So, when exactly is it going to warm up a bit?

There is a warming trend on the way, but we have to get through the weekend first. The last time the temperature stayed under 10 degrees during the day in Boston was back in 2005. On Saturday, we may very well do that again with the high temperature approaching 8 degrees in the afternoon. On Sunday morning, the mercury will be well below zero, and, even in the city of Boston, the low temperature should be 5 or more degrees below zero. Sunday will mark the 13th day below freezing, and Monday would mark the 14th. Either way, this streak of freezing temperatures will be one of the longest on record. But this article isn’t about the cold; it’s about the coming warmth.

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First, I don’t want to overstate the warming. We won’t be seeing readings in the 60s, but 40s are almost assuredly going to happen next week. This graph is an average, but it gives you an idea of the trend, and the trend is clearly milder!

Temperatures next Thursday and Friday should get well into the 40s, and 50 degrees won’t be an impossible feat. Knowing the warming trend is coming should help you get through a very cold weekend ahead.

Why the thaw?

The reason for the change is a new jet stream configuration. For much of December, there was a large ridge in the western part of the country that forced the cold Arctic air into the eastern United States. The jet stream is constantly oscillating into new patterns, but what’s really interesting is that a bunch of thunderstorms circulating around the equator are a big reason for the current weather. The movement of these storms is called the Madden Julian Oscillation, or MJO. I spoke with Michael Ventrice, an expert in tropical meteorology, and he confirmed forecasters are currently observing a blooming cluster of storms moving eastward from the Indian Ocean to the Pacific Ocean along the equatorial belt.

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via GIPHY

As these storms develop and move eastward, they are categorized into different phases. What’s really interesting is that different phases of these thunderstorms have a dramatic effect on our weather here, especially in January, February, and March.

The different phases of the MJO can correlate with warmer or colder average temperatures in the United States. A 0.0 significance means the MJO is highly likely to influence the temperature pattern. Higher significance means it’s more random.

These storms are just one factor, so it’s not a one-to-one correlation with our temperatures, but this can be a main driver of our weather. The MJO is now in Phase 4 and will probably move through Phase 5 and 6 in the coming weeks. As these clusters of storms move through their phases, the atmosphere will respond, and, voila, we’ll have a January thaw. Basically, in the new pattern the cold air will be cut off from moving south by a strong flow of milder Pacific air.

via GIPHY

Is winter over after this weekend?

This doesn’t mean the end of winter. As we enter early February and the MJO continues to evolve, there will probably be a reemergence of the high pressure system out west and renewed cold here in the east after the coming break from the Arctic. Of course, that is a long way off, and forecasts that far out are highly speculative. Let’s just enjoy the thaw next week and beyond, and we can worry about more cold when it gets here.