MAP KEY: G/WX Maps contain the following information (see Symbol Key, Sample Maps, and Sample Verification Maps for examples):
- The Map Period Date is located on the upper left corner.
- The Map Generation Date is located the lower left corner.
The circles represent Percent Probability of High Atmospheric Pressure (+); from 50% (smallest circle) to 100% (largest circle). Areas of High Pressure are colored in shades of red/yellow.
The rectangles represent Percent Probability of Low Atmospheric Pressure (-); from 50% (smallest rectangle) to 100% (largest rectangle). Areas of Low Pressure are colored shades of blue.
The dark blue line indicates the approximate path of the Polar Jet Stream according to the G/WX model, and the green line indicates an approximate path of the Sub-tropical Jet Stream according to the model. These jet stream lines represent the Long-Wave pattern in the Northern Hemisphere, which is the ‘Big Weather Picture,’ technically known as the Synoptic Scale Pattern.
The G/WX Maps cannot show Short-Wave impulses embedded in the Long-Wave pattern. These disturbances can generate significant short-term local weather. Therefore, it is important to pay attention to the ‘Verification Guidelines’ at the end of this section.
Expect the G/WX Long-Wave pattern to be the primary feature during any two or three-day Map Period, and the occasional 4–day Map Period.