End of Current "Model War" Likely to Reveal Very Impactful Winter Storm This Weekend
Potentially Historic Magnitude In Play
Throughout the entire evolution of long range prognostications concerning the potential major storm system this weekend, the computer guidance has been particularly fraught with inconsistency and disagreement given the sensitive nature of the phasing steams at play. This has continued in varying degrees and forms as this potential crosses the threshold from the long to medium range.
Points of Model Uncertainty
Initially, the model uncertainty centered around the issue of whether or not the southern stream would eject energy from the sub tropical jet over the Baja region quickly enough to afford the opportunity to phase with the northern stream energy parcel. Eastern Mass Weather outlined early on Sunday morning why a faster ejection, which would increase the likelihood of subsequent phasing, was the most likely scenario. Over the last 36-48 hours all guidance has trended into unanimous agreement that this will indeed be the case, thus the main points of uncertainty that remain are whether said energy will eject quickly enough, and whether or not the northern stream will be aggressive enough to trigger a full phase. Current trends in guidance coupled with the proclivity for the northern stream to be very prevalent this season imply that the answer is an emphatic "yes".
Guidance Converging on More Phasing
The current discrepancy between the 18z operational GFS and EURO is very apparent.
It is evident from the annotation above that the latest deterministic GFS guidance offers a much more cohesive and proficient phase owed to both a more assertive northern stream contribution, and a faster ejection of southern stream energy from the sub topical jet in the vicinity of Baja, Mexico. A cursory glance at the respective ensemble mean solutions reveals a similar contrast with one important distinction.
The difference is not as glaring, which is illustrated by the disharmony between the operational EURO model and its own ensemble mean.
The high degree of dispersiveness amongst the European ensemble suite in conjunction with the support for the GFS suite offered from the Canadien ensemble lends support to a more phased solution. Confidence in this outcome is further buttressed by trends among both the European and Canadian ensembles.
Increasing Importance of Trends in the Medium Range
The Canadien suite represents a compromise between the proficiently phased GFS suite and the more disjointed European ensembles. However, such a precarious and subtle phasing evolution is relatively unlikely to yield a middle ground compromise. Thus trends become paramount as the shift focuses from the longer range to the medium range given a high stakes, potentially binary evolution such as this. All three ensembles packages have trended toward more phasing today, which takes on a grate magnitude of importance now that the window of time in which the phase would take place is within 4-5 days. The highly phased GFS suite:
The partially phased Canadian ensemble mean:
And the European ensemble suite, which was already parting ways with the highly disjointed deterministic model, has continued to trend towards more phasing today.
In conclusion, although there remains a high degree of disagreement amongst current guidance, Eastern Mass Weather is relatively confident in a highly phased solution, which would yield a major storm next weekend. This is due to not only to the tendency for the northern stream to be prevalent thus far this winter season, but also the fact that the compromise solution of the Canadian suite is more supportive of the aggressive GFS guidance. Additionally, all three major ensemble suites have continue to trend towards more phased solutions during the day on Monday.
First Call for a Saturday Night into Sunday storm likely to be issued on Wednesday night-
