Category Archives: PHL Climate Forecasts


…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.


Two more rain storms forecast for this week –one Thursday (possibly missing us, staying to the south) and on Saturday.   The Saturday storm may be a nor’easter, but the lack of cold air makes this an atypical nor’easter for January.  It looks like rain!

The current weather pattern is quite anomalous for January.  There’s little evidence of deep intrusions of cold air into the  continental US for the first two to three weeks of January!

There will be short duration cold air intrusions  into the Northeastern US which will alternate with mild air and wet flows from the southwest.

The current climate model forecast captures this nicely:

CFS Forecast for the first week in January (areas in red/orange are above average upper air heights associated with above normal temperatures.)

What we need for winter to return is for the height contours (shown in black) to take the following configuration, (shown in blue.)

Blue line drawn shows typical configuration for cold air intrusion in January

Obviously, there  would have to be giant changes in the current weather pattern to support my early December climate forecast of significant cold weather and significant precipitation.  I’m not very confident about that forecast at this time.

So enjoy the relatively mild weather!

The current long range climate models show colder intrusions around the third to fourth week in January, a time when we usually get the “January Thaw”.


It’s about that time of year when I take a stab at the long range winter forecast. I always preface this with the disclaimer that predicting a seasonal trend is really climate science, not weather forecasting. Climate science isn’t as advanced as weather forecasting. That said, there’s always interest in this, so here goes:

Basically, the current pattern suggests colder than average temperatures this winter due to the nadir in the sunspot cycle and higher precipitation due to an El Niño.   Let me explain-

Climate forecasts boil down to temperature, moisture and jet stream position.

Regarding temperature, we are about to entering a solar minimum.The solar cycle is a regular, periodic change in sunspot number and the mimimum correlates with reduced total solar irradiance. The Lasco Project has shown that total solar irradiance drops almost 1 watt/m2 during solar minimums.

While not universally accepted, solar minimums allow for these colder conditions.

Global Temperatures
Current Global Temperatures Dark Violet -30-35 Degrees C

The current global models show very cold temperatures already developing in the polar region, Siberia and Greenland. The appearance now is similar to that seen in the middle of winter.

So we have one ingredient- very cold air this season. This winter will likely be colder than average in the Northeast.

Regarding the moisture component, an expected El Niño in the Pacific is developing – warm ocean temperatures that will provide a stream of moisture along what is referred to as the southern jet stream.

So we have a second ingredient- moisture picked up from the warmer Pacific ocean. Precipitation will likely continue above average in the Northeast.

Does that mean we will have more snow than average? Probably, but not necessarily. That depends on the jet position.

While TV forecasters often suggest the jet stream is moving in ways with a mind of it’s own, the jet stream really flows between boundaries of air masses. It’s the edge of the air masses that determine the jet position, not the other way around. Large cold air masses developing at the poles have to sag down and mix. In doing so, their boundary sags and dips, causing a dip in the jet. Warm air masses in the tropics push their edge north. The boundary is where jet stream is and where low pressure systems develop,

While it would make sense that we get more snow, the actual random shape of the cold air mass boundary (jet stream) might spin up storms to our east (snow) or to our west (rain).

One more thing— With plenty of warm air in the southern hemisphere from global warming, it likely that wide swings in temperature will occur, with extended below average cold periods interrupted by much shorter periods of warm temperatures. 

This is my best guess for Winter 2018-2019.