Tuesday 6 August 2013

Tradition

     A cold front brought showers to southern Manitoba overnight. However, as usual rainfall skirted past Winnipeg the entire night with just 0.5 mm in South St Vital and *0.8 mm* in Charleswood. Here's a radar estimated rainfall accumulation map along with actual rainfall accumulations since yesterday evening:



     Starbuck, a short distance to the west, received 10.5 mm according to Manitoba Agriculture, all thanks to a small line of downpours last night. Note that showers are still falling east of Morden and Steinbach southwards.

     Hopefully you enjored the nice mid twenty temperatures yesterday. We might not even reach 20°C today, especially if we stay cloudy most of the day.

20 comments:

  1. Answer to the rainfall poll: 0.4 mm
    There are no winners, with only 2 respondents.

    ReplyDelete
    Replies
    1. Damn it all, I voted 20+ MM for fun!

      Delete
  2. Not so sure about that 28C forecast for Sunday. Although I do think temps may finally return to seasonal over the weekend, at least I hope so, I'm not sure it will be that warm Sunday.

    ReplyDelete
    Replies
    1. It does look warmer, I agree. Anything will be nicer than what we're seeing this week... but it sure doesn't look like the nice dog days of summer some of us are missing.

      Delete
  3. Cloud cover was a saving grace overnight and only allowed our temperatures to drop to 10°C. We'll see if we can as lucky tonight... models have us clearing but then again most were showing the same thing last night and it remained cloudy all night...

    ReplyDelete
  4. Still looking warmer for this weekend and into next week, but upper twenties, i'd say not likely at this point. Yes the vortex finally moves away this weekend but there is no real surge of warmth coming in, in behind it so I would say mid twenties is more likely and more conservative but we will certainly even take that compared to the rubbish weather we've seen in the last 3 weeks.

    ReplyDelete
  5. Hey JJ. Fantastic blog! I was just reading through some of your earlier posts this year and how Winnipeg has seemingly missed out on storms every single set-up. Well, I'll let you know that Altona has had a fantastic summer. A few good elevated events and a really nice supercell back on July 18th early in the evening. Can't say I'm complaining ;)

    Looks like we're finally getting back to more summer-like weather. Upper low by Hudson Bay will finally move east and allow western ridging to build further east. Storm wise, it doesn't look like much to get excited about through the middle of next week. Long range models do hint at a more active pattern developing late next week. Too far away to get excited, though.

    ReplyDelete
    Replies
    1. Hiya Derek, glad you like it =)

      No kidding, Winnipeg has missed out a lot for the 3rd straight year. I'm glad I got to do some chasing to make this year at least moderately OK.

      Nice to see that warmer weather in the long range... Don't see any big storm events until later next week neither. Still got lots of time for a few more storms before the season's over...

      Delete
  6. Well here's a positive spin on this cool down: it sure didn't turn out as bad as expected! (Not that I'm complaining ;) )

    Lots of sun in the day and cloud and higher dewpoints in the night helped keep things warmer.

    Looks like today might actually be the cloudiest day so we may not reach 20°C depending on how many clear breaks we manage to get under.

    ReplyDelete
  7. JJ, I have a weather question for you, can a thunderstorm form with out a cold front/warm front or a troph?

    ReplyDelete
    Replies
    1. The types of lifting mechanisms you have mentioned would be included in the 'frontal thunderstorms' category, however not all thunderstorms form thanks to these. 'Orographic thunderstorms' and 'air mass' or 'pulse' thunderstorms also exist.

      Orographic storms form when air is lifted by mountains or large hillsides (Alberta is a great example of where this happens fairly often thanks to the mountains).

      Air mass storms (or pulse storms, pop-up storms, garden-variety storms...) form in an unstable airmass with daytime heating, and are usually localized and short-lived.

      Storms can also form along local convergence boundaries not associated with cold/warm fronts, such as thanks to lake-effect boundaries or from outflow boundaries sent out by other storms.

      Delete
    2. An interesting question with respect to this is whether or not there is such a thing as an air mass thunderstorm. Some people would argue that it is not possible for a storm to develop just due to daytime heating (i.e. due to a thermal rising from the surface forming a storm). The argument is that you need some kind of trigger, be it a hill, or a lake breeze front, or a host of other things to set that storm in motion. I'm not sure what I believe in this case. We certainly do see cases where thunderstorms/showers seemingly develop purely from daytime heating...but who's to say they didn't actually form from a hill or other unperceptive triggering mechanism. So in short, I'm not sure what the reality is, but I think the category of "air mass storm" is about the best we can do to define those types of storms at the present time.

      Delete
    3. You make a good point Scott and you bring up a similar question I had about 'air mass storms'. You would think some type of trigger would still be necessary, such as lake-breeze boundaries or a large hill/mountain or any other type of local feature to provide enough lift when there is no weather front around... but at this point I'm just assuming.

      Delete
    4. You guys have a good point, I personally would say that for a thunderstorm to be a thunderstorm it needs to form like a thunderstorm. As both of you mentioned, my argument is that a storm needs some sort of a trigger to be called a thunderstorm. A simple way of explaining my argument is the following: if a thunderstorm has formed without a trigger or any one of the things that a thunderstorm needs then it should be have another name.

      Delete
    5. I totally agree with you frank.

      Delete
    6. My perspective is that a thunderstorm is a thunderstorm. Regardless of how that storm developed, it's still a thunderstorm. However, actually defining what type of storm it is can be quite difficult. We've managed to come up with a massive number of classifications for storms, ranging from air mass to multicell to supercell to derecho to MCS, and so on and so on. I think the challenge usually is figuring out what type of storm you are dealing with rather than figuring out if it is a thunderstorm.

      The lines are more blurry when you are trying to compare showers, thundershowers, and thunderstorms. They all possess similar characteristics, with the later two being defined as having lightning.

      I suppose if we knew all the answers to these questions weather would not be very interesting...

      Delete
  8. Man, if GFS is right, we'll really be back into summer weather later next week. It brings in 20+C dewpoints by Friday. Not so sure about that however, but it certainly really does look like summer is finally gonna be making a comeback especially 2nd half of next week.

    ReplyDelete
  9. Well, it was a nice day but it sure isn't anymore. After a brief break from the cooler fall air this afternoon we are right back into that cooler air as rain from the west is moving in. So all in all another chilly and miserable evening tonight.

    ReplyDelete
    Replies
    1. Of course the clouds came in as soon as I finished work... Yucky summer.

      Delete