Lake-Effect Snowfall Forecasts with SPoRT Datasets

Brian Bernard runs a website in Southern Canada called Golden Horseshoe Weather.  Brian obtains near real-time sea surface temperature (SST) and green vegetation fraction (GVF) products from SPoRT for ingest into a version of the Environmental Modeling System (EMS) that he runs.  This model is a 4-km Advanced Research Weather and Research Forecasting (WRF-ARM) model that encompasses Southern/Central and part of Northern Ontario.  It uses 40 vertical layers, with most of the layers between 1013 to 650 mb in order to better resolve lake-breeze boundaries and lake effect areas.  As a result, use of the high-resolution SPoRT SST data is critical for resolving some of these boundaries.

Southern and Central Ontario is bounded by water on three-sides and one of the forecasting challenges for the meteorologist is the interaction of the marine layer and the land area. Most of our severe thunderstorm events occur during interactions with lake-breeze boundaries.  In winter, parts of Southern/Central and Northern Ontario are downwind in cyclonic flow events and are susceptible to lake-effect snows.  Areas downwind of Lake Huron can also be affected by multi-lake effect snows.

Brian posts numerous output fields from his real-time WRF runs to a modeling subsection of his website, which is frequented by Canadian, provincial, and U.S. government meteorologists, private sector and media meteorologists, as well as weather enthusiasts and storm chasers. The model is initialized daily at 00Z and run for 36 hours; output is generally available by 1:00 A.M. local time.

A recent lake-effect snowfall event in Southern Ontario was captured well by WRF with the inclusion of the SPoRT SST.  The 24 November 1200 UTC radar image from the King City radar in Ontario shows two distinct lake-effect snow bands (one southwest of Barrie and Midland; one near London).  The corresponding 36-hr WRF forecast (initialized at 0000 UTC on 23 November; valid at 1200 UTC on 24 November) of 900 mb omega shows that the strongest vertical motions associated with snow bands occurred almost exactly in the location of the two snow bands observed in the radar.

Radar reflectivity (dBZ) from the King City radar from 1200 UTC (left) and Exeter radar from 1210 UTC (right) on 24 November 2013 showing two distinct lake-effect snow bands over Southern Ontario.

Radar reflectivity (dBZ) from the King City radar from 1200 UTC (left) and Exeter radar from 1210 UTC (right) on 24 November 2013 showing two distinct lake-effect snow bands over Southern Ontario.

36-hr WRF forecast of low-level vertical velocities valid at 1200 UTC on 24 November 2013.  The larger magnitude vertical velocities are snow bands.

36-hr WRF forecast of low-level vertical velocities valid at 1200 UTC on 24 November 2013. The larger magnitude vertical velocities are snow bands.

In addition to his use of the SPoRT data for modeling applications, Brian also obtains satellite imagery products from SPoRT’s publically-accessible FTP server and generates relevant imagery over Southern Canada for his website users.  As an additional verification of this snow event, Brian used SPoRT’s MODIS false color snow cover product to compare with forecasted snow depth output from WRF.  In the false color image below, the red areas outline where there is snow on the ground, and the outline of the fallen snow matches very closely with the areas where snow was forecasted to fall in the 36-hr forecast.  While the MODIS false color product is unable to provide any quantitative information about snow depth, the MODIS image is annotated with reports from the two areas where the heaviest snowfall occurred.  The heaviest snowfalls in the 36-hr WRF forecast also match nicely with the bull’s eyes of where the heaviest snowfall was reported.

MODIS false color imagery from 1640 UTC on 24 November 2013 showing the extent of the snowfall that occurred during this lake-effect snowfall event over southern Ontario.  The red areas indicate snow on the ground.  The circled areas with annotations show the areas of the heaviest reported snowfall.

MODIS false color imagery from 1640 UTC on 24 November 2013 showing the extent of the snowfall that occurred during this lake-effect snowfall event over southern Ontario. The red areas indicate snow on the ground. The circled areas with annotations show the areas of the heaviest reported snowfall.

36-hr WRF forecast of model snow depth valid at 1200 UTC on 24 November 2013.  The spatial extent of the snow on the ground and largest snowfall areas over southern Ontario coincide with what is seen in the MODIS false color image and snowfall reports.

36-hr WRF forecast of model snow depth valid at 1200 UTC on 24 November 2013. The spatial extent of the snow on the ground and largest snowfall areas over southern Ontario coincide with what is seen in the MODIS false color image and snowfall reports.

 

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