Thursday, February 2, 2017

No Big Snowstorm Next Monday Because Jet Streams Don't Play Nice Together

Here's a schematic map for this coming Monday.
You see one small storm over southern Quebec, thanks
to one northern stream dip centered over New York.
The southern stream trough is further east off the coast
prompting another small storm off the North Carolina
coast. Had the two jet streams dips lined up perfectly
there could well have been a big nor'easter instead
of two wimpy little storms.
Thanks go to Dave Epstein for this illustration. 
Some of you might have heard rumors that there might be a nifty nor'easter snowstorm next Monday.

Bad news for snow lovers: Ain't happening. unless there's some kind of miracle.

This all involves two jet streams and whether they play nice together. On Monday, the jet streams won't be models of playground etiquette, so therefore, no big storm.

The jet stream is the river of fast moving upper level air that controls where storms go and how intense they might be.

Very often in the winter there are two jet streams, one going across the southern tier of the United States, another one zipping along or near the Canadian border.

Jet streams usually have bulges, called ridges, that curve to the north and dips, called troughs, that curve southward.

If you're looking at a map that shows the jet streams, you'll usually find some sort of storm system just to the right of where the dip reaches its southernmost point.

When there's the north and south jet stream, there's often fairly small storms accompanying little dips in both the north and south, each with a packet of mostly light precipitation.

Every once in awhile, the north and south jet streams cooperated. They set up troughs, those dips in exactly the same longitude or right above or below each other.

This creates one big dip. This is a bit oversimplified but when this happens, instead of getting two little storms you get one big one.  Often in the winter, when the southern and northern jet streams cooperate and form a big trough over the eastern United States, you get a nice big fat nor'easter.

Earlier this week, some of the computer models were hinting the two jet streams would play nice with each other and coordinate to form that one big trough by Monday.

But in the interim, there must have been some sort of playground spat. It looks like one small trough in the jet stream will cause a small storm to maybe drop a couple, few inches of snow on Vermont.

Meanwhile, another little trough in the southern jet stream won't quite line up with the northern one. That means  another weak storm that will zip off the coast of the Carolinas and not amount to much until it's over the open Atlantic, much too far away to affect us.

After that, there's some suggestion that there might be another opportunity for the north and south jet streams to interact and create a pretty good sized storm about a week from now. Early indications are that larger storm would go by to our west, which would encourage mixed precipitation.

But that's still really, really iffy, and we don't know what kind of storm, if any, will develop out of that.

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