“Forecast Uncertainty” and “Three Scenarios” – Let’s Cut the Bull$hit and Get Right to the Truth

The Same Old Bull$hit

For those of you who have followed my weather blog you know the drill here in Washington. The “experts” clamor on about the various, “mind-numbing” solutions with the same three potential scenarios depending upon the outcome of the exact storm track.  There is a “50% chance of snow in DC changing to a wintry mix” and a “50% chance of all snow” — really? Why not just tune in 36 hours before the event for an accurate forecast?

Has anyone ever noticed that the same folks say the same thing with every winter storm 3 to 4 days out? There is always “three scenarios” to include:

  • The storm tracks from Cape Hatteras to Cape Cod dropping heavy snow from Washington to Boston
  • The storm tracks too far east and misses DC
  • The storm tracks too far inland wrapping in warmer air with snow changes over to rain

Why waste everyone’s time with potential scenarios?  Well for one, the media wants to get out ahead of the narrative for ratings (to pay their bills) and to ensure that they garner your interest — I mean nothing will get ratings like a potential snow storm that will shut the big cities down for a few days.

The Facts 

Forecast models utilize mathematical equations and the solutions 3 to 4 days ahead of a storm system are only as good as the input data.  How do we get input data? With weather stations and weather balloons of course.  A good sampling of the atmosphere is needed and that accurate input data will produce an accurate solution (where the storm will eventually track).  Until the upper-level energy that is responsible for the evolution of this storm tracks over a land mass (western Canada) on Friday, the forecast models will continue to fluctuate. In other words, don’t trust any potential outcome until Friday afternoon. 

Where is the upper level energy now? 


When will these features begin to really become accurately sampled? 

Early Friday morning, especially the 12z (7AM) run of the models will be key

The Atmosphere behaves like a River in Motion

The Timelapse below shows how the two pieces of energy interact to produce rapidly rising air and pressure falls along the Mid-Atlantic coast that induces cyclogenesis.

Where the surface area of surface low pressure forms and its exact track will determine the outcome of the weather in your neighborhood on Sunday afternoon through Monday.

The Ensemble Models below reflect the uncertainty in the input data that I mentioned and will begin to converge on a solution by Friday morning

European Forecast model showing its 50 various ensembles

GFS Ensembles

Canadian Ensembles

I would anticipate that Winter Storm Watches will be issued by the National Weather Service on Friday. Stay Tuned.