An “amplified” upper air pattern means what, exactly?

You may recall (or, most likely, how could you forget?) that the past summer was dominated by the Sonoran heat ridge. That kept the southwest and south central states in near-constant searing heat, which of course in Texas lingered for most of September. The jet stream was semizonal and hovered along and above the border with Canada.

Typically that flow aloft starts to show more turns, bends, and segmentation as we move through the fall. This being an El Nino year, you might think and outright split would occur, with the northern branch staying across Arctic Canada and the subtropical jet stream taking storms and small pockets of cold air on a path from California to Texas and into the Southeast.

But you know what? So far that “typical” configuration for a defined +ENSO signature is -not- happening. Usually there are some signs of the alignment in October. Instead, the 500MB depiction is still uniform. Stronger ridges and troughs are appearing. There is even a fair chance that a trough complex in the West will scoop out a tropical disturbance or cyclone from the eastern equatorial Pacific Ocean. That could translate to a significant precipitation event in Texas, the Deep South, and Eastern Seaboard from October 10-14. More importantly, cooler air will be drawn southward, much like what the ECMWF and GGEM panels are hinting at east of the Continental Divide in the second half of October.

Before then, look out for a severe weather and heavy rain event in Oklahoma, Texas and Arkansas during the next 48 hours.

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