EAS 372 exercise of Thurs 7 Feb 2013 -- a forecast for Sat 9 Feb

Available guidance

• The GOES vis (here at 1445Z today) showed streamers of convective cloud off the coast. From the GOES ir image (at the same time) we infer this is low cloud, because we don't see the red colours that indicate a cold (high) target. The cause can be diagnosed from the 850 hPa analysis where we see cold winds off the continent onto the (relatively) warm ocean.
• As to the forecasts, a sequence of panels from the NAM prog initialized 12Z today (Thurs 7 Feb.) gives a nice sense of the big picture:
  • NAM 36hr prog, valid 00Z Sat 9 Feb. The low in the Yukon is relevant to Ab
  • NAM 42hr prog, valid 06Z Sat 9 Feb. Windy in Ab? The east coast storm is affecting NY
  • NAM 48hr prog, valid 12Z Sat 9 Feb Windy, cold advection, light precip in N. Ab
  • NAM 54hr prog, valid 18Z Sat 9 Feb There has been cooling in C. Ab. Strong NW wind
  • NAM 60hr prog, valid 00Z Sun 10 Feb Thickness in C. Ab. down to about 520 dam from about 534 dam Friday afternoon (7 degrees of cooling).
• GEMreg 48hr prog, valid 12Z Sat 9 Feb. Note the storms
• Meteograms for New York (courtesy of UQAM meteocentre) based on NAM and based on GEMreg show New York cloudy with 40 kph northerly winds (00Z-12Z Saturday), with GEM's winds lighter. Rapid cooling occurs in the interval, precip may start as rain but will later be snow.
• This side-by-side comparison of NAM and GEM glbl progs for 18Z Saturday 9 Feb shows the ongoing cooling in N. Ab. and the storm (more intense in NAM) at New York.
• Accuweather.com (15Z Thurs 7 Feb): "New York City and the northern mid-Atlantic are on the edge of a major storm that will hit New England as a blizzard Friday and Friday night. Only if two storms, an Alberta Clipper from the west and a storm from the South, merge very quickly will there be more than a manageable amount of snow (a foot) in New York City, northern New Jersey, southwestern Connecticut, Long Island, northeastern Pennsylvania and upstate New York." (In the context of this storm, Weather Underground gave this explanation of the Alberta Clipper).

Follow-up, east coast storm

• Here's a satellite view (GOES east, ir) of the storm at 23Z Friday 8 Feb.
• Surface analysis 18Z Friday 8 Feb.
• The New York Times reports that some locations in the eastern U.S. received about 1 m of snow.

Follow-up, Alberta

• The low that the progs (correctly) anticipated would be affecting N. Alberta on Saturday is seen here on the surface analysis (18Z Saturday 9 Feb.), and evidently would cause cooling in the NE of the province.
• Fort McMurray experienced the expected cooling trend on Saturday, but Edmonton was distant enough from the low to enjoy a mild, albeit rather windy afternoon.

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Last Modified: 12 Feb., 2013