SO WHERE’S THE SNOW THIS WINTER?

…Update added Arctic Temperature Anomaly chart below.

When temperatures reach into the 60s this weekend (the Canadian model has us near 70!), it’s appropriate to wonder where’s the snow this winter?   I don’t have any good answers, but I have some interesting observations.

Taking last year as an example, we would have jet stream configurations and air mass positions that would suggest the possibility of coastal storm development and snow.  Most of the times last year, these model forecasts of snowstorm development would fall apart just a few days before the forecast event.  But there were possibilities.

What’s fascinating about this year’s weather pattern is that the models haven’t even projected a potential storm for us. I haven’t seen any instance of southern and northern jet stream phasing over the western Atlantic in a way that would allow a coastal low to form near the Carolinas or Virginia.

The jet stream, which really represents the “air river valley” at the periphery of cold air masses sagging southward has been broad in shape instead of a sharp dip in most cases.  Where there have been some sharp dips, they have occurred in the Western and Central US. Where there was any sort of dip, the shape was positively tilted instead of negatively tilted (tilted back westward), which induces deep storm formation and slower movement.

There has been no large blocking North Atlantic high pressure that results in these sharp dips along the coast.

Not only have there been no sharp dips along the east coast in any model projections during December or the first week in January, the current GFS which forecasts 16 days in advance shows no potential snowstorms through January 24th.

Things could change, but the Climate Prediction Center shows our area with above normal temperatures and precipitation through the spring and summer.

One more thing —the amount of cold air dropping south is dependent upon the amount of cold air that accumulates in the arctic.  Here’s December’s temperature anomaly for the arctic:

Arctic air temperature departure Dec 2019 at 925 mb height

There’s simply less cold air pooling in the arctic circle.

WINTER WEATHER UPDATE

6:20 PM : Latest GFS and NAM show almost no snow accumulating in Philadelphia and much of NJ.  Areas north and west of Allentown may have more than an inch.

Latest GFS snowfall forecast

12:35 PM: Latest Canadian and NBM models show decreased QPF and temps too warm to accumulate near Philadelphia.  This supports the new GFS.  Some light snow falling, but not expected to accumulate. A coating, at most. The earlier NAM and NAM Nest are now outliers.


10:43 AM: Latest GFS just available has less than 1/2 inch for most of our area. Too warm! The HRRR has almost nothing.


Last update before I head out the door.  So many models, so little time!

Latest NBM, NAM-NEST and WRF-ARW available.    I’ll cut to the chase:

This morning’s NAM NEST high res snow depth
This morning’s lower resolution NAM snow depth

I think the NAM-NEST is the best bet and supported by the NBM.

WINTER WEATHER UPDATE

Last night’s models (they’re re-run again at 1AM, EST and become available between 3 AM and 6AM) had a wide range of snow totals.

The NAM had extremely high QPF values, which I think is an outlier, although in the ‘old days’ of doing my forecasts I would have taken it more seriously,   The high resolution NAM NEST had the following snow totals by 11 PM tonight—

NAM NEST Snow depth forecast- click for larger image

The statistical version of the GFS, the GEFS, which is a lower resolution model had the following—

GEFS snow depth forecast. 

Last night’s European (ECMWF) had a similar map as the NAM NEST above, with a coating in the city.

I’ll be posting some of the latest models from this morning  (HRRR and NAM NEST) when they become available, before I head out the door for work.