

 OO(1) 0.0030 159.20 0.0050 217.30 -.0020 -58.10 

 LAMBD 0.0050 352.30 0.0130 356.10 -.0080 -3.80 

 S1 ****** ****** 0.0180 173.90 ****** ******* 

 M(1) 0.0050 188.50 0.0050 243.30 0.0000 -54.80 

 J(1) 0.0060 169.00 0.0050 213.50 0.0010 -44.50 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0530 50.50 ****** ******* 

 SA ****** ****** 0.0780 176.30 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0030 206.60 0.0040 198.00 -.0010 8.60 

 Q(1) 0.0140 207.90 0.0170 198.90 -.0030 9.00 

 T2 0.0080 351.30 0.0150 19.90 -.0070 -28.60 

 R2 0.0010 351.10 0.0050 263.80 -.0040 87.30 

 2Q(1) 0.0020 217.60 0.0020 207.10 0.0000 10.50 

 P(1) 0.0240 180.20 0.0360 198.30 -.0120 -18.10 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0170 114.80 ****** ******* 

 L(2) 0.0220 326.60 0.0340 5.00 -.0120 -38.40 

 2MK(3 ****** ****** 0.0050 30.60 ****** ******* 

 K(2) 0.0370 351.10 0.0300 37.10 0.0070 -46.00 

 M(8) 0.0030 296.90 0.0000 0.00 0.0030 -63.10 

 MS(4) ****** ****** 0.0100 237.70 ****** ******* 

 GAIN (-): 0.86 

 PHASE (HR): -0.77 

 EST. RMS (M): 0.20 

 

 
42

Table 4.8. ADCIRC vs. NOS Harmonic Analysis Results at Mayport, FL for January 2006 

 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.7940 13.50 0.6760 25.30 0.1180 -11.80 

 S(2) 0.1540 13.80 0.1050 48.30 0.0490 -34.50 

 N(2) 0.1800 347.30 0.1570 7.30 0.0230 -20.00 

 K(1) 0.0820 191.90 0.0840 202.50 -.0020 -10.60 

 M(4) 0.0120 105.20 0.0330 159.40 -.0210 -54.20 

 O(1) 0.0790 203.10 0.0580 210.90 0.0210 -7.80 

 M(6) 0.0170 98.50 0.0090 196.00 0.0080 -97.50 

 MK(3) ****** ****** 0.0080 20.40 ****** ******* 

 S(4) 0.0010 268.30 0.0050 290.70 -.0040 -22.40 

 MN(4) ****** ****** 0.0130 156.00 ****** ******* 

 NU(2) 0.0350 350.80 0.0320 2.70 0.0030 -11.90 

 S(6) 0.0010 297.30 0.0000 0.00 0.0010 -62.70 

 MU(2) ****** ****** 0.0120 31.20 ****** ******* 

 2N(2) 0.0240 321.00 0.0190 354.60 0.0050 -33.60 

 OO(1) 0.0030 180.60 0.0040 212.60 -.0010 -32.00 

 LAMBD 0.0060 13.70 0.0090 47.80 -.0030 -34.10 

 S1 ****** ****** 0.0110 158.30 ****** ******* 

 M(1) 0.0060 197.50 0.0030 221.20 0.0030 -23.70 

 J(1) 0.0060 186.30 0.0050 210.20 0.0010 -23.90 

 MM ****** ****** 0.0250 230.40 ****** ******* 

 SSA ****** ****** 0.0770 55.40 ****** ******* 

 SA ****** ****** 0.1150 190.20 ****** ******* 

 MSF ****** ****** 0.0390 202.70 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0030 207.90 0.0020 214.50 0.0010 -6.60 

 Q(1) 0.0150 208.70 0.0110 209.50 0.0040 -0.80 

 T2 0.0090 13.80 0.0100 22.10 -.0010 -8.30 

 R2 0.0010 13.80 0.0050 291.80 -.0040 82.00 

 2Q(1) 0.0020 214.30 0.0020 219.20 0.0000 -4.90 

 P(1) 0.0270 192.70 0.0290 202.20 -.0020 -9.50 

 2SM(2 ****** ****** 0.0030 60.10 ****** ******* 

 M(3) ****** ****** 0.0060 186.40 ****** ******* 

 L(2) 0.0260 347.30 0.0410 31.40 -.0150 -44.10 

 2MK(3 ****** ****** 0.0080 44.00 ****** ******* 

 K(2) 0.0420 13.90 0.0280 48.20 0.0140 -34.30 

 M(8) 0.0020 349.00 0.0030 4.20 -.0010 -15.20 

 MS(4) ****** ****** 0.0130 175.80 ****** ******* 

 GAIN (-): 1.15 

 PHASE (HR): -0.62 

 EST. RMS (M): 0.16 

 

 

 
43

Table 4.9. ADCIRC vs. NOS Harmonic Analysis Results at Naples, FL for January 2006 

 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.2500 126.40 0.2860 144.20 -.0360 -17.80 

 S(2) 0.1250 114.30 0.0960 156.10 0.0290 -41.80 

 N(2) 0.0460 104.90 0.0570 130.60 -.0110 -25.70 

 K(1) 0.1420 3.90 0.1580 9.90 -.0160 -6.00 

 M(4) 0.0090 165.80 0.0170 123.50 -.0080 42.30 

 O(1) 0.1650 8.10 0.1430 2.80 0.0220 5.30 

 M(6) 0.0060 153.40 0.0080 124.80 -.0020 28.60 

 MK(3) ****** ****** 0.0090 322.00 ****** ******* 

 S(4) 0.0020 191.80 0.0040 235.20 -.0020 -43.40 

 MN(4) ****** ****** 0.0080 88.40 ****** ******* 

 NU(2) 0.0090 107.80 0.0130 142.30 -.0040 -34.50 

 S(6) 0.0000 60.10 0.0000 0.00 0.0000 60.10 

 MU(2) ****** ****** 0.0090 55.20 ****** ******* 

 2N(2) 0.0060 83.40 0.0080 109.40 -.0020 -26.00 

 OO(1) 0.0070 359.60 0.0050 22.30 0.0020 -22.70 

 LAMBD 0.0020 120.80 0.0020 149.70 0.0000 -28.90 

 S1 ****** ****** 0.0170 104.00 ****** ******* 

 M(1) 0.0120 6.00 0.0080 34.00 0.0040 -28.00 

 J(1) 0.0130 1.80 0.0100 7.90 0.0030 -6.10 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0300 66.70 ****** ******* 

 SA ****** ****** 0.0750 167.90 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0060 9.90 0.0060 359.50 0.0000 10.40 

 Q(1) 0.0320 10.20 0.0300 349.40 0.0020 20.80 

 T2 0.0070 114.80 0.0050 147.70 0.0020 -32.90 

 R2 0.0010 113.80 0.0010 156.70 0.0000 -42.90 

 2Q(1) 0.0040 12.30 0.0040 327.60 0.0000 44.70 

 P(1) 0.0470 4.20 0.0520 8.80 -.0050 -4.60 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0000 0.00 ****** ******* 

 L(2) 0.0070 104.90 0.0080 186.80 -.0010 -81.90 

 2MK(3 ****** ****** 0.0090 301.60 ****** ******* 

 K(2) 0.0340 113.30 0.0270 149.40 0.0070 -36.10 

 M(8) 0.0020 268.40 0.0000 0.00 0.0020 -91.60 

 MS(4) ****** ****** 0.0080 152.20 ****** ******* 

 GAIN (-): 0.98 

 PHASE (HR): -0.44 

 EST. RMS (M): 0.09 
44

Table 4.10. ADCIRC vs. NOS Harmonic Analysis Results at Panama City, FL for January 2006 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.0350 98.20 0.0340 91.10 0.0010 7.10 

 S(2) 0.0240 79.20 0.0200 94.50 0.0040 -15.30 

 N(2) 0.0060 96.00 0.0070 102.00 -.0010 -6.00 

 K(1) 0.1350 6.70 0.1450 17.00 -.0100 -10.30 

 M(4) 0.0010 60.20 0.0110 315.10 -.0100 105.10 

 O(1) 0.1630 10.40 0.1410 8.50 0.0220 1.90 

 M(6) 0.0050 46.80 0.0030 77.00 0.0020 -30.20 

 MK(3) ****** ****** 0.0000 0.00 ****** ******* 

 S(4) 0.0010 7.40 0.0030 77.50 -.0020 -70.10 

 MN(4) ****** ****** 0.0050 281.20 ****** ******* 

 NU(2) 0.0010 96.30 0.0010 100.50 0.0000 -4.20 

 S(6) 0.0010 282.40 0.0000 0.00 0.0010 -77.60 

 MU(2) ****** ****** 0.0000 0.00 ****** ******* 

 2N(2) 0.0010 93.80 0.0010 113.00 0.0000 -19.20 

 OO(1) 0.0070 3.10 0.0040 24.60 0.0030 -21.50 

 LAMBD 0.0000 89.40 0.0000 0.00 0.0000 89.40 

 S1 ****** ****** 0.0050 46.30 ****** ******* 

 M(1) 0.0120 8.50 0.0060 62.90 0.0060 -54.40 

 J(1) 0.0130 4.90 0.0080 20.30 0.0050 -15.40 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0460 39.80 ****** ******* 

 SA ****** ****** 0.1130 152.00 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0060 11.90 0.0050 353.40 0.0010 18.50 

 Q(1) 0.0320 12.20 0.0310 353.80 0.0010 18.40 

 T2 0.0010 79.90 0.0010 94.30 0.0000 -14.40 

 R2 0.0000 78.40 0.0000 0.00 0.0000 78.40 

 2Q(1) 0.0040 14.00 0.0040 327.40 0.0000 46.60 

 P(1) 0.0450 7.00 0.0490 17.60 -.0040 -10.60 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0000 0.00 ****** ******* 

 L(2) 0.0010 96.00 0.0010 80.00 0.0000 16.00 

 2MK(3 ****** ****** 0.0000 0.00 ****** ******* 

 K(2) 0.0060 77.60 0.0050 75.10 0.0010 2.50 

 M(8) 0.0010 314.50 0.0000 0.00 0.0010 -45.50 

 MS(4) ****** ****** 0.0050 325.50 ****** ******* 

 GAIN (-): 1.04 

 PHASE (HR): -0.16 

 EST. RMS (M): 0.03 
45

Table 4.11. ADCIRC vs. NOS Harmonic Analysis Results at Sabine Pass, TX for January 2006 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.1780 260.90 0.1230 275.50 0.0550 -14.60 

 S(2) 0.1110 244.00 0.0390 271.50 0.0720 -27.50 

 N(2) 0.0320 238.30 0.0330 254.40 -.0010 -16.10 

 K(1) 0.1730 19.40 0.1320 40.70 0.0410 -21.30 

 M(4) 0.0030 34.50 0.0050 318.90 -.0020 75.60 

 O(1) 0.2040 21.00 0.1230 34.60 0.0810 -13.60 

 M(6) 0.0010 296.80 0.0000 0.00 0.0010 -63.20 

 MK(3) ****** ****** 0.0070 141.20 ****** ******* 

 S(4) 0.0010 87.30 0.0000 0.00 0.0010 87.30 

 MN(4) ****** ****** 0.0000 0.00 ****** ******* 

 NU(2) 0.0060 241.30 0.0070 269.50 -.0010 -28.20 

 S(6) 0.0010 151.30 0.0000 0.00 0.0010 151.30 

 MU(2) ****** ****** 0.0050 210.30 ****** ******* 

 2N(2) 0.0040 215.70 0.0050 220.40 -.0010 -4.70 

 OO(1) 0.0090 17.80 0.0060 61.40 0.0030 -43.60 

 LAMBD 0.0010 253.00 0.0010 273.60 0.0000 -20.60 

 S1 ****** ****** 0.0120 306.30 ****** ******* 

 M(1) 0.0150 20.20 0.0060 36.90 0.0090 -16.70 

 J(1) 0.0160 18.60 0.0070 47.10 0.0090 -28.50 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0770 52.00 ****** ******* 

 SA ****** ****** 0.0650 135.70 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0080 21.70 0.0060 23.80 0.0020 -2.10 

 Q(1) 0.0400 21.80 0.0260 21.80 0.0140 0.00 

 T2 0.0070 244.70 0.0020 271.70 0.0050 -27.00 

 R2 0.0010 243.30 0.0000 271.30 0.0010 -28.00 

 2Q(1) 0.0050 22.60 0.0030 28.50 0.0020 -5.90 

 P(1) 0.0570 19.50 0.0400 33.10 0.0170 -13.60 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0000 0.00 ****** ******* 

 L(2) 0.0050 238.30 0.0040 5.10 0.0010 -126.80 

 2MK(3 ****** ****** 0.0060 132.80 ****** ******* 

 K(2) 0.0300 242.60 0.0080 338.50 0.0220 -95.90 

 M(8) 0.0000 352.20 0.0000 0.00 0.0000 -7.80 

 MS(4) ****** ****** 0.0000 0.00 ****** ******* 

 GAIN (-): 1.57 

 PHASE (HR): -0.94 

 EST. RMS (M): 0.11 
46

Table 4.12. ADCIRC vs. NOS Harmonic Analysis Results at Galveston Pleasure Pier, TX for 

January 2006 

 HARM29 ACCEPTED VALUES DIFFERENCE 

 AMPL(m) KPRIME AMPL(m) KPRIME AMPL(m) KPRIME 

 M(2) 0.1280 272.00 0.1390 276.10 -.0110 -4.10 

 S(2) 0.0730 255.70 0.0340 267.90 0.0390 -12.20 

 N(2) 0.0240 244.70 0.0360 254.60 -.0120 -9.90 

 K(1) 0.1590 21.60 0.1710 28.00 -.0120 -6.40 

 M(4) 0.0020 315.90 0.0060 203.30 -.0040 112.60 

 O(1) 0.1920 22.10 0.1610 20.30 0.0310 1.80 

 M(6) 0.0020 355.80 0.0000 0.00 0.0020 -4.20 

 MK(3) ****** ****** 0.0000 0.00 ****** ******* 

 S(4) 0.0000 249.20 0.0000 0.00 0.0000 -110.80 

 MN(4) ****** ****** 0.0000 0.00 ****** ******* 

 NU(2) 0.0050 248.30 0.0080 270.90 -.0030 -22.60 

 S(6) 0.0000 148.50 0.0000 0.00 0.0000 148.50 

 MU(2) ****** ****** 0.0050 197.10 ****** ******* 

 2N(2) 0.0030 217.30 0.0060 228.80 -.0030 -11.50 

 OO(1) 0.0080 21.10 0.0060 46.20 0.0020 -25.10 

 LAMBD 0.0010 264.40 0.0010 272.20 0.0000 -7.80 

 S1 ****** ****** 0.0140 327.00 ****** ******* 

 M(1) 0.0140 21.90 0.0080 24.20 0.0060 -2.30 

 J(1) 0.0150 21.30 0.0100 34.50 0.0050 -13.20 

 MM ****** ****** 0.0000 0.00 ****** ******* 

 SSA ****** ****** 0.0900 55.20 ****** ******* 

 SA ****** ****** 0.0770 157.40 ****** ******* 

 MSF ****** ****** 0.0000 0.00 ****** ******* 

 MF ****** ****** 0.0000 0.00 ****** ******* 

 RHO(1 0.0070 22.30 0.0070 4.00 0.0000 18.30 

 Q(1) 0.0370 22.40 0.0360 7.00 0.0010 15.40 

 T2 0.0040 256.30 0.0020 268.10 0.0020 -11.80 

 R2 0.0010 255.00 0.0000 267.50 0.0010 -12.50 

 2Q(1) 0.0050 22.60 0.0040 349.50 0.0010 33.10 

 P(1) 0.0530 21.60 0.0510 24.30 0.0020 -2.70 

 2SM(2 ****** ****** 0.0000 0.00 ****** ******* 

 M(3) ****** ****** 0.0000 0.00 ****** ******* 

 L(2) 0.0030 244.70 0.0040 352.10 -.0010 -107.40 

 2MK(3 ****** ****** 0.0000 0.00 ****** ******* 

 K(2) 0.0200 254.40 0.0060 275.60 0.0140 -21.20 

 M(8) 0.0010 356.20 0.0000 0.00 0.0010 -3.80 

 MS(4) ****** ****** 0.0040 224.70 ****** ******* 

 GAIN (-): 1.08 

 PHASE (HR): -0.12 

 EST. RMS (M): 0.04 
47

 

Table 4.13. ADCIRC vs. NOS Harmonic Constituent Weighted Gain and Phase Results 

For January-April 2006. 

Gain is ADCIRC/NOS amplitude and Phase Difference is ADCIRC – NOS. 

Thus a negative sign indicates a lead in phase. 

 

 

 

 

 

 

 

Station Gain (-) Phase Difference (Hrs) 

 Jan Feb Mar Apr Jan Feb Mar Apr 

Eastport, ME 0.92 0.86 0.86 0.90 -0.59 -0.57 -0.45 -0.32 

Portland, ME 1.11 1.05 1.05 1.09 -0.36 -0.35 -0.21 -0.06 

Boston, MA 1.09 1.03 1.03 1.07 -0.33 -0.32 -0.17 0.00 

Woods Hole, MA 1.25 1.17 1.24 1.28 -0.86 -0.70 -0.63 -0.35 

Sandy Hook, NJ 0.97 0.91 0.94 0.97 -0.32 -0.27 -0.09 0.08 

Atlantic City, NJ 0.95 0.90 0.92 0.96 -0.16 -0.15 0.05 0.20 

Cape May, NJ 0.89 0.85 0.87 0.91 -0.14 -0.14 0.00 0.15 

Lewes, DE 0.92 0.88 0.91 0.94 -0.38 -0.39 -0.23 -0.08 

Duck, NC 0.99 0.94 0.97 1.01 -0.13 -0.11 0.04 0.22 

Wilmington, NC 0.94 0.89 0.92 0.94 -2.59 -2.54 -2.41 -2.26 

Springmaid Pier, SC 0.94 0.89 0.92 0.94 -0.17 -0.11 0.01 0.23 

Charleston, SC 0.86 0.82 0.85 0.87 -0.77 -0.74 -0.59 -0.42 

Fort Pulaski, GA 0.92 0.87 0.88 0.91 -0.69 -0.67 -0.50 -0.33 

Fernandina Beach, FL 0.95 0.90 0.92 0.95 -1.03 -1.01 -0.83 -0.67 

Mayport, FL 1.15 1.09 1.11 1.14 -0.62 -0.59 -0.41 -0.25 

Naples, FL 0.98 0.96 1.04 1.02 -0.44 -0.52 -0.28 0.04 

Clearwater Beach, FL 1.12 1.09 1.18 1.16 -0.04 -0.11 0.19 0.52 

Apalachicola, FL 1.26 1.30 1.47 1.40 -0.50 -0.57 -0.41 0.02 

Panama City, FL 1.04 1.13 1.28 1.21 -0.16 -0.36 -0.02 0.45 

Pensacola, FL 0.84 0.96 1.11 1.04 0.35 0.24 0.56 1.15 

Sabine Pass, TX 1.57 1.60 1.72 1.68 -0.94 -1.10 -0.76 -0.35 

Galveston Pleasure Pier, TX 1.08 1.11 1.20 1.18 -0.12 -0.24 0.06 0.43 

Freeport, TX 1.12 1.16 1.26 1.23 -0.15 -0.27 0.02 0.45 
48

Table 4.14. ADCIRC vs. NOS Harmonic Constituent Estimated RMS Error (meters) 

 for January-April 2006. 

 

 

 

 

Station Estimated RMS Error (m) 

 Jan Feb Mar Apr 

Eastport, ME 0.54 0.53 0.53 0.49 

Portland, ME 0.23 0.22 0.22 0.21 

Boston, MA 0.23 0.21 0.21 0.21 

Woods Hole, MA 0.14 0.13 0.13 0.12 

Sandy Hook, NJ 0.07 0.06 0.06 0.05 

Atlantic City, NJ 0.05 0.05 0.05 0.04 

Cape May, NJ 0.07 0.08 0.07 0.07 

Lewes, DE 0.08 0.08 0.07 0.06 

Duck, NC 0.04 0.04 0.04 0.05 

Wilmington, NC 0.53 0.52 0.52 0.51 

Springmaid Pier, SC 0.06 0.06 0.06 0.06 

Charleston, SC 0.20 0.19 0.18 0.17 

Fort Pulaski, GA 0.23 0.22 0.21 0.19 

Fernandina Beach, FL 0.30 0.29 0.29 0.27 

Mayport, FL 0.16 0.15 0.15 0.14 

Naples, FL 0.09 0.09 0.09 0.09 

Clearwater Beach, FL 0.06 0.06 0.08 0.07 

Apalachicola, FL 0.06 0.07 0.10 0.09 

Panama City, FL 0.03 0.04 0.06 0.06 

Pensacola, FL 0.04 0.02 0.04 0.06 

Sabine Pass, TX 0.11 0.13 0.15 0.12 

Galveston Pleasure Pier, TX 0.04 0.05 0.07 0.07 

Freeport, TX 0.04 0.05 0.07 0.07 
49

5. MODEL COMPARISON WATER LEVEL ANALYSIS RESULTS 

Here we utilize the procedures outlined in Chapter 2, to compare all four forecast models over 

November 2008. In Table 5.1 the total water level forecast guidance RMSEs are presented at East 

Coast and Gulf of Mexico stations for each the three total water level models, ADCIRC, G-NCOM, 

and RTOFS. In general the order of performance is ADCIRC, G-NCOM, and RTOFS. The 

operational RTOFS does not appear to include the tidal improvements. 

In Table 5.2 the subtidal water level forecast guidance RMSEs are presented at East Coast and Gulf 

of Mexico stations for ETSS and each of the three total water level models, ADCIRC, G-NCOM, 

and RTOFS. In general, the order of performance is ETSS, ADCIRC, RTOFS, and G-NCOM. The 

ADCIRC and RTOFS subtidal water levels are determined by 30 hour low pass filtering the 

concatenated nowcasts over January 2006. The G-NCOM subtidal water level determination is 

somewhat problematical. First, the water levels are available only at 3 hour intervals, and the tide 

has been included in the USN distributed product based on a reconstruction from the OSU tide 

model TPXO6.2 (Egbert and Erofeeva, 2002) results. The approach followed in Table 5.2, is to use 

the NOS accepted harmonic constants to predict the tide used in the detiding. As a result, any 

mismatch between the tide model results and the NOS accepted predictions will be included within 

the subtidal water level error. To examine the consistency of the subtidal errors from month to 

month, ADCIRC subtidal water levels are given in Table 5.3 for January, February, March, and 

April of 2006. These results are consistent with results obtained for RTOFS and indicate that there is 

a relatively small variability in the RMSEs from month to month. 

All models with the exception of ETSS are degraded from north of Boston, MA. ETSS which does 

not contain the tides, exhibits the lowest errors. Of the three other models, which include the tides, 

ADCIRC, G-NCOM, and RTOFS range from the best to worst performance in RMSE. To aid in the 

intercomparison of the models, comparisons of ADCIRC and G-NCOM are shown in Figure 5.1, 

with ADCIRC showing superior results in the mid-Atlantic region. Next G-NCOM (total water 

level) is compared with ETSS (subtidal water level) in Figure 5.2. Note ETSS is presently used to 

provide subtidal water level boundary conditions to the near-shore OFS models and NOS tide gauge 

data are used to provide the tidal water level. Thus the tidal error is near zero and ETSS subtidal 

error approximates the total water level error. The two-dimensional ETSS model with higher 

resolution shows the superior RMSE profiles in Figure 5.2. Finally, in Figure 5.3 the operational 

version of RTOFS replaces G-NCOM in the comparison with ADCIRC, indicating that additional 

improvements in the tidal dynamics are necessary in RTOFS.
50

Table 5.1. ADCIRC, G-NCOM, and RTOFS Forecast Guidance Monthly Total Water Level 

Comparisons to NOS Observations November 2008 (RMSE [meters]). Forecast hours 6-36 are used 

in the comparisons. All three forecasts include tides. Eastport, ME not included in North Atlantic 

Coast statistics. ** Wilmington, NC not included in Mid Atlantic Coast statistics. 

Station ADCIRC G-NCOM RTOFS 

Eastport, ME * 0.64 1.04 3.48 

Portland, ME 0.29 0.18 1.87 

Boston, MA 0.30 0.38 1.89 

Woods Hole, 

MA 

0.17 0.12 0.32 

North Atlantic 

Coast 

0.20 0.19 1.36 

Sandy Hook, NJ 0.17 0.20 0.97 

Atlantic City, NJ 0.10 0.13 0.77 

Cape May, NJ 0.34 0.44 1.04 

Lewes, DE 0.11 0.28 0.87 

Duck, NC 0.11 0.22 0.62 

Wilmington, 

NC** 

0.65 0.63 1.10 

Mid Atlantic 

Coast 

0.17 0.25 0.85 

Springmaid Pier, 

SC 

0.12 0.14 1.04 

Charleston, SC 0.23 0.24 1.19 

Fort Pulaski, GA 0.28 0.33 1.64 

Fernandina 

Beach, FL 

0.35 0.27 1.55 

Mayport, FL 0.29 0.29 1.46 

South Atlantic 

Coast 

0.25 0.25 1.33 

Naples, FL 0.16 0.13 0.64 

Clearwater, FL 0.18 0.24 0.48 

Apalachicola, FL 0.12 0.17 0.21 

Panama City, FL 0.12 0.10 0.14 

Pensacola, FL 0.09 0.15 0.21 

Sabine Pass, TX 0.18 0.12 0.62 

Galveston 

Pleasure Pier, 

TX 

0.12 0.08 0.47 

Freeport, TX 0.13 0.10 0.22 

Gulf of Mexico 0.14 0.14 0.37 
51

 Table 5.2. ETSS, ADCIRC, G-NCOM, and RTOFS Forecast Guidance Monthly Subtidal Water 

Level Comparisons to NOS Observations (RMSE [meters]). Forecast hours 6-36 are used in the 

comparisons. Note ETSS water levels are subtidal, while the other three forecasts include tides. 

Station ETSS 

 (11/2008) 

ADCIRC 

(1/2006) 

G-NCOM 

(11/2008) 

RTOFS 

(1/2006) 

Eastport, ME 0.08 0.11 0.97 0.12 

Portland, ME 0.08 0.11 0.14 0.10 

Boston, MA 0.07 0.12 0.35 0.11 

Woods Hole, 

MA 

0.06 0.10 0.10 0.10 

North Atlantic 

Coast 

0.07 0.11 0.20 0.11 

Sandy Hook, NJ 0.09 0.11 0.17 0.10 

Atlantic City, NJ 0.08 0.11 0.12 0.10 

Cape May, NJ 0.23 0.10 0.40 0.10 

Lewes, DE 0.07 0.10 0.27 0.10 

Duck, NC 0.06 0.07 0.22 0.21 

Wilmington, NC 0.06 0.09 0.61 0.14 

Mid Atlantic 

Coast 

0.11 0.10 0.24 0.12 

Springmaid Pier, 

SC 

0.05 0.05 0.12 0.10 

Charleston, SC 0.05 0.06 0.21 0.09 

Fort Pulaski, GA 0.05 0.07 0.27 0.09 

Fernandina 

Beach, FL 

0.06 0.06 0.24 0.08 

Mayport, FL 0.06 0.04 0.16 0.08 

South Atlantic 

Coast 

0.05 0.06 0.20 0.09 

Naples, FL 0.04 0.06 0.11 0.07 

Clearwater, FL 0.05 0.06 0.26 0.07 

Apalachicola, FL 0.10 0.07 0.15 0.08 

Panama City, FL 0.04 0.07 0.04 0.06 

Pensacola, FL 0.03 0.06 0.15 0.07 

Sabine Pass, TX 0.08 0.06 0.10 0.09 

Galveston 

Pleasure Pier, 

TX 

0.07 0.07 0.06 0.07 

Freeport, TX 0.06 0.06 0.06 0.06 

Gulf of Mexico 0.06 0.06 0.12 0.07 
52

Table 5.3. ADCIRC Nowcast Subtidal Water Level Comparisons to NOS Observations January 

– April 2006 (RMSE [meters]). Nowcast hours 1-24 are used in the comparisons. 

Station January February March April 

Eastport, ME 0.11 0.13 0.11 0.06 

Portland, ME 0.11 0.09 0.12 0.06 

Boston, MA 0.12 0.10 0.08 0.06 

Woods Hole, 

MA 

0.10 0.09 0.06 0.05 

Sandy Hook, NJ 0.11 0.12 0.07 0.04 

Atlantic City, NJ 0.11 0.10 0.06 0.04 

Cape May, NJ 0.10 0.09 0.06 0.05 

Lewes, DE 0.10 0.10 0.07 0.05 

Duck, NC 0.07 0.08 0.05 0.05 

Wilmington, NC 0.09 0.08 0.06 0.09 

Springmaid Pier, 

SC 

0.05 0.06 0.04 0.05 

Charleston, SC 0.06 0.06 0.04 0.03 

Fort Pulaski, GA 0.07 0.06 0.05 0.04 

Fernandina 

Beach, FL 

0.06 0.06 0.05 0.04 

Mayport, FL 0.04 0.04 0.04 0.03 

Naples, FL 0.06 0.03 0.03 0.03 

Clearwater, FL 0.06 0.04 0.03 0.03 

Apalachicola, FL 0.07 0.05 0.03 0.02 

Panama City, FL 0.07 0.05 0.04 0.03 

Pensacola, FL 0.06 0.05 0.03 0.03 

Sabine Pass, TX 0.06 0.06 0.05 0.03 

Galveston 

Pleasure Pier, 

TX 

0.07 0.06 0.04 0.04 

Freeport, TX 0.06 0.05 0.04 0.03 
53

(a) 

(b) 

Figure 5.1. G-NCOM vs. ADCIRC Total Water Level Forecast Guidance RMSE (meters) for 

East Coast Stations (a) and for Gulf of Mexico Stations (b) for November 2008.
54

(a) 

(b) 

Figure 5.2. G-NCOM Total Water Level vs. ETSS Subtidal Water Level Forecast Guidance 

RMSE (meters) for East Coast Stations (a) and for Gulf of Mexico Stations (b) for 

November 2008.
55

 (a) 

(b) 

Figure 5.3. RTOFS vs. ADCIRC Total Water Level Forecast Guidance RMSE (meters) for 

East Coast Stations (a) and for Gulf of Mexico Stations (b) for November 2008.
56
57

6. CONCLUSIONS

Total Water Level 

Two experimental versions of RTOFS have been compared with the original operational version 

assessed by Richardson and Schmalz (2007), in which they noted that the major source of the tidal 

error is in the M2 and S2 tidal constituents as determined by 29 day harmonic analysis of 

concatenated RTOFS nowcasts for each of the four months January – April 2006. Experimental 

RTOFS version 1 exhibits significant improvement in the tidal dynamics with a reduction in total 

water level error of nearly 40 cm in the middle Atlantic region, with almost no improvement in the 

Gulf of Mexico. Even with the improvements, RTOFS total water level RMSEs are significantly 

larger than either G-NCOM or ETSS. 

RTOFS experimental version 2 includes the tidal improvements as well as SSH assimilation, which 

slightly improves total water level RMSE with respect to RTOFS experimental version 1. 

Additional improvements in tidal dynamics are necessary to make RTOFS competitive with GNCOM. However, G-NCOM water level predictions are at three hour intervals and include the OSU 

tide model (TPXO6.2 Egbert and Erofeeva, 2002) results added after the fact; e.g., this separate 

modeling of the tidal contribution is added to the G-NCOM simulation result. 

ADCIRC and ETSS are two-dimensional vertically integrated models, with ADCIRC including the 

tides. ADCIRC total water level results are superior to both of the three-dimensional models RTOFS 

and G-NCOM. 

Subtidal Water Level 

ADCIRC subtidal results are comparable to ETSS and RTOFS subtidal water level results 

previously reported by Richardson and Schmalz (2007). With respect to RTOFS subtidal water 

levels, one notes that the preceeding 30 day nowcasts and the latest forecast guidance could be 

concatenated and then 30 hr low pass filtered to obtain the subtidal forecast guidance signal, which 

could then be adjusted over the 6-36 hour forecast guidance horizon and used as the subtidal forecast 

guidance. 

Summary 

With respect to both total and subtidal water levels, the cause of the differences is in part due to the 

use of different wind and sea level atmospheric forcings. G-NCOM uses the U.S. Navy NOGAPS, 

while RTOFS and ETSS use the NWS GFS forcings and ADCIRC uses NWS NAM. Note prior to 

the water level comparisons, surface wind forecasts could be compared using the methods in 

Richardson and Schmalz (2005). 

The analysis procedures developed here are sufficiently general to compare both subtidal water level 

models and total water level models. Additional comparison with the total and subtidal water level 

forecasts could be performed on a routine monthly basis using a more standardized analysis software 
58

package. While the present study focuses on water levels, salinity and temperature structures should 

be compared with XBT and CTD casts to further assess the ability of the RTOFS and G-NCOM to 

predict shelf density patterns. 

REFERENCES 

Blain, C.A., R.H. Preller, and A.P. Rivera, 2002: Tidal Prediction Using the Advanced Circulation 

Model (ADCIRC) and a Relocatable PC-Based System, Oceanography, Vol 15, No. 1, 77-87. 

Bleck, R., G. Halliwell, A. Wallcraft, S. Carroll, K. Kelley, and K. Rushing, 2002: HYCOM User’s 

Manual, Manual Version 2.0.01. 

Blumberg, A.F. and G.L. Mellor, 1987: A Description of a Three-dimensional Ocean Circulation 

Model, in Three Dimensional Coastal Ocean Models, N.S. Heaps (editor), American Geophysical 

Union, Washington, DC. 

Blumberg, A.F. and H.J. Herring, 1987: Circulation Modeling Using Orthogonal Curvilinear 

Coordinates, in Three-Dimensional Models of Marine and Estuarine Dynamics (J.C.J. Nihoul 

and B.M. Jamart, eds), Elsevier Oceanography Series, 45, 55-88. 

Chen, J., W.A. Shafer, and S.C. Kim, 1993: A Forecast Model for Extratropical Storm Surge, 

Advances in Hydro-Science and Engineering, (ed.) Sam S.Y. Wang, Volume I Part B, University 

of Mississippi, 1437-1444. 

Egbert, G.D. and S.Y. Erofeeva, 2002: Efficient Inverse Modeling of Barotropic Ocean Tides, 

Journal of Atmospheric and Oceanic Technology, 19(2), 183-204. 

Hess, K.W., 1994: Tampa Bay Oceanography Project: Development and Application of the 

Numerical Circulation Model, NOAA Technical Memorandum NOS OES No. 5, Silver Spring, 

MD. 

Kolar, R.L, W.G. Gray, J.J. Westerink, and R.A. Luettich, 1994: Shallow Water Modeling in 

Spherical Coordinates: Equation Formulation, Numerical Implementation, and Application, Journal 

of Hydraulic Research, 32, 3-24. 

Leuttich, R.A., J.J. Westerink, and N.W. Scheffner, 1992: ADCIRC: An Advanced Threedimensional Circulation Model for Shelves, Coasts, and Estuaries, Report1: Theory and 

Methodology of ADCIRC-2DDI and ADCIRC-3DL, USACE, Technical Report DRP-92-6, 

Vicksburg, MS. 

Martin, P.J., 2000: Description of the Navy Coastal Ocean Model Version 1.0, NRL Report 
59

FR/7322-00-9962, Stennis Space Center, MS. 

Richardson, P.H. and R.A. Schmalz, 2004: ETSS vs. DGOM Model Water Level Comparisons: 

Program Documentation and Monthly Analysis. NOAA, National Ocean Service, Coast Survey 

Development Laboratory, CSDL Informal Technical Note No. 3, Silver Spring, MD. 

Richardson, P.H. and R.A. Schmalz, 2005: GFS vs. ETA12 Forecsat Model Wind Comparisons: 

Monthly Analysis and Program Documentation. NOAA, National Ocean Service, Coast Survey 

Development Laboratory, CSDL Informal Technical Note No. 4, Silver Spring, MD. 

Richardson, P.H. and R.A. Schmalz, 2007: Comparison of NOAA Water Level Forecast Guidance 

from the Real Time Ocean Forecast System, Extratropical Storm Surge System, and the National 

Ocean Service Gulf of Mexico System: January-April 2006 Monthly Analysis. NOAA, National 

Ocean Service, Coast Survey Development Laboratory, CSDL Informal Technical Note No. 8, 

Silver Spring, MD. 

Zervas, C.E., 1997: User’s Guide to the Tidal Prediction and Detiding Program. NOAA, National 

Ocean Service, Center for Operational Oceanographic Products and Services, Unpublished Internal 

Report, Silver Spring, MD. 
60
61

APPENDIX A : SOFTWARE OVERVIEW AND PROGRAM DESCRIPTIONS

Software Overview 

Read_tdl.f was developed to read forecast guidance water level output from ETSS. The program 

reads water level results from either 00Z or 12Z forecast files. The program writes the output for all 

stations; e.g. in standard ETSS block format (8f7.4) rather than single station format. 

Readhycom.f was developed to read RTOFS water level forecast guidance. The program reads 

water level results from 00Z forecast files. The program writes the output in standard ETSS block 

format, hours 1-24. Readrtofs.f is used to consider hours 6-36. Read_monrtofs.f is used to process 

monthly netCDF RTOFS concatenated daily (1-24 hr) forecast files. 

Read_adcirc.f and readncom.f are used to read and reformat as above for ADCIRC and G-NCOM 

for hours 6-36. Read_adcnew24.f is used to read and reformat ADCIRC files for hours 1-24. 

 

Adjust_blk.f was written to adjust the daily forecast by adding or subtracting, to each forecast point, 

the offset obtained from the difference of the initial observed point and the initial forecast point. 

Adjust_blk24.f was used to adjust 1-24 hr forecast data in standard ETSS block format, and to write 

the output in the same format. 

A subset of programs was developed to carry out the harmonic analysis of and the processing of the 

nowcast data. 

Readhyc_nowc.f reads the nowcast water levels from the nowcast/forecast files and writes the output 

in standard ETSS block format. 

Hycom29.f performs two functions necessary to run the harmonic analysis program (harm29). The 

nowcast data are read from the previously created daily nowcast files. The daily nowcast data are 

written to output files (by station) and concatenated. Having a continuous data stream is necessary 

to perform either the 30 hour low pass filtering or the harmonic analysis. For the harmonic analysis, 

the program also creates the necessary control files. 

Hyc_reform.f was created to read nowcast data from these month long (by station) data files and 

create from them the daily nowcast files in standard ETSS block format, hours 6 – 36. 

The harmonic analysis was performed by running a script, harm29.jcl. The script incorporates the 

standard harmonic analysis program, harm29. Const2.f was created to display the harmonic 

constants derived from harm29 along with the “accepted” harmonic constants from CO-OPS. 

The statistical analysis is performed by wl_sa.ph.f for forecast guidance hrs 6-36. RMSE and 

standard deviation statistics of the error signal are calculated on a daily forecast basis, and combined 

for the entire month. Note the program was modified to incorporate the G-NCOM three hour data 

interval. The mean and standard deviation for the observed and model water levels are also 
62

calculated. Wl_sa.ph24.f was used to analyze forecast data from standard ETSS block format over 

hrs 1-24. 

Plot_wlanblk.pro is written in the IDL programming language. The program will plot the observed 

water level along with points representing the high, low, start and end points for each daily forecast 

or nowcast. Symbols used to represent these points are plus, square, triangle, and asterisk. 

Plot.wlanal.pro generates one plot per page. Plot_wlanforc.pro is used to plot all forecast points 

from standard ETSS block format. 

All *.f program files are written in FORTRAN 95, while *.pro files are written in IDL. All 

programs are run at CSDL on Linux workstations and are discussed in turn below. 

A.1. Program Readhycom.f 

Program readhycom.f was created to read water level values from the daily RTOFS combined 

nowcast/forecast files. 

Variables read from the control file include idebug, filehyc, nsta, stat_nam(ns), and fileout. Idebug

controls the debug option, filehyc is the name of the RTOFS nowcast/forecast file, nsta is the 

number of stations, stat_nam(ns) are the station names, and fileout gives the forecast guidance 

output filename. 

After the RTOFS 00Z forecast data file is opened, the program reads the station name from the first 

line of data. Only data from the desired stations are read. The program skips over 24 hours of 

nowcast data, then skips over the first five hours of forecast output. Starting with hour six, the next 

31 values are stored in array wl_hyc(). The forecast guidance water level values are then written to 

output in standard “block” format (8f7.4). 

A.2 Program Adjust24.f 

A revision of adjust_blk.f was set up to adjust points 1 through 24 of the forecast cycle instead of the 

6 through 36 which had been done previously. 

A.3. Program Wl_sa.ph24.f 

Wl_sa.ph24.f is a revision of wl_sa.phblk.f. Wl_sa.ph24.f was set up to analyze hours 1 through 24, 

instead of hours 6 through 36 which had been done previously. 

A.4. Program Read_monrtofs.f 

Read_monrtofs.f was created to read and convert into standard ETSS block format the RTOFS daily 

forecast data from netCDF format. The “new” RTOFS data were provided in the form of monthly, 

concatenated, files. Read_monrtofs will read from the control file idebug, ndays, filehyc, nsta, and 

statnam. Idebug controls the debug function, ndays is the number of concatenated daily files, and 
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filehyc is the name of the RTOFS file to be read from. Nsta is the number of stations and stat_nam

gives the station names. The program calls subroutine readwl_mo which actually reads the netCDF 

data. After the call to readwl_mo, the program writes the forecast guidance output in standard ETSS 

block format. 

A.5. Program Read_adcirc.f 

Read_adcirc.f was created to read water level values from daily ADCIRC forecast files.Variables 

read from the control file include idebug and adcfile. Idebug controls the debug option, while 

adcfile is the ADCIRC forecast file to be read from. The program first reads 3 header lines from the 

ADCIRC forecast file. The program then skips through the appropriate number of hours (5) in order 

to begin reading water level values at hour 6. A total of 8053 lines of data are skipped over to begin 

reading the forecast output at hour 6 and continuing through hour 36. Read_adcirc.f writes the 

forecast output into standard ETSS block format. 

A.6. Program Adjust_blk.f 

The purpose for Adjust_blk.f is to adjust each data point of the daily forecast guidance by adding the 

offset obtained from the difference between the initial observed point and the initial forecast point. 

While other adjustment methods are possible (based on longer term observations and associated 

ramping), these more elaborate techniques have not been used here. The program is generally run 

for all stations at once, then run for each day of the comparison period. The adjusted forecast 

guidance files are used for all analysis work. Adjust_blk.f reads the forecast guidance or nowcast 

data in standard ETSS block format, and writes the output in the same format. 

A.7. Program Readadcnew24.f 

Readadcnew24.f is a revision of read_adcirc.f. Read_adcnew24.f was created to read ADCIRC 

nowcast water level values for hours 1 through 24. 

A.8. Program Readadcirc24.f 

A revision of read_adcirc.f. Readadcirc24.f skips the appropriate number of lines (1153) to get to 

hour 1 of the forecast guidance. This version of the program reads values for hours 1 through 24, 

instead of hours 6 through 36 as had been done previously. 

A.9. Program Readrtofs.f 

Readrtofs.f was created to read and convert into standard ETSS block format the RTOFS daily 

forecast guidance data from netCDF. The program reads from a control file idebug, filehyc, nsta, and 

stat_nam. Idebug controls the debug function, filehyc is the name of the RTOFS file to be read 

from. Nsta is the number of stations and stat_nam gives the station names. The program calls 

subroutine readwl which actually reads the water level data from netCDF files. After the call is 

made to readwl, the program writes the forecast guidance model output in standard ETSS block 
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format. 

A.10. Program Readncom.f 

Readncom.f was created to read and convert into standard ETSS block format the G-NCOM daily 

forecast guidance data from netCDF files. The program reads from a control file idebug, path, fname

and stat_nam. Idebug controls the debug function, while path and fname give the name of the GNCOM netCDF forecast guidance file to be read. Stat_nam(ns) gives the station names. The 

program makes a call to subroutine readwl. Readwl actually reads the netCDF data including the 

variable zeta, which contains all water level data. 

A.11. Program Read_tdl.f 

Program read_tdl.f first reads nstn_r, the number of stations to read. There are forecast data for 61 

stations in an East Coast ETSS file. There are data for 22 stations in a Gulf Coast ETSS file. Next 

read is nstn_wr, the number of stations to write forecast output for. For this comparison, nstn_wr(1) 

will equal 15 for the East Coast. Nstn_wr(2) will equal 9 for the Gulf Coast. The program then 

reads tdl_file(1) and tdl_file(2), the ETSS forecast guidance files for the East Coast and the Gulf 

Coast, respectively. For each of stations 1 through nstn_wr, a station number is read, a logical unit 

number, and the forecast guidance output filename. Read_tdlblk.f is a very straight forward program. 

The ETSS forecast guidance data file (00Z or 12Z) is opened, and the output files are opened for 

stations 1 through nstn_wr. Read_tdl.f will read water level values for hours 1 through 24, storing 

the values in the array iwl. The next line is read for hours 25 through 48. If the forecast guidance 

file is 12Z, the output file for a given station will begin at 0.75 of that Julian day, and will proceed 

from 0.0 to 1.00 of the following day. If the file is 00Z, the output file will begin at 0.25 of that day, 

and proceed through 1.50 of the following day. Basically, one skips 6 hours into the forecast 

guidance file (either 00Z or 12Z) and uses the next 30 hours. This condition simulates the use of the 

forecast guidance within a nowcast/forecast system mode; e.g., there is a 6 hour meteorological 

forecast processing time. The output is written in the standard ETSS block format (8f7.4). 

A.12. Program Wl_sa.ph.f 

Following the parameter and dimension statements, and after the character variables are declared, 

wl_sa.ph.f will read necessary information from the control file. Variables read from the control file 

include idebug, istat, statnam, fout, rjd_start, rjd_stop, and tdmax. Idebug controls the debug 

function. Istat is the number of stations. Statnam is the station name. Fout is the output file name. 

Rjd_start is the start time, and rjd_stop is the stop time. Tdmax is the maximum allowable time 

difference between two data points. The 600 loop is the day loop, beginning with nd = 1, and 

finishing with nd = ndays. The forecast model file is opened, along with the observed data file. 

Wl_sa.ph.f calculates the variance and mean for the model water level values, and for the observed 

data. Subroutine compare is called to calculate the rms difference between the model values and the 

observed. The daily statistics are written to output in the 850 loop, which begins with nd = 1 and 
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ends with nd = ndays. The statistics for the entire month are calculated in the 1000 loop, and the 

results are written to the monthly summary table. 

A.13. Program Plot_wlanblk.pro 

Plot_wlanblk.pro is an IDL program used to plot a month of observed water level data, along with 

points from each of the daily forecast. From each daily forecast guidance, four points are plotted: 

the start, the end, the max, and the min. The symbols used to represent forecast guidance values 

include pluses, triangles, squares, and asterisks. From the control file is read ptype, idebug, 

stat_name, titlnam, strttime, and endtime. Ptype is for plot type, in this case postscript. Idebug

controls the debug function. Stat_name is the station name, titlnam is the plot title. Strttime and 

endtime specify start and end times. Plot_wlanblk.pro is a conventional IDL program in which the 

plot command is used to plot the observed curve, while oplot is used to plot the forecast guidance 

points. The plots are annotated with a title, station name, and a legend. 

A.14. Program Plot_wlforc.pro 

Plot_wlforc.pro is identical to Plot_wlanblk.pro with one exception. There is an option to plot only 

the four points from the forecast guidance (start, end, max, and min) or to plot all the forecast 

guidance points from each cycle. 

A.15. Program Hycom29.f 

Hycom29.f was created to perform two steps necessary to run harm29, the harmonic analysis 

program. The nowcast data are read from the daily nowcast files created from Readhyc_nowc.f. 

Hycom29.f will create, for each station, a concatenated, continuous, month long stream of data. The 

program will also create the control files necessary to run harm29. A continuous stream of values is 

also necessary for the 30 hour low pass filter. The daily nowcast files are opened in the 50 loop. The 

nowcast data are read in the 100 loop (day loop) and the 150 loop (station loop). The 100 day loop 

begins with a read statement. The read statement reads the time and date information from the daily 

nowcast data file. The water level data are read in the station loop (150). For each station, the water 

level values are read from standard ETSS block format (8f7.4) for hours 1 through 24. The 

concatenated nowcast values, by station, are written to output in the 200 loop. 

A.16. Program Readpred.f 

Readpred.f was created to de-tide RTOFS forecast data. Readpred will read from a control file all 

necessary parameters including idebug, nsta, filecons, iyear, tconv, cdfout, nday, and hycfile. Idebug

is the debug switch. Nsta is the number of stations. Filecons is the file containing values for the 

model harmonic constituents, output from harm29. Cdfout is the output file for the calculated 

astronomic tide, by station. Tconv is the time meridian for which the kappa primes in the harmonic 

constants were derived. Nday is the number of days (number of daily forecasts). Hycfile(nd) are the 

daily RTOFS forecast guidance files. The program first opens filecons. It then reads from this file 
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the constituent amplitudes and phase angles. Readpred.f will call subroutine predk to calculate the 

astronomic tide. We converted the tidal prediction program pred to a subroutine for this usage and 

called it predk. Predk will calculate the astronomic tide based on the constituent values calculated 

from harm29. The tidal prediction values are stored in array hyc_pred(ns,np), by station. Daily 

RTOFS forecast output is read, then stored in array wl_mod(nd,ns,nhr), where nd is the day, ns is the 

station number, and nhr is the forecast hour. The detided values are obtained by first looping 

through by day, then looping through by station and by hour, subtracting hyc_pred(ns,nprhr) from 

wl_mod(nd,ns,nhr). The detided output is written in standard ETSS block format for hours 6 

through 36 of each forecast cycle. 

A.17. Program Hyc_reform.f 

Hyc_reform was created to read nowcast water level data, either filtered or non-filtered, from the 

concatenated, station data files. From this, the program will create the daily nowcast water level 

data file in standard ETSS block format for hours 6 through 36. The nowcast data are read in the 175 

loop (day) and the 100 loop (station). The water level values are stored in wl_hyc(nd,ns,l) where nd

is the day, ns is the station, and l is the hour. The water level values are written to output in the 250 

(day) loop and the 200 (station) loop. The output is written in standard ETSS block format for idat = 

1 through 31. Idat = 1 through 31 corresponds to hours 6 through 36 of that day’s nowcast. 

A.18. Program Const2.f 

Const2.f was created to compare tidal constituents obtained from the harmonic analysis program, 

harm29, with the “accepted” harmonic constants from CO-OPS. The program reads both the 

amplitude and phase angle from the file containing the accepted CO-OPS constants, and from the 

file containing the calculated (harm29) constants. The file containing the calculated constants is in 

standard “NOS” format (7(f5.3,f4.1)). The output includes not only the amplitude and phase angle 

for both the calculated constants and the accepted constants, but the amplitude difference and phase 

angle difference, Harm29 – accepted, as well. Gain, phase, and an estimated RMS error are 

computed. 
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APPENDIX B. SCRIPT AND CONTROL FILES

Table B.1 presents an inventory of all programs used in this analysis. Also listed are an appropriate 

script file and control file. ~ designates the users home area, and 3model is the project directory. 

~/3model/observed/reform_coops.f 

 ~/3model/model/RTOFS/readhycom.f 

 ~/3model/comp/adjust/24hour/adjust24.f 

 ~/3model/comp/wl_sa.ph24.f 

 ~/3model/model/RTOFS/monthly/read_monrtofs.f 

 ~/3model/model/ADCIRC/read_adcirc.f 

 ~/3model/comp/adjust/adjust_blk.f 

 ~/3model/model/ADCIRC/new/read_adcnew24.f 

 ~/3model/model/ADCIRC/old/read_adcirc24.f 

 ~/3model/model/RTOFS/readrtofs.f 

 ~/3model/model/NCOM/readncom.f 

 ~/3model/model/read_tdl.f 

 ~/3model/plot/anal/1plot/24hr/plot_wlforc.pro 

Table B.1. Script, Source File, and Control File Inventory 

Script Source File Example Control File 

readhy.jcl readhycom.f readhy_jan06.n 

adjust24.jcl adjust24.f adj_rtofs.jan06.n 

wl_sa.jcl wl_sa.ph24.f wl_rtofs.jan06.n 

month.jcl read_monrtofs.f readhy_jan06.n 

readadc.jcl read_adcirc.f adc_jan06.n 

adjust.jcl adjust_blk.f adj_adcirc.jan06.n 

readadcnew24.jcl read_adcnew24.f adcnew24_jan06.n 

readadcirc24.jcl read_adcirc24.f adc24_jan06.n 

rtofs.jcl readrtofs.f readhy.nov08.n 

readncom.jcl readncom.f readncom.nov08.n 

read_tdl.jcl read_tdl.f read_nov08.n 

plot_wlforc.pro cnt.rtofs_new.jan06.n 

Script and control files are similar to those in Appendix B of Richardson and Schmalz (2007). The 

IDL plot program does not have a script file. To run the IDL program, type idl <return>, then type .r 

plot_wlforc.pro <return>.