School vacation week begins tomorrow, after the close of school, and some of you may be headed to warmer climates, ski areas, or just hanging around locally planning to do some fun activities with the kids. No matter what you have on the agenda for the next week, the weather is always a factor. Unfortunately, for skiers, I don't see a clear cut situation with a major amount of snow in the next few days. However, there will be a storm that should miss us late this weekend as it passes well to the south of New England.
The big weather system I will be watching the next few days is a storm that will develop across the southeastern US and then make the turn up the coastline. With the exception of the October snowstorm no major snowstorms have affected the big cities of the northeast. There are many reasons that we have not had any snowstorms this winter. As of mid-afternoon, most indications are this storm will not affect New England in any significant way.
As you know, meteorologists review all sorts of computer models from all over the world before making a forecast. The models work this way. First, they ingest data from weather balloons (radiosondes), that are launched across the globe twice each day. Our closet radiosonde site is Chatham. These radiosondes have sensors that take readings of temperature, moisture, wind and pressure and give us a good picture of the actual state of the atmosphere worldwide. Using this actual real picture of the atmosphere gives the models a good place to start to predict the future. Using math and physics, computers evaluate the data from the radiosondes and attempt to predict how it will all change in the future. Those complicated equations are then solved by the computers to give forecasters a prediction for how that original radiosonde data, will look later in time. The equations keep moving that picture of the atmosphere ahead in little chunks, about 5 minutes each. Eventually, we see predictions for one, two, five even fifteen days into the future. It all goes back to that first look from the radiosonde data. That is why we get new model forecasts twice each day, it starts with a new balloon launch, new radiosonde data and leads to a changing forecast.
There is a whole suite of data that meteorologists are able to review. We get to see the predictions from two United States computer models, one from Japan, one from Canada, one from the Europeans and one from the United Kingdom. There is also another model from the Navy and some additional data that is basically combinations of other models. In other words, a lot of different solutions for how the atmosphere will look at some point in time. The closer to the actual weather event we get, the closer together the each solution the models present will become. I tell my students, forecasting these storms 4 and 5 days out is a bit like asking folks who will win the World Series in April. In April, everyone has a different opinion on who will win the series they are, like the models, far apart. By September the answers are closer together in the same way the predictions for this weekend will get better with each new 'model run'. Later tomorrow, we will have a much better handle on the forecast for late this weekend.
All the models use the latest radiosonde data, but each model uses that data slightly differently with different equations and has a unique ways to see the atmosphere. Those subtle differences can cause wide swings in the maps we look at. One model can bring a storm over our area while another takes it safely out too sea, hundreds of miles to the south.
Most of the models have been taking the storm across the Gulf Coast then up to about the Carolinas before moving it out to sea. This would give most of New England a few clouds and maybe some light snow or rain across the south coast, but no big storm and no accumulating snow.
Only, one model, the GFS, a NOAA model was moving the storm up the coast and close enough to New England to give us a moderate to major snowstorm. Even that model is now tending to keep the storm away. Nearly all the other models are keeping the storm to our south, another miss. Every 12 hours we get another round of models and another chance to revise the forecast. Keep coming back to my blog for updates throughout the weekend. Follow me on Twitter as well, where I will discuss the forecast with some other meteorologists.
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