Monday, July 09, 2012

Hot week ahead.. Scattered thunderstorms possible later in week

Mid summer heat will be spreading across southern Manitoba this week as a large upper ridge of high pressure over western Canada slowly pushes east across the Prairies. This ridge is resulting in widespread temperatures in the low to mid 30s across southern Alberta and Saskatchewan, which will be spreading east into southern MB this week. In Winnipeg, temperatures are expected to approach the 30C mark today, and surpass the 30C mark the rest of the week into the weekend, with maximum temperatures of 35C possible. Conditions will be generally sunny and hot, although there will be a threat of scattered thunderstorms Wednesday through Friday as some minor impulses track across southern Manitoba, triggering a few scattered thunderstorms that could be heavy at times given the building heat and humidity.  Other than that, looks like an extended spell of hot weather ahead.. plan to stay cool!

74 comments:

  1. Today will be one of those days where backyard stations are registering temperatures a couple degrees higher than official readings. Strong sun and lack of wind will make for superheated yards across the city with 30c temps easy. 30c will be tougher to reach at airport, but with strong sun, light flow and moderate dewpoints, I think YWG should make it. We're running about 1.5C warmer than yesterday with less cloud today, and we hit 29.1c yesterday.. so highs of 30-31c possible today at the airport.

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  2. Edmonton may break their all-time high humidex record today. Old record is 38.7, and with dewpoints near 20°C today, they will come close.

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  3. Rob, do you recall ever seeing humidex advisories in Alberta? Today's the first time I've seen it.

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  4. No I don't recall a humidex advisory for Alberta, but I do recall actual 40c temperatures over eastern Alberta a few years back. I didn't realize that Edmonton has never hit a 40 humidex... They're currently at 37 humidex with a 21 dewpoint. They need to hit 32c to get a 40 humidex with that dewpoint.

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  5. Hi Rob, This week is definitely looking interesting. Had a look at the GFS CAPE Model run on Wundermap and it appears that Winnipeg will be under 2700 to 4000 J/Kg of CAPE from Wednesday 1800 GMT to Thursday at 0600 GMT. Along with relative humidities at 60%. What do you think of this potential? I think we might be in for some severe storms depending if a system is sitting over us at the time.

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  6. Wednesday looks interesting though capping will likely be an issue. Wind profiles don't look all that bad. We'll have to wait and see tomorrow when things should become clearer.

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  7. Really, there will be potential for storms Wednesday right through the weekend. Maybe even into early next week.

    Instability and moisture should be fine but shear could be lackluster. As Chris mentioned, capping could be a problem early on.

    Stuff to watch, though. Let's hope the bounces and breaks go our way this time.

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  8. Speed shear doesn't look all that impressive but directional shear actually looked pretty decent as per the 00z NAM. Instability and moisture will be more than adequate. Triggers are a little less clear over the period as models are having a tough time with the eastward propagation of the ridge. Can never rule out smaller mesoscale features as triggers in S. MB though!!

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  9. Mike.. Keep in mind that one of the key letters in CAPE is the "P"... which stands for "potential". CAPE is "potential" energy in the atmosphere, but you need something to lift that energy upward to grow into a thunderstorm. Without lift, you're left with a lot of hot and humid air sitting at the surface. There are several things that can act as a trigger to initiate lift, such as a front, upper or surface trof, dryline, lake breeze front, even upslope over higher terrain. Likewise, there are several factors that can inhibit lift such as a capping inversion, large scale subsidence, or lack of surface convergence. At this point, the best we can say about thunderstorm potential later this week is that there is potential for locally heavy thunderstorms given the instability that will be present, but lack of overall shear will likely mean they will be short lived pulse type storms with heavy rain, strong downburst winds, and marginal hail. If the pattern changes a bit and we can get some stronger winds aloft, then the severe potential will increase.

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  10. Some on and off sprinkles in south end in the past 30 minutes. Nothing major where I am, but quite the downpour just south of the Perimeter earlier is now dissipating. No thunder or lightning so far.

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  11. Those cells popping along a convergence line. Looks like more boundaries dropping towards the city from the north..

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  12. A high of 30.2C today at YWG airport.. the 30C streak begins! Looks like we could be seeing 5 or more straight days of 30C or higher through this week, barring any heat busting thunderstorms later this week, and a possible brief cooldown Saturday. Record highs in Winnipeg however will be tough to break over the next few days as this week coincides with the granddaddy of all heat waves over southern Manitoba which occurred July 5-17, 1936. Record highs in Winnipeg over the next 4 days range from 37-42C, all set in 1936 when we went a record 13 straight days above 30C, and hit our all time high of 42C on July 11th. Click on my name for a previous post on the remarkable 1936 heat wave.

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  13. Mike,

    John Sauder says "Now... I must mention that the instability involved in our weather set-up over the next few days is 'through the roof"... especially Wednesday afternoon."

    He must be looking at the GFS like you were, which has a LI of -14.1, 4-layer LI of -12.5, SBCAPE spiking above 5000 and MUCAPE spiking above 4000. Problem is the GFS is a global model and not well suited for a short-range (or any) severe weather forecast.

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  14. Cap vs CAPE...time will tell.

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  15. Anon....
    Really, that is interesting and a coincidence. I don't think he looked at Wundermap though, a little low tech for him.


    My thoughts are that wednesday may be the most active day this week, considering how high the CAPE and LI Values will be.It is interesting that are forecast to be at 5000+ J/Kg of SBCAPE, and 4000+ J/kg of MLCAPE, along with -14C lifted indicies. This is looking a lot like the tornado Season scenarios in the states. What I also think is that we are due for severe storms and we may see that tomorrow afternoon/evening. The rest of the week not so much in terms of energy, potential is still there for storms. Taking the fact that with all the heat and humidity we may see some pretty good action. Gotta love Summer!

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  16. I'd be surprised if there was tornadic activity in southern Manitoba. While we do have lots of instability and moisture to work with, shear at all levels is almost non-existent. Widespread pulsers are the best bet tomorrow through Friday. Localized hail, wind, heavy rain, and lightning the main threats.

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  17. Derek...

    Is it all possible if the pulse type storms will be severe, with all the instability? Hopefully some good lightning....

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  18. Tomorrow could be interesting given the high instability and potentially decent low level flow. If the upper level flow was even a bit better I'd be more excited. As Derek mentioned, pulse type storms are most likely given the overall low shear environment. Wouldn't completely rule out supercells just yet though. I'll be watching tomorrow closely...

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  19. A note about high CAPE/low shear environments. Derek is correct that generally these don't support tornadoes given the lack of shear to sustain tornadic supercells. However, in cases of extreme CAPE (like 3000+ J/kg) some storms can spin up tornadoes, even strong ones, with limited shear. Brunkild tornado of July 24 2000 is an example, and there are others. These storms can generate their own low level inflows to increase storm relative shear, and induce mesocyclonic rotation conducive to tornadic development. Even without tornadoes, thunderstorms that develop in extreme CAPE environments can sometimes produce very damaging downburst winds equivalent to an F0 or F1 tornado.

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  21. Rob....

    Either way It will be something to watch, just hope that major damage doesn't occur like A tornado hitting the city of winnipeg, or a nearby town. It would be a heck of a way to start off with the july storm season. A lightning show would be fine....

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  22. Anon....
    A Microburst would be good too..

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  23. Rob,

    Excellent post. I guess you can't count anything out in July with such high instability. Brunkild a great example and that was a large tornado.

    By no means does a pulse storm environment mean that nothing exciting will happen. I really enjoy watching storm interactions. Storms going up quickly and dissipating shortly after. Get caught under a strong/severe pulser and you can get a lot of interesting weather in a short period of time.

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  24. Finally got around to getting my weather station in NE Transcona online. Can be found at:

    http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=IMANITOB48&day=10&month=07&year=2012

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  25. Rob........

    Given the fact that storms will be possible in the coming days, how much humidity will be present to give them the extraboost? does 60 to 70% humidity sound about right?

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  26. Good stuff Chris.. welcome to the online weather club!

    Mike.. I think we'll need dewpoints in the 20C range to help with firing things up.. with 32-35C temps, that would equate to about 50% humidity.

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  27. A little more heat and a little more humid today.. temps should get up to around 35C in Winnipeg today, with dewpoints of around 18C which will give humidex values approaching 40 this afternoon across the RRV. Forecast high of 31C for Winnipeg today seems a bit underdone. 850 temps climb to around 23-24C which would give us a high of about 35-36C. NAM is giving 37C for Winnipeg while RAP is giving an unrealistic 39C. Even the 06Z GEM is giving 35C for Winnipeg. We do have a little more cloud today, but with enough sunshine, I think Winnipeg should be able to reach the 35C mark. Stay cool!

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  28. 7-11 giving away free slurpees today.. I think they may run out :)

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  29. That high of 31 forecast is suspicious, I agree Rob. I see there's no humidex advisories as a result.
    I'm thinking there could be some last minute humidex advisories again today...

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  30. Yeah, the 00z GEM run came up with a high of 31c, the only run that was that low for today. All other GEM runs have been consistent around 35C. Odd.

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  31. Unfortunately EC believed the one GEM run that was a bit "off" and now had to issue an amendment for the daytime highs in S. MB. They've increased the high to 34C now. This really reflects poorly on EC's confidence and forecasting abilities. CJOB was really emphasizing EC's waffling this morning.

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  32. Ah, was wondering why the 31C forecast high. Thanks.

    The latest GFAs look interesting. "NRMS CB 400 2SM +TSRAGR G40KT" is shown over western MB this evening. Wonder if it will survive to Winnipeg.

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  33. Models had been overdoing Winnipeg's high by 2-4 degrees pretty much every day for the last week, so perhaps when a new synoptic hour run came in with a lower high there was reason to believe that perhaps it had finally clued in? Cloud cover was also a big question mark for today (last night's GFS had us cloudy all day), so I'm sure there were strong reasons behind whatever decision was made at EC. Just didnt't work out, that's all. Live and learn!

    Gorgeous out there, but I feel it might get a little stifling out there this afternoon. Also worth mentioning is that the NAM, which has notoriously had too much moisture at the surface this year, actually under-forecast our dewpoint for today. I'm a little curious what will happen storm wise if we actually make it to 36°C!

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  34. "NMRS CB 400 2SM +TSRAGR G40KT" is Numerous Cumulonimbus topping out at 40,000 feet. 2 statute miles visibility, Heavy thundershowers with hail, winds gusting to 40 knots.

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  35. Good bet for some storm activity tonight. Best shot is tomorrow when a front slowly pushes through. Should be numerous cells roaming about southern Manitoba tomorrow.

    Looks like a somewhat active pattern this weekend. Models are then bringing a rather significant system across the Prairies early next week. Could be thunderstorms on Monday and/or Tuesday next week.

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  36. Garth,

    Models have been hinting at the activity lasting into the night. Don't think it will be severe but heavy rain and lightning seems like a decent bet somewhere in southern MB.

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  37. Yeah, I'm sure the decision was well thought out. It's just too bad. EC's in such a tough position with the media. Flip-flopping is viewed poorly when the actual forecast is quite a delicate process. The general public truly have no idea. Sorry if I came across negatively regarding EC's forecasts...that was not my feeling at all!

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  38. It's astounding how poorly the models are handling the moisture with this system. I've attached a sounding from the RAP that's embarrassingly bad. Dewpoints of 12-13°C over the RRV! Couldn't be more wrong. See: https://img.skitch.com/20120711-rep12wwaq9bxcuxig972gk49sj.png

    It'll be a bit of a wildcard as to what happens this afternoon. Convective potential is hard to figure out given the poor handling of the low-level thermodynamics by the model.

    Sure would be a great day to have a sounding from Winnipeg.

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  39. SSW flow will likely advect drier air northwards. You have to get down almost to the southern plains before you reach good gulf moisture.

    Things here are getting desperately dry. Yellowing and browning showing up with some trees starting to drop their leaves. Drought pattern finally asserted itself as was speculated back in spring. YWG has picked up only 11 mm of rain since June 16 with above normal temperatures through the period. With this strong upper ridge persisting and lack of forcing, any significant precipitation will be localized.. and with our bubble effect odds may not be great for the city.

    Analogues for this year include 2011, 2006, 1997, and possibly 2003. Most if not all the cases were preceded by moderate La Nina conditions during winter. It leads to upper ridge elongation during the summer, and a lack of dynamics/ lifting as cold lows are deflected NW and LLJ is suppressed south. Convection goes only in ares with stronger mesoscale forcing like around lake breezes, escarpments etc.

    Hopefully we will transition back to an El Nino regime by late summer as some projections indicate.

    Daniel

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  40. Daniel, when you refer to gulf moisture, I'm assuming you mean deep moisture. It's pretty gulf-like out there today! Where have you seen trees dropping already? Things look all right here in my neighborhood, but we also got 4"+ of rain back in the stormy season which is just now starting to wear out (as evidenced by my garden, which I finally -have- to water).

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  41. Brad.. Yeah, I noticed the RAP was way too dry for Winnipeg.. probably why they were advertising a super-adiabtic high of 39C for us!

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  42. 36 degrees in Portage today!
    Also, Fort Smith, NWT registered 35 degrees yesterday, which was the second-highest temperature in Canada yesterday. Just a degree short of the 36 degrees in Coronach and Val Marie, SK.

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  43. Re dewpoints..

    Have a look at Td's down around Nebraska and Kansas.. values of 12-15 C are common. High dewpoints have pooled along the back side of a large surface high mainly from ET. It is quite distinct from the region of high td's south of a stationary front over Arkansas and Tennessee.

    As for yellowing/browning.. trees planted in areas of thinner soils or where road salt is applied are showing moisture stress and leaf burning. If we do not receive significant rain, you will see it spread to more areas within the next week/ 10 days.

    Daniel

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  44. An amazing 36C today way up in Gillam today as well! Looks like Winnipeg has peaked with a high of 33.6C today.. some late day cloud prevented us from hitting that 35C mark.

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  45. Duck Mountain area just getting hammered with heavy thunderstorms and intense lightning with heavy rain likely. Storms showing little motion. Wouldn't be surprised to hear of some over overflowing creeks and possible road washouts out that way, especially along and west of Highway 10 between Pine River and Ethelbert.

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  46. Temperature at YWG aiport has just shot up to 34.5C just before 6 pm with that bit of late day sun. So we almost hit that 35C after all!

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  47. That temperature jump also coincided with a gusty southwest wind picking up and a 6C drop in our dewpoint from 22C to 16C between 5 and 6 pm.

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  48. 76 mm of rain in Swan River with thunderstorms between 4:30-6 pm.

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  49. Wow! 3" in 90 minutes...that'll be tough to handle.

    Think the dewpoint drop was due to mixing?

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  50. Brad.. I think the dewpoint drop was due to a subtle wind shift into the SW, rather than from the straight south which we had most of the day. Dewpoints had been lower over the western RRV all day, and I think that wind shift tapped some of that drier air.

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  51. Rob,

    Questions....

    What are thunderstorm chances for us tonight here winnipeg and for tomorrow as well?

    Also, could we possibly be looking at one of our warmest July's on record in 2012 when it's all said and done at the end of the month?

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  52. Really? Our winds were from 200 a good chunk of the day. 10° shift to 210° enough to make that big of a difference?

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  53. Brad.. Well, we went from 18015Kt at 22Z to 21015G24kt at 23Z, so a 30 degree shift at that time, which tapped some drier TDs to our west. Or, did we just get convectively unstable at that time for stronger winds to surface, which dried us out? Could be either..

    BTW.. max of 34.5C at YWG airport today, 35.8C at Portage, and the provincial hot spot was Gillam at 36.4c!

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  54. I do wonder if it was convective ly unstable...temperature cooled just a tiny bit and we were back to 220 with a rising dewpoint. Interesting. Do you happen I have Morden/Gretna's high for today?

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  55. Rob,

    That Gillam temperature seems suspect. WGX was 3 to 4 degrees cooler at the same time.

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  56. Brad.. Some RRV highs today..

    Portage ........ 35.8C
    Winnipeg YWG.... 34.5C
    Winnipeg Forks.. 34.1C
    Morden ......... 33.9C
    Carman ......... 33.8C
    Gretna ......... 33.3C
    Emerson ........ 32.5C

    Hottest spot in south was in downslope area off escarpment just west of Portage with MB ag-wx mesonet showing 36C temps in Westbourne and Gladstone. Also hot up through the Interlake with 35C in Fisher Branch and unofficial 37C from CWB Narcisse.

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  57. Thunderstorm potential looks interesting for tomorrow over southern MB. Weak upper low over SE SK this afternoon which spawned scattered but numerous cells, some severe, over SE SK and western MB today will drift over SW MB Thursday towards Pilot mound area. Best lift with this feature today was to the notheast of the low, which depending on progression of low Thursday would put southern Interlake and perhaps northern RRV under best chance for thunderstorms, perhaps yes, even Winnipeg! Still not a slam dunk.. all depends on evolution of this slow moving upper low, and where storms start to fire up.. but potential is there for some strong storms given the heat and humidity. Here's hoping we see something in Winnipeg!

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  58. Eastern Canada is having even drier weather than Southern Manitoba.

    Sudbury, Ontario is currently at 16 consecutive days with basically no rain (0.5 mm or less).

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  59. A few thunderstorms over the southern RRV this morning as an upper feature spins across northeast ND, providing some lift for elevated storms this morning. Looks like one cell over Morris trying to spread north towards WInnipeg as we get some cloud and outflow winds from it. We'll see if it can hold together to bring some rain for us.

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  60. Getting dark to my SW with thunder increasing.. already heavy rain over Whyte Ridge/Oak Bluff and Sanford.. nothing here in Charleswood yet... but should be any minute now.

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  61. Already 6-10 mm of rain from Sanford to Linden Woods.. must be quite the downpours in that line.

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  62. Unfortunately, it appears only a fraction of the city will be getting the much-needed rain.. unless if more storms form to the south.

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  63. This band actually missing me just to my south and east.. no rain here in Charleswood... but pouring along McGillavary.

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  64. Getting a little light rain here in Charleswood now.. but nothing like just to my southeast! Oak Bluff up to 30 mm so far!! Whyte Ridge 16 mm.

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  65. I could see the lightning from those storms in St. James on my way home too. Right now it's just spitting a bit.

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  66. Activity weakening over city.. heavier storms off to our west especially from near Elie to Elm Creek to Miami. Slow moving storms today will be capable of 25-50 mm of rain in a short period.. provided they hit you!

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  67. As if the storm split as it was approaching the city. What causes this?

    I see a severe thunderstorm watch is now posted on EC.

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  68. Had a nice thunderstorm in Altona after 6am. Heavy rain and intense lightning. Beneficial rain for us although we are not as dry as parts of Winnipeg.

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