Is there a weather pattern change coming to the USA?

Yes, but I will emphasize the gradual nature of the shift and the fact that no real extremes are on the table. The majestic Sonoran heat ridge is basically gone, so hot air will have less impacts outside of the south central states. 500MB flow is now faster and expansive, which cuts back on chances for meaningful tropical cyclone development or landfalls along the Gulf Coast and Eastern Seaboard. In general, conditions through the lower 48 states will be fairly benign during the next ten days.

But there are alterations in the flow which need to be monitored. The Madden-Julian Oscillation is flaring strongly in Phases 7 and 8, with visible linkage to the polar westerlies. A Kelvin wave complex in the Bay of Bengal and Southeast Asia will give a further “boost” to the MJO in a couple of weeks, which should have the effect of amplifying the three jet stream segments. That means the trough West vs. flat ridge Central/East 500MB configuration will turn into a +PNA ridge alignment, kicking the trough and frontal structures first through the Great Plains and then into the Eastern Seaboard by the middle of October. Strong thunderstorms would be followed by more fall-like cool weather, which might even reach Texas and the Gulf Coast.

However, that is a long way off. In the meantime we stay with cool West vs, warm Central/East in the forecast through at least October 5.

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