Estimating And Correcting Global Weather Model Error

Latest analysis indicates that there is a lot of instability available, but pockets of capping inversions spread out across the Great Lakes, which is likely going to suppress storms for a little while longer. This system is working with little energy and flying eastward on the wings of the advancing push of arctic cold. The cold weather will hit late in the day Saturday and Sunday could be another where temperatures are in the -20 vicinity in the morning and struggle to zero during the afternoon. In January, the western valleys regularly drop to 5 degrees below zero. So, perhaps dry-air advection from west of metro caused the large drop in dewpoint. We can see this trying to happen in the West US, with that Pacific high pressure apparently trying to progress into the Pacific Northwest region. When the polar vortex collapses in spring, high pressure takes over the stratosphere, ending the risk for sudden stratospheric warming events. The frozen Great Lakes can assist us however since they no longer have the same magnetic pull on developing low pressure systems.

If we use this rule on the model image above, a rather strong upper level low with the accompanying threat of some cold Arctic air may begin affecting the US around September 17-21st, within the six-to-ten day timeframe discussed above. As we see a stormy period begin in East Asia over November 28th, I would expect December 4-8 to be the timeframe for a winter storm in the US as a result of this East Asian correlation. Thanks to everyone for the compliments over the past few days (encouraged of course by Eric at MRG) . Its approaching “prime-time” at MRG and things are looking very “up” as the NAO goes “down”. These are the months right before the rains begin. You may be surprised at how rapidly your track can take shape once you begin moving that dirt about. Steady precipitation is probably not going to begin until after the ski day Saturday (although we may get a shower early). Snowmelt over the next two weeks will actually occur slowly and much of the base will get retained well into March.

As of Sunday, Mad River Glen was on the fringe of a developing coastal system impacting much of New England. This particular weather system has an elongated zone of overrunning that will extend across half of the country Saturday night. It will thus ultimately be a question of whether the pattern allows for a major weather event to track far enough north for major snows. However, in past decades they have expanded their range up North America. The period Sunday through Wednesday will be wintry as the return to colder weather this upcoming weekend will get reenforced early next week by a temporary re-positioning of the ridge/trough set up in North America. In March, you can open a small window of opportunity for winter weather and can get some big powder. The open wave character of the pattern was what was observed this morning. Considering how “blocked” the pattern has become, major weather systems will find some resistance as they proceed up the Atlantic Coast (if one becomes organized enough to do that).

We here at the Weather Centre will keep you notified. At the very least we should see snow from a “clipper” or a “mauler”, or “bomber” and this will provide at least one powder day. The first two chances at precipitation are from more or less one interconnected system, which, after a dry period Sunday will threaten to bring more precipitation on Monday. Don’t let this change your vacation plans, though, if you find that no hurricanes are predicted! Within 24-48hrs it is relatively well predicted. Now, as for the Northeast, the same cold front is sliding south, but poses a tornado threat, as well as an enhanced damaging wind threat. A cold front is sagging south at the moment. This system has a slight chance exploding off the Atlantic coast and providing more than the 2-5 inches that I might guess would fall at the moment. So yes, an east coast storm is possible and has been indicated in a few of the cycle of recent model runs but is far from a certainty and is still more on the unlikely side.

There are a few individual skirmishes where we can score a victory but it is not likely to come late Thursday into Friday. The month when scorpions are born. Big storms, the ones which are really good for SCWB ratings are unlikely until Christmas week but the pattern is certainly capable of producing such an event between the 20th and 25th of the month. Most drivers are aware of proper safety precautions to take in the event of heavy rains or other adverse weather conditions. The key point is that the observed sea surface temperature distribution in the tropics can forced the observed anomalous weather patterns in the midlatitudes. Over the weekend, the real spring-thaw will be confined to the mid-atlantic and southeastern United States while Vermont will be in no-man’s land, or stuck in the middle of a broad south to north temperature gradiant. Temperature changes can also be accompanied by precipitation.