Sunday, December 8, 2013
Across the state of Maine the weather looks quiet for the next several days with just the chance for a few flurries overnight and early Wednesday. Temperatures will remain cold, but not bitter as a northwest flow of air from Canada continues.
You may have heard of a potential storm for Friday. Over the past several years our computer models have gotten better, but not perfect at long-range forecasting. One of those models, of the many we use, is predicting a big storm here for some time later this week. The storm, if it occurs, would be a typical nor'easter with wind and snow. The problem for me is that several of the other models I use are indicating that the storm will develop too far out in the ocean to give us a blockbuster snowstorm.
I'll be sending out updates about the storm potential on Twitter at @growingwisdom so please find me there. I would love to hear from you.
What the models are having a hard time forecasting is what is called phasing or coming together of two jet streams. You may not realize that there are several jet streams circling the globe at any time and they are most active in winter. The two primary jet streams are the polar jet (the northern one) and the subtropical jet (the southern one). To get a classic snowstorm here in New England we generally need both of those jet streams to merge and provide both cold energy with warm moisture. If that happens then our chances for snow increases. The images below show what is being forecast for Friday and shows an old map from the Blizzard of 1978, one of the most well developed nor'easters in history. While the maps are not from the exact same height in the atmosphere, it gives you an idea how different things can look in a big storms versus a small event.
Each day we get new model predictions called "a run" which has updated information put into the forecast. The American models, the GFS is run 4 times each day. We receive new maps every 6 hours starting at about 10AM each day. The European models are run twice a day and we get that data in early afternoon and then again about 12 hours later. This is one of the reasons the forecast can dramatically change in a few hours. Most likely your favorite meteorologist is adjusting their forecast based on the latest computer model.
As I close out this blog it's already about 9:30 AM and new weather data is pouring into Washington, DC. Within a few hours there will be more maps and another forecast to fine-tune for Friday.
This week I am putting up a video on how to build the perfect container. While you might not be thinking of gardening this week, you can plant pansies in 8 weeks and if you have protective covering some vegetables can be planted in another 5 weeks. More on how I do that in upcoming blogs.
David Epstein has been a meteorologist for more than 25 years. He spent 16 years in Boston and currently freelances at WGME13 in Portland.
In 2006, David founded GrowingWisdom.com, a business producing educational and marketing videos for the green industry. He currently is a professor at Framingham State College, teaches Jan Plan at Colby College and owns Bloomscapes Inc., a landscape design business.
David authored "Gardens Of New England" and his work has been published in Grolier's Science Annual for 10 years. He lives in South Natick, Mass., and has a summer home in Harpswell.