The “T”-Rex Block: How is it affecting Kitsap County?

According to the poll I conducted on the right hand side bar, many of your are eager to read about things pertaining directly to the Kitsap Peninsula. That’s not too surprising to find, as this blog is called “Forecasting Kitsap” after all! But I hope you will forgive me for the lack of coverage of weather events within the peninsula lately, as summer tends to yield the same weather over and over again in the Northwest: sunny skies and mild temperatures.

However, as I was reading a forecast discussion provided by the National Weather Service in Idaho Falls (I know, that’s random!), I noticed they used the term “Rex block” in describing our current weather pattern. I must admit, I wasn’t exactly sure what that was, so naturally I looked up the definition on the NWS site. Now, before we talk about the Rex block, let’s discuss what blocking means in meteorology!

First of all, this term can be broken down through a personal example: if you encounter a road block on your way to work due to construction (which probably is hitting home to some of you more than others!) what options are given to you? Usually if the project is wide-scale enough, they’ll provide a detour. Such is the case in weather. Sometimes “road blocks” are set up in the atmosphere and this will usually cause the jet stream to take a detour. Here’s an example:


This is called an “omega block”, primarily because of its shape of the jet stream: Ω. As you can see from the picture, a ridge of high pressure built in the interior west and forced all our would-be active weather up and over our region and sliding it down into the northeast. This is definitely not an uncommon pattern during El Nino years! We get a handful of these “omega” blocks, and…well, my personal bias is…they’re not fun!

So, if you haven’t given up reading by now, let’s take a look at the Rex block, named after the meteorologist who discovered the pattern. I call it the “T”-Rex block for three reasons: 1) it’s stubborn, 2) it can be aggressive (for those on the other end of the block!) and 3) it eventually goes extinct. So, with that horrifying blood-thirsty monster firmly planted in our minds, let’s look at its counterpart in weather:

Very often in a Rex block scenario, an area of high pressure is situated to the very north of an area of low pressure, and air flow tends to move very slowly during this process which can mean the same type of weather for weeks at a time. Take a look at this weather chart that depicts where we are right now:

**Note: Commenter Donna noticed an actual shape of a dinosaur right over the coast! Do you see the curved head and large nose over the Canadian coastline into the Pacific? Thanks, Donna, for pointing that out!**

The area of high pressure (signaled by a small “H” along the coast of western Canada) is directly north of an area of low pressure (situated southwest of LA). This of course is the reason why we’ve been stuck on repeat the past several weeks and the northeast has been so chilly!

And it looks like this block will remain stubborn for at least the next week or so. Aside from areas of morning clouds/fog over the next couple of days, we’ll remain largely pleasant with seasonable highs in the upper 60s/low 70s under partly sunny skies. It also looks like we’re still on for a pattern change within the first few days of October.

So the next time you have to take a detour, just think of good ol’ Rex!

Matthew Leach

Forecasting Kitsap

3 thoughts on “The “T”-Rex Block: How is it affecting Kitsap County?

  1. Matt:

    Thanks for the lesson. Exactly what I was looking for when I took the poll. I was also taken by the vagaries of weather forecasting when you mentioned how a typhoon off Japan would be likely to affect the forecast here.

  2. Don’t laugh, while I was studying the map, looking for the ‘h’, my eyes reorganized and I suddenly saw the T-Rex. “Oh, my Gosh, there is a dinosaur!’ Or a dancing dino?, bird? It was only a minor distraction from your interesting post. But did bring a smile.

  3. Ron: I’m glad you enjoyed it! It’s comforting to know I’m not the only one that thinks things like “Rex blocks” are super awesome and fascinating to study! And it is true, many weather factors from Japan, the Gulf of Alaska and even Hawaii effect our weather here! Amazing to think about how complex Pacific Northwest weather really is.

    Donna: Thanks for pointing that out! How fun! Here I was talking about dinosaurs, and I missed the very thing on a weather map! Good eye :)

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