WHY Has This Winter Been A Dud?

IT WAS SUPPOSED TO BE A COLD WINTER. WHAT HAPPENED?

Back in late October when I was assembling the winter forecast, I was becoming convinced that this winter would be different than last. The winter of 2018-2019 was kind of a dud with only one sizable snow event (in January) and one significant cold snap (at the very end of January). The data for this winter suggested that this year certainly had a better chance of at least being “average” and odds were decent of it being colder than average. All these factors suggested cold:

Our “analog” winters were all on the cold side and some significantly so:

So I went out with a cold forecast although I did not advertise cold as zealously as many other winter forecasts. I said “the atmosphere just wants to be warm” and so I hesitate to go “all in” with cold until the atmosphere proves it can produce that kind of winter again.

OUR WARM WINTER: IS THE INDIAN OCEAN TO BLAME?

I try to learn lessons from every forecast bust, whether it be a snow forecast or a seasonal forecast. I have been thinking long and hard about what went wrong this winter and I have a theory.

Stuff that happened in the Indian Ocean, on the total opposite side of the globe, during the fall and early winter created a chain-reaction that doomed the prospect of any sustained cold for the first 2/3 of winter.

Say what? The Indian Ocean? Yep. The atmosphere is extraordinarily complex and nearly everything is connected. We make seasonal forecasts by looking at water temperature patterns across the Pacific Ocean, the Atlantic Ocean, the Arctic Ocean….and I need to look more at the Indian Ocean. Why?

THE IOD (INDIAN OCEAN DIPOLE)

You probably saw lots of news coverage of the devastating heat and wildfires in Australia earlier this winter (summer for them). It was absolutely horrible. Yes there are wildfires in Australia nearly every summer but this year’s were off the charts in terms of coverage and intensity. Why did that happen? Certainly climate change played some role. But a more localized phenomena likely is the main culprit. It’s called the Indian Ocean Dipole. This is basically the Indian Ocean version of the Pacific Ocean’s El Nino/La Nina. When there is colder than average water in the eastern Indian Ocean and warmer than average water in the west, the dipole is said to be in the “positive” phase. Well in 2019 the dipole went crazy…crazy positive. It was the strongest in years, probably decades.

So this extremely positive dipole likely triggered extreme heat and dry weather in Australia. What does that have to do with our winter? Well one of the premises of our winter forecast was that we would essentially be in a “neutral” phase of ENSO, or the El Nino-Southern Oscillation. In other words, not really an El Nino or a La Nina.

This has, in fact, been the case. The waters of the ENSO region of the Pacific have been running warm but not significantly so. Not enough to declare an El Nino.

While there is no El Nino, studies have shown some relationship between the IOD and the ENSO phase in the Pacific. I think the crazy positive IOD has made weather patterns over the Pacific (and then downstream into North America) MUCH more El-Nino-like than would have been the case in the absence of much an anomalous IOD event.

December’s temperatures compared to average:

January:

These maps have a very “moderate to strong El Nino”-ish look to them. Had I constructed the forecast under the premise that we would essentially be operating with a moderate/strong El Nino background state, I would have made a different forecast.

The 2 best analogs probably would have been 2006-2007 and 2004-2005, which give a map that looks like this:

WHAT ABOUT THE REST OF WINTER????

That crazy positive IOD is dead.

October’s water temperature anomalies (when the dipole was most positive):

Compare that to this week:

So the impacts of the crazy IOD spike are waning. I think the lack of “blocking” in the northern Atlantic and the Gulf of Alaska is likely to still be a factor in February, preventing cold from “sticking” for very long in the East. BUT…I do think a volatile pattern is likely with MORE FREQUENT cold hits than earlier in the winter. I also think February will be our snowiest month of this winter. The colder ideas are certainly hinted at by the most recent long range models.

Mid February

Mid/Late February

The latest long-range European model also has a colder look although it also suggests the cold will have a hard time planting it’s flag for extended periods as the ridge over the Southeast persists.

Long range forecasting is hard, and as I have mentioned before, is probably getting harder in a rapidly warming world. But I love the challenge and I love learning things about the atmosphere. The learning will never end.