We’re Trapped! (Between Troughs, That Is)

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Yep, we’re trapped between troughs, and it’s the same with most of western North America, and is looking to stay that way for a while. This pattern, also referred to as an “omega block”, is more common later in the storm season when troughs deepen more frequently, and ridges get trapped. An “omega block” is when a ridge gets trapped between two separate troughs.

Graphic depicting what a typical "Omega Block" looks like, and what is expected to dominate our weather for the next week or two.

Graphic depicting what a typical “Omega Block” looks like, and what is expected to dominate our weather for the next week or two.

Most models and their ensembles indicate this pattern sticking around for quite a while, keeping the eastern U.S. somewhat active, while the western U.S. remains dry, and generally pretty warm.

To give you an idea of how long models want to keep this pattern around, below is a GEFS (GFS ensembles) map valid for Sunday this weekend. After you’ve seen that one, take a peak at the following image.

Image courtesy of Tropical Tidbits.

The image below is valid for October 27th, 12 days from now.

Image courtesy of Tropical Tidbits.

Now, while in the second graphic we’re still for the most part dominated by the stuck ridge, it appears the ridge begins to get undercut by some lower latitude storms. That is very far out model/weather wise, and changes are very much possible.

Pacific storm and ridge patterns are like a game of chess. If the ridge moves slightly, it could lead to a larger change in the pattern once lows and troughs begin pushing under or under a given ridge. In this case, it seems likely the ridge will end up being broken down from under, seeing how the ridge pushes up so far north. Also, when rex blocks like this set up, quite a bit of energy can build up in the western Pacific, whether it be in the form of abundant tropical moisture, or large cutoff lows floating around waiting for a pattern change.

Anyway, I don’t think this pattern will last too long into November, if at all. In fact, I think it’s possible we could see a pattern change somewhere between the 29th and November 5th based on passed rex blocks such as this and current model trends. Things can always change, though, so don’t count anything out earlier than that.

Once we do get a pattern change, expect this barren blog to come to life with more activity. The pattern lately has just been too predictably boring.

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