display of regional spectral model results on an internet...

Display of Regional Spectral Model Results on an Internet Web Site Doyle Pittman and Ken Wastrack

Tennessee Valley Authority The Tennessee Valley Authority (TVA) uses short-range forecasts of temperature and precipitation in the Tennessee Valley to help make daily decisions concerning power load management, power marketing, and river system management. These decisions necessarily allow for uncertainty in the accuracy of the forecast. Improvements in forecast accuracy can improve decision-making and could save millions of dollars each year. For instance, a one-degree Fahrenheit (1°F) improvement in the accuracy of the forecast maximum daily temperature can translate into $100,000 in power sales. Conversely, errors in forecasting precipitation volume and timing can result in lost hydroelectric generation if water is prematurely released from reservoirs to prepare for stormwater runoff that doesn’t occur. Significant advances in short-range weather forecasting are now feasible because increased computer processor speeds enable application of more sophisticated models. The Regional Spectral Model TVA is using the National Weather Service (NWS) Regional Spectral Model (RSM) to achieve forecast improvements. The RSM is a limited-area (that is, regional) version of the Global Spectral Model (GSM) developed at the National Centers for Environmental Predictions (NCEP). Output from the GSM defines initial, internal, and boundary for the RSM. The GSM solves the divergence and vorticity equations, the RSM solves the momentum equations.

A spectral model takes the spatial pattern of a forecast variable and breaks it down into sine and cosine waves. This is preferred over the more traditional grid-point approach since it provides a more accurate representation of small atmospheric disturbances. The RSM divides the atmosphere into 28 vertical layers and has a horizontal spatial resolution of about 20 km (compared to 45 km for other NWS models). This is small enough to depict the complex topography of the eastern portion of the Tennessee Valley. TVA currently uses the RSM for a domain of about 82º to 90º west longitude and about 32º to 40º north latitude (Figure 1).

- Forecast Cities

Figure 1. RSM Domain

Displaying RSM Output on A Web Site of 9

RSM Operation at TVA TVA uses the RSM in a nested mode to predict perturbations from the large-scale conditions of the GSM and generate forecasts out to 72 hours. It has been used to provide quantitative precipitation forecasts for the Tennessee and Cumberland River watershed (figure 2). It potentially could be used for forecasting parameters used in thermal compliance and energy load projections.

FORECAST AREAS FORECAST SUB-BASINS

M S

K E N T U C K Y

G E O R G I A

N C

S C

V A

SOUTHWEST(SW)

EAST(ET)

NORTHEAST(NE)

A L A B A M ATennessee RiverDrainage Basin

I L

CENTRAL(CN)

NORTHWEST(NW)

T E N N E S S E E

SOUTHWEST(SW)

EAST(ET)

NORTHEAST(NE)

Tennessee RiverDrainage Basin

CENTRAL(CN)

NORTHWEST(NW)

K E N T U C K Y

G E O R G I A

N O R T HC A R O L I N A

S O U T HC A R O L I N A

V I R G I N I A

A L A B A M A

T E N N E S S E E

Nashville

Chattanooga

Bristol

Knoxville

Norris

Cherokee

Ocoee #1 &Apalachia

EastCentral

Douglas

West Central

Little Tenn.above

Chilhowee

Figure 2. Quantitative Precipitation Forecast Areas and Sub-Basins

Although NCEP runs the GSM four times a day, TVA currently uses only the 00Z output each day. Shortly after midnight (Central time), a TVA DEC Alpha 4100 computer automatically downloads several large GSM output data files (total size ~100 MB) from an NCEP computer. The Alpha 4100 computer then runs the RSM model for the TVA Region and converts results to text and postscript graphic format. Under normal circumstances, the RSM results are available by 4:00 am.


Displaying RSM Output The DEC Alpha 4100 computer is appropriate for performing the processing that the RSM requires. However, it presents some problems in providing program results to users in a form that is easily understood. To accomplish this, TVA uses its IntraNet to make the RSM information available. • While the RSM provides short-range forecasts of sufficient detail for the TVA Region, data

results on UNIX computer are not easily accessible.

• Using an IntraNet web server allows information to be widely distributed throughout TVA. • Using JPEG and animated GIF graphics formats allows viewing with a standard web browser.

Result: Complex information is presented in a form that is easy to understand and can be readily accessed from desktop computers.

The IntraNet web server allows general access to the forecast information throughout TVA. It does not at this time, however, permit access external to TVA. There are currently about 100 hits on the forecast information daily. Access to the general forecast products is being offered as a means to possibly generate interest in more specific forecast information.


Sample Web Displays

Precipitation Forecast - Major Forecast Areas: RSM 60h PRECIPITATION FORECAST, STARTING FROM 6AM CST, ON 19990226 |<----- DAY - 1 ------>|<----- DAY - 2 ----->|<- DAY-3 ->| 6am 12p 6pm 12a 6am 12p 6pm 12a 6am 12p / / / / / / / / / / TOTAL 12p 6pm 12a 6am 12p 6pm 12a 6am 12p 6pm ---|-----------------------|-----------------------|-----------|------- NE 0.00 0.00 0.00 0.00 0.01 0.06 0.47 0.39 0.14 0.04 1.11 ET 0.00 0.00 0.00 0.00 0.01 0.01 0.17 0.24 0.04 0.03 0.49 CN 0.00 0.00 0.00 0.01 0.07 0.23 0.40 0.44 0.03 0.01 1.18 SW 0.00 0.00 0.00 0.07 0.20 0.36 0.41 0.33 0.00 0.00 1.39 NW 0.00 0.00 0.01 0.05 0.61 0.43 0.21 0.01 0.01 0.00 1.33 ---|-----------------------|-----------------------|-----------|------- Note: 1. DAY-1, DAY-2, and DAY-3 refer to today, tomorrow, and day after tomorrow, respectively; 2. Central Standard Time (CST) is used in the table above; 3. Numerical values in each column represent 6-hour accumulation of rainfall in inch; 4. Truncation error may occur in the values of TOTAL.


Precipitation Forecast - Eastern Sub-Basins: RSM 60h QPF FOR 9 SUB-BASINS, STARTING FROM 6AM CST, ON 19990226 |<------ DAY - 1 ------>|<------ DAY - 2 ------>|<- DAY-3 ->| 6am 12p 6pm 12a 6am 12p 6pm 12a 6am 12p / / / / / / / / / / TOTAL 12p 6pm 12a 6am 12p 6pm 12a 6am 12p 6pm ---|-----------------------|-----------------------|-----------|------- Nor 0.00 0.00 0.00 0.00 0.02 0.12 0.71 0.39 0.13 0.05 1.43 Che 0.00 0.00 0.00 0.00 0.00 0.02 0.34 0.39 0.14 0.03 0.94 Dou 0.00 0.00 0.00 0.00 0.00 0.00 0.21 0.19 0.03 0.02 0.45 Lit 0.00 0.00 0.00 0.00 0.01 0.00 0.11 0.23 0.06 0.04 0.44 Oco 0.00 0.00 0.00 0.00 0.01 0.03 0.20 0.27 0.03 0.02 0.56 Ecn 0.00 0.00 0.00 0.01 0.04 0.12 0.35 0.52 0.03 0.02 1.09 Wcn 0.00 0.00 0.00 0.02 0.09 0.45 0.56 0.07 0.03 0.02 1.24 SW 0.00 0.00 0.00 0.07 0.20 0.36 0.41 0.33 0.00 0.00 1.39 NW 0.00 0.00 0.01 0.05 0.61 0.43 0.21 0.01 0.01 0.00 1.33 ---|-----------------------|-----------------------|-----------|------- Note: 1. Nine sub-basins are referred to as: Nor - Norris Che - Cherokee Dou - Douglas Lit - Little Tennessee above Chilhowee Dam Oco - Ocoee#1 and Apalachia Ecn - East Central Wcn - West Central SW - Southwest NW - Northwest; 2. DAY-1, DAY-2, and DAY-3 refer to today, tomorrow, and day after tomorrow, respectively; 3. Central Standard Time (CST) is used; 4. Numerical values in each column represent 6-hour accumulation of rainfall in inch; 5. Truncation error may occur in the values of 60h TOTAL.


Temperature Forecast - Valley Cities: DATE HR BNA CHA MEM TRI TYS HSV 19990225 18 53.1 57.0 61.9 39.0 50.0 57.0 19990225 19 50.3 53.5 57.3 38.1 48.1 52.8 19990225 20 47.8 50.8 54.4 37.2 46.2 50.1 19990225 21 45.5 48.6 52.7 36.2 44.4 48.5 19990225 22 43.4 46.9 51.9 34.9 42.5 47.4 19990225 23 41.4 45.3 51.4 33.3 40.5 46.7 19990225 24 39.5 43.6 50.9 31.2 38.5 45.8 19990226 01 37.7 41.8 49.9 28.6 36.3 44.4 19990226 02 36.1 40.1 48.8 26.0 34.2 42.8 19990226 03 35.1 38.6 47.8 23.6 32.6 41.4 19990226 04 34.7 37.7 47.2 22.0 31.7 40.3 19990226 05 35.2 37.6 47.5 21.5 31.7 40.1 19990226 06 36.8 38.6 48.9 22.6 33.1 40.9 19990226 07 39.6 40.8 51.6 25.7 35.9 43.1 19990226 08 43.3 43.9 55.3 30.1 39.7 46.2 19990226 09 47.4 47.4 59.4 35.1 44.0 49.9 19990226 10 51.5 50.9 63.6 40.3 48.2 53.7 19990226 11 55.1 54.0 67.3 44.7 51.9 57.1 . . . . . . . . . . . . . . . . . . . . . . . . 19990228 17 46.3 49.2 49.6 45.3 47.9 47.8 19990228 18 42.9 45.3 47.5 41.3 43.0 44.9

Pressure and Wind Forecast Graphics (simultaneous 54-hour forecasts):

Note the low-pressure trough and wind-shifts along a line from southern Indiana to northern Alabama.

Pressure Wind


Precipitation Forecast Graphics (24-hour sequence):

Note the progression of precipitation maximums across the TVA Region.

36-Hour Forecast 42-Hour Forecast

48-Hour Forecast 54-Hour Forecast


Temperature Forecast Graphics:

54-Hour Forecast (Instantaneous Snapshot) 66-Hour Time Series


Other Applications In addition to standard weather forecasts, TVA is also evaluating other uses of the RSM. One example is a plume particle model that uses meteorological data based on the results of the RSM. TVA plans to use the results of the plume particle model to assist in airborne plume tracking in a field study during the summer of 1999.

Plume particle model output (selected images from animation):

Hour 6 Hour 11

Hour 16 Hour 21


display of regional spectral model results on an internet...

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