https://doi.org/10.7289/V5/TM-NOS-CS-40

NOAA Technical Memorandum NOS CS 40

UPGRADE OF NOS LAKE ERIE OPERATIONAL 

FORECAST SYSTEM (LEOFS) TO FVCOM: MODEL 

DEVELOPMENT AND HINDCAST SKILL ASSESSMENT 

Silver Spring, Maryland

February 2018 

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 shore-based 

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. 
 https://doi.org/10.7289/V5/TM-NOS-CS-40

NOAA Technical Memorandum NOS CS 40 

UPGRADE OF NOS LAKE ERIE OPERATIONAL 

FORECAST SYSTEM (LEOFS) TO FVCOM: MODEL 

DEVELOPMENT AND HINDCAST SKILL ASSESSMENT 

John G. W. Kelley and Yi Chen 

 National Ocean Service 

Office of Coast Survey, Coast Survey Development Laboratory

Silver Spring, Maryland 

Eric J. Anderson and Gregory A. Lang 

Office of Oceanic and Atmospheric Research 

Great Lakes Environmental Research Laboratory 

Ann Arbor, Michigan 

Jiangtao Xu

National Ocean Service 

Center for Operational Oceanographic Products and Services 

Silver Spring, Maryland 

February 2018 

noaa National Oceanic and Atmospheric Administration

U. S. DEPARTMENT National Oceanic and National Ocean Service

OF COMMERCE

Wilbur Ross, 

Atmospheric Administration 

RDML Tim Gallaudet, 

Dr. Russell Callender, 

Assistant Administrator

Secretary Acting Under Secretary

Office of Coast Survey Coast Survey Development Laboratory

Rear Admiral Shepard Smith Captain Edward J. Vandenameele

Division Chief
 

NOTICE

Mention of a commercial company or product does not constitute an endorsement 

by NOAA. Use of information from this publication concerning proprietary

products or the tests of such products for publicity or advertising purposes is not 

authorized. 

ii
TABLE OF CONTENT 

LIST OF FIGURES ........................................................................................................................ v

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

LIST OF ACRONYMS ................................................................................................................ iix

EXECUTIVE SUMMARY ........................................................................................................... xi

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

2. LAKE ERIE............................................................................................................................... 3 

3. MODEL SYSTEM AND SETUP FOR HINDCASTS ............................................................. 5

3.1. Description of Model .............................................................................................................. 5

3.2. Grid Configuration.................................................................................................................. 6

3.3. Lateral Boundary Conditions.................................................................................................. 7

3.4. Surface Boundary Forcing ...................................................................................................... 7

3.5. Initial Conditions .................................................................................................................. 12

4. DESCRIPTION OF HINDCAST PERIODS........................................................................... 13

5. METHOD OF EVALUATION ............................................................................................... 19

5.1. Evaluation of Water Level Hindcasts ................................................................................... 21

5.2 Evaluation of Surface Water Temperature Hindcasts ............................................................ 22

5.3 Evaluation of Sub-Surface Water Temperature Hindcasts .................................................... 24

6. HINDCAST SKILL ASSESSMENT RESULTS .................................................................... 27

6.1. Assessment of Water Level Hindcasts .................................................................................. 27

6.1.1. Hourly Water Levels .......................................................................................................... 27

6.1.2. Extreme High Water Level Events .................................................................................... 27

6.1.3. Extreme Low Water Level Events ..................................................................................... 37

6.2. Assessment of Water Temperature Hindcasts ...................................................................... 37

6.2.1. Offshore Locations............................................................................................................. 38

6.2.2. Coastal Station Locations .................................................................................................. 47

6.3. Assessment of Sub-Surface Water Temperature Hindcasts .................................................. 47

7. SUMMARY AND DISCUSSION ........................................................................................... 63

ACKNOWLEDGMENTS ............................................................................................................ 65

iii
 

REFERENCES ............................................................................................................................. 67

APPENDIX A. Information about NOS/CO-OPS water temperature observing stations in Lake 

Erie. ....................................................................................................................................... 69

APPENDIX B. Time series plots of hourly hindcasts of water levels vs. observations at water 

levels gauges for 2005........................................................................................................... 71

APPENDIX C. Time plots of hourly hindcasts of water levels vs. observations at water level 

gauges for 2006. .................................................................................................................... 75

iv
LIST OF FIGURES 

Figure 1. Map depicting Lake Erie bathymetry (feet) including longitudinal cross section. 

Modified from figure by Ted Walke of Pennsylvania Angler and Boater Fact Sheet. ............ 6

Figure 2. Map of the FVCOM model bathymetry (meters) for Lake Erie. ................................... 8

Figure 3. Map depicting the FVCOM grid domain for Lake Erie. The horizontal resolution 

ranges from 100 m near the shore to 2.5 km offshore with 21 vertical levels. ........................ 8

Figure 4. Map depicting the locations of the two NOS/CO-OPS NWLON gauges whose water 

level observations were used in specifying the lateral boundary conditions ........................... 9

Figure 5. Flowchart depicting the inputs for generating the water temperature and water level 

lateral boundary conditions for LEOFS-FVCOM hindcast runs. ............................................ 9

Figure 6. Flowchart depicting the method used to create a surface meteorological analysis and 

integrate into a single netCDF file for FVCOM hindcast runs for Lake Erie. ....................... 11

Figure 7. Map depicting the locations of different observing stations and platforms whose 

observations were used in the creation of surface meteorological analyses. (Dark 

blue=NDBC and EC buoys, Red=NWS C-MAN and NOS/CO-OPS stations, and GLOS 

stations, Yellow=Other Marine Reports, and Green=Surface Airway Stations [ASOS, 

AWOS]). ................................................................................................................................ 12

Figure 8. Daily mean water levels at the NOS Buffalo, N.Y. (a) and Toledo, Ohio (b) gauges 

during 2005. The time zone is EST. ....................................................................................... 14

Figure 9. Daily mean water levels at NOS Buffalo, N.Y. (a) and Toledo, Ohio (b) gauges during 

2006. The time zone is EST. .................................................................................................. 14

Figure 10. NWS Daily Weather Map valid at 12 UTC (07 UTC) on Dec. 9, 2005 (Day 343). ... 15

Figure 11. NWS Daily Weather Map valid at 12 UTC (07 EST) on Dec. 1, 2006 (Day 335). ... 15

Figure 12. Time series plots of Surface water temperatures at the NWS/NDBC and ECCC 

offshore fixed buoys during 2005 and 2006........................................................................... 16

Figure 13. Time series plots of surface water temperatures at NOS NWLON gauges at 

Marblehead, Ohio, Cleveland, Ohio, and Buffalo, N.Y. during 2005 and 2006. ................... 17

Figure 14. Map depicting the locations of the water level gauges used to evaluate the hindcasts 

of water levels. ....................................................................................................................... 21

Figure 15. Map depicting the locations of offshore and coastal platforms used to evaluate the 

hindcasts of surface water temperatures, indicated by red boxes. ......................................... 24

Figure 16. Map depicting the locations of NOAA/GLERL thermistors used to evaluate the 

hindcasts of sub-surface water temperatures during 2005. .................................................... 26

Figure 17. Time series plots of hourly hindcasts of water level vs. observations at NOS NWLON 

gauges at Toledo, Ohio and Buffalo, N.Y. during 2005. ....................................................... 28

Figure 18. Time series plots of hourly hindcasts of water level vs. observations at the NOS 

NWLON gauges at Toledo, Ohio and Buffalo, N.Y. during 2006. ....................................... 29

v 
Figure 19. Time series plots of hourly hindcasts vs. observations at NOS NWLON Buffalo, N.Y. 

gauge during the period from Dec. 1 to Dec. 16, 2005 (top) and from Nov. 26 to Dec. 6, 

2006 (bottom). ........................................................................................................................ 36

Figure 20. Time series plots of hourly hindcasts vs. observations at NOS NWLON Toledo, Ohio 

gauge during the period from Dec. 1 to Dec. 16, 2005 (top) and from Nov. 26 to Dec. 6, 

2006 (bottom). ........................................................................................................................ 42

Figure 21. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at three offshore fixed buoys during 2005. ............................................................................ 44

Figure 22. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at three offshore fixed buoys during 2006. ............................................................................ 46

Figure 23. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at NOS NWLON gauges at Marblehead, Ohio, Cleveland, Ohio, and Buffalo, N.Y. during 

2005........................................................................................................................................ 48

Figure 24. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at NOS NWLON gauges at Marblehead, Ohio, Cleveland, Ohio, and Buffalo, N.Y. during 

2006........................................................................................................................................ 50

Figure 25. Time series plots of hourly hindcasts vs. observations at 4 and 11.9 m depths during 

2005 at the Thermistor Station T05 Located in the Western Basin of Lake Erie. ................. 52

Figure 26. Hindcasts of water temperature (b) vs. observations (a) from 4 to 11 m depth at 

Thermistor Station T05 in the Eastern Basin from early May to late October 2005. ............ 53

Figure 27. Time series plots of hourly hindcasts of water temperature vs. observations at six 

depths of the Thermistor String T07 located in the central basin of Lake Erie during 2005. 55

Figure 28. Hindcasts of water temperature (b) vs. observations (a) from 1 to 25 m depth at 

Thermistor Station T07 in the Central Basin from early May to late October 2005. ............. 57

Figure 29. Time series plots of hourly hindcasts of water temperature vs. observations during 

2005 at eight depths of the Thermistor Station T12 located in the eastern basin of Lake 

Erie. .........................................................................................................................................59 

Figure 30. Hindcasts of water temperature (b) vs. observations (a) from 1 to 53 m depth at 

Thermistor Station T12 in the Eastern Basin from early May to late October 2005. ............ 61

Figure A-1. Satellite imagery depicting location of NOS/NWLON station in Marblehead, Ohio. 

The red circle indicates the location of the station. Also shown is a photo of the station. ... 69

Figure A-2. Satellite imagery depicting location of NOS/NWLON station in Cleveland, Ohio. 

The red circle indicates the location of the station. Also shown is a photo of the station. ... 69

Figure A-3. Satellite imagery depicting location of NOS/NWLON station in Buffalo, New York. 

The red circle indicates the location of the station. Also shown is a photo of the station. ... 70

Figure B-1. Time series plots of hourly hindcasts of water levels vs. observations at NOS and 

CHC water levels gauges in Lake Erie for 2005.................................................................... 71

Figure C-1. Time series plots of hourly hindcasts of water levels vs. observations at NOS and 

CHC water levels gauges in Lake Erie for 2006.................................................................... 75

vi
LIST OF TABLES 

Table 1. Description of NOS skill assessment statistics (Modified from Hess et al., 2003) along 

with NOS Acceptance Criterion (targets) used to evaluate GLOFS hindcasts. ..................... 20

Table 2. Information on NOAA/NOS/CO-OPS NWLON and CHS stations whose observations 

were used to evaluate hindcasts of gauges. NS indicates that an official NWS station ID has 

not been assigned to the station yet. ....................................................................................... 22

Table 3. Information about NWS/NDBC and ECCC fixed buoys whose surface water 

temperature observations were used to evaluate the hindcasts offshore. ............................... 25

Table 4. Information about NOS/CO-OPS NWLON stations whose water temperature 

observations were used to evaluate the hindcasts along the coast. ........................................ 25

Table 5. Information about GLERL thermistor stations whose observations were used to 

evaluate the hindcasts of sub-surface water temperatures. .................................................... 25

Table 6. Summary of skill assessment statistics evaluating the ability of the hindcasts to predict 

hourly water levels at NOS NWLON stations in Lake Erie for 2005. Gray shading, if 

present, indicates that it did not meet the NOS acceptance criteria. ...................................... 30

Table 7. Summary of skill assessment statistics of hindcasts of hourly water levels at Canadian 

Hydrographic stations in Lake Erie for 2005. Gray shading, if present, indicates that it did 

not meet the NOS acceptance criteria. ................................................................................... 30

Table 8. Same as Table 6 except for 2006. ................................................................................. 31

Table 9. Same as Table 7 except for 2006. .................................................................................. 31

Table 10. Summary of skill assessment statistics evaluating the ability of the hindcasts to predict 

extreme high water level events at NOS NWLON stations in Lake Erie during 2005. Gray 

shading, if present, indicates that it did not meet the NOS acceptance criteria. .................... 32

Table 11. Summary of skill assessment statistics evaluating the ability of the hindcasts to predict 

extreme high water level events at CHS stations in Lake Erie during 2005. Gray shading, if 

present, indicates that it did not meet the NOS acceptance criteria. ...................................... 33

Table 12. Same as Table 10 except for 2006. .............................................................................. 34

Table 13. Same as Table 11 except for 2006. .............................................................................. 35

Table 14. Summary of skill assessment statistics evaluating the ability of hindcasts to simulate 

extreme low water level events at NOS NWLON Stations in Lake Erie during 2005. Gray 

shading, if present, indicates that the statistic did not pass the NOS acceptance criteria. ..... 38

Table 15. Summary of standard statistics evaluating the ability of hindcasts to simulate extreme 

low water level events at Canadian Hydrographic stations in Lake Erie during 2005. Gray 

shading, if present, indicates that the statistic did not pass the NOS acceptance criteria. ..... 39

Table 16. Same as Table 14 except for 2006. .............................................................................. 40

Table 17. Same as Table 15 except for 2006. .............................................................................. 41

vii 
 

Table 18. Summary of skill assessment statistics of the hourly hindcasts of surface water 

temperatures at the fixed buoys in Lake Erie during 2005. Gray shading indicates that the 

statistic did not pass the NOS acceptance criteria. ................................................................. 45

Table 19. Same as Table 18 except it is for 2006. ....................................................................... 45

Table 20. Summary of skill assessment statistics of the hourly hindcasts of surface water 

temperatures at coastal stations in Lake Erie during 2005. Gray shading indicates that the 

statistic did not pass the NOS acceptance criteria. Observational data were not available 

from Fairport, Ohio station. .................................................................................................... 49

Table 21. Same as Table 21 except it is for 2006. ....................................................................... 49

Table 22. Summary of skill assessment statistics of the hourly hindcasts of subsurface water 

temperatures at the Thermistor String T05 in the western basin of Lake Erie during 2005. 

Gray shading indicates that the statistic did not pass the NOS acceptance criteria. .............. 51

Table 23. Summary of skill assessment statistics of the hourly hindcasts of subsurface water 

temperatures at the Thermistor String T07 in the central basin of Lake Erie during 2005. 

Gray shading indicates that the statistic did not pass the NOS acceptance criteria. .............. 56

Table 24. Summary of skill assessment statistics of the hourly hindcasts of subsurface water 

temperatures at the Thermistor String T12 in the eastern basin of Lake Erie during 2005. 

Gray shading indicates that the statistic did not pass the NOS acceptance criteria. .............. 60

viii 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

LIST OF ACRONYMS

AGL Above Ground Level 

ASOS Automated Surface Observing System 

AWOS Automated Weather Observing System 

CMMB Coastal Marine Modeling Branch 

C-MAN Coastal-Marine Automated Network 

CO-OPS Center for Operational Oceanographic Products and Services

CSDL Coast Survey Development Laboratory 

ECCC Environment and Climate Change Canada 

FVCOM Finite Volume Community Ocean Model 

GLCFS Great Lakes Coastal Forecast System 

GLERL Great Lakes Environmental Research Laboratory

GLOFS Great Lakes Operational Forecast System 

GLSEA Great Lakes Surface Environmental Analysis

GRIB2 GRIdded Binary (Version 2) 

HRRR High Resolution Rapid Refresh numerical weather prediction system 

IFYLE International Field Year of Lake Erie 

LEOFS Lake Erie Operational Forecast System 

LMOFS Lake Michigan Operational Forecast System 

NAM North America Mesoscale Model 

NCEP National Centers for Environmental Prediction

NCO NCEP Central Operations

NDBC National Data Buoy Center 

NDFD National Digital Forecast Database

NOAA National Oceanic and Atmospheric Administration 

NOS National Ocean Service 

NWLON National Water Level Observation Network 

NWRI National Water Research Institute

NWS National Weather Service 

OCS Office of Coast Survey 

OSU The Ohio State University 

POMGL Princeton Ocean Model – Great Lakes version

UMASS University of Massachusetts 

USGS United States Geological Survey 

WCOSS Weather and Climate Operational Supercomputer System 

WFO Weather Forecast Office 

ix
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EXECUTIVE SUMMARY 

NOS Lake Erie Operational Forecast System (LEOFS) is a three-dimensional lake forecast system 

which uses near real-time atmospheric observations and meteorological forecasts to generate 

hourly nowcast and forecast guidance out to 60 hours of three-dimensional water temperature and 

currents and two-dimensional water levels for Lake Erie. The original version of LEOFS uses the

Great Lakes version of the Princeton Ocean Model (POMGL) as its core three-dimensional

numerical oceanographic forecast model and has a horizontal resolution of 5 km and 11 vertical 

sigma (terrain-following) levels. A new version of LEOFS has been developed to use the Finite

Volume Community Ocean Model (FVCOM) with a horizontal resolution ranging from 100 m 

near the shore to 2.5 km offshore and with 21 vertical sigma levels. The new version is a

collaborative project between NOAA’s Great Lakes Environmental Research Laboratory 

(GLERL), the National Ocean Service’s Coast Survey Development Laboratory (CSDL) and the

Center for Operational Oceanographic Products and Services (CO-OPS), and the FVCOM

Development Team at the University of Massachusetts-Dartmouth. 

The accuracy of predictions from the new LEOFS version was evaluated by comparisons to 

observations for three NOS skill assessment scenarios: 1) hindcast, 2) the semi-operational 

nowcast, and 3) the semi-operational forecast guidance. This report describes the results of the

hindcast skill assessment. A similar skill assessment report for the semi-operational nowcasts and 

forecast guidance is being prepared by CO-OPS. 

The hindcast simulations were conducted for 2005 and 2006. These simulations were forced by

hourly observed water levels at NOS NWLON gauges at Gibraltar, Mich. and Buffalo, N.Y., 

estimated water temperatures at the mouth of the Detroit River and hourly surface meteorological 

analyses generated by interpolating overwater and adjusted overland observations. The hindcasts

were compared to water level observations at gauges along the U.S. and Canadian shore, to water 

temperature observations at coastal stations and offshore fixed buoys, and to water temperature 

data from thermistor strings during April – October 2005. 

The hindcasts demonstrated excellent skill for hourly water levels and surface water temperatures 

during both years and met the NOS acceptance criteria at the majority of stations. However, the 

hindcasts failed to meet the NOS acceptance criteria at all verification gauges in predicting the 

amplitude and timing of extreme high and low water level events. The hindcasts of sub-surface 

water temperatures demonstrated satisfactory or excellent skill during 2005 in the top layers, but 

performed poorly in the mid-layers and in the deep portion of the eastern basin. 

xi
 

xii 
 

 

 

 

 

 

 1. INTRODUCTION 

NOS’ Great Lakes Operational Forecast System (GLOFS) provides hourly nowcasts and shortrange forecast guidance of two-dimensional water levels and three-dimensional currents and 

water temperatures. GLOFS has been operational at NOS for Lakes Erie and Michigan since 

September 30, 2005 and for Lakes Ontario, Huron, and Superior since March 30, 2006. GLOFS 

predictions are used by commercial and recreational mariners, NWS marine weather forecasters, 

and by U.S Coast Guard Search and Rescue Operations. 

The present GLOFS uses the Great Lakes version of the Princeton Ocean Model (POMGL)

(Blumberg and Mellor, 1987) with separate computational grids for each lake. The horizontal 

grid resolutions used for Lakes Erie, Michigan, Ontario, and Huron is 5 km and is 10km for Lake

Superior. The number of vertical sigma layers is 11 for Lake Erie and 20 for the other four lakes. 

GLOFS has hourly nowcast cycles and four daily forecast cycles which generate forecasts out to 

60 hours. The nowcast cycles are forced by surface meteorological analyses of near-real-time 

data from overwater and overland observing platforms which are used to provide heat and 

radiation fluxes and wind stress to POMGL. The forecast cycles are forced by gridded surface 

wind and air temperature forecasts from the NWS National Digital Forecast Database. There 

are no heat or radiation fluxes input during the forecast cycle. 

The present GLOFS nowcasts and forecast guidance of water levels generally meets the NOS 

acceptance criteria for the amplitude of hourly and high and low water events. However, GLOFS

nowcasts and forecast guidance under predicts water levels at certain locations, which is likely

due to a combination of model grid and bathymetric data resolution. Also, GLOFS does not 

meet the NOS acceptance criteria for timing of extreme water events at most water gauges in the

lakes. 

For water temperatures, GLOFS predicts well the surface water temperatures in terms of 

amplitude, horizontal distribution and seasonal time evolution. However, GLOFS exhibits an 

overestimation of water temperature during the nowcast cycle, possibly due to an 

underestimation of cloud cover over the lakes or an error in the SOLAR subroutine. In addition, 

GLOFS does poorly in predicting water temperatures during the spring and early summer warm

up and also often exhibits unrealistic, high frequency water temperature oscillations. Because 

of these oscillations, the time series plots of water temperature predictions at forecast points are 

not shown on the CO-OPS’ GLOFS web site. Finally, comparisons of hindcasts to subsurface

water temperature data collected during field projects have indicated that GLOFS reproduces the 

basic features of the evolution of the three-dimensional thermal structures of the lakes, but 

produces a thermocline that is too diffuse and fails to capture frequent temperature fluctuations 

(Kelley et al., 2008). 

In 2013, NOS and NOAA’s Great Lakes Environmental Research Laboratory (GLERL) began 

a project to develop a new version of GLOFS to provide improved predictions of water levels, 

surface and subsurface water temperatures and currents for the Great Lakes. The Finite Volume

Community Ocean Model (FVCOM) was selected for the new version due to its unstructured 

grid design that would allow for higher horizontal resolution along the shore. LEOFS was

identified as the first of the five GLOFS domains to be migrated to FVCOM since GLERL had

already done work on the development and testing of potential FVCOM grids. 

1 
 

 

This report documents the development of the new version of LEOFS using the FVCOM as its

core oceanographic forecast modeling system and the results of the hindcast skill assessment 

(the skill assessment of the semi-operational nowcast and forecasts was conducted by CO-OPS 

and its results will be published in a separate CO-OPS technical report). A brief overview of

Lake Erie’s physical limnology is given first. 

2 
 

 

 

 

 

2. LAKE ERIE 

Lake Erie is the smallest of the Great Lakes and the 13th largest lake in the world with a breadth

of 92 km (57 mi) and a length of 388 km (241 mi). It has three distinct basins: a shallow western

basin (mostly less than 10 m deep), a deep eastern basin (maximum depth of 64 m), and a

relatively flat central basin (mostly 20-24 m deep) (Fig. 1). Water from Lakes Huron and St. 

Clair enters the lake in the western basin via the Detroit River and exits the lake via the Niagara 

River in the eastern basin. 

Lake Erie, except for its shallow western basin, has a pronounced annual thermal cycle ranging 

from vertically well-mixed water in late autumn to thermal stratification across the entire lake 

with a well-developed summer thermocline (Boyce et al., 1989; Schertzer et al., 1987). Given

the lake’s relative shallowness, the entire water column cools rapidly in the autumn to the

temperature of maximal density near 4o

C (Assel, 1990). In the winter, the surface water cools 

to 0o

C making ice formation possible. Ice formation on the lake proceeds from the shallow 

western basin in December to the deeper central and eastern basins in January (Assel, 1990). 

Similarly, in the spring and early summer, the lake warms rapidly. The central basin can be

stratified as early as May (Boyce et al., 1989). The shape of the thermocline varies according to

the basin. Typically, starting in July, a bowl-shaped thermocline begins to form in the central 

basin while a dome-shaped thermocline develops in the eastern basin (Beletsky et al, 2013). 

Lake Erie responds quickly to the passage of weather systems due to its shallowness and 

southwest to northeast orientation. The lake responds to the wind stress by a combination of free 

and forced mode oscillatory responses in water level and thermocline position which give rise to

periodic velocity and current structures (Bedford, 1992). The free mode is when the lake is

subject to an imposed wind stress on its surface resulting in frequent and sometimes dramatic 

storm surges. Frequently, strong southwest winds will cause an increase in water level at 

Buffalo, N.Y. and a drawdown at Toledo, Ohio, at the western end. The positive surge will occur

approximately three hours before the corresponding maximum drawdown at Toledo. After the

storm passage, the potential energy stored in the surge is released and expressed as free 

oscillation gravity waves called seiches (Bedford, 1992). The lake, due to its relatively small 

size its circulation, is driven by a combination of tributary flow, water temperature gradients and

wind (Simons, 1976; Beletsky et al., 2013). Additional information about the physical limnology 

of Lake Erie can be found in Beletsky et al. (1999), Boyce et al. (1989), Dingham and Bedford 

(1984), Bartish (1987), Mortimer (1987), and Saylor and Miller (1987). 

3 
4 
 

 

 

 

 

 

 

 

3. MODEL SYSTEM AND SETUP FOR HINDCASTS 

This section provides descriptions of the numerical three-dimensional hydrodynamic model, the 

model grid configuration, and how the lateral boundary, surface boundary, and initial conditions 

were specified for the hindcast runs. The configuration for the version of LEOFS-FVCOM to 

be run operationally on NOAA WCOSS will be different in terms of surface meteorological 

conditions and lateral boundary conditions for water temperatures.

3.1. Description of Model 

FVCOM is a prognostic, unstructured-grid, finite-volume, free-surface, three-dimensional

primitive equation coastal ocean circulation prediction model developed by the researchers at 

the UMASS-Dartmouth and Woods Hole Oceanographic Institution (Chen and Beardsley, 2003; 

Chen et al., 2013). The model consists of momentum, continuity, temperature, salinity and

density equations and is closed physically and mathematically using turbulence closure submodels. The horizontal grid is comprised of unstructured triangular cells. A generalized terrainfollowing vertical coordinate system is used. Several different turbulent closure schemes (TCS) 

are available in FVCOM. For LEOFS, the Mellor Yamada 2.5 TCS was used for the vertical 

and the Smagorinsky TCS was utilized for the horizontal. FVCOM is solved numerically by a 

second-order-accurate discrete flux calculation in the integral form of the governing equations 

over an unstructured triangular grid. According to Chen et al. (2007), this approach combines

the best features of finite-element methods (grid flexibility) and finite-difference methods 

(numerical efficiency and code simplicity). The model three-dimensional solution is determined 

using a mode-splitting technique by which a two-dimensional external mode is updated at 

frequent intervals while the more slowly evolving internal mode is obtained less frequently. For 

LEOFS, an external mode time step of 10 seconds was used. 

FVCOM has been successfully applied in several coastal ocean regions to simulate 

oceanographic conditions. Presently, NOS’ Northern Gulf of Mexico Operational Forecast

System (Wei et al., 2014, Wei et al., 2015) and the San Francisco Operational Forecast System

(Peng et al., 2014; Schmalz, 2013) use FVCOM as their core numerical ocean circulation

forecast model.

The FVCOM version used for the hindcasts was Version 3.2.0. This version includes the Fortran 

subroutines UZL and SOLAR. The SOLAR subroutine, which is also used by the present 

POMGL-GLOFS, calculates insolation and surface heat flux (McCormick and Meadows, 1988; 

Kelley, 1995). SOLAR relies on the subroutine UZL to calculate bulk aerodynamic coefficients 

for momentum and heat over a lake surface as a function of 10m AGL wind speed and air-sea 

temperature difference (Kelley, 1995). The SOLAR subroutine has the following inputs: 1) 

surface air temperature, 2) surface dew point temperature, 3) surface wind speed, 4) cloud cover,

5) surface water temperature, 6) bulk aerodynamic coefficient for heat, 7) bulk aerodynamic 

coefficient for momentum, 8) latitude, 9) longitude (west of Greenwich), 10) day of year, and

11) hour of day (local standard time). The output from the routine includes total surface heat

flux and short wave radiation. 

5 
 

 

Figure 1. Map depicting Lake Erie bathymetry (feet) including longitudinal cross section. 

Modified from figure by Ted Walke of Pennsylvania Angler and Boater Fact Sheet.

3.2. Grid Configuration 

LEOFS-FVCOM uses a model domain which covers all of Lake Erie and takes into account 

many land features including the islands in the western basin (e.g. Kelley Island, South Bass 

Island) as well as Long Point, Presque Isle, Rondeau Provincial Park, and Point Pele. The grid 

generation module of the Surface-Water-Modeling System (SMS) software was used by GLERL

to generate the unstructured model grid. The grid size distribution is configured as dependent 

on the GLERL bathymetry (NOAA NGDC, 3 arc-second). The model bathymetry was obtained 

by interpolating the GLERL digital bathymetry onto each unstructured FVCOM model grid 

node. The model bathymetry is shown in Fig. 2. 

High resolution NOAA coastline data was applied to delineate the land boundary. Since the 

Detroit River and Niagara River define the input and output for the lake, higher grid resolution 

was specified at the mouths of these rivers. The model grid in the horizontal is composed of 

11,509 triangular elements and 6,106 nodes. The resolution varies from approximately 100 m 

near the shore to about 2.5 km offshore. The grid is depicted in Fig. 3. The model has 21 sigma

levels with distribution referenced to the Great Lakes low water datum of 173.5 m. The sigma

6 
 

 

 

 

 

 

 

levels are the following: 0.0, -0.05, -0.1, -0.15, -0.2, -0.25, -0.3, -0.35, -0.4, -0.45, -0.5, -0.55, -

0.6, -0.65, -0.7, -0.75, -0.8, -0.85, -0.9, -0.95, and -1.0. 

3.3. Lateral Boundary Conditions 

For the hindcasts, the lateral boundary condition (LBC) for the temperature of the water entering

the lake from the Detroit River and water levels at the western and eastern ends of the lake were 

specified in the following manner. The water temperatures at the Detroit River were specified 

using a relationship between observed river water temperatures and observed air temperatures

recorded at the Automated Weather Observing System (AWOS) station at the Grosse Ile, 

Michigan, Municipal Airport (KONZ). The airport is located on Grosse Ile which is the largest 

island in the Detroit River. Using this method, the observed air temperature time series is

smoothed and given a 7-day lag, resulting in time-series that closely approximates water 

temperatures entering the lake through the Detroit River. The method has been verified against 

observed water temperatures of the Detroit River. 

The LBCs for water levels at the inlet and outlets of the lake were specified using FVCOM’s 

open boundary conditions “Active (ASL)” method. The method used hourly observed water

levels from the NOS/CO-OPS NWLON gauge at Gibraltar, Michigan, near the mouth of the 

Detroit River and the NWLON gauge at Buffalo, N.Y. near the mouth of the Niagara River (Fig.

4). This is different from the original, POMGL-based GLOFS which does not use water level 

boundary conditions and thus does not track absolute water level changes. The hourly water 

levels are contained in the file erie_elj_obc.dat and are referenced to the IGLD85 datum for Lake 

Erie of 173.5 m (this file was created by the Fortran program eriebc.pro). The text files of water 

levels and water temperatures are translated to netCDF by the Fortran program xobc.pro. The 

resulting netCDF file is tsobc.nc (Fig. 5) 

3.4. Surface Boundary Forcing 

For the hindcasts, the air-water surface boundary forcing consisted of hourly gridded surface 

meteorological analyses of u-wind and v-wind components, surface (2m AGL) air and dew point 

temperatures, and total cloud cover. The gridded analyses were created by interpolating surface 

observations of wind velocity, air temperature, dew point temperature, and total cloud cover 

using a natural neighbor technique (Sambridge et al., 1995). The interpolation is accomplished 

by the Fortran program interpun.f (Fig. 6). The observations are from both land-based stations 

such as ASOS and AWOS stations, coastal stations including NWS/NDBC C-MAN stations, 

ECCC automated stations on lighthouses and offshore platforms, NOS/CO-OPS NWLON 

meteorological stations, and Other Marine Reports (Fig. 7). 

The LBCs consisted of verified hourly water level observations from the NOS Gibraltar and 

Buffalo NWLON stations obtained from the NOS/CO-OPS archives at

https://tidesandcurrents.noaa.gov/stations.html?type=Historic+Water+Levels#GreatLakesDetroitRiver. 

7 
Figure 2. Map of the FVCOM model bathymetry (meters) for Lake Erie. 

Figure 3. Map depicting the FVCOM grid domain for Lake Erie. The horizontal resolution

ranges from 100 m near the shore to 2.5 km offshore with 21 vertical levels.

8 
 

 

Figure 4. Map depicting the locations of the two NOS/CO-OPS NWLON gauges whose water 

level observations were used in specifying the lateral boundary conditions

Figure 5. Flowchart depicting the inputs for generating the water temperature and water level

lateral boundary conditions for LEOFS-FVCOM hindcast runs. 

9 
 

 

 

 

 

Before being interpolated, the surface wind observations are adjusted to a common anemometer 

height of 10m above the ground or water. Surface observations of wind direction, wind speed, 

air temperature, and dew point temperature from overland stations such as ASOS stations (e.g. 

airport stations) are adjusted to be more representative of overwater conditions. Both the height 

adjustment and adjustment of observations from overland stations use the previous day’s lake 

average water temperature from GLERL’s Great Lakes Surface Environmental Analysis 

(GLSEA). The adjustments to the observations are done by the Fortran program metedit.f. The 

Fortran program xsurfaceforce.f translates the text files of gridded surface meteorological 

analyses into a netCDF file called erie_forcing.nc for use by FVCOM. 

The analyses are interpolated onto the FVCOM model domain at each node. The sensible heat,

latent heat, and the net heat flux are then calculated at each node by the SOLAR subroutine of 

FVCOM.

3.5. Initial Conditions 

LEOFS-FVCOM requires initial three-dimensional conditions including surface elevation field 

and three-dimensional velocity and water temperature fields at the beginning of the hindcasts. 

The model was initialized one year prior to the start of the hindcast period with uniform

temperature of 2o

C, 0.0 m elevation, and 0 m/s currents. The model was continuously forced 

with observed LBCs and surface meteorological analyses. The restart file after the one-year run

was used as the initial conditions for the start of the hindcasts. The dates for the hindcast periods 

are given in the next section. 

10
Figure 6. Flowchart depicting the method used to create a surface meteorological analysis and 

integrate into a single netCDF file for FVCOM hindcast runs for Lake Erie. 

11
 

Figure 7. Map depicting the locations of different observing stations and platforms whose 

observations were used in the creation of surface meteorological analyses. (Dark blue=NDBC 

and EC buoys, Red=NWS C-MAN and NOS/CO-OPS stations, and GLOS stations,

Yellow=Other Marine Reports, and Green=Surface Airway Stations [ASOS, AWOS]). 

12
 

 

4. DESCRIPTION OF HINDCAST PERIODS 

Two hindcast model simulations using LEOFS-FVCOM were conducted by GLERL on their 

Linux cluster. Hindcast #1 covered the period from Jan. 1, 2005, to Dec. 31, 2005. A plot of 

the verified daily mean water levels at the NOS Buffalo, N.Y. gauge during the year is given in 

Fig. 8. Hindcast #2 covered the period from Jan. 1, 2006, to Dec. 31, 2006. A plot of verified 

daily mean water levels at NOS Buffalo, N.Y. gauge during the year is given in Fig. 9. 

The year 2005 was selected for Hindcast #1 because there was a significant amount of physical 

limnological data available for the lake due to the data collected during the 2005 International 

Field Year on Lake Erie (IFYLE). The IFYLE was conducted from May through October 2005. 

The IFYLE includes data from thermistor strings, transmissometers, ADCPs, and wave sensors. 

Additional information about the IFYLE datasets can be found at

https://www.glerl.noaa.gov/res/projects/ifyle/data/data.mooring.html. During this hindcast 

period, there were several strong extratropical cyclones which caused significant water level 

events: Jan. 18-19, Jan. 23-24, Mar. 22-23, Apr. 2-3, Apr. 23-24, May 12-13, Sep. 28-29, Nov. 

5-6, Nov. 15-16, Nov. 23-24, and Dec. 10, 2005. The highest water level and most dramatic 

change in water levels at the Buffalo gauge in 2005 occurred during the storm of Dec. 10 (Fig. 

10). Surface water temperatures at the three offshore buoys and coastal stations are given in Fig. 

12 and 13, respectively. 

Hindcast #2 was for the year 2006. During this hindcast period, there were also several intense

storms which resulted in significant water level events on Lake Erie: Jan 17-18, Feb. 4-5, Mar. 

13-14, May 20-21, Sep. 2-3, Oct. 12-13, Oct. 28-29, Dec. 2-4, Dec. 8-9, and Dec. 23-24, 2006. 

The highest wave levels observed at the Buffalo gauge in 2006 were during the storm of Dec. 1-

2 (Fig. 11). Surface water temperatures at the buoys and coastal stations during 2006 as well as 

2005 are given in Fig. 12 and 13, respectively. 

In comparing the observed surface water temperatures between the two hindcast periods at the 

three offshore buoys (Fig. 12), temperatures in 2006 were warmer than 2005 during the spring 

months until Day 155 (Jun. 4), about the same or slightly cooler during the summer, Day 155-

240 (Jun. 4 – Sep. 2), and colder during the fall months. Similar differences between 2005 and 

2006 water temperatures were observed at the coastal stations (Fig. 13) but the dates differed. 

For example, temperatures in 2006 were colder than 2005 at coastal stations starting around Day 

220 (Aug. 8) compared to Day 245 (Sep. 2) at the buoys. 

13
 

 

Figure 8. Daily mean water levels at the NOS Buffalo, N.Y. (a) and Toledo, Ohio (b) gauges 

during 2005. The time zone is EST. 

Figure 9. Daily mean water levels at NOS Buffalo, N.Y. (a) and Toledo, Ohio (b) gauges during 

2006. The time zone is EST. 

14
Figure 10. NWS Daily Weather Map valid at 12 UTC (07 UTC) on Dec. 9, 2005 (Day 343). 

Figure 11. NWS Daily Weather Map valid at 12 UTC (07 EST) on Dec. 1, 2006 (Day 335). 

15
Figure 12. Time series plots of Surface water temperatures at the NWS/NDBC and ECCC 

offshore fixed buoys during 2005 and 2006. 

16
Figure 13. Time series plots of surface water temperatures at NOS NWLON gauges at 

Marblehead, Ohio, Cleveland, Ohio, and Buffalo, N.Y. during 2005 and 2006. 

17
 

18
 

 

 

 

 

5. METHOD OF EVALUATION 

LEOFS-FVCOM’s hourly hindcasts of water levels and water temperatures for 2005 and 2006 

were compared to hourly observations from coastal and offshore observing platforms in Lake 

Erie. In addition, subsurface water temperatures were compared to data from thermistor strings 

in 2005. The evaluation used the standard NOS suite of skill assessment statistics. These

statistics included Error, or more commonly referred to as Mean Algebraic Error (MAE), Root

Mean Squared Error (RMSE), Central Frequency (CF), Positive Outlier Frequency (POF), 

Negative Outlier Frequency (NOF), Maximum Duration of Positive Outliers (MDPO), and 

Maximum Duration of Negative Outliers (MDNO). These statistics are described briefly in

Table 1 while more detailed descriptions can be found in Hess et al. (2003). The comparisons 

were done using the NOS standard skill assessment software (Zhang et al., 2010 and Zhang et 

al., 2013). 

The calculation of the target frequency of occurrence skill statistics, CF, POF, MDPO and

MDNO, required the assignment of 1) acceptable magnitude errors for water level and water

temperature amplitudes, 2) acceptable timing error for water levels, and 3) maximum allowable 

time durations for consecutive positive and negative water level outliers. The same acceptable 

errors and maximum allowable time duration used to evaluate GLOFS, when it was first 

implementation operationally at NOS, were employed in evaluating the 2005 and 2006 hindcasts 

(see last column in Table 1). These specific values for the water level and temperature skill 

assessments will be discussed in the Sections 5.1 and 5.2, respectively. 

Standard skill assessment code has a coarse quality assurance function that is applied to all 

downloaded CO-OPS and NDBC buoy observation data. It calculates a "quality control range" 

first; any data that is out of this range will be regarded as unrealistic and then be deleted. The 

quality-control-range is calculated in subroutine refwl.f. The code in the subroutine calculates 

average and standard deviation for the whole data set, and uses average +/-5 times standard 

deviation as upper and lower boundaries and writes out data that are within this range. This +/-

5 SD QA check erroneously removed several high amplitude water level events at NOS/COOPS in Lake Erie. This QA check was commented out in order to include all high amplitude

water level and water temperature events when skill assessing the LEOFS hindcasts. However, 

both the water level and water temperature observational data were plotted and obvious spikes 

were manually deleted from the data prior to running the skill assessment program. 

Extreme high or low water events were selected from the observed data and hindcasts using the 

equations hupper=mean+factor*SD and hlower=mean-factor*SD where the value for factor was

set to 2.0 (Zhang et al., 2013). 

The resulting values for each statistic were then judged against the NOS Acceptance Criteria

(Table 1) for that statistic. The critieria includes target frequencies of occurrence for CF, NOF, 

and POF and limits on the duration of errors (i.e. maxium length of time of consecutive 

occurrences) for MDPO and MDNO. Any new or upgraded NOS nowcast/forecast modeling 

system is expected to meet or exceed most of the NOS Acceptance Criteria (targets) in order to 

be implemented operationally. 

19
 

 

Table 1. Description of NOS skill assessment statistics (Modified from Hess et al., 2003) along 

with NOS Acceptance Criterion (targets) used to evaluate GLOFS hindcasts. 

Statistic Units Description

NOS 

Acceptance 

Criterion

Mean 

Algebraic Error 

Meters 

or Hours 

The error is defined as the predicted value, p, minus the 

reference (observed value) NA 

SD Meters or 

Hours Standard Deviation NA 

RMSE Meters or 

Hours Root Mean Square Error NA 

SM Meters or 

Hours Series Mean. The mean value of a series y NA 

CF(X) % Central Frequency. Fraction (percentage) of errors that 

lie within the limits +X. => 90% 

POF(X) % Positive Outlier Frequency. Fraction (percentage) of

errors that are greater than X. <= 1% 

NOF(X) % Negative Outlier Frequency. Fraction (percentage) of 

errors that are less than -X. <= 1% 

MDPO(2X) Hours 

Maximum Duration of Positive Outliers. A positive 

outlier event is two or more consecutive occurrences of

an error greater than +2X. MDPO is the length of time 

in hours (based on the number of consecutive

occurrences) of the longest positive outlier event. 

<= L 

MDNO(2X) Hours 

Maximum Duration of Negative Outliers. A negative 

outlier event is two or more consecutive occurrences of

an error less than -2X. MDNO is the length of time in

hours (based on the number of consecutive

occurrences) of the negative outlier longest event. 

<= L 

NOS Standard Criteria 

where X=acceptable error magnitude (cm or minutes) 

 X = +- 15cm for water level amplitude errors 

 X = +- 1.5 hours (90 minutes) for water level timing 

errors 

X = +- 3.0o

C for water temperature amplitude errors 

where 

L=time limit 

or 

max. 

allowable 

duration 

L=24 hours 

20
 

 

 

 

5.1. Evaluation of Water Level Hindcasts 

The comparison of time series differences between the 2005 and 2006 water level hindcasts used 

the statistics SM, RMSE, SD, NOF, POF, MDPO, and MDNO described in the previous section. 

The assessment evaluated the ability of the hindcasts to predict hourly water levels and also 

extreme high and low water events. The identification of extreme high and low water events 

during the hindcast periods in the Great Lakes was accomplished using the method described in 

Chu et al. (2007). 

The acceptable magnitude errors for water levels was set at +- 15 cm (0.5 ft) and the acceptable 

timing error was set at +- 1.5 hours. In addition, for the calculation for the MDPO and MDNO 

statistics, a maximum allowable time duration of consecutive occurrences with an error greater 

than the acceptable amplitude or timing error was specified at 24 hours. 

The time series of hourly hindcasts were compared to observed hourly water levels recorded at 

NOS/CO-OPS NWLON and Canadian Hydrographic Service (CHS) stations along the Lake Erie 

shore (Fig. 14). The NWLON station at Fairport, OH was not used in the assessment because of 

noticeable subsidence in the area of the station, which affected the water level data. The 

NWLON station at Gibraltar was also not used since its observations were used in defining the 

lateral boundary conditions. CO-OPS has adjusted the archived data from the Fairport gauge 

back to Sept. 2006 in order to bring the values more in line with the rest of the lake (Grodsky, 

2016). Information about these stations is given in Table 2. The hourly water level observations 

for the NOS NWLON gauges were obtained from CO-OPS online archives at

http://tidesandcurrents.noaa.gov. Hourly water levels for CHS gauges were obtained from 

Canada’s Dept. of Fisheries and Oceans online archives at http://www.meds-sdmm.dfompo.gc.ca/isdm-gdsi/twl-mne/inventory-inventaire/list-liste-eng.asp?user=isdmgdsi®ion=CA&tst=1. All observations were plotted as time series and visually inspected for 

erroneous data. Any erroneous data was removed prior to conducting the skill assessment. 

Figure 14. Map depicting the locations of the water level gauges used to evaluate the hindcasts 

of water levels.

21
 

 

Table 2. Information on NOAA/NOS/CO-OPS NWLON and CHS stations whose observations 

were used to evaluate hindcasts of gauges. NA indicates that an official NWS station ID has not 

been assigned to the station yet or not available since it is a Canadian station. 

Station Name State or 

Prov. 

NOS or CHS 

Station ID 

NWS 

Station ID 

Coordinates 

Lat. (deg N) Lon. (deg W) 

Buffalo NY 9063020 BUFN6 42.88 78.89 

Sturgeon Point NY 9063028 PSTN6 42.69 79.05 

Erie PA 9063038 EREP1 42.15 80.08 

Cleveland OH 9063063 CNDO1 41.54 81.64 

Marblehead OH 9063079 MRH01 41.55 82.73 

Toledo OH 9063085 THR01 41.69 83.47 

Fermi Power Plant MI 9063090 NS 41.96 83.26 

Bar Point ON C12005 NA 42.05 83.12 

Kingsville ON C12065 NA 42.03 82.92 

Erieau ON C12250 NA 42.27 81.92 

Port Stanley ON C12400 NA 42.67 81.22

Port Dover ON C12710 NA 42.78 80.20 

Port Colborne ON C12865 NA 42.87 79.25 

5.2. Evaluation of Surface Water Temperature Hindcasts 

The evaluation of hourly hindcasts of surface water temperatures was based on comparisons of 

time series differences between the hindcasts and observations at both offshore and coastal

locations in Lake Erie. The comparisons were done using SM, RMSE, SD, NOF, POF, MDPO,

and MDNO. In evaluating predicted water temperature in tidal regions, NOS sets an acceptable

error of 7.7o

C to meet the acceptable error of draft of 7.5 cm (3 inches), as water density is a 

function of temperature and salinity. However for the Great Lakes, a 3oC criteria for water

temperature was assigned, the same criteria used in earlier evaluations of GLOFS (Chu et al., 

2007; Kelley et al., 2008). 

During the generation of the hindcasts, it was discovered that FVCOM outputted unrealistic 

water temperatures as low as -4o

C during the winter months. CO-OPS decided to impose a

-2o

C lower limit on FVCOM’s water temperature predictions in the operational version of 

LEOFS. Thus, for the evaluation of the 2005 and 2006 hindcasts, this lower limit was imposed 

on the hindcasts. 

22
 

 

 

 

 

Hindcasts at offshore locations were compared to observations at three 3-m fixed disk buoys in 

the lake. The buoys are operate d by the NOAA/NWS/National Data Buoy Center (NDBC) or 

ECCC (Fig. 15). The comparison of the hindcasts to observations from Canadian as well as

NDBC buoys follows the recommendation of Kelley et al. (2008). The lake surface temperatures 

at NDBC Buoys are measured using a Yellow-Springs thermistor sealed in epoxy in a copper 

slug clamped to the inside of the buoy’s hull (Gillhousen, 1987). The thermistor depth is 0.5 m 

and is sampled once per hour. The point evaluations were conducted by comparing surface 

(highest sigma layer) temperature hindcasts at the nearest grid points to the buoys. Geographic 

information for the three buoys is given in Table 3. 

Hindcasts at coastal locations were compared to observations at the three NOS/CO-OPS

NWLON stations at Marblehead, OH, Cleveland and Buffalo (Fig. 15). The water temperature

sensors at the NWLON stations are located approximately 1.5 m below the low water datum

(LWD) for the lake. According to Grodsky (personal communication, 2014), the sensors are 

located fairly close to the shore structure that the water level gauges are mounted to. The Buffalo

and Cleveland gauges are attached to the seawall located next to the gauge house. The sensor at 

the Marblehead station is mounted in a conduit that is welded to the bulkhead. The sensors do 

not have any heating element directly associated with them (Grodsky, 2014). This station is the

least sheltered by manmade wave breakers or landforms of the three locations while the

Cleveland station is the most sheltered. Geographic information about the NWLON temperature 

stations is provided in Table 4 with more detailed information about sensor exposure at each 

station in Appendix A. 

The hourly water temperature observations for the NWS fixed buoys were obtained from the 

NDBC online archives at http://www.ndbc.noaa.gov. Hourly temperatures at the two Canadian 

buoys were obtained from Government of Canada’s Department of Fisheries and Oceans’

Oceanography and Scientific Data Web sites: http://isdm.gc.ca/isdm-gdsi/waves-vagues/searchrecherche/list-liste/data-donnees-eng.asp?medsid=C45132 and http://isdm.gc.ca/isdm-gdsi/waves-vagues/searchrecherche/list-liste/data-donnees-eng.asp?medsid=C45132. Hourly temperatures from the NOS coastal

stations were obtained from the CO-OPS online archives at http://tidesandcurrents.noaa.gov. All

the observations were plotted as time series and visually inspected for erroneous data. The 

temperature data at the CO-OPS stations were found to have a considerable number of spikes. 

These spikes were removed from the datasets prior to conducting the comparisons. 

23
 

 

Figure 15. Map depicting the locations of offshore and coastal platforms used to evaluate the

hindcasts of surface water temperatures, indicated by red boxes. 

5.3. Evaluation of Sub-Surface Water Temperature Hindcasts 

The evaluation of the sub-surface water temperature hindcasts were based on comparisons to 

observed temperatures at three thermistor strings locations in Lake Erie during 2005. The three 

thermistor stations were selected from an extensive array of thermistor stations operated by 

GLERL and Canadian National Water Research Institute (NWRI) during International Field 

Year of Lake Erie (IFYLE) 2005. The stations were chosen in order to evaluate subsurface water 

temperatures in each of the three basins of the lake. These stations were found to be 

representative of the data collected at nearby stations in their respective basins. The three 

stations were T05 in the western basin, T07 in the central basin, and T12 in the eastern basin 

(Table 5). A map depicting the locations of the thermistor strings is given in Fig. 16. 

Temperature data from the thermistor stations were available every 30 minutes from

approximately mid-June to late-October 2005. Data were recorded at different depths depending 

on location. Data were available at 4 and 11m at T05, at 1, 3, 5, 7, 9, 13, 15, 16.5, 17.0, and 17.5 

m at T07, and at 1, 3, 5, 7, 9, 11, 13, 15, 18.5, 19.0, 28.5, 43.5, and 52.5 m at T12. 

The types of thermistors varied at some stations. At T05, Brancker T-1000 thermistors were 

used. At T07 and T12, three different types of thermistors were used: Onsett, Seabird SBE 39, 

and Brancker T-1000. Additional information on thermistor arrays can be found at 

https://www.glerl.noaa.gov/res/projects/ifyle/data/Mooring/therm/Station.php?sta=All&year=2

005. 

24
 

Table 3. Information about NWS/NDBC and ECCC fixed buoys whose surface water 

temperature observations were used to evaluate the hindcasts offshore. 

Buoy Name Agency Prov. or 

State 

NWS Buoy 

Platform ID 

Coordinates 

Latitude

(deg N) 

Longitude 

(deg W)

West Erie NWS/NDBC OH 45005 41.68 82.40 

Port Stanley Envir. Canada ON 45132 42.47 81.22 

Port Colborne Envir. Canada ON 45134 42.74 79.29 

Table 4. Information about NOS/CO-OPS NWLON stations whose water temperature

observations were used to evaluate the hindcasts along the coast.

Station Name State NOS Station ID NWS Station ID 

Coordinates 

Latitude

(deg N) 

Longitude 

(deg W)

Marblehead OH 9063079 MRHO1 41.55 82.73 

Cleveland OH 9063063 CND01 41.50 81.64 

Buffalo NY 9063020 BUFN6 42.88 78.89 

Table 5. Information about GLERL thermistor stations whose observations were used to 

evaluate the hindcasts of sub-surface water temperatures.

Station Name Station ID Basin 

Coordinates 

Depth Latitude (m) (deg N) 

Longitude 

(deg W)

Station 5 T05 Western 41.67 82.62 12 

Station 7 T07 Central 41.94 81.65 24.5 

Station 12 T12 Eastern 42.57 79.91 53.5 

25
 

 

Figure 16. Map depicting the locations of NOAA/GLERL thermistors used to evaluate the 

hindcasts of sub-surface water temperatures during 2005. 

26
 

 

 

 

 

 

6. HINDCAST SKILL ASSESSMENT RESULTS 

6.1. Assessment of Water Level Hindcasts 

Time series plots of the water level hindcasts vs. observations at the Buffalo and Toledo gauges 

are given for 2005 and 2006 in Fig. 17 and 18, respectively. Toledo and Buffalo, located at the

extreme SW and NE ends of the lake, respectively, experience the greatest hourly water level 

variability. Plots for all the NOS and CHS gauges are given in Appendices B and C for 2005 

and 2006, respectively. 

The standard suite of skill assessment statistics evaluated the ability of the hindcasts to predict 

hourly and extreme high and low water levels at NOS and CHS gauges during 2005 and 2006. 

The results of the assessment of the hourly hindcasts are described in Section 6.1.1 and the 

assessment results of extreme high and low water events is given in Section 6.1.2. 

6.1.1. Hourly Water Levels 

The skill statistics assessing the ability of the hindcasts to predict hourly water levels at NOS 

and CHS gauges in 2005 are given in Tables 6 and 7. Similar tables for 2006 are given in Tables 

8 and 9. The mean algebraic errors (MAE) during 2005 ranged between -6.3 and 0.0 cm and the 

RMSE ranged between 6.1 and 10.9 cm. For 2006, the MAEs ranged from -6.9 to -1.8 cm and 

the RMSE ranged from 6.0 to 11.0 cm. The greatest MAEs during 2005 and 2006 were at 

Toledo. The hindcasts for 2005 and 2006 passed all the NOS Acceptance Criteria at all NWLON 

and CHS stations, except for the NOF and CF at Toledo during 2005, CF at Toledo during 2006, 

and NOF at Port Colborne and Port Dover during 2006. However, it failed to meet the CF and

NOF targets at these stations by very small amounts. 

6.1.2. Extreme High Water Level Events 

The skill statistics assessing the ability of hindcasts to predict the amplitude and timing of 

extreme high water level events at NOS and CHS gauges during 2005 and 2006 are given in 

Tables 10 and 11, respectively. Similar tables for NOS and CHS gauges for 2006 are given in 

Tables 12 and 13. Examples of extreme high water level events at Buffalo are depicted in Fig.

19, corresponding to the extra-tropical cyclones of Dec. 9, 20015 (Fig. 8) and the Dec. 1, 2006 

(Fig. 9). 

During 2005, the hindcasts under-predicted the extreme high events at all stations with MAEs 

ranging from -18 cm at Dover to -4 cm at Cleveland. The RMSEs ranged from 10.8 cm to 

Cleveland to 23 cm at Port Dover. The MAEs for timing ranged from -0.026 hour at Sturgeon 

Point to about +0.4 hour at Cleveland and Port Stanley. The RMSEs for timing generally ranged 

from 0.54 to 1.3 hours. The hindcasts of extreme high events passed all the NOS Acceptance 

Criteria for amplitude at only Cleveland and Erieau. (However, there were only six events at 

Erieau due to the short data period available.) The NOS targets for timing were met at Fermi 

Power Plant and Bar Point. 

27
Figure 17. Time series plots of hourly hindcasts of water level vs. observations at NOS NWLON 

gauges at Toledo, Ohio and Buffalo, N.Y. during 2005. 

28
Figure 18. Time series plots of hourly hindcasts of water level vs. observations at the NOS 

NWLON gauges at Toledo, Ohio and Buffalo, N.Y. during 2006. 

29
Table 6. Summary of skill assessment statistics evaluating the ability of the hindcasts to predict 

hourly water levels at NOS NWLON stations in Lake Erie for 2005. Gray shading, if present, 

indicates that it did not meet the NOS acceptance criteria.

Statistic, Acceptable 

Error [ ], and Units ( ) Buffalo Sturgeon Pt. Erie 

Cleveland 

Toledo 

Fermi 

Power 

Plant 

N 8759 8740 8759 8759 8759 8752 

Mean Alg. Error (m) 0.000 0.007 -0.021 -0.020 -0.063 -0.030 

RMSE (m) 0.084 0.080 0.066 0.059 0.109 0.071 

SD (m) 0.084 0.080 0.062 0.055 0.089 0.065 

NOF [2x15 cm] (%) 0.7 0.6 0.2 0.0 1.2 0.2 

CF [15 cm] (%) 94.0 94.9 96.8 98.4 86.5 96.5 

POF [2x15 cm] (%) 0.2 0.1 0.0 0.1 0.1 0.1 

MDNO [2x15 cm ] (hr) 4.0 6.0 4.0 0.0 14.0 6.0 

MDPO [2x15 cm ] (hr) 5.0 5.0 1.0 1.0 2.0 1.0 

Table 7. Summary of skill assessment statistics of hindcasts of hourly water levels at Canadian 

Hydrographic stations in Lake Erie for 2005. Gray shading, if present, indicates that it did not 

meet the NOS acceptance criteria.

Statistic, Acceptable 

Error [ ], and Units ( ) 

Port 

Colborne 

Port 

Dover 

Port 

Stanley Erieau Kingsville

Bar 

Point 

N 8315 8472 8134 8472 8472 8472 

Mean Alg. Error (m) -0.009 -0.018 -0.032 -0.029 -0.029 -0.040 

RMSE (m) 0.081 0.073 0.061 0.069 0.069 0.067 

SD (m) 0.080 0.071 0.052 0.062 0.062 0.053 

NOF [2x15 cm] (%) 0.7 0.4 0.0 0.0 0.0 0.0 

CF [15 cm] (%) 94.0 95.4 98.4 96.8 96.8 97.6 

POF [2x15 cm] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm ] (hr) 7.0 5.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm ] (hr) 2.0 0.0 0.0 1.0 1.0 0.0 

30
 

 

Table 8. Same as Table 6 except for 2006.

Statistic, Acceptable 

Error [ ], and Units ( ) Buffalo Sturgeon Pt. Erie 

Cleveland 

Marblehead Toledo 

Fermi 

Power 

Plant 

N 8759 8362 8759 8759 451 8648 8759 

Mean Alg. Error (m) -0.018 -0.009 -0.036 -0.028 -0.061 -0.069 -0.033 

RMSE (m) 0.089 0.084 0.077 0.061 0.074 0.110 0.071 

SD (m) 0.088 0.084 0.068 0.054 0.043 0.086 0.063 

NOF [2x15cm] (%) 1.0 0.8 0.4 0.0 0.0 1.0 0.0 

CF [15cm] (%) 92.2 93.7 95.5 99.1 99.1 85.7 97.6 

POF [2x15cm] (%) 0.1 0.1 0.0 0.0 0.0 0.1 0.1 

MDNO [2x15cm ] (hr) 6.0 6.0 7.0 0.0 0.0 8.0 0.0 

MDPO [2x15cm] (hr) 8.0 5.0 1.0 0.0 0.0 2.0 2.0 

Table 9. Same as Table 7 except for 2006. 

Statistic, Acceptable 

Error [ ], and Units ( ) 

Port 

Colborne 

Port 

Dover 

Port 

Stanley Erieau Kingsville Bar Point 

N 8059 8472 8472 8472 8472 8472 

Mean Alg. Error (m) -0.029 -0.037 -0.043 -0.037 -0.042 -0.045 

RMSE (m) 0.092 0.086 0.064 0.060 0.072 0.073 

SD (m) 0.088 0.078 0.048 0.048 0.059 0.058 

NOF [2x15 cm] (%) 1.3 1.1 0.0 0.0 0.0 0.0 

CF [15 cm] (%) 91.7 93.6 99.1 99.8 97.5 97.8 

POF [2x15 cm] (%) 0.1 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm ] (hr) 12.0 8.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm ] (hr) 5.0 0.0 0.0 0.0 0.0 0.0 

31
Table 10. Summary of skill assessment statistics evaluating the ability of the hindcasts to predict 

extreme high water level events at NOS NWLON stations in Lake Erie during 2005. Gray 

shading, if present, indicates that it did not meet the NOS acceptance criteria.

Statistic, 

Acceptable Error [ ], 

and Units ( ) 

Buffalo 

N=31 

Sturgeon Point 

N=38 

Erie 

N=32 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (hr) -0.200 0.000 -0.149 -0.026 -0.128 0.094 

RMSE (m) (hr) 0.258 1.136 0.219 1.064 0.167 1.159 

SD (m) (hr) 0.167 1.155 0.162 1.078 0.109 1.174 

NOF [2x15 cm or 90 min] (%) 22.6 0.0 13.2 0.0 9.4 0.0 

CF [15 cm or 90 min] (%) 48.4 77.4 57.9 78.09 71.9 78.1 

POF [2x15 cm or 90 min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Cleveland

N=27 

Toledo 

N=31 

Fermi Power 

Plant 

N=24 

Amp. Time Amp. Time Amp. Time 

-0.071 0.407 -0.116 -0.129 -0.113 -0.208 

0.108 1.319 0.143 0.842 0.128 0.540 

0.083 1.279 0.086 0.846 0.060 0.509 

0.0 0.0 0.0 0.0 0.0 0.0 

92.6 66.7 67.7 93.5 70.8 100.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

32
Table 11. Summary of skill assessment statistics evaluating the ability of the hindcasts to predict 

extreme high water level events at CHS stations in Lake Erie during 2005. Gray shading, if 

present, indicates that it did not meet the NOS acceptance criteria.

Statistic, 

Acceptable Error [ ], 

and Units ( ) 

Port Colborne 

N=26 

Port Dover 

N=21 

Port Stanley 

N=12 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (hr) -0.122 0.038 -0.180 -0.238 -0.102 0.417 

RMSE (m) (hr) 0.190 1.056 0.230 1.215 0.120 1.041 

SD (m) (hr) 0.149 1.076 0.146 1.221 0.065 0.996 

NOF [2x15 cm or 90 min] (%) 19.2 0.0 23.8 0.0 0.0 0.0 

CF [15 cm or 90 min] (%) 61.5 80.8 47.6 76.2 75.0 83.3 

POF [2x15 cm or 90 min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Erieau

N=6 

Kingsville 

N=26 

Bar Point 

N=31 

Amp. Time Amp. Time Amp. Time 

-0.044 -0.500 -0.108 0.308 -0.105 -0.129 

0.062 1.354 0.131 1.000 0.117 0.622 

0.049 1.378 0.075 0.970 0.054 0.619 

0.0 0.0 0.0 0.0 0.0 0.0 

100.0 66.7 73.1 84.6 83.9 96.8 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

33
Table 12. Same as Table 10 except for 2006. 

Statistic, 

Acceptable Error [ ], 

and Units ( ) 

Buffalo, NY 

N=34 

Sturgeon Point, NY 

N=39 

Erie, PA 

N=34 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (hr) -0.186 0.176 -0.151 0.128 -0.134 0.000

RMSE (m) (hr) 0.249 1.000 0.203 1.098 0.162 1.029 

SD (m) (hr) 0.167 0.999 0.138 1.105 0.092 1.044 

NOF [2x15 cm or 90 min] (%) 23.5 0.0 15.4 0.0 5.9 0.0 

CF [15 cm or 90 min] (%) 58.8 82.4 59.0 74.4 64.7 82.4 

POF [2x15 cm or 90 min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Cleveland

N=31 

Toledo 

N=16 

Fermi Power Plant 

N=21 

Amp. Time Amp. Time Amp. Time 

-0.088 0.323 -0.147 0.062 -0.106 -0.048 

0.104 1.016 0.172 0.829 0.127 0.845 

0.055 0.979 0.091 0.854 0.071 0.865 

0.0 0.0 12.5 0.0 4.8 0.0 

87.1 83.9 75.0 87.5 76.2 95.2 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

34
Table 13. Same as Table 11 except for 2006. 

Statistic, 

Acceptable Error [ ], and Units ( ) 

Port Colborne 

N=32 

Port Dover 

N=32 

Port Stanley 

N=10 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (hr) -0.177 -0.125 -0.151 -0.094 -0.053 -0.400 

RMSE (m) (hr) 0.231 0.968 0.195 1.046 0.066 1.265 

SD (m) (hr) 0.151 0.976 0.124 1.058 0.040 1.265 

NOF [2x15 cm or 90 min] (%) 15.6 0.0 12.5 0.0 0.0 0.0 

CF [15 cm or 90 min] (%) 53.1 87.5 62.5 81.2 100.0 70.0 

POF [2x15 cm or 90 min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Erieau

N=9 

Kingsville 

N=18 

Bar Point 

N=25 

Amp. Time Amp. Time Amp. Time 

-0.097 0.111 -0.112 0.556 -0.111 -0.120 

0.104 1.291 0.126 1.106 0.128 0.917 

0.038 1.364 0.060 0.984 0.066 0.927 

0.0 0.0 0.0 0.0 4.0 0.0 

88.9 66.7 77.8 77.8 76.0 88.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

35
Figure 19. Time series plots of hourly hindcasts vs. observations at NOS NWLON Buffalo, N.Y.

gauge during the period from Dec. 1 to Dec. 16, 2005 (top) and from Nov. 26 to Dec. 6, 2006 

(bottom). 

36
 

 

 

 

 

 

During 2006, the hindcasts under-predicted the extreme high events at all stations. MAEs ranged 

from -14.7 cm at Buffalo to -5.3 cm at Port Stanley. The RMSEs ranged from 10 to 25 cm. The 

MAEs for timing ranged from -0.40 hour at Port Stanley to +0.32 hour at Cleveland. The RMSEs 

ranged between 0.89 and 1.29 hours. The hindcasts of extreme high events passed all the NOS 

acceptance criteria for amplitude only at Port Stanley. The NOS targets for timing were only 

completely met at Fermi Power Point. 

6.1.3. Extreme Low Water Level Events 

The skill statistics assessing the ability of the hindcasts to predict extreme low water level events

at the NOS and CHS gauges in Lake Erie during 2005 are given Tables 14 and 15, respectively. 

Similar tables for 2006 are presented in Tables 16 and 17. Examples of extreme low water level 

events at Toledo are depicted in Fig. 20, corresponding to the extra-tropical cyclones of Dec. 9, 

2005 (Fig. 8) and Dec. 1, 2006 (Fig. 9). 

During 2005, the hindcasts over-predicted the extreme low water events at 11 of the 12 stations 

with MAEs ranging from 3.3 cm at Fairport to 13.1 cm at Buffalo. The RMSEs ranged from 1.9 

cm to 15.9 cm. MAEs for timing ranged from -0.35 hour at Fermi Power Plant to 0.41 hour at 

Port Stanley. The RMSEs ranged from -0.35 to 0.27 hours. The hindcasts of extreme low events 

only passed all the NOS Acceptance Criteria for amplitude at Erie, Erieau, Bar Point, and Port 

Stanley, but came very close to passing at Kingsville and Port Dover. The NOS targets for timing 

were completely met only at Fermi Power Plant, but came very close to passing at Bar Point and 

Kingsville. 

During 2006, the hindcasts over-predicted the extreme low water events at nine stations but 

under predicted at three stations, including Port Stanley, Toledo, and Bar Point. At the under 

predicting stations, the MAEs ranged from -0.3 cm at Bar Point to -6.5 cm at Toledo. At the

over predicting stations, the MAEs ranged from 0.5 cm at Erieau to 11 cm at Buffalo. The

RMSEs ranged from -6.5 to 18 cm. Comparing the hindcasts at the two stations at the opposite 

ends of the lake, the MAE at Buffalo was 11cm and -6.5 cm at Toledo. The MAEs for timing 

ranged from -0.07 hour at Toledo to 0.62 hour at Erie. The RMSEs at the majority of stations

were approximately 1 hour. The hindcasts of extreme low events only passed all the NOS 

Acceptance Criteria for amplitude at Cleveland, Erieau, King Point, Bar Point, and Port Stanley 

but came very close at Fermi Power Plant. The NOS targets for timing were not met completely 

at any station. 

6.2. Assessment of Water Temperature Hindcasts 

The results of the skill assessment of LEOFS-FVCOM hindcasts of surface water temperatures

for 2005 and 2006 are given in this section. As noted earlier in Section 5.2, the assessment was

conducted with the -2o

C lower limit on the water temperature hindcasts. The assessment results 

for the three offshore locations are presented in Section 6.2.1 and for the three coastal locations

are described in Section 6.2.2. 

37
 

6.2.1. Offshore Locations 

Time series plots of the hindcasts vs. observations at buoys West Erie (45005), Port Stanley 

(45132), and Port Colbrone (45142) for 2005 and 2006 are depicted in Fig. 21 and Fig. 22, 

respectively. The skill statistics assessing the ability of the hindcasts to predict surface water 

temperatures at the three offshore fixed buoys for 2005 and 2006 are given in Tables 18 and 19, 

respectively. 

Table 14. Summary of skill assessment statistics evaluating the ability of hindcasts to simulate 

extreme low water level events at NOS NWLON Stations in Lake Erie during 2005. Gray 

shading, if present, indicates that the statistic did not pass the NOS acceptance criteria. 

Statistic, 

Acceptable Error [ ], 

and Units ( ) 

Buffalo 

N=45 

Sturgeon Point 

N=40 

Erie 

N=49 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (hr) 0.131 0.267 0.123 0.100 0.064 0.204 

RMSE (m) (hr) 0.159 1.555 0.148 0.949 0.091 1.069 

SD (m) (hr) 0.091 1.136 0.083 0.955 0.064 1.060 

NOF [2x15 cm or 90min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

CF [15 cm or 90 min] (%) 66.7 77.8 72.5 87.5 91.8 83.7 

POF [2x15 cm or 90 min] (%) 4.4 0.0 2.5 0.0 2.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Cleveland

N=39 

Toledo 

N=45 

Fermi Power Plant 

N=53 

Amp. Time Amp. Time Amp. Time 

0.068 0.462 -0.014 -0.067 0.067 -0.340 

0.111 1.177 0.142 0.978 0.120 0.824 

0.089 1.097 0.143 0.986 0.100 0.758 

0.0 0.0 2.2 0.0 0.0 0.0 

82.1 79.5 77.8 88.9 77.4 92.5 

2.6 0.0 2.2 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

38
Table 15. Summary of standard statistics evaluating the ability of hindcasts to simulate extreme 

low water level events at Canadian Hydrographic stations in Lake Erie during 2005. Gray 

shading, if present, indicates that the statistic did not pass the NOS acceptance criteria. 

Statistic, 

Acceptable Error [ ], 

and Units ( ) 

Port Colborne 

N=41 

Port Dover 

N=48 

Port Stanley 

N=39 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (min) 0.113 0.024 0.078 0.250 0.019 0.410 

RMSE (m) (min) 0.129 1.158 0.100 1.225 0.061 1.155 

SD (m) (min) 0.062 1.172 0.063 1.212 0.059 1.093 

NOF [2x15 cm or 90min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

CF [15 cm or 90 min] (%) 70.7 75.6 89.6 72.9 97.4 76.9 

POF [2x15 cm or 90 min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Erieu 

N=30 

Kingsville 

N=55 

Bar Point 

N=63 

Amp. Time Amp. Time Amp. Time 

0.039 -0.200 0.049 0.145 0.025 -0.206 

0.081 1.238 0.095 0.953 0.071 0.917 

0.072 1.243 0.082 0.951 0.067 0.901 

0.0 0.0 0.0 0.0 0.0 0.0 

90.0 70.0 87.3 89.1 98.4 87.3 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

39
Table 16. Same as Table 14 except for 2006. 

Statistic, 

Acceptable Error [ ], and Units ( ) 

Buffalo 

N=34 

Sturgeon Point 

N=28 

Erie 

N=34 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (min) 0.112 0.147 0.099 0.357 -0.134 0.618 

RMSE (m) (min) 0.148 1.098 0.139 1.000 0.162 1.071 

SD (m) (min) 0.098 1.105 0.100 0.951 0.092 0.888 

NOF [2x15 cm or 90min] (%) 0.0 0.0 0.0 0.0 5.9 0.0 

CF [15 cm or 90 min] (%) 76.5 82.4 78.6 89.3 64.7 82.4 

POF [2x15 cm or 90 min] (%) 5.9 0.0 3.6 0.0 0.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Cleveland

N=44 

Toledo 

N=54 

Fermi Power 

Plant 

N=76 

Amp. Time Amp. Time Amp. Time 

0.055 0.205 -0.054 0.037 0.042 0.132 

0.092 1.034 0.154 1.000 0.095 0.889 

0.074 1.025 0.146 1.009 0.085 0.885 

0.0 0.0 9.3 0.0 0.0 0.0 

93.2 84.1 68.5 88.9 90.8 93.4 

0.0 0.0 0.0 0.0 1.3 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

40
Table 17. Same as Table 15 except for 2006. 

Statistic, 

Acceptable Error [ ], and Units ( ) 

Port Colborne 

N=32 

Port Dover 

N=35 

Port Stanley 

N=13 

Amp. Time Amp. Time Amp. Time 

Mean Alg. Error (m) (hr) 0.082 0.219 0.056 0.400 -0.012 -0.692 

RMSE (m) (hr) 0.126 1.075 0.097 1.069 0.071 1.144 

SD (m) (hr) 0.097 1.070 0.080 1.006 0.072 0.947 

NOF [2x15 cm or 90min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

CF [15 cm or 90 min] (%) 84.4 84.4 88.6 80.0 92.3 76.9 

POF [2x15 cm or 90 min] (%) 0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

MDPO [2x15 cm or 90 min] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 

Erieau

N=35 

Kingsville 

N=63 

Bar Point 

N=74 

Amp. Time Amp. Time Amp. Time 

0.005 0.400 0.022 0.079 -0.003 -0.027 

0.051 1.095 0.072 0.951 0.072 0.944 

0.051 1.035 0.070 0.955 0.073 0.950 

0.0 0.0 0.0 0.0 0.0 0.0 

100.0 80.0 95.2 88.9 95.9 86.5 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 0.0 0.0 0.0 0.0 

41
Figure 20. Time series plots of hourly hindcasts vs. observations at NOS NWLON Toledo, Ohio 

gauge during the period from Dec. 1 to Dec. 16, 2005 (top) and from Nov. 26 to Dec. 6, 2006 

(bottom). 

42
 

 

 

 

During 2005, hindcasts agreed closely with observations at the three sites throughout the year. 

MAEs ranged from 0.9 to 1.1 o

C. The RMSEs were between 1.2 to 1.3oC. The hindcasts passed

the NOS Acceptance Criteria at all three buoys. Although the hindcasts closely matched

observations at the buoys throughout the year, there were differences depending on time of year 

and location. The best agreement during the year at all the buoys occurred in the spring until to 

approximately Day 170 (Jun. 19) when hindcasts were within +- 0.5oC of observations. 

Hindcasts at 45005 continued to match very well beyond Day 170 (Jun. 19) during summer, 

autumn, and early winter. However, at the Port Stanley buoy (45132) and at the Port Colborne 

buoy (45142), the hindcasts ran warmer than observations by approximately 1 to 1.5o

C, 

especially at the Port Colborne buoy, until Day 310 (Nov. 6). After that the hindcasts were

almost identical to observations up to the last day the buoys were still in the lake for the warm

season. 

During 2006, hindcasts matched observations at the buoys throughout the year. The MAEs

ranged from 0.09 to 0.88o

C. The RMSEs ranged from 1.0 to 1.4oC. The hindcasts passed the 

acceptance criteria at all the buoys. Although the hindcasts matched the observations throughout 

the year, there were a few notable departures between observations and hindcasts during a 

portion of the year. At West Erie buoy (45005), the hindcasts ran warmer than observations by 

approximately 1-1.5o

C from Day 160 (Jun. 9), following a rapid rise in observed water 

temperatures during the previous 15 days, to Day 250 (Sep. 7). At the Port Stanley buoy (45132), 

the hindcasts ran warmer by about 1-1.5oC from Day 230 (Aug. 18) to Day 270 (Sep. 27). In 

addition, hindcasts did not simulate well three spikes in the observations at Port Stanley which 

occurred around Days 110 (Apr. 20), 130 (May 10), and 150 (May 30) and a similar spike on 

Day 110 at 45132. 

43
Figure 21. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at three offshore fixed buoys during 2005.

44
 

 

Table 18. Summary of skill assessment statistics of the hourly hindcasts of surface water

temperatures at the fixed buoys in Lake Erie during 2005. Gray shading indicates that the 

statistic did not pass the NOS acceptance criteria. 

Time Period, Statistic, 

Acceptable Error [ ], and 

Units ( ) 

45005 

West Erie 

N=5179 

45132 

Port Stanley 

N=5318 

45142 

Port Colborne 

N=5122 

Time Period 5/3-12/5/05 6/25-10/19/05 6/13-11/27/05 

Mean Alg. Error (o

C) 0.886 0.940 1.064 

RMSE (o

C) 1.210 1.177 1.289 

SD (oC) 0.825 0.708 0.727 

NOF [2x3o

C] (%) 0.0 0.0 0.0 

CF [3o

C] (%) 99.1 99.8 99.3 

POF [2x3oC] (%) 0.0 0.0 0.0 

MDNO [2x3oC] (hr) 0.0 0.0 0.0 

MDPO [2x3oC] (hr) 0.0 0.0 0.0 

Table 19. Same as Table 18 except it is for 2006.

Time Period, Statistic, 

Acceptable Error [ ], and 

Units ( ) 

45005 

West Erie 

N=5007 

45132 

Port Stanley 

N=3977 

45142 

Port Colborne 

N=5484 

Time Period 6/13-11/27/06 3/25-4/16/06 9/24-11/24/06 

Mean Alg. Error (oC) 0.875 0.600 0.089 

RMSE (o

C) 1.242 1.361 0.985 

SD (oC) 0.882 1.221 0.981 

NOF [2x3oC] (%) 0.0 0.0 0.0 

CF [3oC] (%) 99.7 96.6 98.5 

POF [2x3o

C] (%) 0.0 0.0 0.0 

MDNO [2x3o

C] (hr) 0.0 0.0 1.0 

MDPO [2x3oC] (hr) 0.0 0.0 0.0 

45
Figure 22. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at three offshore fixed buoys during 2006. 

46
 

 

 

 

 

 

 

 

6.2.2. Coastal Station Locations 

Time series plots of the hindcasts vs. observations at Marblehead, Cleveland, and Buffalo for

2005 and 2006 are depicted in Fig. 23 and Fig. 24, respectively. The skill statistics assessing the 

ability of the hindcasts to predict surface water temperatures at the three coastal stations for 2005 

and 2006 are given in Tables 20 and 21, respectively. 

For 2005, the hindcasts agreed very closely with observations at the three sites throughout the 

year. However, the hindcasts were consistently slightly warmer than observations at Marblehead 

and Buffalo during the warm season from approximately Day 170 (June 19) until 270 (Sept. 27). 

In addition, at Cleveland, the hindcasts were consistently cooler than observations starting 

around Day 300 (Oct. 27). At Marblehead and Buffalo, where there were a full year of 

observations for statistical comparison, the MAEs were -0.1 and -0.4o

C, respectively. The 

RMSEs at these two stations were between 1.8 and 2.0o

C. The hindcasts met all NOS

Acceptance Criteria at Buffalo and Marblehead.

For 2006, the hindcasts agreed very closely with observations. However, once again the 

hindcasts were consistently warmer than observations at Marblehead and Buffalo during the 

warm season, this time from approximately Day 180 (Jun. 29) to Day 270 (Sept. 27) and at 

Cleveland from about Day 170 (Jun. 19) to Day 260 (Sept. 17). At Cleveland, the hindcasts 

were cooler than observations during the cold season from about Day 300 (Oct. 27, 2015) until 

Day 125 (May 5, 2016) and from Day 310 (Nov. 6) through the end of 2016 (Dec. 31, 2016). 

The MAEs ranged from -1.5o

C at Cleveland to 0.1oC at Marblehead. The RMSEs ranged

between 1.2o

C at Marblehead and 2.5oC at Cleveland. The hindcasts met all NOS Acceptance

Criteria at Buffalo and Marblehead but did not pass the CF criteria at Cleveland. 

6.3. Assessment of Sub-Surface Water Temperature Hindcasts 

The results of the skill assessment of LEOFS-FVCOM’s hindcasts of sub-surface water 

temperatures at the three thermistor locations, one in each of the three basins of Lake Erie during 

2005, are given in this section. The results are presented for each thermistor station. 

Station T05 – Western Basin 

Time series plots of the hindcasts vs. observations at Station T05 in the western basin at 4 and

11 m depths is depicted in Fig. 25. Plots of temperature vs. depth and time for both hindcasts 

and observations are given in Fig. 26. The skill statistics assessing the ability of the hindcasts to 

accurately predict sub-surface water temperatures at the two depths are given in Tables 22. 

Overall, the hindcasts closely matched observations at 4 and 11 m depths. However, the

hindcasts were consistently slightly warmer than observations at the 4 m depth from Day 170 

(Jun. 19) to Day 280 (Oct. 7). The hindcasts successfully predicted five high amplitude (up to 

7oC) temperature events at the 11 m depth and four events at the 5 m depth which occurred 

between approximately June 1 and August 28. The MAE at 4m depth was about 1oC and 0.2oC 

at the 11.9 m depth. The RMSEs were 1.3 and 1.4o

C at the 4 and 11 m depths, respectively. The 

hourly hindcasts passed the NOS Acceptance Criteria at both depths.

47
Figure 23. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at NOS NWLON gauges at Marblehead, Ohio, Cleveland, Ohio, and Buffalo, N.Y. during 2005

48
Table 20. Summary of skill assessment statistics of the hourly hindcasts of surface water

temperatures at coastal stations in Lake Erie during 2005. Gray shading indicates that the 

statistic did not pass the NOS acceptance criteria. Observational data were not available from 

Fairport, Ohio station. 

Time Period, Statistic, 

Acceptable Error [ ], and 

Units ( ) 

Marblehead

N=8759 

Cleveland

N=3364 

Buffalo 

N=8759 

Time Period 1/1/05-1/2/06 8/15/05-1/2/06 1/1/05-1/2/06 

Mean Alg. Error (oC) 0.078 -1.163 -0.242 

RMSE (o

C) 1.634 1.867 1.594 

SD (oC) 1.632 1.460 1.575 

NOF [2x3oC] (%) 0.0 0.0 0.0 

CF [3oC] (%) 95.3 83.9 96.1 

POF [2x3o

C] (%) 0.0 0.0 0.0 

MDNO [2x3oC] (hr) 1.0 0.0 0.0 

MDPO [2x3o

C] (hr) 0.0 0.0 0.0 

Table 21. Same as Table 21 except it is for 2006. 

Time Period, Statistic, 

Acceptable Error [ ], and 

Units ( ) 

Marblehead

N=8464 

Cleveland

N=8759 

Buffalo 

N=8368 

Time Period 6/24/06-1/2/07 1/1/06-1/2/07 3/14/06-8/29/06 

Mean Alg. Error (oC) 0.118 -1.472 0.081 

RMSE (oC) 1.205 2.456 1.264 

SD (oC) 1.199 1.966 1.261 

NOF [2x3o

C] (%) 0.1 0.4 0.0 

CF [3oC] (%) 98.8 73.8 97.2 

POF [2x3oC] (%) 0.0 0.0 0.0 

MDNO [2x3oC] (hr) 5.0 18.0 0.0 

MDPO [2x3oC] (hr) 0.0 0.0 2.0 

49
Figure 24. Time series plots of hourly hindcasts of surface water temperatures vs. observations 

at NOS NWLON gauges at Marblehead, Ohio, Cleveland, Ohio, and Buffalo, N.Y. during 2006. 

50
Table 22. Summary of skill assessment statistics of the hourly hindcasts of subsurface water 

temperatures at the Thermistor String T05 in the western basin of Lake Erie during 2005. Gray 

shading indicates that the statistic did not pass the NOS acceptance criteria.

Time Period, Statistic, 

Acceptable Error [ ], and 

Units ( ) 

Depths (meters) NOS Acceptance 

Criteria -4.0 -11.0 

Time Period 6/1-10/31/05 6/1-10/31/05 na 

Number of Hours 3663 3663 365 

Mean Alg. Error (oC) 0.990 0.220 na 

RMSE (o

C) 1.302 1.417 na 

SD (o

C) 0.845 1.400 na 

NOF [2x3o

C] (%) 0.0 0.3 < 1% 

CF [3oC] (%) 98.8 95.5 > 90% 

POF [2x3o

C] (%) 0.0 0.0 < 1% 

MDNO [2x3o

C] (hr) 0.0 11.0 < 24 hrs 

MDPO [2x3oC] (hr) 0.0 0.0 < 24 hrs 

51
Figure 25. Time series plots of hourly hindcasts vs. observations at 4 and 11.9 m depths during 

2005 at the Thermistor Station T05 Located in the Western Basin of Lake Erie. 

52
 

Figure 26. Hindcasts of water temperature (b) vs. observations (a) from 4 to 11 m depth at 

Thermistor Station T05 in the Eastern Basin from early May to late October 2005. 

53
 

 

 

 

 

 

 

 

Station T07 – Central Basin 

Time series plots of the hindcasts vs. observations at 1, 5, 11, 15, 20.5, and 23.5 m depths at 

Station T07 are given in Fig. 27. Plots of the hindcasts and observations vs. depth and time are 

given in Fig. 28. The skill statistics at all 15 available depths are given in Table 23. The 

hindcasts closely matched observations throughout the year at all depths except at the depths

from 13 to 18.5 m, with the worst agreement at 13 and 15 m. The hindcasts met the NOS 

Acceptance Criteria at 1, 21.5, 22.5, and 23.5 m depths and came very close at 3, 5, 7, and 9 m. 

A detailed assessment of the hindcasts at 1, 5, 11, 15, and 20.5 m depths at T07 station is given 

next. At 1 and 5 m depths at T07, the hindcasts were warmer than observations by 1-2oC from

Day 130 (May 10) until about Day 250 (Sept. 7). After that date the hindcasts and observations 

were within 1 degree C. For the entire period, the MAEs were about 1.3o

C and RMSEs were 

around 1.8oC. 

At 11 m depth, the hindcasts were warmer from Day 130 (May 10) until Day 165 (Jun 14) and 

then they were colder than observations until Day 215 (Aug. 3). After Day 215, the hindcasts 

closely matched the observations through Day 304 (Oct. 31) when the thermistors were removed 

from the lake. However, during this period, the hindcasts failed to simulate a sudden 5 degree 

C drop in temperature at Day 215 (Aug. 3) and simulated a significant but brief 9o

C drop in 

temperature around Day 260 (Sep. 17), which was not seen in the observations. 

At the 15 m depth, the hindcasts were significantly colder than observations from Day 170 (Jun. 

19) until Day 215 (Aug. 3). The hindcasts failed to simulate large fluctuations ranging from 5

to 20oC, which lasted from 1 to 5 days. After Day 215, hindcasts switched back and forth from 

between being warmer or colder than observations until Day 240 (Aug. 28). From that date until 

Day 275 (Oct. 2), the hindcasts were over 10oC colder. After Day 275, the hindcasts closely 

matched the observations. 

At the 20.5 m depth, the hindcasts were 1-1.5o

C colder than observations from Day 135 (May 

15) to Day 215 (Aug. 3) and then slightly warmer until Day 270 (Sept. 27). The hindcasts 

successfully simulated the sudden 8oC rise in temperature at Day 270, although it was about 

2.5oC colder than the observed maximum. However, the hindcasts simulated a sudden drop 

around Day 285 (Oct. 11) that was not observed. At 23.5 m, comparisons between the hindcasts 

and observations were similar to those at 20.5 m. 

54
Figure 27. Time series plots of hourly hindcasts of water temperature vs. observations at six 

depths of the Thermistor String T07 located in the central basin of Lake Erie during 2005. 

55
Table 23. Summary of skill assessment statistics of the hourly hindcasts of subsurface water 

temperatures at the Thermistor String T07 in the central basin of Lake Erie during 2005. Gray 

shading indicates that the statistic did not pass the NOS acceptance criteria.

Time Period, 

Statistic, Acceptable 

Error [], and Units () 

Depths (m)

-1.0 -3.0 -5.0 -7.0 -9.0 -11.0 -13.0 -15.0 

Time Period 5/6-10/26 5/6-10/26 5/6-10/26 5/6-10/26 5/6-10/26 5/6-10/26 5/6-10/26 5/6-10/26

Number of Hours 4151 4151 4151 4151 4151 4151 4151 4151 

Mean Alg. Error (o

C) 1.155 1.282 1.438 1.385 0.194 -0.953 -2.998 -1.567 

RMSE (oC) 1.754 1.880 2.063 2.102 1.786 2.737 5.148 4.536 

SD (o

C) 1.320 1.376 1.478 1.581 1.776 2.565 4.185 4.257 

NOF [2x3o

C] (%) 0.0 0.0 0.0 0.0 0.0 2.9 27.4 19.4 

CF [3oC] (%) 93.0 88.8 84.9 85.9 87.9 75.8 51.2 68.4 

POF [2x3oC] (%) 0.0 0.0 0.1 1.8 0.0 0.0 1.4 1.7 

MDNO [2x3oC] (hr) 0.0 0.0 0.0 0.0 0.0 40.0 474.0 320.0 

MDPO [2x3oC] (hr) 0.0 0.0 2.0 9.0 0.0 0.0 10.0 11.0 

Depths (m)

-16.5 -17.0 -17.5 -18.5 -20.5 -21.5 -22.5 -23.5 

5/6-10/26 5/6-10/26 5/6-10/26 5/6-10/26 5/6-10/26 7/21-10/26 5/6-10/26 8/3-10/26

4151 4151 4151 4151 4151 4058 4151 4014 

-1.579 -1.518 -1.654 -1.250 -0.739 -0.744 -0.864 -0.702 

3.933 3.908 3.697 2.768 1.488 1.615 1.715 1.605 

3.602 3.602 3.307 2.470 1.292 1.434 1.482 1.443 

15.3 15.1 15.2 8.2 0.0 0.0 0.0 0.0 

80.0 79.3 83.4 87.7 96.0 93.9 91.7 94.5 

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 

320.0 311.0 312.0 186.0 0.0 0.0 0.0 0.0 

1.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 

56
Figure 28. Hindcasts of water temperature (b) vs. observations (a) from 1 to 25 m depth at 

Thermistor Station T07 in the Central Basin from early May to late October 2005. 

57
 

 

 

 

 

Station T12 Eastern Basin 

Time series plots of the hindcasts vs. observations at 1, 5, 11, 15, 20.5, and 23.5 m depths at 

Station T12 are given in Fig. 29. Plots of the hindcasts and observations vs. depth and time are 

given in Figure 30. The skill statistics at all 15 depths are given in Table 24. 

MAEs ranged from 0.8 to 4.2o

C and RMSEs ranged from 1.9 to 5.8oC. However, the hindcasts 

did not meet the NOS Acceptance Criteria at these depths but came close to passing the criteria 

at 1, 3, 5, and 9 m depths. The hindcasts were significantly far from meeting the criteria at the 

mid depths of 11, 13, 15, 18.5, 19, 28.5, 48.5, and 52.5 m.

A detailed assessment of the hindcasts at difference depths at T12 station is given next. At the

shallower depths of 1 – 9 m, the hindcasts closely matched the observations throughout the year 

but was 1 to 2o

C warmer until Day 280 (Oct. 7). After that date, hindcasts were less than 0.5oC 

from observations. For the entire period, MAEs ranged from 0.8 to 1.9oC and RMSEs 1.9 to 

2.5o

C. 

At the mid depths of 11, 13, 15, 18.5, and 19 m, the hindcasts simulated the seasonal warmup 

and cool down. However, the hindcasts failed the majority of the time to simulate the large 

amplitude and frequency of water temperature fluctuations as well as extended periods of colder 

or warmer water. The hindcasts matched very closely the observations starting on Day 280 (Oct. 

7). MAEs and RMSEs ranged from 1.7 to 4.2oC and 3.6 to 5.8oC, respectively. 

At the bottom depths of 28.5, 43.5 and 52.5 m, the hindcasts were within 1oC of the observations 

until Day 190 (Jul 20). After Day 190, the hindcasts continued to rise steadily while observations 

remained at approximately 9oC at 23.5 m, 6oC at 43.5 m, and 5oC at 52.5 m until approximately

Day 290 (Oct. 17), the day the thermistor strings were removed from the lake. By that date, the 

observed temperatures had risen at all three depths but the differences between hindcasts and

observed varied at the three depths. At 28.5 m, the observed temperature had suddenly risen to 

17oC and matched the hindcasts almost exactly. However, at the 43.5 and 52.5 m depths, the 

difference between hindcasts and observations was about 6oC. At the three bottom depths, 

MAEs ranged from 2.6 to 3.7o

C and RMSEs ranged from 3.7 to 5.0oC for the entire period.

58
Figure 29. Time series plots of hourly hindcasts of water temperature vs. observations during 

2005 at eight depths of the Thermistor Station T12 located in the eastern basin of Lake Erie. 

59
 

Table 24. Summary of skill assessment statistics of the hourly hindcasts of subsurface water 

temperatures at the Thermistor String T12 in the eastern basin of Lake Erie during 2005. Gray 

shading indicates that the statistic did not pass the NOS acceptance criteria.

Time Period, Statistic, 

Acceptable Error [ ], 

and Units ( ) 

Depths (meters) 

-1.0 -3.0 -5.0 -7.0 -9.0 -11.0 -13.0 

Time Period 5/4-10/27 5/4-10/27 5/4-10/27 5/4-10/27 5/4-10/27 5/4-10/27 5/4-10/27

Number of Hours 4212 4212 4212 4212 4212 4212 4212 

Mean Alg, Diff. (oC) 1.469 1.608 1.907 1.702 0.829 2.182 1.716 

RMSE (oC) 1.901 2.063 2.507 2.342 1.919 3.611 3.585 

SD (o

C) 1.207 1.293 1.628 1.610 1.731 2.877 3.149 

NOF [2x3o

C] (%) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 

CF [3o

C] (%) 88.6 85.9 80.8 84.5 88.1 74.7 79.3 

POF [2x3oC] (%) 0.0 0.0 3.0 3.0 0.7 11.4 11.3 

MDNO [2x3o

C] (hr) 0.0 0.0 0.0 0.0 0.0 0.0 1.0 

MDPO [2x3o

C] (hr) 0.0 0.0 15.0 25.0 8.0 68.0 171.0 

Depths (meters) 

-15.0 -18.5 -19.0 -28.5 -43.5 -52.5 

5/4-10/27 5/4-10/27 5/4-10/27 5/4-10/27 5/4-10/27 5/4-10/27 

4212 4212 4212 4212 4212 4212 

1.584 4.151 3.368 3.689 2.932 2.561 

3.678 5.787 5.077 4.983 4.126 3.667 

3.319 4.032 3.800 3.351 2.903 2.626 

0.0 0.0 0.1 0.0 0.0 0.0 

75.2 52.6 59.6 51.9 60.1 64.1 

14.7 35.6 29.0 30.5 22.4 16.4 

0.0 1.0 3.0 0.0 0.0 0.0 

276.0 390.0 345.0 807.0 352.0 560.0 

60
 

Figure 30. Hindcasts of water temperature (b) vs. observations (a) from 1 to 53 m depth at 

Thermistor Station T12 in the Eastern Basin from early May to late October 2005. 

61
 

62
 

 

 

 

 

 

 

 

 

7. SUMMARY AND DISCUSSION 

NOAA/GLERL’s water level and water temperature hindcasts from LEOFS-FVCOM for 2005 

and 2006 were compared to water level observations at NOS NWLON and Canadian 

Hydrographic Service gauges. Hindcasts of surface water temperatures were compared to

observations from NWS/NDBC and ECCC fixed offshore buoys and coastal NWLON gauges. 

In addition, the hindcasts of subsurface temperatures were compared to data from three 

thermistor chains in each basin collected during April to October 2005. 

Water Levels 

The hindcasts for 2005 and 2006 did well overall in predicting hourly water levels including the 

reproduction of seiches following strong wind events. The MAEs ranged from -6.9 to 0 cm and 

RMSE ranged from 6 to 10 cm. The greatest MAE and RMSE in both years were found at 

Toledo while the smallest values were at the eastern end of the lake at Buffalo, Sturgeon and 

Port Colborne. The skill assessment of LEOFS-POMGL’s nowcasts for 2004 also exhibited the 

greatest MAEs at Toledo (Kelley, 2007). The hourly hindcasts passed the NOS acceptance 

criteria at nine of the 12 NOS and CHS gauges and came very close to passing at the other three 

gauges. 

However, the hindcasts did not do well in predicting the amplitude and timing of extreme high 

or low water level events. The hindcasts under predicted the amplitude of extreme high water 

level events during both years. The MAEs ranged from -18 to -4 cm and RMSEs were between 

10 and 28 cm. For extreme low water level events, the hindcasts over predicted the amplitude 

at 11 of the 12 gauges during 2005. MAE ranged from 3 to 13 cm and RMSE ranged from 2 to 

16 cm. During 2006, the hindcasts over predicted at nine gauges but under predicted at three

stations. MAEs ranged from -6.5 cm at Toledo to 11 cm at Buffalo. With regards to timing of 

high water levels, the MAEs ranged from -0.4 to 0.3 hours and the RMSEs were from 0.5 to 1.3 

hours and for low water level events, the MAEs ranged from -0.1 to 0.6 hours and the RMSEs 

were mainly around 1 hour. The hindcasts of high water level events in terms of amplitude and 

timing only passed the acceptance criteria at one or two gauges depending on the year. For low 

water level events, the hindcast passed the amplitude acceptance criteria at five gauges in 2005 

and four gauges in 2006 but passed the timing acceptance criteria at only one gauge during 2005 

and at no gauges in 2005. 

The lack of skill of the hindcasts to predict the amplitude and timing of extreme water level

events was also seen in the evaluation of LEOFS-POMGL 2004 nowcasts (Chu et al., 2007). 

The difficulty of hydrodynamic models to predict the amplitude and timing of high and low

water level events in Lake Erie has been discussed by Kelley et al. (1998), O’Connor et al. 

(2010), Beletsky et al. (2013) and others. These studies stressed the importance of accurately

representing the surface wind fields in both space and time over the lake for hydrodynamic

models. Underestimation of wind speeds over the lake will lead to reduced surface momentum 

flux and heat fluxes which will in turn affect the simulation of the water level amplitudes, water

temperatures, and currents (Beletsky et al., 2013). 

63
 

 

 

 

 

 

 

 

 

 

 

 

Surface Water Temperatures 

The surface water temperature hindcasts agreed closely with observations at the three fixed 

offshore buoys during both 2005 and 2006. The MAEs ranged from 0.1 to 0.9oC and RMSE 

ranged from 1.1 to 1.4oC. These MAE and RMSE values are similar to results of the skill 

assessment of LEOFS-POMGL (5 km horizontal resolution, 11 vertical layers) 2004 nowcasts. 

However, a significant improvement was that the hindcasts did not exhibit the unrealistic high 

frequency and high amplitude water temperature fluctuations exhibited by the 2004 nowcasts 

(Chu et al., 2007) and the present operational nowcasts and forecast guidance. The hindcasts 

passed the NOS Acceptance Criteria at all three buoys in both years.

Although the hindcasts performed well and passed acceptance criteria, there are some notable 

seasonal differences in the skill. The hindcasts differed the most from observations at the three 

buoys from approximately early summer to early autumn 2005. During this period, the hindcasts 

were 1 to 1.5oC warmer than observations. The 2006 hindcasts at the central basin buoy (45132) 

also showed a warm bias during these same months which was not seen at the buoys in the 

eastern and western basins that year. This may be related to the ability of the interpolated 

meteorological analyses over the central basin to accurately represent the spatial structure of the 

meteorological fields (e.g. cloud cover, winds) due to their dependence on land-based stations 

and buoys close to the shoreline. A similar conclusion was made by Beletsky et al. (2013) that 

observations-based wind fields may not always be suitable for central basin hydrodynamic

modeling in summer when attempting to simulate the structure of the thermocline and circulation 

pattern. An examination of hindcasts vs. observations for additional years would be necessary 

to confirm it. 

The water temperature hindcasts at the three coastal stations Marblehead, Cleveland, and Buffalo 

agreed closely with observations during 2005 and 2006. The MAEs ranged from 0.1 to -1.5o

C 

and the RMSE ranged between 1.2 to 2.5oC. The hindcasts met all NOS Acceptance Criteria at 

Buffalo and Marblehead for both years and did not meet all the criteria in Cleveland in either

year. The poor performance at Cleveland may be related to the CO-OPS station in Cleveland 

being located in a marina sheltered by a large peninsula, a manmade wave breaker which itself

is behind an extensive wave breaker, in shallow water (~5 ft), and near three concrete public boat 

ramps. During the cold months (e.g. mid-Oct to late April), the observed temperatures at 

Cleveland were warmer than the hindcast by as much as 3oC. 

An examination of the observations at the three coastal stations indicate a significant temperature 

disturbance with a sudden drop of approximately 6 to 11oC within 2 to 5 days during the stratified

summer months, first appearing at Marblehead on Day 208 (July 28), at Cleveland on Day 225 

(August 13), and then at Buffalo on Day 245 (Sept. 2). The apparent counter-clockwise time 

progression of the temperature disturbance would suggest the movement of an internal Kelvin 

wave (a stratified response). Internal Kelvin waves propagate counter-clockwise along the shore

of the Great Lakes (Boyce et al., 1989). The hindcasts during this period also show a similar

temperature disturbance at these stations but about one half the amplitude present in the 

observations. 

64
 

 

 

 

 

Sub-Surface Water Temperatures 

The sub-surface water temperature hindcasts for 2005 agreed closely with observations in the 

top part of the water column (above 11 m depth) in the three basins. The MAEs in this part of

the water column ranged from -1 to 2.2o

C and RMSEs ranged between 1.3 to 3.6oC. The

hindcasts did very well in simulating several large water temperature fluctuations in the upper

water column that occurred in all three basins. 

However, the hindcast did not do as well in the mid-layers of the central and eastern basins (~

12 to 20 m). The MAEs ranged from -3.0 to 4.2oC and RMSEs from 2.8 to 5.7oC. Although the

hindcasts simulated the time evolution of thermocline very well when compared to observations, 

it was more diffuse and extended too deep, especially in the eastern basin. In addition, the 

hindcasts frequently could not simulate several large temperature fluctuations seen in the 

observations (e.g. 14oC change in five days) in both the central and eastern basins. 

The hindcasts also did poorly in the deep parts of the eastern basin (~ 22 to 53 m). The hindcasts 

deviated significantly from observations starting in mid-June 2005 and by early-October was 

over 7o

C warmer than the observed temperature. This reflected the fact that the hindcasts

simulated a thermocline too diffuse and deep. Following the convective overturning in fall, the 

hindcasts more closely matched observations. The MAEs ranged from -0.7 to 3.7oC and RMSEs

from 1.6 to 5o

C. 

The difficulty of the hindcasts to simulate the thermocline in Lake Erie is not surprising given 

the results of previous modeling-based studies. Beletsky et al. (2013) states that Lake Erie is a 

difficult lake to model because its thermocline is one of the sharpest of all the Great Lakes and 

thermal structure is very sensitive to wind vorticity. He found that the maximum model errors

occurred in the thermocline at and below 15 m, similar to what was found in this skill assessment. 

He attributes his model’s poor performance in simulating temperatures in the mid layers to the

following: 1) a diffuse model thermocline possibly due to numerical diffusion, penetrative shortwave radiation specification, and unresolved internal waves, and 2) large vertical displacement

errors of the thermocline due to improperly simulated Ekman pumping caused by inaccuracies 

in the analyzed wind field (Beletsky et al., 2013). 

LEOFS-FVCOM code package was delivered to NOS/CO-OPS for setting up real-time semioperational nowcast/forecast runs on NOAA’s WCOSS in FY2014 Q4. Changes were made in 

the specification of the lateral boundary conditions and in the choice of surface meteorological 

forcing. The system was run in semi-operational nowcast/forecast mode starting in April 2015. 

The system was delivered to NCO for parallel testing on WCOSS in December 2015. NCO’s 

30-day evaluation period was conducted from March 10 to April 9, 2016. LEOFS-FVCOM

became operational on WCOSS on April 26, 2016. 

ACKNOWLEDGMENTS

The upgrade of the Great Lakes Operational Forecast System and its implementation on the

NOAA WCOSS is a collaborative NOAA joint effort between OAR GLERL, NOS/OCS/CSDL,

NOS/CO-OPS, and NWS/ NCEP/Central Operations. 

We express our thanks to the reviewers Jason Greenlaw and Kurt Hess for their helpful 

comments and suggestions to improve this document. 

65
 

66
 

 

 

 

 

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APPENDIX A. Information about NOS/CO-OPS water temperature observing 

stations in Lake Erie. 

Figure A-1. Satellite imagery depicting location of NOS/NWLON station in Marblehead, Ohio. 

The red circle indicates the location of the station. Also shown is a photo of the station. 

Figure A-2. Satellite imagery depicting location of NOS/NWLON station in Cleveland, Ohio. 

The red circle indicates the location of the station. Also shown is a photo of the station. 

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Figure A-3. Satellite imagery depicting location of NOS/NWLON station in Buffalo, New York. 

The red circle indicates the location of the station. Also shown is a photo of the station. 

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APPENDIX B. Time series plots of hourly hindcasts of water levels vs. 

observations at water levels gauges for 2005. 

Observational data were not available at Marblehead during 2005. 

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Figure B-1. Time series plots of hourly hindcasts of water levels vs. observations at NOS and 

CHC water levels gauges in Lake Erie for 2005. 

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APPENDIX C. Time plots of hourly hindcasts of water levels vs. observations at 

water level gauges for 2006. 

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Observational data were not available from Port Colborne gauge during 2006. 

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Figure C-1. Time series plots of hourly hindcasts of water levels vs. observations at NOS and 

CHC water levels gauges in Lake Erie for 2006. 

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