March 05, 2009

Cold, Snow and Double Convergence Zone.

This morning I mentioned there was a double convergence that was obvious in the satellite and radar (see images). Why? Because there was convergence of air streams behind two barriers...the mountains of Vancouver Island and the Olympics.
Take a look at the surface observations this morning (image)--you can see the converging air streams behind both barriers in the winds.

The air was cold enough today that where there was substantial precipitation intensity, snow was able to reach the elevations down to a few hundred feet. And the mountains were hammered with a foot.

Better get used to it...more probably on the way.

Tomorrow will be splendid...sunny and dry...but things change on Saturday morning when a cold front moves through, with very cold air behind. There could be some rain and snow showers after frontal passage..but I suspect the real fun will be later on Saturday and on Sunday morning when another convergence zone sets up. So don't be surprised to see some light snow somewhere over the Puget Sound lowlands. And the mountains will get plenty more.


  1. Knowing that CZ`s can be tricky, maybe with the CZ, we might see moderate or maybe even heavy snow? We just don`t know until it happens.

    Interestingly enough, the 00zWRF shows the CZ for early Sat morning and then possible re-development for Sat afternoon. We all will see how this plays out.

  2. Saturday will be much more "splendid" than tomorrow! Being on the cool, cloudy, comfortable conditions!!

    Cliff, has there ever been a study done on what percentage of meteorologists like weather?

  3. Letshavefun1536...

    It seems to be you much prefer cloudy days over sunny days. Is this really so, and if it is, then why?

    I much prefer partly to mostly sunny warm days over cloudy, gloomy ones.

  4. Well, Andy, cloudy days aren't gloomy.

    When it's sunny, the sun makes it too warm (and much too hot in the summer). It makes me uncomfortable. It's too bright for me; I am quite sensitive to light.

    Anything over 50 degrees or so (unless it's cloudy), and I get uncomfortable. A nice cloudy day with no rain and a breeze, and around 50 degrees is perfect (but I wouldn't mind it colder with snow!). I am so much more comfortable with that. To feel the refreshing cool breeze on my skin, to be able to see and not have to close or cover my eyes when I'm walking around... it's just so much more comfortable to me.

    I also like weather; when it's sunny there aren't even clouds to look at. It's pretty boring. I studied meteorology.

    I grew up in the Midwest, not here in the Northwest. I'm not use to long months on end of sun; we have thunderstorms to break it up and make things exciting. I used to run every day, and I had my best runs when it was cool in rain and/or snow. When it was sunny, no matter how much water I had, I couldn't run; I'd nearly pass out. I've tried playing tennis in the sun and heat, and I've passed out even with lots of water. My body can't handle it.

    There are other reasons too, but I'll start with that.

  5. fun 1536

    go live in Alaska in the winter.
    go live in New Zealand in our summer.

    Being from the midwest you are probably miss the heat index which for the most part is worse. You must also of like running in 70deg heat with 80% humidity. There isn't much of a high heat index here just once in a while. By the way, in the summer you need that sun to get the "refreshing" sea breeze. We been down this road before, haven't we?

  6. Everyone is different, but I just don`t see how someone can enjoy 50 degree weather with total sky covered in clouds and no sunshine. For most, that is long pants, t-shirt and possibly a light jacket. I like interesting weather as well. But I would much rather see sunshine and warmth than a bland 50 degree cloudy day. Just my take on it. :o)

  7. I think it's really sad how you can't accept how people feel. You can't even try to understand. You don't care and are quite inconsiderate. This is particularly for you, Josh-B.

    Ironically, the humidity makes it feel a little better in the Midwest in the summer than here. For one, they have this thing called air conditioning that they've seem to have never heard of here. Secondly, the humidity in the air actually creates haze, which blocks out some of the worst of the sun there in the summer. You don't get there here; instead you just get a blazing hot sun.

  8. Everyone will have their own subjective views of the weather (the state of the atmosphere).

    Since we all create those opinions from personal views, experiences, prejudices, etc. we rarely will reach a broad consensus of those subjective terms. It is just as futile to argue whether pizza or spinach salad is the best tasting food. I don't believe arguing those types of views is constructive as it will always lead to subjectively "un-defense-able" arguments.

    Granted subjective terms will creep into most people's comments but arguing those "definitions" is pointless as they can never be proven correct or incorrect. How about observing people's subjective views or even ignoring them if you disagree. Focus on content that can be objectively analyzed... model forecasts, instrumental observations, user forecasts... as those have quantifiable values that can be discussed/argued over logically.

  9. Well, I'm not sure if LetsHaveFun is serious. However, I'll tell you that at least two groups of people prefer clouds and rain:

    1. Migraine sufferers
    2. Allergy sufferers.

    I've had migraine disease all my life and I'm now to the point where light means pain, just about all the time -- whether I have a migraine or not. This is a progression that neuro diseases like migraines just sometimes take. Cloudy days are such a relief.

    My husband is a severe allergy sufferer (yes he's had allergy shots, etc, but some people just have freakish immune systems). He literally can't go outside right now unless it's raining. If he does, he'll suffer for at least an hour.

    So we aren't all the same. The whole notion that "you're so wierd because you don't like "X" is just wrong on it's face. One of my favorite sayings is "Normal is just a setting on the washing machine". I think it was Wynona Judd who said that, not that I'm a fan of Wynona Judd, but definitely of that saying.

  10. I'll be glad when we have a string of sunny days again. This off and on snow is lingering around like a bad cold.

  11. Teresa, Thanks for the post. Yes, I am serious, actually. I don't get migraines or allergies to the extent you or your husband do, but I do get them occasionally as well.

    I'm glad I'm not alone.

  12. futile this is.

    What about the allergy sufferers who have a hard time with mold. Cool and rainy weather is not so good for that. We can go round and round with this. are funny. That's all from me.

  13. Teresa - you might find this interesting, re: migraines. Sorry folks, it's not about weather. I couldn't find a way to forward this to you directly Teresa:

  14. Josh-B.

    If you were to read my post, I said that we're all different, our preferences are different, than "normal is a cyle on the washing machine."

    I guess I should have said "pollen allergy sufferers". About the only thing my husband isn't allergic to is mold. However, warm weather does encourage mold growth, so if you have a rain followed by warm weather, shady areas are much more likely to bloom molds.

    I have zero interest in arguing, though. I really think we're on the same page. We're all different, have different weather preferences, for different reasons. Some of us actually have health-related weather preferences. I'm sure many people prefer sunlight for health reasons.

    Jessica: I've read about that. Thankfully, I have common migraine (without aura) so I'm probably less affected. To turn this in a weather-related direction, one other point, I've made before is that about ~47% of migraineurs can predict weather changes by the effects the barometric pressure change or possibly humidity change (or something else) has on their head pain.

  15. NWS just posted a Winter Weather Advisory for where I live. Good sign that they are serious about this snow, if you didn't believe it already. Calling for 2-5" for the east puget sound lowlands. But they mentioned it could be more, depending on the convergence zone. Lets hope it really gets going!

  16. Speaking of`s not just due to "light sensitive" people. Small/big head aches as we know, can be caused by high and low pressure systems, specifically strong ones. So weather does have an affect on us all.

    But if I had to take a wild guess, I would say most folks in general prefer sunny/partly sunny days over cloudy/rainy days. I like sunshine and that is a good thing!

  17. That is an awesome example of a double convergence zone! It made me wonder whether there are regions on SE Vancouver Island that are in the rain shadow of Vancouver Island mountains and thus have a similar climate to Sequim, WA. So, I looked up some numbers:

    Annual rainfall
    Forks = 121" Sequim = 16"
    Tofino = 127" Nanaimo = 41"

    Not really as marked of a difference for the example I chose, but maybe there are areas other than Nanaimo which have less than 20 inches of rainfall related to a Vancouver Island mountain rainshadow.

  18. Gator,

    I see that Victoria (a favorite family destination spot) averages 24" annually and just 80km away Port Renfrew gest 145".

  19. olyroller,
    I wonder how much of Victoria's rainshadow effect is due to Olympic Mtns versus Vancouver Island Mtns.

    If Victoria's rainshadow is mostly due to the Olympics, maybe we could put a tariff on the dry weather they're receiving, eh?


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