HOW G/WX WORKS
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 of the G/WX map.
· The Map Generation Date is located the lower left corner of the G/WX map.
The circles represent Percent Probability of High Atmospheric Pressure (+); from 50% (smallest circle) to 100% (largest circle). Areas of High Pressure are typically warm to hot, and 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 draw in cool to cold arctic source air, and are colored in shades of blue.
The dark blue line indicates the approximate path of the Polar Jet Stream, and the green line indicates the approximate path of the Sub-tropical Jet Stream. These jet stream lines represent the likely path of storm systems and temperature variance distribution. They represent the Long-Wave Pattern in the Northern Hemisphere, which is the ‘Big Weather Picture,’ technically known as the Synoptic Scale Pattern.
Expect the G/WX Long-Wave pattern to be the primary feature during any Map Period. The G/WX forecast Long-Wave Pattern often does not fully mature until the last day of the period, as some of the samples below indicate.
If desired, further understanding of how the Synoptic Scale affects your weather may be obtained by accessing weather tutorials such as this page from the National Weather Service: https://www.weather.gov/jetstream/basic.
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.
Below are some historical examples of G/WX maps, paired with NOAA or COLA real-time analyses for verification.
The Daily Weather Map (DWM) samples next to the sample North America G/WX Maps is the recommended source for North America. The 540mb line (5400meters) is the approximate polar jet core line, and the 570mb line (5700meters) is the approximate effective extent of the polar jet. These lines can be ‘highlighted’ to give definition to the polar jet stream pattern. The polar jet stream ‘rides’ at a higher altitude, but its effect is mirrored in the lower atmosphere.
Also, a good verification source is the 700mb map for this NOAA site (prior dated maps are also available on this site). The 309mb (309meters) line is the approximate polar jet stream line, which can be ‘highlighted’ to give definition to the jet stream pattern.
Another excellent source is Cola Iges:
Cola also provides maps for Europe and Asia.
Additional source for regions in the Northern Hemisphere is this website:
G/WX can provide no guarantees. This unusual weather research project is now over 30 years old and on-going. The average accuracy of the maps over this period has been around 70%.
The recommended way to work with the G/WX Maps is to follow these steps:
- If the G/WX Map Period is more than a month away, check the NWS “Seasonal Color Maps” http://www.cpc.ncep.noaa.gov/products/predictions//multi_season/13_seasonal_outlooks/color/churchill.php
- As the Map Date nears check NWS “8 – 14 Day Outlook” https://www.cpc.ncep.noaa.gov/products/predictions/814day/
- For the best ‘read’ on the near-current weather Cola Iges is recommended: http://wxmaps.org/pix/clim.html
If the above NWS outlooks and forecasts track with the G/WX Maps, then one can assume the G/WX Maps will prove out. If the NWS 8 – 14 Day Outlook is diverging from the G/WX Map, then the NWS is likely to be correct. If the Cola maps diverge from the G/WX Maps, then Cola and the NWS must be considered correct.
G/WX Maps provide probable atmospheric pressure predictions. The G/WX Maps have had long runs of proving correct, with one map or a series of maps coming up incorrect. Therefore, verification is highly recommended. No refunds after purchase of G/WX Maps.