Doesn’t get much weirder than this in the weather world. The 12z GFS sent a shot heard around the meteorological world with an exceptionally dramatic blizzard with no other model support. The shots kept coming through today with the American models going crazy with an extreme westerly track that pummels the Mid Atlantic and southern new England with snow.
Shortly after all of this model insanity the Hydrometeorological Prediction Center sent out this statement (they run the American models) saying to basically ignore them.
INITIALIZATION ERRORS IN NUMEROUS DIAGNOSTIC QUANTITIES… INCLUDING HEIGHT/VORTICITY FIELDS/RH…ARE EVIDENT IN
BOTH THE 12Z NAM/GFS WITH SMALL BUT LIKELY SIGNIFICANT SHORTWAVE TROUGHS OVER SOUTH DAKOTA/NEBRASKA ALONG WITH SASKATCHEWAN/MANITOBA…WITH THESE AREAS ALSO NOT PARTICULARLY RESOLVED OR PREDICTED WELL BY THE 00Z ECMWF. THUS…THE SPECIFIC PREDICTIONS BY ALL DETERMINISTIC GUIDANCE ARE IN QUESTION…WITH THE RECOMMENDATION TO FOLLOW CONTINUITY…WITH THE FINAL OUTCOME MOST BELIEVED TO LIE BETWEEN THE 06Z GFS AND 00Z ECMWF…WITH ALL ENSEMBLE GUIDANCE INCLUDING THE SREF MEAN/GEFS MEAN (EXCEPT NOT
THE 12Z VERSION)/ECMWF ENSEMBLE MEAN ALSO CONSIDERED USEFUL TO ADDRESS THE CONTINUED UNCERTAINTY. THIS APPROACH DISREGARDS THE SUBSTANTIALLY DEEPER AND WESTWARD SHIFT OF THE 12Z GFS REGARDING THE POWERFUL LOW TRACKING UP THE EASTERN SEABOARD…AND TO A LESSER EXTENT THE 12Z NAM WHICH LIES NEAR THE FAST EDGE OF THE GUIDANCE WITH THE DEVELOPING LOW.
Though the 12z GFS may have been an aberration it was quite a shock to many of us to see all subsequent American models come west at 18z. In fact the ensembles (both the GEFS and SREF) are west as well. Every GEFS member comes close to bringing blizzard conditions to parts of Connecticut.
It’s important to note that if the 12z data assimilation and initialization was wrong the GFS subsequent run can be impacted. The 18z GFS and NAM use the 12z GFS 6-hour forecast as a first guess. From there additional data is assimilated (at 18z we’re talking about surface obs, remotely sensed or satellite data, and aircraft data) and the model is re-initialized. An egregious error with the 12z initialization could reappear at 18z. By 00z the additional data that’s assimilated includes 00z RAOB data which should help things significantly.
The 12z GFS (and 18z) both show 2 very strong shortwaves phasing and blowing up a monster storm. The 12z Euro (with a superior initialization scheme – no one disputes that) initialized both shortwaves weaker than the 12z GFS. I’d go with the Euro right now but I’m sweating this one out.
It’s hard to go against the foreign global models in a situation like this. If you like snow we’re rooting for a 1980-style Lake Placid miracle.