The weather patterns are continually recurring. When the seasons change the pattern correlation loses continuity. Such as the "beginning of a new pattern", like Lezak and Heady declare each Autumn. This declaration might be attributed to events such as the Indian Summer Monsoon and it's ability to displace energy. As the jet meanders from the pole to the equator and vise versa the recurring pattern traverses different terrain. This friction gives each recurring pattern it's own characteristics. This takes place intraseasonally, but is more apparent seasonally.
Gary and Doug both suggest that the weather patterns are still evolving.
My take is a bit different. Currently I see two waves of weather pattern correlation. One suggests a frequency in the low-mid 50s and another a frequency in the mid-upper 30s. These two waves phase together to show the simple harmonics of the standing wavelengths of correlation. Reference the current system moving into Wisconsin.
GFS 500mb 6
Recurring Rossby Wave Train Frequency
~34 Days Ago
~54 Days Ago
Autumn does not foretell a brand new, completely unique pattern. I put together a similar comparison the other day. It is located here. If there are any questions, comments, or suggestions on the material presented please let me know. Click on the images for a larger view. Thanks for reading!