At Providence, everyone wants to know what the weather will be Mon through Wed, with some news media predicting as much as a couple of feet of snow. Dire forecasts of that sort are at the very least premature, with NWS officially stating low confidence in the details. In my opinion, it is irresponsible for broadcast media to sensationalize weather information without clearly disclosing the degree of uncertainty, because if the storm they promise fizzles out then public confidence in weather forecasting is damaged. This is a very difficult forecast because if all of the necessary factors come together, we could see blizzard conditions with heavy snowfall over a long duration. At the other extreme, there is a 20% chance we will see no snow at all. Rather than throw out a guess and hope its close, the proper way to present this forecast is to explain the nature of the inherent uncertainty. What could happen to give us a blizzard is that a low pressure center could develop off the coast to our south, a process technically termed cyclogenesis (a low pressure center is a cyclone while a high pressure center is an anti-cyclone), because of the interaction of troughs between warm and cold air masses. If such a low pressure center develops, its effects will be determined by its strength, its position, and its track. For any given combination of these key factors, a track sufficiently far to the south would give us a relatively small amount of snowfall with amounts increasing toward the coastline, but a track sufficiently far to the north would give us rain or other mixed precipitation that reduces accumulation. To get blizzard conditions and high snow accumulation, we would have to land right in a narrow band of maximal snowfall. I dont want to minimize the necessity of preparing for a severe weather event of this kind. High winds could take down tree limbs and power lines, and some areas could without electricity for days. This is a real possibility, and a large part of southeastern New England could be shut down for several days. Make plans for what to do if you have no heat and no electricity. However, keep in mind that you are planning for a low-probability high-consequence event: it could happen and if it does you will have to deal with it, but it is likely will not be as bad as the worst case scenario for which it is prudent to plan. As the event moves closer in time, forecast accuracy can be expected to improve rapidly, so keep alert to updates.
Posted on: Sun, 25 Jan 2015 05:23:06 +0000