CGT’s Composite Temperature Calculation Just Got Better

Thursday, July 03, 2008

Good day, sunny San Jose! California Gas Transmission meteorology personnel keep trained eyes on the weather and they know if it is overcast in Oakland, rain-free in Redding or fair in Fresno. Recently, CGT improved its gas system composite temperature forecasting method by adding an additional weather station data point to the calculation. Extensive testing by CGT indicates that the new composite temperature methodology improves gas demand forecasts.

CGT uses the system composite temperature in addition to other information to estimate gas demand on the system. Demand and supply forecasts are used to create the System Inventory Forecast. When the System Inventory Forecast indicates pipeline inventory is trending toward the upper or lower limit, an Operational Flow Order may be announced. The composite temperature forecast is shown on Pipe Ranger's Current Pipeline Status page on the top line of the daily plan This link will open in a new window.

How It’s Calculated

The PG&E system composite temperature forecast is based on the weighted sum of the average daily temperatures at six sites: Sacramento, San Jose, Oakland, Fresno, Redding and Salinas. An example is shown in the following table.

Weather Site   Average Temperature  Weight  Avg Temp x Weight
 Sacramento  71.3 0.39516  28.2
 San Jose (New)  66.3 0.28400  18.8
 Oakland  63.1 0.17977  11.3
 Fresno  78.9 0.05873  4.6
 Redding  74.2 0.04216  3.1
 Salinas  64.2 0.04018  2.6
 System Composite Temperature      68.6

The revised composite temperature forecast methodology reflects our commitment to continually improve processes and service to our customers. If you have additional questions regarding the system composite temperature, please contact a CGT Account Services Representative.

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