North America “Polar Vortex” Pattern The Next 15 Days

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A large area of much warmer-than-normal ocean water off the North America West Coast persistent since 2013-14 and commonly referred to as the “warm blob” has a tendency to correlate to high pressure in the upper atmosphere across the northeast Pacific sometimes “bridging” northward across Alaska to the polar region. The 15-day upper air forecast by the GFS ensemble indicates this pattern emerges for late October. The upper ridge is compensated for by a downstream deep cold upper trough in central North America (“polar vortex”). In this case Western Canada turns very cold across building snow cover the next 10+ days! East of the polar vortex a southerly flow out of the tropics carries latent heat released from convective clouds (and possibly a significant late season tropical cyclone) into the northern latitudes to cause a high pressure block. The pattern described (and present the next 15 days) driven by the “warm blob” could certainly repeat during winter ahead and disrupt the projected (and expected) mild La Nina winter pattern.