Tuesday, February 2, 2016

Weather Geekitude and the Return of Winter

Well folks, after the spring like weather that we've been enjoying here in the Mile High City for the past few weeks, winter has returned in dramatic fashion.


The weather forecasters told us that Saturday would be the last warm day, so CatMan and I decided to go for a bike ride.

The thermometer at my house read a balmy 72 degrees (22C) when I left my house at around a quarter to 2 in the afternoon. The storm was supposed to arrive later that afternoon, so I was in a bit of a quandary as to which clothes to wear.

I thought about wearing my knickers... that would be these knickers...


... as opposed to these knickers...


But ultimately I decided to err on the side of more clothes rather than less, and I went for my full length insulated tights, with an insulated turtleneck and my warm bike jacket.


I was a little bit too warm at first, and felt a bit overdressed, as the paths were full of people dressed like this:


But about 15 miles out, the winds shifted, and the warm westerly wind suddenly became a bitterly cold northerly one. Holy Moly! It was like the temperature dropped by 20 degrees over the course of about 10 minutes!

So. This might be a good time to put on my weather geek wannabe hat and explain about the winds here in Denver. Denver sits on a high plain, just to the east of the Rocky Mountains. This geography creates a unique weather pattern for us known as the Chinook wind.


It basically works the same way as a heat pump or air conditioner does. When air is compressed, it warms up, and when it decompresses, it cools down. Have you ever felt the air coming out of a tire or an aerosol can? It's cold because it is decompressing... well, the opposite happens when the air pushes down off of the mountains. So upslope winds are cold and wet, and downslope winds are warm and dry - and this is one of the reasons that Denver has such a wonderful climate in the winter time.

Quite often - like the past few weeks - we'll have storms dropping snow by the feet in the mountains, but the temperatures here in town are almost spring-like. But... when conditions are right, the storm will push over the mountains and we'll get dramatic temperature shifts like we did on Saturday, when the westerly winds get cut off, and replaced by a wind blowing in from the north.


Anyhow, by the time I got home on Saturday just a few minutes after 5pm, my thermometer read 39 degrees (4C). Brrrr! My fingers (even with two pairs of gloves on) were so cold that I almost couldn't get my helmet off! I was pretty darned glad I'd opted for the warmer clothes because I would have been an ice cube if I'd been wearing fewer layers!

We had light snow off and on all day Sunday and Monday, but the big snow maker arrived last night.

Ready for more weather geekitude?

So, there are several ingredients required for us to get a really big storm here in Denver. If you look at the Chinook graphic above, you see that when the wind blows up against the mountains (which is called an upslope) it cools, and it leads to precipitation. So winds coming from the east are one ingredient, and the way we get those is when a low pressure system with it's counter-clockwise flow sets up to the south and east of us.

The second ingredient is moist air - generally this is moist air coming up from the gulf of Mexico. And finally, the position of the jet stream has to be right, with us sitting in a big trough, allowing cold air to come down from the north.

This graphic illustrates the phenomenon pretty well:


Here's another one from a different storm, but the same idea.


Anyhow, that's what happened last night, and I woke up to nearly a foot of fresh snow this morning!

Oh well... it was a nice little respite from winter, and I got in three good rides before the snow came back. I did get some good exercise shoveling though!

Well, at any rate. Happy Groundhog Day! At least Punxutawney Phil didn't see his shadow, and that's supposed to mean an early spring. Not holding my breath on that one, since I think his track record is around 40%, but hopefully, he's better at predicting the outcome of football games!


So tell me, how's the weather in your neck of the woods? Does the geography in your area create any unique weather patterns? Geeky minds want to know!



30 comments :

  1. The frilly knickers made me laugh! Although I would call modern ladies' underwear knickers too... (Or maybe pants, but that is more for man-underwear!)

    Anyway, I enjoyed learning about your weather- the weather graphics are so brightly coloured!
    Here is a what our TV weather maps look like: http://www.chroniclelive.co.uk/news/north-east-news/north-east-weather-wintry-mix-8913026
    Though usually with someone pointing and explaining: http://www.express.co.uk/celebrity-news/575229/Carol-Kirkwood-blue-dress-BBC-weather please excuse the awful 'look, woman wearing clothes' nature of the article. She's a meteorologist! She knows many interesting and complex things about weather! Her clothes are much less interesting than that!

    Anyway... I don't think our weather patterns are particularly exciting... I live in East Anglia (under where it says 'Norwich' on the weather map at the top of the first article) and we are the driest part of the U.K. (And probably the least stormy) as generally our weather comes from the Atlantic in the west. So most of the rain all falls on Ireland Cornwall/Wales/the Lake District/west coast of Scotland and we get the leftovers. It is still pretty damp here, but less so than the west.
    We do sometimes get a cold North wind from Scandinavia, which brings cold weather and migrating birds!

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    1. Huh. Her dress would be "normal" around here and wouldn't invite a lot of comments. About a year ago, I saw a feature on the news--a male newscaster wore the same suit every day for an entire year and no one noticed. (he had it cleaned periodically!). He did it to make a point about how people focus on female newscaster's style choices but don't even really see the men.

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    2. Ha! "Look, woman wearing clothes!" Oh my! It does seem that your weather forecasts are much more subdued than ours. We generally get at least half a dozen different graphics in each one - all with different wild colors and other attention grabbing stuff - like a choreographed special effects bonanza. Perhaps that's what's required with the American psyche! Here's one local station's forecast pages - I think the actual video changes every few hours though:
      http://www.thedenverchannel.com/weather/forecast-parent/forecast/denver-weather-forecast-and-colorado-forecast

      I'm betting that your weather is much more temperate than ours, especially being so close to the ocean. But it sounds like the land to the west of you provides some of the same cover that our mountains do for us - ie: absorbing the worst of it all before it gets to you!

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  2. :)) We just had the third storm in a week, we do not seem to get out from under those "yellow weather warnings" any more...I live in the central belt of Scotland though - whoever heard of rain, wind and snow on an island in the Atlantic in winter??? They just like the made up "drama" of it all. Oh, there are areas that were flooded for the fourth time this winter, but they flood traditionally and the fact they are building houses on floodplains down south doesn't help. Why are they called "floodplains"? Doh! ♥nic

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    1. Sorta hard to have sympathy for folks dealing with flooding if they've built in a floodplain! But I can't imagine the amount of rain y'all seem to get! We've had a few uncharacteristically wet seasons in recent years, and it just about drove me batty! I'm very spoiled with Denver's sunny weather (300+ days a year of sunshine!)

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  3. With heavy rains and melting snow we are under a flood advisory today. The same system that cause tornadoes in the south yesterday is here today. We can expect some thunderstorms, but I haven't heard anything about tornadoes.

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    1. I think that's the same system that brought us the snow. I've gotta say, thunderstorms in February sounds just wrong to me! Thunderstorms in July are normal, but in February?!? Is that normal for you?

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    2. No, it's not normal. But even more unusual was the thunder and lightning we had with a snow storm a few weeks ago.

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    3. Wow! Thunder snow... we occasionally get that out on our eastern plains, but I'm not sure I've ever witnessed it personally.

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  4. Ooh, you did a weathergeek post just for me, didn't you? It's fascinating, but I admit my brain doesn't naturally work that way, so I have to think about what you said. It seems for you that having a mountain range to the west of you makes your weather highly variable--for us, it's having a great lake. Colder air over a (relatively) warmer lake sets off all sorts of interesting weather for us--lake effect snow and rain--our average annual snowfall is 93.7 inches (compared to 47.4 inches in the area of Michigan where I grew up). The most we've had since I've lived here was 144 inches. We tend to get a lot of fog, especially in the spring with the warmer air coming over the cooler lake (and the snowpack on the ground adds to it). I'm not a fan of fog ... anyway, the slightest shift of wind over the lake can dramatically change our forecast. We woke up one Sunday morning with an unexpected 12 inches of snow--we drove 10 miles to church, where they had about 2 inches. We happened to be in a tiny bullseye that got hit with a lot of snow--most of it stayed over the lake.

    While I envy your occasional bouts of springlike weather, I think it might make me go crazy--I find it hard enough to dress myself and my kids with our up and down temperatures--your variance is much more dramatic than ours!

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    1. Ha! Yes, you inspired me to do the weather geek stuff - I figured if you thought it was interesting, perhaps there was some chance I wasn't the only crazy person who likes this stuff!

      Lake effect snow sounds just crazy... I can't even imagine the crazy amounts of snow that I've seen reported. Do you have special building codes so that buildings don't collapse?

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    2. We don't get THAT much snow, typically--a foot at a time, each day, isn't unusual, but you can deal with that with a roof rake. It varies winter to winter. So far, it hasn't been a terribly snowy winter. Often we get mild weather (it's been in the 40s with rain--we also got thunder yesterday) which will melt off some of the snow. Buffalo, NY, on the far end of Lake Erie, really gets walloped. Lois did a good job of describing it. What I find more difficult is dealing with road conditions--snow blowing across the road, especially when temps are in the teens or single digits, ices the roads and makes them treacherous. It's easier to drive through mounds of snow than it is to drive in icy conditions.

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    3. I totally agree about driving in snow vs. ice. Surprisingly, winter road conditions in Norway were generally pretty good because with the lack of sunshine you don't get any melting & re-freezing.

      I had to go look for images of a roof rake - I haven't seen those before. The few times I've been concerned about the roof (well, the patio roof when we got 3 feet of snow) the drifts were so high that I could basically walk all the way up to roof level! I just used a regular sidewalk broom.

      And I think the pictures I've seen were from Buffalo... things like people opening their front doors to reveal a solid wall of snow. OY!

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  5. Good thinking on your part, what a drop in temperatures over such a short time. We don't have any fancy words to describe our weather here, but a bit further north along Lake Erie we have "Lake Effect" to describe the storms that come across the great lakes from Canada bringing cold weather and picking up moisture from the lake that a few miles inland will drop astounding amounts of snow.

    I've got my fingers crossed for your Broncos on Sunday. Good luck.

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    1. I'll bet you're glad not to have to deal with that kind of snow any more!

      So what's up with your blog? I keep trying to get there, but I get some sort of message that you've been hacked! Hope everything is OK. If you're gonna move, please let me know your new blog address.

      I keep wavering back and forth about the Superbowl. Some days I'm just sure we're gonna get plastered, but others I think we've got a real good chance. I mean, Carolina looked pretty much unstoppable - but then again, I didn't think anybody could beat Kansas City either, and New England obliterated them - then we beat New England. Anyhow, fingers crossed...

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    2. I was wondering the same thing about your blog, Lois. Hope you are able to get everything straightened out. Let us know where you are.

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    3. Yep, I was hacked. Turns out the security programs doen't protect or repair when hacked. You should have seen the password I had it was so long and random I really thought that with it and the security stuff I was safe. Anyway, everything is gone for good. After spending a few days thinking I was done and deleting a bunch of photos I had read to use I changed my mind and started a new blog. I'm technologically challenged so I guess I just learned I'm not supposed to have a self-hosted blog and went back to wordpress. You can find me at http://livingindenim.wordpress.com

      Anyway about the Superbowl, I'm looking forward to it. I don't have any real attachment to either team, although I think Peyton should really consider retirement before he is permanently injured and it would be nice for him to get a ring first I just hope it's not a blow out either way. Of course I'm super excited not to have to watch another Patriot game. :-)

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    4. Yup... I'm really hoping that we all get to watch Peyton ride off into the sunset with a Superbowl victory.

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  6. It's clear, sunny, warm, and gorgeous. But with very strong winds, so I still feel cold!

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    1. Ha! Well, the sun came out today, but it's still down in the 20's so my fingers got cold when I went out to finish up the shoveling that I didn't get to yesterday. I'm betting you wouldn't like winters here!

      So do you ever get severe weather in Austin, or is it just beautiful all the time?

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    2. Our severe weather mostly happens in the summer. We can go many weeks with the low temperature never dropping below 80. Our average high temperature in the summer is at least 95, 99 in August. So we often have long streaks of high temperatures above 100 degrees. Our humidity is between that of Phoenix (around zero) and Houston (around 100%)--and humidity makes heat feel worse. I'm from Houston, so the humidity feels good to me!

      We also get flash floods, hail, and tornadoes. And we have a lot of allergens, as well, which one could describe as severe interior whether for those who are allergic (not me yet!).

      We usually have one icy day per year (freezing rain) and one snowy day every few years--they shut down the schools and some businesses for these, which makes our nasty cold days awesome. (Not so much now that I'm retired, but back in the day....)

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    3. OY! I think I'd rather deal with blizzards than that kind of heat and humidity. But I think it's the allergy issue that would be the real deal killer for me.

      I have such a hard time picturing the environment in Texas. The only part of it I've seen is Midland, and for your sake I'm really hoping the rest is different!

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    4. I've only seen the intersection of Midland they show in "True Stories" (their one traffic light--back in the 1980s).

      Texas includes beaches, (small) mountains, rivers, deserts, forests, and probably other stuff I'm forgetting. My part has plants although many are brownish and our trees do not get very big, though they can provide shade. We have lots of wildflowers (as does Colorado), so I really love it here. And I do think scrub and gnarly trunks are cool, and we have some of that here, too. Also, I don't have allergies (yet).

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    5. My mother actually owned a time share on a beach near Galveston - you don't know anybody who would want one do you... we'd sell it real cheap, like will someone please take this thing off of our hands kind of cheap. I sort of imagine Texas to be a whole little country of sorts.

      Anyhow, I was in Midland for a wedding in the early '90's and it was really weird. It was after the last oil crash and the place was like a ghost town. The couple getting married had bought a fancy new house in a new housing development... but the developer had basically pulled out half way through building the area. So there were a few completed houses, but the rest were cul-du-sacs with empty lots and even some with frames that were just abandoned. It was just sorta creepy...

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  7. I was interested to read about the Chinook - we have the same kind of foehn wind phenomenon in my part of NZ, and the temperature can indeed plummet quickly when the wind changes. Your spring will come! Best wishes. - Valerie

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    1. OK... I had to go look up "foehn wind" and it does look like it's the same phenomenon. Are you on the north or south island? I spent a week or so in NZ when I was a kid and I thought it was a beautiful country.

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  8. I just wanted to stop by and be the first to congratulate you on the Bronco win! Hope you are celebrating and having fun tonight.

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    1. Awwww thanks. I was soooo nervous through that whole game. Seriously, my fingers and toes were like little blocks of ice because my hands and feet break out into a cold sweat when I'm nervous or scared. I still wish they'd let Peyton throw the ball more, but at least he got that 2 point conversion.

      But I'm very happy for my boys. They fought through a lot this season, and it was so nice to see them come out on top.

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    2. Did you see the shot of Peyton's family in the box at the end of the game where Eli had a completely blank facial expression? That's been the big story here so it was fun to watch this and get Peyton's take on Eli. Peyton does have quite a sense of humor :-)

      https://youtu.be/NlLEReokX14

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    3. OMG. That clip is hilarious! Seriously though, I think I totally had the Eli face goin' after that touchdown because I was thinking "Oh no... did he get in? Was his knee down? What if they overturn it? And now we've gotta go for two... what play are they gonna call?

      The problem with a defensive struggle is that at any point, one tiny mistake can mean a huge play and a touchdown for the other team, so I literally felt like I couldn't let my guard down the entire game!

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