NOAA Technical Memorandum NOS CS 23

SKILL ASSESSMENT OF NOS LAKE HURON OPERATIONAL 

FORECAST SYSTEM (LHOFS) 

Silver Spring, Maryland 

October 2010 

noaa National Oceanic and Atmospheric Administration 

U.S. DEPARTMENT OF COMMERCE 

National Ocean Service 

Coast Survey Development Laboratory 
Office of Coast Survey 

National Ocean Service 

National Oceanic and Atmospheric Administration 

U.S. Department of Commerce

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

United States scientific organization, dating from 1807, this office has a long history. 

Today it promotes safe navigation by managing the National Oceanic and Atmospheric 

Administration’s (NOAA) nautical chart and oceanographic data collection and 

information programs. 

There are four components of OCS: 

The Coast Survey Development Laboratory develops new and efficient techniques 

to accomplish Coast Survey missions and to produce new and improved products 

and services for the maritime community and other coastal users. 

The Marine Chart Division acquires marine navigational data to construct and 

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

States. 

The Hydrographic Surveys Division directs programs for ship and 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. 
NOAA Technical Memorandum NOS CS 23 

SKILL ASSESSMENT OF NOS LAKE HURON 

OPERATIONAL FORECAST SYSTEM (LHOFS) 

John G. W. Kelley 

Office of Coast Survey, Coast Survey Development Laboratory, 

Silver Spring, MD 

Ai-Jun Zhang 

Center for Operational Oceanographic Products and Services, 

Silver Spring, MD 

Philip Chu 

Naval Research Laboratory, Stennis Space Center, MS 

Gregory A. Lang 

Office of Oceanic and Atmospheric Research, 

Great Lakes Environmental Research Laboratory, Ann Arbor, MI 

October 2010

noaa National Oceanic and Atmospheric Administration 

U. S. DEPARTMENT National Oceanic and National Ocean Service 

OF COMMERCE Atmospheric Administration John H. Dunnigan 

Gary Locke, Secretary Jane Lubchenco, Ph.D. Assistant Administrator 

 Under Secretary 

Office of Coast Survey Coast Survey Development Laboratory 

Captain Steven R. Barnum, NOAA Mary Erickson 
ii 

NOTICE 

Mention of a commercial company or product does not constitute an 

endorsement by NOAA. Use for publicity or advertising purposes of 

information from this publication concerning proprietary products or 

the tests of such products is not authorized.
iii 

TABLE OF CONTENT 

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

LIST OF TABLES .............................................................................................................. v 

LIST OF ACRONYMS .................................................................................................... vii 

EXECUTIVE SUMMARY ............................................................................................. viii 

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

2. LAKE HURON ............................................................................................................... 3 

3. SYSTEM OVERVIEW .................................................................................................. 5 

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

3.2 Grid Domain ............................................................................................................. 5

3.3 Data Ingest ................................................................................................................ 7 

3.4 Nowcast Cycle .......................................................................................................... 7 

3.5 Forecast Cycle ........................................................................................................... 8 

3.6 Operational Environment and Scheduling ................................................................ 8 

4. HINDCAST SKILL ASSESSMENT ............................................................................. 9 

5. SEMI-OPERATIONAL NOWCAST SKILL ASSESSMENT .................................... 11 

5.1 Description of Nowcast Cycles .............................................................................. 11 

5.2 Method of Evaluation ............................................................................................ 11 

5.3 Assessment of Water Level Nowcasts ................................................................... 19 

5.4 Assessment of Surface Water Temperature Nowcasts .......................................... 23 

6. SEMI-OPERATIONAL FORECAST SKILL ASSESSMENT .................................. 25 

6.1 Description of Forecast Cycles .............................................................................. 25 

6.2 Method of Evaluation ............................................................................................ 25 

6.3 Assessment of Water Level Forecast Guidance ...................................................... 26 

6.4 Assessment of Surface Water Temperature Forecast Guidance ............................. 29 

7. SUMMARY .................................................................................................................. 31 

8. RECOMMENDATIONS FOR FUTURE WORK ...................................................... 33 

ACKNOWLEDGMENTS ................................................................................................ 34 

REFERENCES ................................................................................................................. 35 

APPENDIX A. Skill Assessment Statistics of Semi-Operational Water Level 

Nowcasts and Forecast Guidance at NOS Gauges in Lake Huron for 

2004.........................................................................................................39 
iv 

APPENDIX B. Time Series Plots of Semi-Operational Water Level Nowcasts vs. 

Observations at NOS Gauges in Lake Huron during 2004. ....................43 

APPENDIX C. Time Series Plots of Semi-Operational Water Level Forecast 

Guidance vs. Observations at the NOS Gauges in Lake Huron during 

2004.........................................................................................................49 

APPENDIX D. Skill Assessment Statistics of Semi-Operational Surface Water 

Temperature Nowcasts and Forecast Guidance at the NWS/NDBC 

Fixed Buoys in Lake Huron for 2004. ....................................................55 

APPENDIX E. Time Series Plots of Semi-Operational Nowcasts and Forecast 

Guidance of Surface Water Temperature vs. Observations at the 

NWS/NDBC Fixed Buoys in Lake Huron during 2004. ........................57 
v 

LIST OF FIGURES 

Figure 1. Map depicting the POMGL grid domain (10km spatial resolution) used by 

NOS’ Lake Huron Operational Forecast System. .................................................6 

Figure 2. Map depicting locations of NOS/CO-OPS NWLON stations in Lake Huron. ..17 

Figure 3. Map depicting locations of NWS/NDBC fixed buoys in Lake Huron. ..............18 

LIST OF TABLES 

Table 1. NOS Skill Assessment Statistics (Hess et al. 2003). ...........................................12 

Table 2. Data series groups and the variables in each. Note that upper case letters 

indicate a prediction series (e.g., H), and lower case letters (e.g., h) indicate a 

reference series (observation) (Modified from Hess et al. 2003). ......................13 

Table 3. Acceptance error limits (X) and the maximum duration limits (L) modified 

from Hess et al. (2003) for use in the Great Lakes. ............................................13 

Table 4. Information on NOAA/NOS/CO-OPS NWLON stations whose observations 

were used to evaluate LHOFS semi-operational nowcasts and forecasts of 

water levels. ........................................................................................................16 

Table 5. Information on NOAA/NWS/NDBC fixed buoys whose observations were 

used to evaluate LHOFS semi-operational nowcasts and forecasts of surface 

water temperatures. .............................................................................................16 

Table 6. Summary of Skill Assessment Statistics of Semi-Operational Nowcasts of 

Hourly Water Levels at NOS NWLON Stations in Lake Huron for the Period 

19 April to 17 December 2004. A total of 5757 to 5832 nowcasts were used 

in the assessment. Gray shading indicates that the statistic did not pass the 

NOS acceptance criteria. .....................................................................................19 

Table 7. Summary of Standard Statistics Evaluating the Ability of the SemiOperational Nowcasts to Predict Extreme High Water Level Events at the 

NOS NWLON stations in Lake Huron during the Period 15 April to 17 

December 2004. Gray shading indicates that the statistic did not pass the 

NOS acceptance criteria. .....................................................................................20 

Table 8. Summary of Standard Statistics Evaluating the Ability of Semi-Operational 

Nowcasts to Simulate Extreme Low Water Level Events at the NOS 

NWLON Stations in Lake Huron for the Period 15 April to 17 December 

2004. Gray shading indicates that the statistic did not pass the NOS 
vi 

acceptance criteria. ..............................................................................................21 

Table 9. Summary of Skill Assessment Statistics of the Semi-Operational Nowcasts

of Hourly Surface Water Temperatures at a NWS/NDBC fixed buoy in Lake 

Huron for the Period from mid-April to early November 2004. Gray shading 

indicates that the statistic did not pass the NOS acceptance criteria. ................24 

Table 10. Summary of Skill Assessment Statistics of 24-hr Semi-Operational Forecast 

Guidance of Hourly Water Levels at NOS NWLON Stations in Lake Huron 

for the Period 15 April to 17 December 2004. Notes: na = not applicable 

Approximately 490 forecasts were used in the assessment. Gray shading 

indicates that the statistic did not pass the NOS acceptance criteria. ................27 

Table 11. Summary of Skill Assessment Statistics Evaluating the Ability of 24-hr 

Semi-Operational Forecast Guidance to Predict Extreme High Water Level 

Events at NOS NWLON Stations in Lake Huron during the Period 15 April 

to 17 December 2004. Gray shading indicates that the statistic did not pass 

the NOS acceptance criteria. .............................................................................28 

Table 12. Summary of Skill Assessment Statistics Evaluating the Ability of 24-hr 

Semi-Operational Forecast Guidance to Predict Extreme Low Water Level 

Events at NOS NWLON Stations in Lake Huron during the Period 15 April 

to 17 December 2004. Gray shading indicates that the statistic did not pass 

the NOS acceptance criteria. .............................................................................29 

Table 13. Summary of Skill Assessment Statistics for Semi-Operational Forecast 

Guidance to Predict Surface Water Temperatures 24 hours in advance at a 

NWS/NDBC fixed buoy in Lake Huron during the period from mid-April to 

early-November 2004. Gray shading indicates that the statistic did not pass 

the NOS acceptance criteria. .............................................................................30 
vii 

LIST OF ACRONYMS

ASOS Automated Surface Observing System 

AVHRR Advanced Very High Resolution Radiometer 

AWOS Automated Weather Observing System 

BUFR Binary Universal Form for the Representation of 

meteorological data 

C-MAN Coastal-Marine Automated Network 

CCS Central Computer System 

COMF Common Ocean Modeling Framework 

CO-OPS Center for Operational Oceanographic Products and Services 

CORMS Continuously Operating Real-Time Monitoring System 

CSDL Coast Survey Development Laboratory 

DOD Department of Defense 

EPA Environmental Protection Agency 

ETA Eta Mesoscale Numerical Weather Prediction Model 

GLCFS Great Lakes Coastal Forecast System 

GLERL Great Lakes Environmental Research Laboratory 

GLFS Great Lakes Forecasting System 

GLOFS Great Lakes Operational Forecast System 

GLSEA Great Lakes Surface Environmental Analysis 

LEOFS Lake Erie Operational Forecast System 

LHOFS Lake Huron Operational Forecast System 

LMOFS Lake Michigan Operational Forecast System 

LOOFS Lake Ontario Operational Forecast System 

LSOFS Lake Superior Operational Forecast System 

MMAP Marine Modeling and Analysis Programs 

NAM North America Mesoscale Model 

NCEP National Centers for Environmental Prediction 

NCOP National Coastal Ocean Program 

NDBC National Data Buoy Center 

NOAA National Oceanic and Atmospheric Administration 

NOS National Ocean Service 

NWLON National Water Level Observation Network 

NWS National Weather Service 

ODAAS Operational Data Acquisition and Archive System 

OSU The Ohio State University 

POMGL Princeton Ocean Model – Great Lakes version 

USCG United States Coast Guard 

VOS Voluntary Observing Ship 
viii 

EXECUTIVE SUMMARY

This document describes the Lake Huron Operational Forecast System (LHOFS) and an 

assessment of its skill. The lake forecast system, based on a hydrodynamic model, uses 

near real-time atmospheric observations and numerical weather prediction forecast 

guidance to produce three-dimensional forecast guidance of water temperature and 

currents and two-dimensional forecasts of water levels for Lake Huron. 

LHOFS is the result of technology transfer of the Great Lakes Forecasting System 

(GLFS) and Great Lakes Coastal Forecasting System (GLCFS) from The Ohio State 

University (OSU) and NOAA’s Great Lakes Environmental Research Laboratory 

(GLERL) to NOAA’s National Ocean Service. 

The model system skill assessment of LHOFS follows scenarios specified by Hess et al. 

(2003) which are applicable to forecast systems for non-tidal water bodies. However, 

this is the first time that the NOS standards have been applied to these freshwater forecast 

systems. These scenarios include 1) hindcast, 2) semi-operational nowcast, and 3) semioperational forecast. The hindcast is a long simulation using the best available observed 

meteorological observations and verification data. The semi-operational nowcast and 

forecast are simulations made in a real-time environment where there are occasional 

periods of missing inputs (i.e. meteorological observations and/or forecast guidance from 

atmospheric forecast models). 

Unfortunately, there was no known research study comparing surface and subsurface 

observations to simulations from the Princeton Ocean Model for Lake Huron as was the 

case for Lakes Michigan and Erie. Therefore, no hindcast scenario skill assessment was 

done for LHOFS. 

For the semi-operational nowcast and forecast scenarios, an evaluation of GLERL’s realtime four times/day nowcast and twice daily forecast cycles from GLCFS for Lake Huron 

was used to satisfy Hess et al. (2003) requirements. Although Hess et al. (2003) 

recommends conducting evaluations for 365 days in order to capture all expected 

seasonal conditions, GLCFS nowcasts and forecasts were evaluated for the ice-free 

period from 15 April to 17 December 2004. Due to the lack of regularly monitored 

currents and sub-surface water temperatures, only water levels and surface water 

temperatures at a few sites could be evaluated for Lake Huron. 

The primary statistics used to assess the model performance for water levels and surface 

water temperatures are those required by Hess et al. (2003) for evaluating predicted water 

levels in non-tidal regions. These included Series Means (SM), Mean Algebraic Error 

(MAE), Root Mean Square Error (RMSE), Standard Deviation (SD), negative outlier 

frequency (NOF), positive outlier frequency (POF), maximum duration of positive outlier 

(MDPO), and maximum duration of negative outlier (MDNO). 
ix 

The skill statistics for the semi-operational nowcast and forecast scenarios are summarized 

below: 

Water levels: 

 

 Nowcasts: 

The hourly nowcasts of water level for amplitude met the NOS acceptance criteria at 

the all six NOS gauges in Lake Huron used in the evaluation. In terms of other 

statistics, the mean algebraic error or difference (MAE) ranged between -4 and 11 cm. 

The root mean square error (RSME) ranged from 4 to 7 cm. 

The nowcast predictions of high water level events passed the NOS criteria for 

amplitude at all six gauges. In terms of timing, the nowcasts failed to meet the NOS 

acceptance criteria. The nowcasts of low water events met the NOS criteria for 

amplitude at six gauges but did not pass the criteria in terms of timing at any of the 

gauges. 

Forecast Guidance: 

The hourly forecast guidance met the NOS criteria for predicting water level amplitude 

at the six gauges. In terms of other statistics, the MAE ranged between -4.7 and 

4.0 cm and RSME ranged from 3.8 to 6.1 cm. The forecast guidance was similar to the 

nowcasts in that the greatest errors were at the Essexville gauge located in the southern 

end of Saginaw Bay and at the Mackinaw City gauge at the extreme western edge of 

the model domain. 

The forecast guidance of high water events passed the NOS criteria for amplitude at 

three of the six gauges. The forecast guidance failed to meet NOS criteria in predicting 

the times of these extreme events at all gauges. The guidance of low water events 

passed the NOS criteria for amplitude at all gauges but failed the criteria in predicting 

the times of these extreme events at all gauges. 

Surface Water Temperatures: 

Nowcasts: 

The hourly surface water temperature nowcasts were evaluated at the northern and 

southern NDBC buoys in Lake Huron. The water temperature nowcasts passed the 

NOS acceptance criteria at the southern buoy but failed to pass 3 of the 5 criteria 

statistics at the northern buoy. The nowcasts overpredicted temperatures at both bouys, 

with the greatest differences occurring at the northern buoy. The MAE range from 0.8 

to 1.9o

C and RMSE ranged from 1.7 to 2.8oC. The greatest positive departure between 

the nowcasts and observations at both buoys occurred from mid May, when water 

temperature rose above 4oC, till early July. 
x 

 Forecast Guidance: 

The hourly surface water temperature forecast guidance at the 24-hr projection passed 

the NOS acceptance criteria at the southern buoy. The MAE and RSME at this buoy 

were 0.5o

C and 1.4oC, respectively. The hourly guidance at the northern buoy failed 

the majority of the criteria statistics. At this buoy, the MAE and RSME were 1.8oC and 

2.7o

C, respectively. The MAE and RMSE values for 24-hr forecast projection were 

slightly higher than for the nowcast comparisons. The MAE decreased by 0.15oC to 

0.35o

C as the forecast projection increased from 0 to 24 hours. 

Surface Currents: 

Due to the lack of water current observations, no quantitative assessment could be 

conducted for LHOFS. However, animation of surface current nowcasts and forecast 

guidance indicated that LHOFS did simulate the known cyclic clockwise rotation of 

surface currents present in the Great Lakes when the lake water is density stratified. 

This stratification occurs usually from May through October. 

Key Words: short-term lake predictions, nowcasts, model forecast guidance, 

oceanographic forecast systems, Lake Huron, skill assessment, water levels, water 

currents, water temperatures, Princeton Ocean Model, North American Mesoscale 

weather prediction model. 
1 

1. INTRODUCTION 

The Great Lakes Forecasting System (GLFS) was developed by The Ohio State 

University (OSU) and NOAA's Great Lakes Environmental Research Laboratory 

(GLERL) in the late 1980s and 1990s to provide nowcasts and short-range forecasts of 

the physical conditions (temperature, currents, water level, and waves) of the five Great 

Lakes. The development of GLFS was directed by Drs. Keith Bedford (OSU) and David 

Schwab (GLERL) and involved over a dozen OSU graduate students, research assistants 

and post doctoral researchers at GLERL and OSU, as well as other OSU faculty 

members. The development of GLFS was funded by over 36 contracts from 25 different 

sources. From the start, GLERL and OSU were interested in working cooperatively with 

NOAA in “assessing the potential benefits [of GLFS] to NOAA’s scientific and 

operational programs in the coastal ocean”. In April 1991, Drs. Bedford and Schwab met 

with representatives from the National Weather Service (NWS) and the National Coastal 

Ocean Program (NCOP) in Silver Spring, MD to discuss how they could work with 

NOAA line offices (NWS, NOS, etc...) to have GLFS products carefully evaluated 

through a demonstration program prior to NWS adopting the products as ‘guidance tools’ 

and which products might be distributed directly to end users. 

GLFS used the Princeton Ocean Model (Blumberg and Mellor 1987; Mellor 1996) and 

GLERL-Donelan wave model (Schwab et al. 1984). The first 3-D nowcast for the Great 

Lakes was made for Lake Erie in 1992 at the Ohio Supercomputer Center on the OSU 

Columbus campus (Yen et al. 1994; Schwab and Bedford 1994). Starting in July 1995, 

twice per day forecasts were made for Lake Erie. GLFS was recognized with an award in 

2001 by the American Meteorological Society as the first U.S. coastal forecasting system 

to make routine real-time predictions of currents, temperatures, and key trace 

constituents. 

In 1996, GLFS was ported to GLERL in Ann Arbor, MI. GLERL’s workstation version 

of GLFS, called The Great Lakes Coastal Forecast System (GLCFS), has been running in 

semi-operational mode at GLERL for Lake Huron since August 2002. GLCFS for Lake 

Huron generates nowcasts four times/day and forecast guidance out to 60 hours twice per 

day. The predictions are displayed on the GLERL web page 

(http://www.glerl.noaa.gov/res/glcfs/) and digital output is made available in GRIdded 

Binary (GRIB) format to NWS Weather Forecast Offices in the region. GLCFS nowcasts 

and forecasts are archived at GLERL. 

In 2004, the hydrodynamic model code of GLCFS for all five Great Lakes was ported to 

NOS Center for Operational Oceanographic Products and Services (CO-OPS) in Silver 

Spring, MD. GLCFS was reconfigured to run in the NOS Coastal Ocean Modeling 

Framework (COMF) and to use surface meteorological observations from NOS 

Operational Data Acquisition and Archive System (ODAAS) (Kelley et al. 2001). The 

CO-OPS version of GLCFS for Lake Huron was renamed as the Lake Huron Operational 

Forecast System (LHOFS). LHOFS began making routine operational lake nowcasts and 

forecasts for Lake Huron on March 30, 2006 at CO-OPS during the ice-free season. The 

forecast systems for Lake Ontario and Superior were also implemented on this date. 
2 

The predictions from LHOFS, similar to those from NOS estuarine forecast systems, 

must be evaluated to inform users about the skill of the nowcasts and forecasts. In 

evaluating LHOFS, NOS sought to take advantage of previous evaluations done by 

researchers at OSU and GLERL to fulfill the hindcast scenario requirements described in 

Hess et al. (2003). Unfortunately, there was no modeling research study for Lake Huron 

using the Princeton Ocean Model adapted to the Great Lakes (POMGL), as was the case 

for Lakes Michigan and Erie. Therefore, no hindcast scenario skill assessment was done 

for LHOFS. However, NOS did utilize the routinely-produced nowcasts and forecasts 

produced by GLERL to fulfill the semi-operational nowcast and forecast scenarios 

required by Hess et al. (2003). 

This report describes the model performance based on NOS requirements for operational 

nowcast/forecast systems (Hess et al. 2003). Brief descriptions of Lake Huron and an 

overview of LHOFS are given first. 
3 

2. LAKE HURON 

Lake Huron is the second largest of the Great Lakes in terms of surface area (59,565 sq. 

km and the fourth largest lake in the world. The lake has a breadth of 295 km (183 mi) 

and a length of 332 km (206 mi). It has an average depth of 59 m (195 ft) with a 

maximum of 229 m (750 ft). Lake Huron, similar to other Great Lakes, has a pronounced 

annual thermal cycle ranging from vertically well-mixed water body in late autumn to 

thermal stratification across the entire lake with a well-developed thermocline by August 

(Boyce et al. 1989). 

Lake Huron, as all the Great Lakes, experiences two types of water level fluctuations. 

Short-term changes occur due to surface winds and changes in atmospheric pressure. 

Seasonal changes occur with the lowest water levels occurring during the winter and the 

highest levels occurring during the early autumn (GLIN 2006). 

The mean large-scale circulation in Lake Huron is cyclonic both in summer and winter 

but stronger during the winter (Beletsky et al. 1999). A persistent feature during both 

winter and summer is the surface flow into Georgian Bay which implies a return flow at 

deeper depth (Beletsky et al. 1999). Beletsky et al. (1999) states that the strong cyclonic 

circulation in the winter may be due to lake-induced mesoscale vorticity in the wind field 

caused by the lake’s large surface area and stronger lake-atmosphere temperature 

gradients. 

On a short time period (less than a day), Lake Huron and other Great Lakes exhibit a 

cyclic clockwise rotation of surface currents when the lake water is density stratified 

during the warm season (May through October). Observational studies have found that 

the clockwise rotation has a near-inertial period of 18 hours (Saylor and Miller 1987). 

Additional information on currents in the Great Lakes can be found in Boyce et al. 

(1989). 
4 
5 

3. SYSTEM OVERVIEW 

This section provides a brief description of the numerical hydrodynamic model used by 

LHOFS. Detailed descriptions of the model as it has been applied to Lake Michigan can 

be found in Schwab and Beletsky (1998). Similar descriptions of the model as it has 

been applied to Lake Erie are given by Hoch (1997), Kuan (1995), and Kelley (1995). 

3.1 Description of Model 

The core numerical model in LHOFS is the Princeton Ocean Model (POM) developed by 

Blumberg and Mellor (Mellor 1996). The model is a fully three-dimensional, non-linear 

primitive equation coastal ocean circulation model, with a second order Mellor-Yamada 

turbulence closure scheme to provide parameterization of vertical mixing processes. The 

model solves the continuity equation, momentum equation, and the conservation equation 

for temperature simultaneously in an iterative fashion, and the resulting predictive 

variables are free upper surface elevation, full three-dimensional velocity and 

temperature fields, Turbulence Kinetic Energy (TKE), and turbulence macroscale. Other 

main features of the model include: terrain following coordinate in the vertical (sigma 

coordinate), finite difference numerical scheme, Boussinesq and hydrostatic 

approximation, and mode splitting technique. 

POM was modified by researchers at OSU and GLERL for use in the Great Lakes 

(Bedford and Schwab 1991, O’Connor and Schwab 1993). For the rest of this report, the 

modified version of the POM model for the Great Lakes will be referred to as POMGL. 

Lake Huron, like the other Great Lakes, is treated as an enclosed basin. Therefore, there 

are no inflow/outflow boundary conditions: no fluid exchange between the lake and its 

tributaries, between the lake and ground water sources, or between the lake and 

anthropogenic influences. Thus the model simulations do not include seasonal changes 

in lake-wide mean water level due to precipitation and evaporation. GLERL is presently 

evaluating the impact of using climatological estimates of river discharge on POMGL 

simulations. 

3.2 Grid Domain 

The POMGL domain for Lake Huron consists of a rectangular grid with a 5-km 

horizontal resolution in both the x- and y-directions. The domain has a total of 6075 grid 

points with 81 points in the x-direction and 75 points in the y-direction (Fig. 1). The 

bottom topography for the domain is based on GLERL’s 2-km digital bathymetry data 

compiled by Schwab and Sellers (1980) but slightly smoothed to maintain stability and to 

minimize the development of two “delta x noise.” The model uses 20 sigma levels in the 

vertical, with vertical levels spaced more closely in the upper 30 m of water and near the 

bottom to better resolve both the seasonal thermocline and bottom boundary layer 

(Schwab and Beletsky 1998). The levels are located at sigma equal to 0, -.0227, -.0454, -

.0681, -.0908, -.1135, -.1362, -.1589, -.1816, -.2043, -.2270, -.2724, -.3405, -.4313, -

.5448, -.6810, -.7945, -.8853, -.9534, and -1.0. 
6 

Figure 1. Map depicting the POMGL grid domain (5 km spatial resolution) used by 

NOS’ Lake Huron Operational Forecast System along with model 

bathymetry contoured at 50 m intervals.
7 

3.3 Data Ingest 

The nowcast cycle relies on surface meteorological observations obtained from NOS’ 

Operational Data Acquisition and Archive System (ODAAS). ODAAS acquires 

meteorological observations from the NWS/NCEP Central Operations (NCO) 

observational ‘data tanks’ located on NCEP’s Central Computer Systems (CCS) twice 

per hour at approximately 25 and 48 minutes past the top of the hour. The observations 

are originally in unblocked Binary Universal Form of Representation (BUFR) of 

meteorological data format, but are decoded and written out to a text file for use by 

LHOFS and other NOS operational forecast systems. The surface observation text file is 

available to LHOFS within a minute of receiving the observations from the CCS. 

The text file includes surface observations from a variety of observing networks on and 

around Lake Huron. On land, these networks include Automated Surface Observing 

System (ASOS), Coastal-Marine Automated Network (C-MAN), NOS National Water 

Level Observing Network (NWLON), and NOAA GLERL’s Real-Time Meteorological 

Observation Network. Presently, the surface meteorological observations from U.S. 

Coast Guard (USCG) stations around the lake are not available in the NCEP’s operational 

data tanks.

Over water, the networks include the fixed buoys operated by the NWS/NDBC and 

Environment Canada, as well as observations from ships participating in the Voluntary 

Observing Ship (VOS) program. However, observations from VOS ships are not 

presently used by any of the individual nowcast/forecast systems for the Great Lakes. 

3.4 Nowcast Cycle 

The nowcast cycle of LHOFS is run hourly at NOS to generate updated nowcasts of the 

3-D state of Lake Huron, including 3-D water temperatures and currents. The cycle also 

generates hourly nowcasts of 2-D water levels. 

The initial conditions for the nowcast cycle are provided by the previous hour’s nowcast 

cycle. The nowcast cycle is forced by gridded surface meteorological analyses valid at 

two times, one hour prior to the time of the nowcast and the current time of the nowcast. 

The gridded surface meteorological analyses are generated by interpolating surface 

observations of wind, air temperature, dew point temperature, and cloud cover using the 

natural neighbor technique (Sambridge et al. 1995). This is accomplished by the program 

interpnn.f. 

Before being interpolated, the surface wind and air temperature observations are adjusted 

to a common anemometer height of 10 m above the ground or water (10m AGL). Surface 

observations of wind direction, wind speed, air temperature, and dew point temperature 

from overland stations are adjusted to be more representative of overwater conditions. 

Both the height adjustment correction and overland adjustment procedure use the 

previous day’s average water temperature from GLERL’s Great Lakes Surface 

Environmental Analysis (GLSEA). The GLSEA temperature analysis is generated using 

SST retrievals derived from the Advanced Very High Resolution Radiometer (AVHRR) 
8 

on board NOAA’s polar-orbiter satellites. The adjustments to the observations along 

with simple quality control checks are done by the program edit_sfcmarobs.f 

The gridded surface wind fields are then used by POMGL to calculate wind stress at each 

model grid point. The surface meteorological fields along with POMGL surface water 

temperature predictions from POMGL are used by a heat flux scheme (McCormick and 

Meadows 1988) to estimate the net rate of heat transfer for the lake at each grid point. The 

heat flux scheme can be found in POMGL’s subroutine FLUX1. Additional information on 

the wind stress and heat flux schemes can be found in Kelley (1995). 

3.5 Forecast Cycle 

The forecast cycle of LHOFS is run four times per day to generate forecast guidance of 

the 3-D state of Lake Huron. The forecast cycle uses the most recent nowcast for its 

initial conditions. From March 2006 to March 2007, the surface meteorological forcing 

was provided by the latest forecast guidance of surface (10 m AGL) u- and v-wind 

components and surface air temperature (2 m AGL) from the 0, 6, 12, or 18 UTC forecast 

cycles of NWS/NCEP’s North American Mesoscale (NAM) model. NAM has a spatial 

resolution of 12 km and uses the Weather Research and Forecast (WRF) model as its 

core. The surface wind velocity forecast guidance from the NAM model is valid at a 

height of 10 m above the ground or lake surface. However, in April 2007, CO-OPS 

decided to switch to using gridded forecasts of surface wind velocity and surface air 

temperature from the NWS National Digital Forecast Database (NDFD). The NDFD 

fields are obtained from the NWS Weather Forecast Office (WFO) in Cleveland, OH by 

CO-OPS four times/day in netCDF format. The gridded forecasts have a spatial 

resolution of 5km and cover both the U.S. and Canadian Great Lakes waters. The NAM 

guidance is used as backup forcing if the NDFD forecasts are not available. 

3.6 Operational Environment and Scheduling 

LHOFS is run operationally on a Linux workstation at NOS/CO-OPS in Silver Spring, 

MD. Each hourly nowcast cycle is launched at 52 minutes past the top of the hour to 

ensure a sufficient amount of surface meteorological observations from both Canadian 

and U.S. networks are received at NCEP and then processed at CO-OPS. 

The forecast cycle of LHOFS is run four times per day at 0000, 0600, 1200, and 1800 

UTC at 52 minutes past the top of these hours. The forecast horizon of each forecast 

cycle is 30 hours. 

LHOFS and the operational forecast systems for Lakes Ontario and Superior were 

officially implemented as operational forecast systems at CO-OPS on March 30, 2006. 
9 

4. HINDCAST SKILL ASSESSMENT 

NOS standards (Hess et al. 2003) require the hydrodynamic model of any NOS 

nowcast/forecast system to run and be evaluated in a hindcast scenario. A hindcast is 

defined as a long simulation using the best available gap-filled observed data for 

boundary water levels, wind, and river flows. Unfortunately, unlike the skill assessments 

of the operational forecast systems for Lake Erie and Lake Michigan, there were no field 

observing programs in order to compare POMGL simulations to surface and subsurface 

data. Therefore, no skill assessment was done to fulfill the hindcast scenario 

requirement. 
10 
11 

5. SEMI-OPERATIONAL NOWCAST SKILL ASSESSMENT 

This section describes the model system performance based on NOS requirements for a 

semi-operational nowcast scenario (Hess et al. 2003). The definition of the model run 

scenario for a semi-operational nowcast is the following: 

“In this scenario, the model is forced with actual observational input data streams 

including open ocean boundary water levels, wind stresses, river flows, and water density 

variations. Significant portions of the data may be missing, so the model must be able to 

handle this.” 

LHOFS, as described in Chapter 2, is based on NOAA/GLERL’s Great Lakes Coastal 

Forecast System (GLCFS) for Lake Huron. Both LHOFS and GLCFS-Lake Huron have 

a spatial grid increment of 5 km, 20 sigma layers, and use similar surface meteorological 

forcing. Neither of the systems employed any river inflow or assimilated any 

limnological data. GLCFS used surface observations from USCG stations and 

cooperative marine weather observations (MAREPS), whereas LHOFS does not include 

these. However, this difference was not expected to cause a significant difference in the 

nowcasts. 

Due to the similar characteristics of LHOFS and GLCFS, the assessment of the LHOFS 

semi-operational nowcasts was performed using archived nowcasts from GLCFS four 

times/day nowcast cycles. 

This chapter describes the GLCFS nowcast cycles, the evaluation method including time 

period and assessment statistics, and the results of the evaluation. 

5.1 Description of Nowcast Cycles 

GLCFS performs four times/day nowcast cycles for Lake Huron, and the other four Great 

Lakes, year round. The POMGL used by each forecast system are not reinitialized each 

spring. The surface forcing for the nowcast cycles are provided by objective analyses of 

surface meteorological observations from land-based and overwater observing stations. 

The four nowcast cycles produce nowcasts valid at 0000, 0600, 1200, and 1800 UTC 

each day. The nowcast cycles are launched at approximately 80 minutes past the valid 

time of the nowcasts. For example, the nowcast cycle to generate a nowcast valid at 0000 

UTC is launched at 0120 UTC to allow for observations from late reporting NDBC CMAN stations to be received at GLERL via NOAAPORT. Hourly model output from the 

four nowcast cycles are archived at GLERL. 

5.2 Method of Evaluation 

The hourly model results from the GLCFS nowcasts were compared to observations from 

coastal and offshore observing platforms in the lake for the period from mid-April to 

mid-December 2004. This was a period when there was no significant ice cover. The 

evaluation used the standard suite of assessment statistics, as defined in Hess et al. 
12 

(2003). The standard suite of statistics is given in Table 1. The target frequencies of the 

associated statistics are the following: 

 CF(X) 90%, POF(2X) 1%, NOF(2X) 1%, WOF(2X) 0.5% 

 MDPO(2X)  L, MDNO(2X)  L 

There are three types of data sets (Table 2): Group 1, a time series of values at uniform 

time intervals; Group 2, a set of values representing the consecutive occurrences of an 

event (such as high or low water); and Group 3, a set of values representing a forecast 

valid at a given projection time. The acceptable error limits (X) and maximum duration 

limits (L) for the associated variable applied to the LHOFS are presented in Table 3. 

Table 1. NOS Skill Assessment Statistics (Hess et al. 2003). 

Variable Explanation 

Error The error is defined as the predicted value, p, minus the reference (observed or 

astronomical tide value, r : ei = pi - ri. 

SM Series Mean. The mean value of a series y. Calculated as y N yi

i

N

 

1

1

. 

RMSE Root Mean Square Error. Calculated as RMSE e N i

i

N

 

1 2

1

.

SD Standard Deviation. Calculated as SD e e N i

i

N

  



1

1

1

2 ( )

CF(X) Central Frequency. Fraction (percentage) of errors that lie within the limits +X. 

POF(X) Positive Outlier Frequency. Fraction (percentage) of errors that are greater than X. 

NOF(X) Negative Outlier Frequency. Fraction (percentage) of errors that are less than -X. 

MDPO(X) Maximum Duration of Positive Outliers. A positive outlier event is two or more 

consecutive occurrences of an error greater than X. MDPO is the length of time (based 

on the number of consecutive occurrences) of the longest event. 

MDNO(X) Maximum Duration of Negative Outliers. A negative outlier event is two or more 

consecutive occurrences of an error less than -X. MDNO is the length of time (based on 

the number of consecutive occurrences) of the longest event. 

WOF(X) Worst Case Outlier Frequency. Fraction (percentage) of errors that, given an error of 

magnitude exceeding X, either (1) the simulated value of water level is greater than the 

astronomical tide and the observed value is less than the astronomical tide, or (2) the 

simulated value of water level is less than the astronomical tide and the observed value 

is greater than the astronomical tide. 
13 

Table 2. Data series groups and the variables in each. Note that upper case letters 

indicate a prediction series (e.g., H), and lower case letters (e.g., h) indicate a 

reference series (observation) (Modified from Hess et al. 2003). 

Group Variable Symbol 

Group 1 Water level H, h 

(Time Series) Water temperature T, t 

Group 2 Amplitude of high water AHW, ahw 

(Values Amplitude of low water ALW, ahw 

at Extreme Event) Time of high water THW, thw 

 Time of low water TLW, tlw 

Group 3 Water level at forecast projection time of nn hrs Hnn, hnn 

(Values from a Water temperature at forecast projection time of nn hrs Tnn, tnn 

Forecast) 

Table 3. Acceptance error limits (X) and the maximum duration limits (L) modified 

from Hess et al. (2003) for use in the Great Lakes. 

Variables X L (hours) 

H, Hnn, AHW, ALW 15 cm 24 

THW, TLW 1.5 hours+ 25 

T, Tnn, 3oC* 24 

 

_______________________________________________________________________ 

Notes: +1.0 hour for tidal regions, *7.7oC for tidal regions. 

The evaluation utilized the NOS skill assessment software (Zhang et al. 2006), but was 

modified for use in the Great Lakes. The software computes the skill assessment scores 

automatically using files containing observations and nowcast/forecast guidance. Since 

the GLCFS output was not in netCDF, the output was reformatted to meet the text format 

input requirements of the skill assessment code. 

Nowcasts of Water Levels

The evaluation of GLCFS nowcasts of water levels were based on time series of observed 

and model-based water levels at six NOS NWLON stations along the Lake Huron shore 

line (Table 4). A map depicting the locations of the six NOS stations, whose data were 

used in the evaluation, is given in Fig. 2. (The NOS gauges at Rock Cut and Fort Gratiot, 

MI were not used.) 

Since water level nowcasts and forecasts generated by GLCFS were vertical 

displacements relative to the flat lake, further adjustment was necessary to bring the 

water levels relative to the mean lake level. An offset value based on a dynamic 7-day 

average mean lake water level was computed and added to the model nowcast of water 

level displacement from model’s mean. This is the same method used by CO-OPS prior 
14 

to displaying the LHOFS nowcasts on the Web. The final nowcast water levels were then 

compared with the observational data. 

The evaluation of GLCFS water level nowcasts for Lake Huron was done by comparing 

time series differences using SM, RMSE, SD, NOF, POF, MDPO, and MDNO statistics 

described in Hess et al. (2003). Since tides are not significant in the Great Lakes there 

were no comparisons of the times and amplitudes of tidally-forced high and low waters. 

However, significant high amplitude water events do occur in several of the Great Lakes, 

especially in Lake Erie. Following the recommendations of Hess et al. (2003), a method 

was developed and implemented in the NOS skill assessment software to analyze the 

nowcast/forecast system’s ability to simulate large amplitude events. This is the first 

attempt at evaluating the ability of a NOS prediction system to simulate high and low 

water events in non-tidal regions. Other methods such as described by Dingman and 

Bedford (1986) and used by Kelley (1995) and Hoch (1997) may be considered for future 

versions of the NOS standards and skill assessment code. 

The NOS skill assessment software identifies high and low water events in the Great 

Lakes using the following method. 

Step 1. For the observed time series of water level, pick all high and low values. A data 

point is selected if it is either higher than its two neighboring points (both sides), 

or lower than its two neighboring points. 

Step 2. For each selected peak from Step 1, a seven day window is centered on the 

particular peak and the mean value and standard deviation (called sigma 

hereafter) of the observed time series are computed within the seven day period. 

Upper/lower limits are then computed as the mean value +/- 2 sigma. 

Step 3. The peak is identified as a high/low water level event if it exceeds the upper and 

lower limits. (Step 2 was performed to remove the impact of periodical 

variations, such as semi-diurnal and diurnal frequency signals on event 

selection.) 

Step 4. For each high and low water level event in the observed time series, the 

maximum/minimum water level value and occurrence time are selected from 

the model simulated time series within a 12 hour window (the occurrence time 

of the observed event is centered), and paired with the observed events for 

comparison and statistical evaluation. 

Step 5. The paired observed and simulated extreme events are compared to each other 

to assess the ability of the forecast system to simulate large amplitude events. 

Nowcasts of Surface Water Temperatures

The evaluation of GLCFS nowcasts of surface water temperatures was based on 

comparisons of time series of model-predicted temperatures vs. observations at two 3-m 
15 

fixed disk buoys in the lake. The buoys are operated by NOAA/National Data Buoy 

Center (NDBC). Information on the buoys is given in Table 5. 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 it is sampled once per hour. The point evaluations were 

conducted by comparing surface (1st sigma layer) temperature nowcasts at the nearest 

grid points to surface observations from the buoys. A map depicting the locations of the 

NDBC fixed buoys is given in Fig. 3. 

The evaluation of GLCFS surface water temperature nowcasts for Lake Huron was done 

by comparing time series differences using SM, RMSE, SD, NOF, POF, MDPO, and 

MDNO statistics described in Hess et al. (2003). No attempt was made to assess the 

nowcast/forecast system’s ability to simulate diurnal or larger temperature fluctuations. 

Other methods for evaluating water temperature predictions such as those used by Kelley 

(1995) and Hoch (1997) may be implemented in the future. 

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. Since the Great Lakes are fresh water bodies and 

non-tidal, there is no preset standard for a lake temperature prediction. Based on the 10 

years experience of running the Great Lakes Forecasting System and input from the Great 

Lakes user community, Dr. David Schwab of NOAA/GLERL suggested a 3o

C criteria for 

water temperature skill assessment in the Great Lakes region (personal communication). 

Thus, all the statistical evaluation and skill scores are based on a 3oC criteria. 
16 

Table 4. Information on NOAA/NOS/CO-OPS NWLON stations whose observations 

were used to evaluate LHOFS semi-operational nowcasts and forecasts of 

water levels. 

Station Name State NOS 

Station ID 

Number 

NWS 

Station 

ID 

Geographic Coordinates Corresponding I 

and J model 

coordinates 

Latitude 

(deg N) 

Longitude 

(deg W) 

I J 

DeTour 

Village 

MI 9075099 DTLM4 45.99 83.90 15 67 

Mackinaw 

City 

MI 9075080 MACM4 45.78 84.72 2 64* 

Harrisville MI 9075059 NA 44.66 83.29 25* 38 

Essexville MI 9075035 NA 43.64 83.85 15 16* 

Harbor Beach MI 9075014 HRBM4 43.85 82.64 35* 20 

Lakeport MI 9075002 LPNM4 43.14 82.49 37 4 

 

Notes: NA = An official NWS station ID has not been assigned to the station yet. 

*= I and J coordinates assigned to nearest water grid cell.

Table 5. Information on NOAA/NWS/NDBC fixed buoys whose observations were 

used to evaluate LHOFS semi-operational nowcasts and forecasts of 

surface water temperatures. 

Buoy Name Agency 

Prov. 

or 

State WMO 

Buoy 

ID 

Geographic 

Coordinates 

Corresponding 

LHOFS Grid Point 

Coordinates 

Latitude 

(deg N) 

Longitude 

(deg W) 

I J 

45003- North Huron NWS/ 

NDBC 

MI 45003 45.35 82.84 31 53 

45008 – South Huron NWS/ 

NDBC 

MI 45008 44.28 82.42 38 29 
17 

Figure 2. Map depicting locations of NOS/CO-OPS NWLON stations in Lake 

Huron used in the skill assessment. 
18 

Figure 3. Map depicting location of NWS/NDBC fixed buoys in Lake Huron. 
19 

5.3 Assessment of Water Level Nowcasts 

The standard suite of skill assessment statistics evaluating the ability of semi-operational 

nowcasts and forecast guidance to predict hourly and extreme water levels at six NOS 

gauges from 15 April to 17 December 2004 are given in Appendix A. Time series plots 

of the nowcasts compared with observations at the gauges are given in Appendix B. 

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

the four NOS gauges are presented together in Table 6 along with the NOS acceptance 

criteria. The hourly nowcasts passed the criteria at all four locations. The mean 

algebraic errors or differences ranged between -4 and 11 cm and the RMSE ranged 

between 4 and 7 cm. The greatest RMSE was at Essexville gauge located at the extreme 

southern part of Saginaw Bay (Fig. 2). The nowcasts generally over predicted the water 

levels but under predicted levels at Essexville, Harbor Beach and Lakeport. 

Table 6. Summary of Skill Assessment Statistics of Semi-Operational Nowcasts of 

Hourly Water Levels at NOS NWLON Stations in Lake Huron for the 

Period 15 April to 17 December 2004. A total of 5757 to 5832 nowcasts were 

used in the assessment. Gray shading indicates that the statistic did not pass the 

NOS acceptance criteria. 

Statistic, Acceptable 

Error [ ], and 

Units ( )

DeTour 

Village, MI 

Mackinaw 

City, MI 

Harrisville, 

MI 

Essexville, 

MI 

NOS 

Accept. 

Criteria 

Mean Diff. (m) 0.111 0.041 0.001 -0.042 na 

RMSE (m) 0.043 0.055 0.036 0.073 na 

SD (m) 0.042 0.037 0.036 0.061 na 

NOF [2x15cm] 

(%) 

0.0 0.0 0.0 0.0 < 1% 

CF [15 cm] (%) 99.4 99.4 100.0 95.3 > 90% 

POF [2x15 cm] (%) 0.0 0.0 0.0 0.0 < 1% 

MDPO [2x15 cm ] 

(hour) 

0.0 0.0 0.0 0.0 < 24 

hours 

MDNO [2x15 cm ] 

(hour) 

0.0 0.0 0.0 0.0 < 24 

hours 

Notes: na = not applicable 
20 

Table 6 (continued) 

Statistic, Acceptable 

Error [ ], and 

Units ( )

Harbor 

Beach, MI 

Lakeport, 

MI 

NOS 

Accept. 

Criteria 

Mean Diff. (m) -0.011 -0.018 na 

RMSE (m) 0.043 0.052 na 

SD (m) 0.042 0.048 na 

NOF [2x15cm] 

(%) 

0.0 0.0 < 1% 

CF [15 cm] (%) 99.9 99.1 > 90% 

POF [2x15 cm] (%) 0.0 0.0 < 1% 

MDPO [2x15 cm ] 

(hour) 

0.0 0.0 < 24 

hours 

MDNO [2x15 cm ] 

(hour) 

0.0 0.0 < 24 

hours 

The skill statistics assessing the ability of nowcasts to predict extreme high water level 

events at NOS gauges during 2004 are given together in Table 7. The high water level 

nowcasts passed the NOS acceptance criteria for amplitude at four of the six gauges, 

failing at Harbor Beach and Lakeport. The nowcasts ability to simulate the timing of 

these events did not pass the NOS acceptance at any of the six gauges.

Table 7. Summary of Standard Statistics Evaluating the Ability of the SemiOperational Nowcasts to Predict Extreme High Water Level Events at 

NOS NWLON stations in Lake Huron during the Period 15 April to 17 

December 2004. Gray shading indicates that the statistic did not pass the NOS 

acceptance criteria. 

Statistic, 

Acceptable Error [ ], and 

Units ( ) 

DeTour Village 

N=12 

Mackinaw City 

N=25 

Harrisville 

N=5 

Amp. Time Amp. Time Amp. Time 

Mean Diff. (m) (min) -0.077 1.250 -0.002 -1.520 -0.083 0.600 

RMSE (m) (min) 0.090 5.694 0.039 4.940 0.084 2.408 

SD (m) (min) 0.049 5.802 0.040 4.797 0.017 2.608 

NOF [2x15cm or 90min] (%) 0.0 25.0 0.0 32.0 0.0 0.0 

CF [15 cm or 90 min] (%) 91.7 33.3 100,0 36.0 100.0 20.0 

POF [2x15 cm or 90 min] 

(%) 

0.0 25.0 0.0 20.0 0.0 20.0 

MDPO [2x15 cm or 90 min] 

(#) 

0.0 0.0 0.0 0.0 0.0 0 

MDNO [2x15 cm or 90min] 

(#) 

0.0 0.0 0.0 0.0 0.0 0 
21 

Table 7 (continued) 

Essexville 

N=22 

Harbor Beach 

N=17 

Lakeport 

N=28 

NOS 

Accept. 

Criteria 

Amp. Time Amp. Time Amp. Time 

-0.158 0.909 -0.087 -0.647 -0.111 -0.464 na 

0.167 4.442 0.096 4.734 0.124 4.508 na 

0.055 4.450 0.43 4.834 0.054 4.566 na 

0.0 4.5 0.0 29.4 0.0 25.0 < 1% 

54.5 13.6 100.0 23.5 82.1 50.0 > 90% 

0.0 13.6 0.0 23.5 0.0 14.3 < 1% 

0.0 0 0.0 0.0 0.0 0.0 < 24 hrs 

0.0 0 0.0 0.0 0.0 0.0 < 24 hrs 

Notes: na = not applicable 

The skill statistics to predict extreme low water level events at the six NOS gauges during 

2004 are given together in Table 8. Depending on the gauge, there were 11 to 46 events 

during the time period, with the greatest number of events at Lakeport located in southern 

most part of the lake. The extreme low water level nowcasts passed NOS acceptance 

criteria for amplitude at the six gauges. The nowcasts’ ability to simulate the timing of 

these events did not pass the NOS acceptance criteria at any of the gauges. 

Table 8. Summary of Standard Statistics Evaluating the Ability of SemiOperational Nowcasts to Simulate Extreme Low Water Level Events at 

the NOS NWLON Stations in Lake Huron for the Period 15 April to 17 

December 2004. Gray shading indicates that the statistic did not pass the 

NOS acceptance criteria. 

Statistic, 

Acceptable Error [ ], and 

Units ( ) 

DeTour Village 

N=24 

Mackinaw City 

N=31 

Harrisville 

N=11 

Amp. Time Amp. Time Amp. Time 

Mean Diff. (m) (min) 0.088 1.000 0.089 -0.129 0.085 1.455 

RMSE (m) (min) 0.094 2.483 0.098 3.398 0.089 3.104 

SD (m) (min) 0.033 2.322 0.042 3.452 0.027 2.876 

NOF [2x15cm or 90min] (%) 0.0 4.2 0.0 25.8 0.0 9.1 

CF [15 cm or 90 min] (%) 95.8 62.5 93.5 38.7 100.0 36.4 

POF [2x15 cm or 90 min] 

(%) 

0.0 12.5 0.0 16.1 0.0 27.3 

MDPO [2x15 cm or 90 min] 

(#) 

0.0 0.0 0.0 0.0 0.0 0.0 

MDNO [2x15 cm or 90min] 

(#) 

0.0 0.0 0.0 0.0 0.0 0.0 
22 

Table 8 (continued) 

Essexville 

N=37 

Harbor Beach 

N=21 

Lakeport 

N=46 

NOS 

Accept. 

Criteria 

Amp. Time Amp. Time Amp. Time 

0.051 -1.270 0.081 1.190 0.069 -0.022 na 

0.076 3.089 0.088 3.619 0.079 2.463 na 

0.058 2.854 0.035 3.502 0.039 2.490 na 

0.0 24.3 0.0 14.3 0.0 15.2 < 1% 

94.6 43.2 95.2 38.1 95.7 63.0 > 90% 

0.0 2.7 0.0 38.1 0.0 4.3 < 1% 

0.0 0.0 0.0 0.0 0.0 0.0 < 24 hrs 

0.0 0.0 0.0 0.0 0.0 0.0 < 24 hrs 

Notes: na = not applicable 
23 

5.4 Assessment of Surface Water Temperature Nowcasts 

The standard suite of skill assessment statistics evaluating the ability of semi-operational 

nowcasts to predict hourly lake surface water temperatures at the two NWS/NDBC fixed 

buoys in Lake Huron, 45003 in the northern part and 45008 in the southern part, from 

mid-April to early December 2004 are given in Appendix D. Time series plots of the 

nowcasts (1st sigma level) vs. observations at the buoy are given in Appendix E. 

The time series plots indicate that the nowcasts were in close agreement to observations 

from mid-April until mid-May corresponding to the spring warming period. During the 

warming period, surface heating causes convective overturning (destabilization of the 

water column) over the entire lake as the water warms from temperatures close to 

freezing to 4oC (Boyce et al. 1989). The difference between observations and nowcasts 

during this period ranged from 1.5o

C at 45003 and 1oC at 45008. 

However, when the surface water temperature nowcasts reached 4o

C around May 10th

(JD 130-135), the temperature of maximum density for fresh water, the nowcasts at both 

bouys began to deviate from the observations by +2-3oC, with the greatest difference 

occurring at approximately in mid-June (JD 165-170). This continued until 

approximately July 4th (JD 185-190). 

Overall, nowcasts from early July until mid November closely matched observations at 

both buoys. The difference between nowcasts and observations varied between + 0.5 – 

1oC. However, there were short time periods when the nowcasts deviated from the 

observations. At the northern buoy 45003 during mid-Aug (JD 235) to early September 

(JD250), the nowcasts were 1 - 2oC cooler than observations while nowcasts at 45008 

matched the observations within +0.5oC. This corresponded with arrival of significant 

cold air mass in the Great Lakes and New England regions following a cold front passage 

on August 21st. Morning minimum temperatures on August 22nd dropped below 10oC 

over Michigan. Although, both nowcasts and observations also decreased at 45008 

during this time, the nowcasts continued to match the observations within +0.5o

C. 

From late September until mid Novermber, the nowcasts very closely matched 

observations. This corresponds to the time of the year when the vertical temperature 

structure becomes homogeneous through surface cooling and storm induced 

destabilization (Bedford, 1992). However, starting in mid November the nowcasts were 

approximately 1-1.5o

C warmer than observations until the buoys were removed from the 

lake by NDBC for the winter, similar to what occurred in the early Spring. 

The skill statistics assessing the ability of LHOFS to predict hourly surface water 

temperatures at the NDBC buoys are given together in Table 9 along with the NOS 

acceptance criteria. The hourly water temperature nowcasts passed the NOS criteria at 

southern buoy 45008 but failed to pass 3 of the 5 criteria statistics at the northern buoy 

45003. The nowcasts over predicted lake surface temperatures at both buoys with the 

greatest departure at the northern buoy where the MAE and RMSE were 1.9o

C and 2.8oC, 

respectively. 
24 

Table 9. Summary of Skill Assessment Statistics of the Semi-Operational Nowcasts

of Hourly Surface Water Temperatures at two NWS/NDBC fixed buoys in 

Lake Huron for the Period from mid-April to early November 2004. Gray 

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

Time Period, Statistic, 

Acceptable Error [ ], and 

Units ( ) 

45003 

North - Lake Huron 

N=5036 

45008 

South – Lake Huron 

N=5152 

NOS 

Acceptance 

Criteria 

Time Period 29 July to 1 Dec 2004 20 April to 20 Nov. 

2004 

365 days 

Mean Difference (oC) 1.89 0.80 na 

RMSE (oC) 2.79 1.65 na 

SD (oC) 2.06 1.44 na 

NOF [2x3oC] (%) 0.0 0.0 < 1% 

CF [3oC] (%) 79.7 94.4 > 90% 

POF [2x3oC] (%) 8.1 0.0 < 1% 

MDNO [2x3oC] (hours) 0.02 0.0 < 24 hrs 

MDPO [2x3oC] (hours) 45.0 0.0 < 24 hrs 

Notes: na = not applicable 
25 

6. SEMI-OPERATIONAL FORECAST SKILL ASSESSMENT 

This section describes the model system performance for a semi-operational forecast 

scenario based on NOS requirements (Hess et al. 2003). According to Hess et al. (2003), 

the definition of the model run scenario for a semi-operational forecast is the following: 

“In this scenario, the model is forced with actual forecast input data streams, including 

open ocean boundary water levels, wind, river flows, and water density variations. Initial 

conditions are generated by observed data. Significant portions of the data may be 

missing, so the model must be able to handle this.” (Similar to the nowcast scenario, the 

data streams for the Great Lakes could include wind stresses, surface heat flux, and river 

flows.) 

For the assessment of the semi-operational forecast scenario for LHOFS, archived 

forecast guidance from GLCFS twice per day forecast cycles (0000 and 1200 UTC) 

during 2004 were compared to available surface observations in the lake. 

This chapter provides a description of the GLCFS forecast cycles, the method of 

evaluation including time period and assessment statistics, and the evaluation results. 

6.1 Description of Forecast Cycles 

GLCFS performs twice/day 60-hr forecast cycles for Lake Huron. The two forecast 

cycles are initialized at 0000 and 1200 UTC each day. The forecast cycles are launched 

at approximately 2 hours and 45 minutes past the valid time of the nowcasts to allow for 

complete ingestion of atmospheric forecast fields. For example, the forecast cycle with 

initial conditions valid at 1200 UTC is launched at 1445 UTC. The initial conditions for 

each forecast cycle are provided by the nowcast cycle. The surface forcing for the 

forecast cycles consists of surface (10 m AGL) wind velocity and surface (2 m AGL) air 

temperatures from NWS/NCEP North America Mesoscale (NAM) Model. The wind 

velocity and air temperature are used to calculate surface wind stress for input into the 

lake model. The surface heat fluxes into the lake model during the forecast cycle are 

zero. 

6.2 Method of Evaluation 

The semi-operational forecast guidance at 1 hour increments from +1 to +24 hours from 

GLCFS were compared to water level observations from NOS NWLON stations in the 

lake from 15 April to 17 December 2004 and to surface water temperatures at 

NWS/NDBC fixed buoys from mid-April to early November. This was a period when 

there was no significant ice cover on the lake. 

The evaluation used the standard suite of assessment statistics as defined in Hess et al. 

(2003) but modified for non-tidal regions. The evaluation of GLCFS forecasts of water 

levels were based on time series of observed and model-based water levels at the same 
26 

four NOS NWLON stations along the lake shore line used in the evaluation of the 

nowcasts. 

The evaluation of semi-operational forecast guidance of surface water temperatures was 

based on comparisons of time series of observed vs. model-predicted temperatures at the 

same NWS/NDBC fixed buoys used in the nowcast evaluation. There are a few gaps in 

the record of forecast guidance due to computer, and/or network problems, or incomplete 

surface forcing from the NAM Model for a particular forecast cycle. 

6.3 Assessment of Water Level Forecast Guidance 

The standard suite of skill assessment statistics evaluating the ability of semi-operational 

forecast guidance to predict hourly and extreme water levels at four NOS Gauges from 15 

April to 17 December 2004 are given in Appendix A. Time series plots of the forecast 

guidance from the 0000 UTC model forecast cycle vs. observations at the gauges are 

given in Appendix C. 

The skill statistics assessing the ability of the forecast guidance to predict hourly water 

levels at the six NOS gauges are presented together in Table 10 along with the NOS 

acceptance criteria. The hourly forecasts passed all the criteria statistics at all gauge 

locations except for NOF at Essexville. The forecast guidance overpredicted water levels 

at the northern and central gauge locations and underpredicted at the southern gauges. 

The MAE ranged between -4.7 cm at Essexville to +4.0 cm at Mackinaw City and the 

RMSE ranged between 3.8 cm at Harrisville to 6.1 cm at Mackinaw City, similar to the 

statistics for the nowcast evaluation. In addition, the nowcasts were similar to the 

forecast guidance in that the greatest errors were at the Essexville gauge located at 

southern end of Saginaw Bay and at the Mackinaw City gauge at the extreme western 

edge of the model domain. There was no significant increase in the mean differences, 

RMSE values, or CF as forecast projection increased (Appendix A). 

The skill statistics to assess the ability of the forecast guidance to predict extreme high 

water level events at six NOS water levels gauges during 2004 are given together in 

Table 11. There were between 4 and 82 extreme high water level events depending on 

location. 

The forecasts of extreme high water level passed NOS acceptance criteria for amplitude 

at three gauges, DeTour Village, Harbor Beach, and Harrisville. However, it should be 

noted these three gauges had the lowest number of high water events. The forecasts’ 

ability to simulate the timing of these events did not pass NOS acceptance criteria at any 

of the gauges.
27 

Table 10. Summary of Skill Assessment Statistics of 24-hr Semi-Operational 

Forecast Guidance of Hourly Water Levels at NOS NWLON Stations in 

Lake Huron for the Period 15 April to 17 December 2004. Notes: na = not 

applicable Approximately 490 forecasts were used in the assessment. Gray 

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

Statistic, Acceptable 

Error [ ], and 

Units ( ) 

DeTour 

Village 

Mackinaw 

City 

Harrisville Essexville NOS 

Accept. 

Criteria

Mean Diff. (m) 0.005 0.040 0.001 -0.047 na 

RMSE (m) 0.049 0.061 0.038 0.083 na 

SD (m) 0.049 0.046 0.039 0.069 na 

NOF [2x15cm] (%) 0.0 0.0 0.0 0.2 < 1% 

CF [15 cm] (%) 98.8 97.6 100.0 90.8 > 90% 

POF [2x15 cm] (%) 0.0 0.0 0.0 0.0 < 1% 

MDPO [2x15 cm ] 

(hour) 

0.0 0.0 0.0 0.0 < 24 

hours 

MDNO [2x15 cm ] 

(hour) 

0.0 0.0 0.0 0.0 < 24 

hours 

Table 10. (continued) 

Statistic, Acceptable 

Error [ ], and 

Units ( ) 

Harbor Beach Lakeport NOS 

Accept. 

Criteria

Mean Diff. (m) -0.009 -0.014 na 

RMSE (m) 0.044 0.051 na 

SD (m) 0.043 0.050 na 

NOF [2x15cm] (%) 0.0 0.0 < 1% 

CF [15 cm] (%) 100.0 99.0 > 90% 

POF [2x15 cm] (%) 0.0 0.0 < 1% 

MDPO [2x15 cm ] 

(hour) 

0.0 0.0 < 24 hours 

MDNO [2x15 cm ] 

(hour) 

0.0 0.0 < 24 hours 

The skill statistics to assess the ability of the forecast guidance to predict extreme low 

water level events at the six NOS gauges in 2004 are given together in Table 12. The 

number of events ranged from 11 to 47 with the greatest number of events at Essexville 

and Lakeport. 

The forecasts of extreme low water level passed NOS acceptance criteria for amplitude at 

all six gauges. The forecasts’ ability to simulate the timing of these events did not pass 

all the NOS acceptance criteria at any of the gauges. 
28 

Table 11. Summary of Skill Assessment Statistics Evaluating the Ability of 24-hr 

Semi-Operational Forecast Guidance to Predict Extreme High Water 

Level Events at NOS NWLON Stations in Lake Huron during the Period 

15 April to 17 December 2004. Gray shading indicates that the statistic did 

not pass the NOS acceptance criteria. 

Statistic, 

Acceptable Error [ ], and 

Units ( ) 

DeTour Village 

N=11 

Mackinaw City 

N=82 

Harrisville 

N=4 

Amp. Time Amp. Time Amp. Time 

Mean Diff. (m) (min) -0.083 -1.455 0.063 -0.036 -0.088 -2.250 

RMSE (m) (min) 0.092 4.786 0.108 5.729 0.091 5.809 

SD (m) (min) 0.043 4.782 0.089 5.834 0.026 6.185 

NOF [2x15cm or 90min] (%) 0.0 36.4 0.0 35.7 0.0 25.0 

CF [15 cm or 90 min] (%) 100.0 36.4 82.1 17.9 100.0 25.0 

POF [2x15 cm or 90 min] 

(%) 

0.0 9.1 0.0 25.0 0.0 0.0 

Table 11 (cont.) 

Essexville 

N=24 

Harbor Beach 

N=15 

Lakeport 

N=35 

NOS 

Accept. 

Criteria 

Amp. Time Amp. Time Amp. Time 

-0.116 1.500 -0.088 1.000 -0.117 -0.171 na 

0.129 4.311 0.095 4.389 0.133 5.860 na 

0.058 4.128 0.037 4.424 0.064 5.943 na 

0.0 12.5 0.0 20.0 0.0 31.4 < 1% 

66.7 20.8 100.0 26.7 77.1 25.7 > 90% 

0.0 29.2 0.0 33.3 0.0 25.7 < 1% 

 Notes: na = not applicable 
29 

Table 12. Summary of Skill Assessment Statistics Evaluating the Ability of 24-hr 

Semi-Operational Forecast Guidance to Predict Extreme Low Water 

Level Events at NOS NWLON Stations in Lake Huron during the Period 

15 April to 17 December 2004. Gray shading indicates that the statistic did 

not pass the NOS acceptance criteria. 

Statistic, 

Acceptable Error [ ], and 

Units ( ) 

DeTour Village 

N=23 

Mackinaw City 

N=30 

Harrisville 

N=11 

Amp. Time Amp. Time Amp. Time 

Mean Diff. (m) (min) 0.082 0.913 0.070 0.467 0.080 1.727 

RMSE (m) (min) 0.089 3.000 0.088 3.337 0.085 2.780 

SD (m) (min) 0.036 2.922 0.054 3.360 0.031 2.284 

NOF [2x15cm or 90min] (%) 0.0 8.7 0.0 16.7 0.0 0.0 

CF [15 cm or 90 min] (%) 91.3 47.8 93.3 43.3 100.0 45.5 

POF [2x15 cm or 90 min] 

(%) 

0.0 17.4 0.0 20.0 0.0 18.2 

Table 12 (continued) 

Essexville 

N=38 

Harbor Beach 

N=20 

Lakeport 

N=47 

NOS 

Accept. 

Criteria 

Amp. Time Amp. Time Amp. Time 

0.018 1.158 0.074 1.000 0.061 -0.149 na 

0.077 3.095 0.080 4.389 0.072 2.764 na 

0.075 2.909 0.032 4.424 0.038 2.790 na 

0.0 7.9 0.0 20.0 0.0 14.9 < 1% 

92.1 26.3 100.0 26.7 97.9 51.1 > 90% 

0.0 21.1 0.0 33.3 0.0 10.6 < 1%

Notes: na = not applicable 

6.4 Assessment of Surface Water Temperature Forecast Guidance 

The standard suite of skill assessment statistics evaluating the ability of semi-operational 

forecast guidance to predict hourly lake surface water temperatures at the NWS/NDBC 

Lake Huron fixed buoys 45003 and 45008 from mid-April to early December 2004 is 

given in Appendix D. Tables therein provide skill statistics at the forecast projections 0, 

6, 12, 18, and 24 hours. Time series plots of the forecasts (1st sigma level) from the 0000 

UTC forecast cycle compared with buoy observations are given in Appendix E. 

The time series plots indicate that the forecast guidance from the 0000 UTC forecast 

cycle resembles the nowcasts very closely. This reflects the fact that the lake model 

configuration (i.e. POMGL) used for the semi-operational forecast cycles does not 

include any input of surface heat fluxes either directly or indirectly from the NAM-12 
30 

model forecast guidance. Specifically, the lake model uses subroutine FLUX5 in which 

the heat fluxes are zero. Similar to the nowcasts, the semi-operational forecast guidance 

values are in close agreement to observations. 

The skill statistics assessing the ability of semi-operational forecast guidance to predict 

surface water temperatures 24 hours in advance at the two NDBC buoys are given in 

Table 13 along with the NOS criteria. The hourly forecast guidance at the southern buoy 

passed all the criteria. The MAE and RSME at this buoy were 0.5o

C and 1.4oC, 

respectively. However, the hourly guidance at the northern buoy failed all the criteria 

statistics except for MDPO. For this buoy, the MAE and RSME were 1.8oC and 2.7oC, 

respectively. The MAE and RMSE values for the forecast guidance were slightly lower 

than for the nowcasts. It is interesting to note that the mean differences only decreased 

by 0.15oC and 0.35oC at 45003 and 45008, respectively as the forecast projection time 

increased from 0 to 24 hours (Table D.1). 

Table 13. Summary of Skill Assessment Statistics for Semi-Operational Forecast 

Guidance to Predict Surface Water Temperatures 24 hours in advance at 

NWS/NDBC fixed buoys in Lake Huron during the period from midApril to early-November 2004. Gray shading indicates that the statistic did 

not pass the NOS acceptance criteria. 

 Time Period, 

Statistic, Acceptable 

Error [ ], and Units ( ) 

45003 

North - Lake Huron 

N=416 

45008 

South – Lake 

Huron 

N=426 

NOS 

Acceptance 

Criteria 

Time Period 29 July to 1 Dec 

2004 

20 Apr to 20 Nov 

2004 

365 days 

Mean Difference (oC) 1.77 0.50 na 

RMSE (oC) 2.65 1.37 na 

SD (oC) 1.97 1.27 na 

NOF [2x3oC] (%) 0.0 0.0 < 1% 

CF [3oC] (%) 82.2 97.7 > 90% 

POF [2x3oC] (%) 7.5 0.0 < 1% 

MDPO [2x3oC] (hours) 0.24 0.0 < 24 hrs 

MDNO [2x3oC] (hours) 40.0 0.0 < 24 hrs 

Notes: na = not applicable 
31 

7. SUMMARY 

NOS’ Lake Huron Operational Forecast System (LHOFS) generates hourly nowcasts and 

forecast guidance out to 30 hours four times per day. It is based on the Great Lakes 

Coastal Forecasting System (GLCFS) developed by the Ohio State University and 

NOAA/GLERL. 

LHOFS became operational at CO-OPS on March 30, 2006. The hourly nowcast cycles 

are forced by surface wind stress and surface heat flux estimated from objectively 

analyzed surface meteorological fields and the initial conditions are provided by the 

previous hour’s nowcast. The four times/day forecast cycle uses the most recent 

nowcasts for its initial conditions and gridded NWS forecasts of surface air temperature 

and wind forcing from NWS/National Digital Forecast Database. Prior to April 1, 2007, 

LHOFS used forecast guidance from NCEP’s NAM-12 weather prediction model. 

During the forecast cycle, the heat flux is set to zero. 

An assessment of the LHOFS nowcasts and forecast guidance was conducted according 

to the NOS evaluation standards (Hess et al. 2003). To comply with the NOS required 

semi-operational nowcast and forecast scenarios, the evaluation used archived output 

from NOAA/GLERL’s GLCFS semi-operational nowcasts and forecasts for Lake Huron 

from 15 April to 17 December 2004. Unfortunately, neither GLERL nor OSU conducted 

comparisons between POMGL output with field data for Lake Huron which could be 

used to fulfill the hindcast scenario. 

The semi-operational nowcasts and forecast guidance were compared to water level 

observations at six NOS NWLON stations and surface temperatures at two NWS/NDBC 

fixed buoys, 45003 in northern part of the lake and buoy 45008 in the southern part. Due 

to the lack of sub-surface water temperatures and current observations, no quantitative 

assessment of these variables was conducted for LHOFS. 

Water Levels 

The hourly nowcasts of water level for amplitude met the NOS acceptance criteria at the 

six NOS gauges in Lake Huron. The mean algebraic error or difference (MAE) ranged 

between -4 and + 11 cm and the RSME ranged from 4 and 7 cm. The nowcast of high 

water events passed the NOS criteria for amplitude at the six NOS gauges but did not 

meet the NOS criteria for timing. Similarly, the nowcasts of low water events met the 

NOS criteria for amplitude, but did not pass the criteria in terms of timing at any of the 

gauges. 

The hourly forecast guidance met the majority of NOS criteria for predicting water level 

amplitude at all six gauges. The MAE ranged between -4.7 and +4.0 cm and the RMSE 

ranged between 3.8 cm and 6.1 cm. There was no significant increase in the error as 

forecast projection increased from 0 to 24 hours. The forecast guidance of high water 

events passed the NOS criteria for amplitude at the three of the six gauges. The guidance 

failed to meet NOS criteria in predicting the times of these extreme events at all six 
32 

gauges. The guidance of low water events passed the NOS criteria for amplitude at all 

locations but failed to meet NOS criteria in predicting the times of these extreme events 

at the gauges. 

Surface Water Temperatures 

The hourly water temperature nowcasts passed NOS criteria at the NDBC southern buoy 

45008 located in 50 m deep water but not at the northern buoy 45003 situated in 150 m 

water. For the two buoys, the MAE ranged from 0.8 to 1.9o

C and the RMSE ranged from 

1.7 to 2.8o

C. The nowcasts deviated from observations the most during the period from 

mid May, when the water temperature reached 4oC until early July. During this period, 

nowcasts were generally 2 to 3o

C too warm, especially at the northern buoy. 

The hourly water temperature forecast guidance at 24 hours passed NOS criteria at the 

southern buoy but not the northern buoy. The MAE and RMSE values for 24-hr forecast 

projection were slightly higher than for the nowcast comparisons. The MAE decreased 

by 0.15o

C and 0.35oC at the northern and southern buoys, respectively as the forecast 

projection increased from 0 to 24 hours. 

Surface Currents

Due to the lack of water current observations, no quantitative assessment could be 

conducted for LHOFS. However, animation of surface current nowcasts and forecast 

guidance indicated that LHOFS did properly simulate the known cyclic clockwise 

rotation of surface currents present in the Great Lakes when the lake water is density 

stratified. This occurs usually from May through October. Observational studies have 

found that the clockwise rotation has a near-inertial period of 18 hours (Saylor and Miller, 

1987). 
33 

8. RECOMMENDATIONS FOR FUTURE WORK 

Recommendation #1: 

The comparisons of the semi-operational nowcasts and forecast guidance of surface water 

temperature to observations at the NDBC Lake Huron buoys indicate a potential over 

prediction of surface water temperature predictions, from mid May till early July. A 

similar problem occurred with LSOFS, LMOFS, and LEOFS. Since surface water 

temperature comparisons were done only at two buoys, it is difficult to conclude whether 

this is an issue over the entire model grid domain. Therefore, it is recommended that in 

the future, LHOFS SST nowcasts and forecast guidance also be evaluated at the Canadian 

fixed buoys: Southern Lake Huron (45149), Northern Channel East (45154), Georgian 

Bay (45137), and South Georgian Bay (45143). 

Recommendation #2: 

The comparisons of the semi-operational nowcasts and forecast guidance of surface water 

temperature to observations indicate a potential overestimation of the surface heat flux 

during the nowcast cycle. An improved specification of cloud cover via GOES analyses 

instead of interpolation of airport cloud cover observations may improve radiation flux 

estimations and reduce the surface water temperature overprediction similar to work done 

by Chu (1998). The overprediction may be also be reduced by nudging the water 

temperature nowcasts towards GLERL’s GLSEA daily lake wide average surface water 

temperature. 

Recommendation #3: 

A study is needed to determine the reason why POMGL was unable to better forecast the 

timing of water level of extreme high and low water level events in the lake. This would 

likely involve sensitivity tests with POMGL using higher grid resolution and 

incorporating atmospheric pressure forcing. 

Recommendation #4: 

The under prediction of water levels at Essexville, MI could be due to a combination of 

a) model grid resolution, b) bathymetric data resolution in the Saginaw Bay and c) 

physical location of the NOS water level gauge. POMGL sensitivity tests should be 

conducted to determine the impact of improved model grid resolution and higher 

resolution bathymetry on water level predictions. 

Possible research topics for improving LHOFS predictions include incorporating ice 

dynamics, using a coupled lake system, and using hydrologic inputs.
34 

ACKNOWLEDGMENTS 

The development of the Great Lakes Forecasting System was a joint effort of The Ohio 

State University and NOAA’s Great Lakes Environmental Research Laboratory led by 

Dr. Keith Bedford (OSU) and Dr. David Schwab (GLERL). During the eleven-year life 

of the GLFS, the following OSU staff members have been associated with the 

development of the system: fifteen graduate students; seven faculty; six postdocs; and 

seven research scientists. Funding came from over 26 different sources ranging from 

small grants from private foundations and companies to several large federal grants. The 

operation and further development of GLCFS at GLERL has involved two research 

scientists and three support scientists. 

The porting of the GLCFS from GLERL to NOS was conducted by the GLOFS System 

Development and Implementation Team consisting of personnel from GLERL, OSU, 

CO-OPS, CSDL, and Aqualinks.com. In particular, we acknowledge the hard work of 

Dr. Mark Vincent, Greg Mott, Zack Bronder, and others at CO-OPS. 

The archived GLCFS nowcast and forecast guidance used in the skill assessment were 

provided by Greg Lang and David Schwab at NOAA/GLERL. The skill assessment 

software was modified for use in the Great Lakes based on suggestions from Drs. Kurt 

Hess and Eugene Wei in CSDL. 
35 

REFERENCES 

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wetlands. J. Great Lakes Res., 18, 571-589. 

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New Orleans, LA, Marine Technology Society, 206-264. 

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J. Great Lakes Res., 25(1), 78-93. 

Blumberg, A. F. and G. L. Mellor, 1987: A Description of a Three-Dimensional Coastal 

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Report NOS CS 10, 45 pp. [Available from NOAA/NOS Coast Survey 

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2070 Neil Avenue, Ohio State University, Columbus, OH 43210-1275.] 

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Oceanic Sciences, P.O. Box CN710, Sayre Hall, Princeton University, Princeton, 

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37 

Schwab, D. J., and D. Beletsky, 1998: Lake Michigan Mass Balance Study: 

Hydrodynamic Modeling Project. NOAA Technical Memorandum ERL GLERL108, 53 pp. [Available from NOAA/Great Lakes Environmental Research 

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Arbor, MI, 13 pp. [Available from NOAA/Great Lakes Environmental Research 

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38 
39 

APPENDIX A. Skill Assessment Statistics of Semi-Operational Water Level 

Nowcasts and Forecast Guidance at NOS Gauges in Lake 

Huron for 2004. 

Table A.1. Skill Assessment Statistics of Semi-Operational Predictions at the NOS 

DeTour Village, MI Gauge (NOS ID 9075099) for 2004. 

Station: DeTour Village, Lake Huron, MI 

Observed data time period from: 4/15/2004 to 12/20/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

H 5832 176.205 

h 5832 176.194 

H-h 15 cm 24h 5832 0.011 0.043 0.042 0.0 99.4 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 12 -0.077 0.090 0.049 0.0 91.7 0.0 0.0 0.0 

ALW-alw 15 cm 24h 24 0.088 0.094 0.033 0.0 95.8 0.0 0.0 0.0 

THW-thw 1.50 hr 25h 12 1.250 5.694 5.802 25.0 33.3 25.0 0.0 0.0 

TLW-tlw 1.50 hr 25h 24 1.000 2.483 2.322 4.2 62.5 12.5 0.0 0.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 

H00-h00 15 cm 24h 494 0.007 0.042 0.042 0.0 99.8 0.0 0.0 0.0 

H06-h06 15 cm 24h 490 0.014 0.045 0.043 0.0 99.4 0.0 0.0 0.0 

H12-h12 15 cm 24h 490 0.005 0.047 0.047 0.0 99.0 0.0 0.0 0.0 

H18-h18 15 cm 24h 490 0.014 0.048 0.046 0.0 99.2 0.0 0.0 0.0 

H24-h24 15 cm 24h 490 0.005 0.049 0.049 0.0 98.8 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 11 -0.083 0.092 0.043 0.0 100.0 0.0 

ALW-alw 15 cm 24h 23 0.082 0.089 0.036 0.0 91.3 0.0 

THW-thw 1.50 hr 25h 11 -1.455 4.786 4.782 36.4 36.4 9.1 

TLW-tlw 1.50 hr 25h 23 0.913 3.000 2.922 8.7 47.8 17.4 

Table A.2. Skill Assessment Statistics of Semi-Operational Predictions at the NOS 

Mackinaw City, MI Gauge (NOS ID 9075080) for 2004. 

Station: Mackinaw City, Lake Michigan, MI 

Observed data time period from: 4/15/2004 to 12/20/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

H 5832 176.243 

h 5832 176.202 

H-h 15 cm 24h 5832 0.041 0.055 0.037 0.0 99.4 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 25 -0.002 0.039 0.040 0.0 100.0 0.0 0.0 0.0 

ALW-alw 15 cm 24h 31 0.089 0.098 0.042 0.0 93.5 0.0 0.0 0.0 

THW-thw 1.50 hr 25h 25 -1.520 4.940 4.797 32.0 36.0 20.0 0.0 0.0 

TLW-tlw 1.50 hr 25h 31 -0.129 3.398 3.452 25.8 38.7 16.1 0.0 0.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 

H00-h00 15 cm 24h 494 0.033 0.050 0.037 0.0 99.4 0.0 0.0 0.0 

H06-h06 15 cm 24h 490 0.052 0.067 0.042 0.0 97.8 0.0 0.0 0.0 

H12-h12 15 cm 24h 490 0.039 0.056 0.041 0.0 98.2 0.0 0.0 0.0 
40 

H18-h18 15 cm 24h 490 0.050 0.065 0.042 0.0 98.0 0.0 0.0 0.0 

H24-h24 15 cm 24h 490 0.040 0.061 0.046 0.0 97.6 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 28 0.063 0.108 0.089 0.0 82.1 0.0 

ALW-alw 15 cm 24h 30 0.070 0.088 0.054 0.0 93.3 0.0 

THW-thw 1.50 hr 25h 28 -0.036 5.729 5.834 35.7 17.9 25.0 

TLW-tlw 1.50 hr 25h 30 0.467 3.337 3.360 16.7 43.3 20.0 

Table A.3. Skill Assessment Statistics of Semi-Operational Predictions at the NOS 

Harrisville, MI Gauge (NOS ID 9075059) for 2004. 

Station: Harrisville, Lake Huron, MI 

Observed data time period from: 4/15/2004 to 12/3/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

H 5818 176.208 

h 5818 176.208 

H-h 15 cm 24h 5818 0.001 0.036 0.036 0.0 100.0 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 5 -0.083 0.084 0.017 0.0 100.0 0.0 0.0 0.0 

ALW-alw 15 cm 24h 11 0.085 0.089 0.027 0.0 100.0 0.0 0.0 0.0 

THW-thw 1.50 hr 25h 5 0.600 2.408 2.608 0.0 20.0 20.0 0.0 0.0 

TLW-tlw 1.50 hr 25h 11 1.455 3.104 2.876 9.1 36.4 27.3 0.0 0.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 

H00-h00 15 cm 24h 493 0.002 0.036 0.036 0.0 100.0 0.0 0.0 0.0 

H06-h06 15 cm 24h 489 -0.001 0.038 0.038 0.0 100.0 0.0 0.0 0.0 

H12-h12 15 cm 24h 489 0.001 0.037 0.037 0.0 100.0 0.0 0.0 0.0 

H18-h18 15 cm 24h 489 -0.001 0.038 0.038 0.0 100.0 0.0 0.0 0.0 

H24-h24 15 cm 24h 489 0.001 0.038 0.039 0.0 100.0 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 4 -0.088 0.091 0.026 0.0 100.0 0.0 

ALW-alw 15 cm 24h 11 0.080 0.085 0.031 0.0 100.0 0.0 

THW-thw 1.50 hr 25h 4 -2.250 5.809 6.185 25.0 25.0 0.0 

TLW-tlw 1.50 hr 25h 11 1.727 2.780 2.284 0.0 45.5 18.2 

Table A.4. Skill Assessment Statistics of Semi-Operational Predictions at the NOS 

Essexville, MI Gauge (NOS ID 9075035) for 2004. 

Station: Essexville, Lake Huron, MI 

Observed data time period from: 4/15/2004 to 12/20/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

H 5832 176.197 

h 5832 176.238 

H-h 15 cm 24h 5832 -0.042 0.073 0.061 0.0 95.3 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 22 -0.158 0.167 0.055 0.0 54.5 0.0 0.0 0.0 

ALW-alw 15 cm 24h 37 0.051 0.076 0.058 0.0 94.6 0.0 0.0 0.0 

THW-thw 1.50 hr 25h 22 0.909 4.442 4.450 4.5 45.5 13.6 0.0 0.0 

TLW-tlw 1.50 hr 25h 37 -1.270 3.089 2.854 24.3 43.2 2.7 0.0 0.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 

H00-h00 15 cm 24h 494 -0.049 0.078 0.061 0.0 94.3 0.0 0.0 0.0 
41 

H06-h06 15 cm 24h 490 -0.026 0.066 0.061 0.0 96.5 0.0 0.0 0.0 

H12-h12 15 cm 24h 490 -0.047 0.080 0.065 0.4 93.5 0.0 0.0 0.0 

H18-h18 15 cm 24h 490 -0.028 0.070 0.065 0.0 94.9 0.0 0.0 0.0 

H24-h24 15 cm 24h 490 -0.047 0.083 0.069 0.2 90.8 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 24 -0.116 0.129 0.058 0.0 66.7 0.0 

ALW-alw 15 cm 24h 38 0.018 0.077 0.075 0.0 92.1 0.0 

THW-thw 1.50 hr 25h 24 1.500 4.311 4.128 12.5 20.8 29.2 

TLW-tlw 1.50 hr 25h 38 1.158 3.095 2.909 7.9 26.3 21.1 

Table A.5. Skill Assessment Statistics of Semi-Operational Predictions at the NOS 

Harbor Beach, MI Gauge (NOS ID 9075014) for 2004. 

Station: Harbor Beach, Lake Huron, MI 

Observed data time period from: 4/15/2004 to 12/20/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

H 5832 176.211 

h 5832 176.221 

H-h 15 cm 24h 5832 -0.011 0.043 0.042 0.0 99.9 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 17 -0.087 0.096 0.043 0.0 100.0 0.0 0.0 0.0 

ALW-alw 15 cm 24h 21 0.081 0.088 0.035 0.0 95.2 0.0 0.0 0.0 

THW-thw 1.50 hr 25h 17 -0.647 4.734 4.834 29.4 23.5 23.5 0.0 0.0 

TLW-tlw 1.50 hr 25h 21 1.190 3.619 3.502 14.3 38.1 38.1 0.0 0.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 

H00-h00 15 cm 24h 494 -0.008 0.042 0.042 0.0 100.0 0.0 0.0 0.0 

H06-h06 15 cm 24h 490 -0.014 0.045 0.042 0.0 99.8 0.0 0.0 0.0 

H12-h12 15 cm 24h 490 -0.008 0.043 0.042 0.0 100.0 0.0 0.0 0.0 

H18-h18 15 cm 24h 490 -0.013 0.045 0.043 0.0 99.8 0.0 0.0 0.0 

H24-h24 15 cm 24h 490 -0.009 0.044 0.043 0.0 100.0 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 15 -0.088 0.095 0.037 0.0 100.0 0.0 

ALW-alw 15 cm 24h 20 0.074 0.080 0.032 0.0 100.0 0.0 

THW-thw 1.50 hr 25h 15 1.000 4.389 4.424 20.0 26.7 33.3 

TLW-tlw 1.50 hr 25h 20 0.350 3.248 3.313 20.0 25.0 15.0 

Table A.6. Skill Assessment Statistics of Semi-Operational Predictions at the NOS 

Lakeport, MI Gauge (NOS ID 9075002) for 2004. 

Station: Lakeport, Lake Huron, MI 

Observed data time period from: 4/15/2004 to 12/20/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

H 5832 176.214 

h 5832 176.233 

H-h 15 cm 24h 5832 -0.018 0.052 0.048 0.0 99.1 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 28 -0.111 0.124 0.054 0.0 82.1 0.0 0.0 0.0 

ALW-alw 15 cm 24h 46 0.069 0.079 0.039 0.0 95.7 0.0 0.0 0.0 

THW-thw 1.50 hr 25h 28 -0.464 4.508 4.566 25.0 50.0 14.3 0.0 0.0 

TLW-tlw 1.50 hr 25h 46 -0.022 2.463 2.490 15.2 63.0 4.3 0.0 0.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 
42 

H00-h00 15 cm 24h 494 -0.013 0.050 0.048 0.0 99.2 0.0 0.0 0.0 

H06-h06 15 cm 24h 490 -0.022 0.052 0.047 0.0 98.6 0.0 0.0 0.0 

H12-h12 15 cm 24h 490 -0.012 0.051 0.049 0.0 99.0 0.0 0.0 0.0 

H18-h18 15 cm 24h 490 -0.023 0.055 0.050 0.0 98.4 0.0 0.0 0.0 

H24-h24 15 cm 24h 490 -0.014 0.051 0.050 0.0 99.0 0.0 0.0 0.0 

AHW-ahw 15 cm 24h 35 -0.117 0.133 0.064 0.0 77.1 0.0 

ALW-alw 15 cm 24h 47 0.061 0.072 0.038 0.0 97.9 0.0 

THW-thw 1.50 hr 25h 35 -0.171 5.860 5.943 31.4 25.7 25.7 

TLW-tlw 1.50 hr 25h 47 -0.149 2.764 2.790 14.9 51.1 10.6 
43 

APPENDIX B. Time Series Plots of Semi-Operational Water Level Nowcasts 

vs. Observations at NOS Gauges in Lake Huron during 2004. Fig. B.1. Time Series Plot of Semi-Operational Water Level Nowcasts vs. Observations at NOS DeTour Village, MI, NY Gauge during 2004. 
44 

Fig. B.2. Time Series Plot of Semi-Operational Water Level Nowcasts vs. Observations at NOS 

Mackinaw City, MI, NY Gauge during 2004. 
45 

Fig. B.3. Time Series Plot of Semi-Operational Water Level Nowcasts vs. Observations at NOS 

Harrisville, MI Gauge during 2004. 
46 

. 

Fig. B.4. Time Series Plot of Semi-Operational Water Level Nowcasts vs. Observations at 

 NOS Essexville, MI Gauge during 2004. 
47 

Fig. B.5. Time Series Plot of Semi-Operational Water Level Nowcasts vs. Observations at 

 NOS Harbor Beach, MI Gauge during 2004. 
48 

Fig. B.6. Time Series Plot of Semi-Operational Water Level Nowcasts vs. Observations at 

 NOS Lakeport, MI Gauge during 2004.I Gauge during 2004. 
49 

APPENDIX C. Time Series Plots of Semi-Operational Water Level Forecast 

Guidance vs. Observations at the NOS Gauges in Lake Huron during 

2004. 

Fig. C.1. Time Series Plot of Semi-Operational Water Level Forecast Guidance vs. 

 observations at NOS DeTour Village, MI Gauge during 2004.auge during 2004.I 

 Gauge during 2004. 
50 

Fig. C.2. Time Series Plot of Semi-Operational Water Level Forecast Guidance vs. Observations  at NOS Mackinaw City, MI Gauge during 2004. 
51 

Fig. C.3. Time Series Plot of Semi-Operational Water Level Forecast Guidance vs. Observations 

 at NOS Harrisville, MI Gauge during 2004. 
52 

Fig. C.4. Time Series Plot of Semi-Operational Water Level Forecast Guidance vs. Observations 

 at NOS Essexville, MI Gauge during 2004. 
53 

Fig. C.5. Time Series Plot of Semi-Operational Water Level Forecast Guidance vs. Observations at NOS Harbor Beach, 

MI Gauge during 2004. 
54 

Fig. C.6. Time Series Plot of Semi-Operational Water Level Forecast Guidance vs. Observations at NOS Lakeport, MI 

Gauge during 2004. 
55 

APPENDIX D. Skill Assessment Statistics of Semi-Operational Surface 

Water Temperature Nowcasts and Forecast Guidance at 

NWS/NDBC Fixed Buoys in Lake Huron for 2004. 

Table D.1. Skill Assessment Statistics of Semi-Operational Nowcasts and Forecast 

Guidance of Surface Water Temperatures at the NWS/NDBC Fixed Buoy 

45003 (North Lake Huron) for the Period July 29, 2004 to December 1, 2004. 

Station: NDBC Buoy 45003 in Lake Huron 

Observed data time period from: 7/29/2004 to 12/ 1/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

T 5036 11.638 

t 5036 9.752 

T-t 3.0 c 24h 5036 1.886 2.792 2.059 0.0 79.7 8.1 0.0245.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 

T00-t00 3.0 c 24h 420 1.923 2.821 2.066 0.0 80.0 8.3 0.0360.0 

T06-t06 3.0 c 24h 415 1.849 2.761 2.052 0.0 80.0 8.0 0.0204.0 

T12-t12 3.0 c 24h 416 1.857 2.767 2.054 0.0 80.5 8.2 0.0240.0 

T18-t18 3.0 c 24h 415 1.754 2.642 1.978 0.0 81.9 7.0 0.0228.0 

T24-t24 3.0 c 24h 416 1.774 2.649 1.969 0.0 82.2 7.5 0.0240.0 

Table D.1. Skill Assessment Statistics of Semi-Operational Nowcasts and Forecast 

Guidance of Surface Water Temperatures at the NWS/NDBC Fixed Buoy 

45008 (South Lake Huron) for the Period April 20, 2004 to November 20, 

2004. 

Station: NDBC Buoy 45008 in Lake Huron 

Observed data time period from: 4/20/2004 to 11/20/2004 

Data gap is filled using SVD method 

Data are filtered using 3.0 Hour Fourier Filter 

------------------------------------------------------------------------------- 

VARIABLE X N IMAX SM RMSE SD NOF CF POF MDNO MDPO 

CRITERION - - - - - - <1% >90% <1% <N <N 

------------------------------------------------------------------------------- 

 SCENARIO: SEMI-OPERATIONAL NOWCAST 

T 5152 12.992 

t 5152 12.196 

T-t 3.0 c 24h 5152 0.796 1.645 1.440 0.0 94.4 0.0 0.0 0.0 

 SCENARIO: SEMI-OPERATIONAL FORECAST 

T00-t00 3.0 c 24h 430 0.845 1.684 1.459 0.0 93.0 0.0 0.0 0.0 

T06-t06 3.0 c 24h 425 0.731 1.613 1.439 0.0 95.1 0.0 0.0 0.0 

T12-t12 3.0 c 24h 426 0.654 1.573 1.432 0.0 95.5 0.0 0.0 0.0 

T18-t18 3.0 c 24h 425 0.552 1.397 1.285 0.0 97.9 0.0 0.0 0.0 

T24-t24 3.0 c 24h 426 0.504 1.369 1.274 0.0 97.7 0.0 0.0 0.0 
56 

APPENDIX E. Time Series Plots of Semi-Operational Nowcasts and 

Forecast Guidance of Surface Water Temperature vs. Observations at 

NWS/NDBC fixed buoys in Lake Huron during 2004. 

Figure E.1. Time Series of Semi-Operational Nowcasts and Forecast Guidance of Surface Water  Temperature (oC) vs. Observations at the NWS/NDBC Fixed Buoy 45003 (North Lake 

 Huron) for the Period July 29, 2004 to December 1, 2004. The forecast values depicted 

 on the plots are from the 0000 UTC forecast cycle. 
57 

Figure E.2. Time Series of Semi-Operational Nowcasts and Forecast Guidance of Surface Water 

Temperature (oC) vs. Observations at the NWS/NDBC Fixed Buoy 45008 (South Lake 

Huron) for the Period April 20, 2004 to November 20, 2004. The forecast values depicted on the plots are from the 0000 UTC forecast cycle.