Recent deluge of rain had all the signs of a late fall classic: mild temperatures, lots of wind and, of course, a deep plume of moisture. Seems we’re not alone in the heavy rain. A “drought denting” flood is heading to California in the next 24 hrs. Deep, tropical moisture is expected to create a firehose of rain aimed directly at the Golden State.

It’s time we learned what’s behind these intense rain events – both here and there. I’m going to introduce you to a new term that may (or may not depending on how social media treats it) get a lot of buzz in the coming days/months. It’s one that you may (or again, may not) want to put up there with Polar Vortex. The term is Atmospheric River. It’s so named by the Earth System Research Laboratory because weather systems in the jetstream literally tap into a river of available moisture deep in the tropics and transport it to the higher latitudes. Quantifying the water vapor content is the main goal, as is alerting the public to potential flooding/flash flooding. At face value, it’s a neat way to explain how/why we get so much rain in these events.

Here are some real-time examples. First, the Left Coast plume:

Note the direct link to the deep tropics there.

Now here’s ours from yesterday.

Yeah, the connection to the tropics isn’t as defined, nor as deep, but we still got 4+ inches of rain out of it, didn’t we? Moreover, look how we just missed a plume that was directed to the North Atlantic. These Atlantic plumes have consequences all the way to Europe.

This is the newest research on the front of extreme weather events. I’ll be dropping the term in my blogs from now on when we talk about heavy rain here in New England.

Now, back to the forecast.

Hope you like clouds. Our ol’ nor’easter is still unwinding above, and it means that although showers will be fewer and fewer through tonight and tomorrow, the clouds will keep the sun at bay. Hope for the weekend though, as this system finally moves away.

Call your attention to the colder temps tonight. After the heavy rain yesterday, the roads have been scrubbed of any road salt/treatment. That means if there’s any leftover water on them tonight, there might be some patchy black ice by morning. This isn’t a widespread threat (hence the reason it’s at the bottom of my blog) and I might be overplaying it, but ANY threat for icy spots is worth mentioning. One thing in our favor tonight: I’m only seeing a few spots near freezing. Many of us will remain in the mid 30s.

Have a good night.


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