Monday, October 18, 2010

Dry seasonable weather this week.. turning unsettled next week?

The dry weather we've enjoyed for the past 3 weeks will continue this week, with an upper ridge blocking any large weather systems from affecting southern Manitoba. After an exceptionally wet late summer, the taps were finally shut off in late September with only 2.0 mm of rain recorded in Winnipeg in the past 3 weeks (since September 25th) Long range models are indicating a breakdown in the upper ridge by early next week, resulting in cooler and more unsettled conditions moving into southern MB for the last week of October.

17 comments:

  1. Hi everyone..

    Our local climate expert in the office says he expects a large storm to affect parts of the northern Plains a few days either side of Halloween with another signal indicating a large storm sometime in mid November. The long range GFS and now the ECMWF have shown hints at something in that 27-28th time period....of course lots of run to run variability in the GFS.

    Our office was in on the latest long range CPC conf call that NWS office attend. Not too much different. CPC puts all their eggs in the ENSO basket as their skill at the other more shorter range teleconnections such as the NAO, AO, etc are poor. But they did indicate while November itself may tend to be more normalish....the influence of a colder than normal temp pattern will establish itself especially by mid winter and into early Spring. Also several long range climate models indicate normal to a bit above normal snows....though it appears the most persistant storm track will be south of us...with our area in the main belt for clipper type storms.

    Of course...all this subject to change. I for one am ready for a change...October has been way too boring weather forecast wise.

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  2. Thanks for the update Dan.. I see La Nina has recently entered into a "strong" phase, but is forecast to weaken next spring. The prospect of a back-loaded winter with above normal snowfall does not bode well for the Red River next spring given the very wet conditions we have going into freeze up. Hopefully the storm track stays far enough south to keep snowfall to a minimum this winter (although I'm not crazy about a cold dry winter..)

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  3. Rob!

    I was down in the U.S.A this past weekend and was watching the weather channel!

    In this example they calculate winchill when temperatures are 49 F which would give a windchill of 42 F.

    I thought windchill was only calculated when temperatures reached 32 F or colder?????

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  4. WHOA!
    I almost fell out of my chair when I saw the latest GFS runs for that storm next week!!!!

    Howling winds out the north followed by falling temperatures!

    Question is could the airmass be cold enough for our first flakes of snow!
    I know it is way to early to jump on the storm bandwagon but....
    What a storm on the models!!

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  5. GFS tends to overdevelop systems in the long range.. but it's definitely looking colder and wetter (maybe whiter?)) for the last week of October.

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  6. The GFS often goes bonkers with large lows in the very long range. So really cant go with the specifics...but trends are good. Trends are for certainly more chances for storminess...typically early Nov is our time to get into a more stormy pattern in most years. I do hold out hope for a cold pattern to set up but it may take well into the next month to get going. But this is my favorite time of the year, the leaves are not off the trees and the anticipation in me is building for what La Nina will bring. Usually the anticipation doesnt match reality but we are due.

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  7. sorry in last post meant leaves are now off the trees... sometimes whish these blog would have an edit feature to remove typos

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  8. Dan GF or Rob!
    I have a question for you!!!

    I always thought that winds were caused by the pressure gradient (isobars) between a high pressure and departing low pressure system!

    Now every time I read NWS grand forks discussion they always talk about the potential of "mixing" down of the winds!!

    Example:
    850 MB WINDS NR 40
    KTS JUST WEST OF VORT MAX AND SOUNDINGS FROM GFS/NAM SHOW
    EXCELLENT MIXING UP TO 800 LEVEL THIS AFT

    Example:
    NONE THING NEGATIVE IS THAT
    NORTHWEST WIND NOT FAVORABLE FOR THE VALLEY FLOOR IN REGARDS TO
    HIGHEST WIND SPEEDS....BUT WITH SUCH A DEEP MIXED LAYER FEEL
    PRETTY GOOD CHC TO MIX DOWN NR 40 KT WINDS AT TIMES EVEN IN THE
    VALLEY.

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  9. daniel.

    "Mixing" refers to the atmosphere's ability to bring down winds from aloft to the surface based on the stability of the atmosphere in the lower levels. Winds from aloft are brought down more easily or "mixed' to the surface when you have unstable conditions (like with daytime heating for example) that allows the winds aloft to be transported downward. This usually results in stronger and gusty winds at the surface.

    In stable conditions, the winds aloft are effectively blocked from mixing down, (such as above an inversion) resulting in lighter wind speeds at the surface. This is why winds often diminish after sunset, since the atmosphere is stabilizing after the daytime heating is gone.

    Stability is one of the reasons why you can have different wind speeds given the same isobaric spacing. The pressure gradient will give you a general potential wind speed over a given area, but the actual wind speed will vary depending on local topography, terrain roughness, stability, isobaric curvature, pressure change gradients, etc.

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  10. Thanks for the explanation!!!

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  11. Looking at the Lynn Lake webcam from this afternoon shows a coating of snow on the ground!!!

    It getting closer and closer :>)

    Even Gimli's 7 day forecast calls for a periods of SNOW or rain by day 7!!

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  12. No it's not gonna snow. That's what I keep telling myself.

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  13. The models have been pretty consistent on having a storm into Southern Manitoba next week!

    Now over the next few days it will be ironing out the details!

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  14. As it stands right now does next week's airmass look cold enough for snow or will it be a rain event???

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  15. Looks like main pcpn event will be in the form of rain on Tuesday (perhaps 5-15 mm?) before colder air pushes in by Wednesday as the main precipitation shield moves off. We could get see some wet flurries Wednesday in the wrap around from the main system, but overall it looks like we should escape with mostly rain. Colder for Wed-Friday with single digits highs then warming up for the Halloween weekend. At this point, it looks like it should be fairly mild for the trick or treaters with daytime highs possibly above 10C again by Sunday..

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  16. After almost a month of no storms
    I'm really looking forward to this storm next week!

    Bring it on!

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  17. If the latest GFS run is to happen then Southern Manitoba could be in for a wind-driven rain/snow event on Tuesday/Wednesday!

    I can't help but get excited!

    Oh by the way CPC has just issued their winter forecast.

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