Wednesday, May 09, 2018

Very dry weather continues.. Winnipeg closing in on top 5 dry spells of all time


The dry weather of the past 2 months continues into May, with no measurable precipitation recorded so far in the month. In fact, as of May 9th, Winnipeg has gone 27 consecutive days without any measurable precipitation. The last day with measurable precipitation in Winnipeg was on April 12th when 1.2 mm of melted snow was recorded at the airport. (measurable precipitation is defined as a day with 0.2 mm or more of melted precipitation (rain or snow)  With no significant precipitation expected through May 15th, this current dry spell may enter the record books as one of the top 5 longest dry spells in Winnipeg since records began in 1872. The chart above shows the top 5 longest dry spells in the city, the longest being 47 days without measurable precipitation in the fall of 1976. The longest dry spell in the spring (which is a more serious time for dry weather) was in 1980 when Winnipeg went 40 straight days without measurable precipitation.  How long this current dry spell will last is difficult to say at this point.. but increasingly it looks like it may become historic before it's finally over. The dry weather has caused major headaches for city firefighters who have had to battle numerous grass fires in the past few days in and around the city.       

24 comments:

  1. Rob how come its been so stinkin dry? What's the meteorological synopsis responsible for it, and for this long?

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    1. Simply put, the overall storm track has been missing us mainly to the south. Without weather system coming through here, we’re not getting the periodic waves of precipitation you would normally expect every few days or every week. And with it being so dry (both airmass and lack of soil moisture), there just isn’t enough moisture around to help trigger convective showers that would provide temporary relief. Now, as we get into leaf-out and crops start to mature, there should be additional moisture in the air to start getting some convection going. Also, the storm track may swing back closer to us later in May into June. Note that June is our wettest month on average, so there’s still time for us to get some decent rain. But in the meantime, it doesn’t look good for any significant precipitation anytime soon.

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    2. So have we been just stuck in a long term blocking pattern? What synoptic meteorological phenomena would cause the jet stream to set itself up in this way for so long? I see this set up all the time. It seems like the storm track always sets itself up to the south.

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    3. The jet stream (which is basically the storm track) often sets up to our south because of climatology (that’s where it usually is much of the year) But it’s tough to say exactly what causes a blocking pattern. Sometimes different wave cycles or climatic oscillations around the globe causes the upper pattern to lock in for an extended period, but that gets into a lot more complex meteorology that is beyond my expertise and is a lot harder to predict with skill. Sometimes the pattern locks in a certain way for awhile, but we really don’t have a good grasp as to exactly why it happens or how to accurately predict when it may set up (or break down)

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  2. Something odd going on with EC’s Day 5 forecast highs. Past few days have shown a notable cool bias of at least 5C just for that day. Not sure why. Pretty obvious when compared to other models. Their day 5 forecast for Saturday was 14C.. all guidance was showing 20C. Now they’re saying 21C. Their Day 5 now for Monday is 22C.. all guidance saying 27-28C. Looks like an issue with Day 5 post processing.

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  3. Rob,

    Noticed That E.C. is calling for high of 24C Monday and Just 20C on Tuesday.

    Have models backed off on the near thirty degree warmth for both those days or do these forecast highs seem cool?

    Thanks.

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    1. Models have backed off on the warmth for Monday with highs in the low 20s now expected. But Tuesday looks like high temps should be in the 27-30C range.. so that high of 20C is completely at odds with all guidance that day, even CMC’s own model (27C) As I mentioned, there seems to be some odd things going on with EC’s temperature forecasts lately for Day 3-5. Just seem to have some strange cool biases of at least 5C on some of those days. Have no idea what’s happening but could be issues going on with the post processing of temps in that Day 3-5 period.

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    2. EC now saying 30C for Tuesday, a mere 10C change from yesterday. That kind of forecast variability (10C in one day) is not normal in this day and age.

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  4. Hi Rob. Did Winnipeg break the record cold temperature for May 10? I didn't even realize the temperature bottomed out at -8.5C. Seems like a random cold blip this month.

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    1. Yes we broke the record with an amazing low of -8.5C,

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  5. Rob,

    With an increase in humidity and instability for Thursday, thunderstorms appear to be a strong likelyhood across Southern Manitoba.

    Is there a potential for severe thunderstorms on Thursday?

    Thanks.

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    1. Yes, I think the potential is there for some severe thunderstorms over southern MB Thursday afternoon into Thursday evening. Dewpoints will be rising into the upper teens to near 20C, with temperatures climbing into the 27-30C range. That will produce CAPE values of 2000-2500 J/kg which is plenty enough energy to produce severe thunderstorms with large hail or damaging winds. Airmass looks capped for much of the day, but cold front coming through late in the day should be sufficient to break the cap and get some convective initiation going over SW MB Thursday afternoon, pushing into the RRV by evening. Large hail and strong wind gusts would be the main threats given relatively low overall shear, but the tornado threat is not zero given the low cloud bases and fairly decent veering wind profile in the low levels. This of course is based on current model outlooks for Thursday.. risk levels may change depending on trends in upcoming model guidance and actual atmospheric soundings closer to Thursday.

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    2. By the way, note that thunderstorms are currently not in EC's forecast for Thursday. Forecast says cloudy with a 60% chance of showers and a high of 32C. A few things wrong with this forecast.

      1) You don't hit 32C in May with cloudy skies. So either the clouds are overdone or the forecast high is. To get 32C, you'll need some sun. I suspect we will.

      2) If you're talking about 30C temperatures, then any chance of precipitation will be accompanied by thunderstorms, not just "showers". Oddly though, EC does not include thunderstorms in their forecast after Day 2 (tomorrow). Any forecast in the Day 3-7 period (which is automated) that has a chance of precip will only mention showers.. they will never mention thunderstorms even if temperatures are very warm. Here's a tip.. if EC forecast in the Day 3-7 period calls for a chance of showers and the forecast high that day is 25C or more.. then assume showers OR thunderstorms.

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    3. As expected, thunderstorms now in the forecast for Thursday, now that Thursday is Day 2 and human meteorologist has input into the forecast.

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  6. How big is the tornado threat with these storms

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    1. Very low. One of the main ingredients for strong supercells that support tornado development is lacking tomorrow.. and that is strong wind shear. As a result, the main threats with the storms tomorrow should be large hail and strong wind gusts, along with heavy rainfall. That being said, given the instability tomorrow, can't rule out an isolated tornado spinning up with a stronger storm, but as I mentioned, the risk is looking quite low at this point.

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  7. I just wonder how many tornadoes Manitoba will get this year since last year we only had one

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    1. Impossible to predict, and one year has no bearing on the next. Each year is a new roll of the dice.

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  8. Rob
    Is there any signs of a cool down from this heat I was looking and I see it might get cooler around early June

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    1. We stay warmer than normal through the end of May.. then yes, looks like June will be starting off cooler than normal.

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  9. Nice day before another threat of scattered showers/tstorms later today. Lower dewpoints today, so less intense storms than yesterday, but still enough to give some brief downpours and gusty winds.

    Temperature wise, we could hit the 30C mark in Winnipeg again today with plenty of sun, westerly flow and fairly dry air. If we hit 30C, it would be our fifth 30C day of the month, tying 1977 and 1988 as third most 30C days in May since records began in 1872.

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    1. We did it. High of 31.6C Friday was our 5th 30C day of the month. A bit cooler today with a high of 27C (forecast high of 29C seems overdone) then back up to 29C Sunday. Summer in May continues.

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    2. Only 21C at noon.. no way we’re hitting 29C today. 25-26C tops.

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