Autumn and winter forecast progression with an El Nino.

It is too early to make a definitive call on expected weather for the DJF semester. But I am noticing some trends which may help make the “cold season” outcome a bit clearer. With the moderate +ENSO signal being stable (all of the nonsense about a “Super” event must have run into some kryptonite…), the abundance of stronger westerlies in the Northern Hemisphere has largely protected North America from tropical cyclones. Now we are seeing slow suppression of the heat ridges. This does not mean that it will not be warm this fall, but rather the chances for outstanding/record heat will become much more limited.

The gradual drop in the jet stream axes through the middle and lower latitudes of the USA should favor more thunderstorms during the next 4 to 6 weeks. If flat ridging takes over southern Canada as expected, the northern tier of the lower 48 states will turn mild and dry. But since the development of high-amplitude (or blocking) type of ridging is unlikely, risks for a definitive cold snap are unlikely.

Please note, however that the Madden-Julian Oscillation is quite active, albeit incoherent, straddling the entire Phase range of 1 – 8 (Indian and Pacific Oceans). Water temperatures are cooling in ENSO sector 1.2 (Galapagos Islands), while warming in sectors 4 through 3. It may take a while, but I am leaning toward the later evolution of a Modoki El Nino. If so, the winter that starts out in the U.S. as being benign turns amplified and active once we get past the start of 2024.

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