What is the delta-P charting option (Columbia Basin sites)?
This option plots differential pressures between four sites: Portland, TheDalles, Roosevelt, and Richland. The differentials are defined in the chart legend. For example, the trace named “Portland – The Dalles” is calculated as the pressure difference between Portland and TheDalles (using sea-level corrected pressures). Pressure differentials can be useful in predicting wind at Roosevelt WA. Pressure gradients often move from west to east so a good differential between Portland and The Dalles can be a good indicator of wind to come at Rosy. Differentials over about 0.05 inches Hg generally indicate sailable wind.
