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    Brett Anderson

    Weather Pattern Update Through the End of September

    8/30/2013, 11:01:22 AM

    10:45 a.m. Fri update

    Heavy thunderstorms likely to impact southwestern Ontario later this afternoon and evening as thunderstorms over northern areas of Lower Peninsula of Michigan are being enhanced by upper-level disturbance tracking southeastward.

    At this point, it looks like the greatest threat for strong thunderstorms (gusty winds, frequent cloud to ground lightning and blinding rainfall) will be across southwestern Ontario later this afternoon into early this evening as the thunderstorms track from northwest to southeast.

    The GTA will probably have some impact as well late in the day, but I think the strongest storms end up just to the west.

    Interesting weather last night in the Vancouver, BC, area

    EC radar image from 11:10 p.m. PDT last night showing intense line of thunderstorms approaching Vancouver, BC.

    350x362_08301319_screen-shot-2013-08-30-at-9


    Strong thunderstorms erupted in the Vancouver area last night and tracked up toward the Squamish area. The primitive map below shows a close-up of the Vancouver area with the approximate locations (dots) of each lightning strike last night. We detected nearly 500 strikes with this thunderstorm complex.


    590x465_08301313_screen-shot-2013-08-30-at-9


    It appears that the highest concentration of lightning was from West Vancouver through Bowen Island and up into the Squamish area.

    The were several factors that lead to this unusual thunderstorm event. The main factor was the approach of an unusually strong upper-level disturbance. Dew points were fairly high and the atmosphere was unstable. Winds were also converging at the surface which forces the air to rise and condense.

    On average, Vancouver has about six days during the year with a thunderstorm.

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    Here is my latest long-range weather pattern projections through the end of September. These weekly outlooks are based on current observations, short-term atmospheric oscillations, teleconnections and ECMWF model data.


    590x458_08300257_aug29a

    590x458_08300259_aug29b

    590x458_08300300_aug29c

    The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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