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Storm details for Friday still evolving

Posted by David Epstein  February 5, 2013 06:00 PM

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Our weather looks quiet for the next two days with a few flurries overnight and early tomorrow. Cape Cod could see an inch of accumulation with Boston getting even less. 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. First one and now two of those models, of the many we use, are predicting a big storm here for Friday into early Saturday. The storm, if it occurred would be a typical nor'easter with wind and heavy snow and rain along parts of the coast. This afternoon several of the computer models are now beginning to agree a major winter storm will take place to close out the workweek . However, there are still enough questions in the forecast that I am not ready to commit to a blockbuster scenario. I'll be updating frequently on Twitter at @growingwisdom about the latest details on the storm potential for Friday.

You might ask if all the models are equally accurate and that would be a great question. Both the European model, that is quite accurate and actually did the best job with predicting hurricane Sandy, and other models are now forecasting a big storm. As of late afternoon one of our other models, the GFS or Global Forecasting System, is showing a strong storm of snow or snow to rain Friday. It's still way too early to say much more than we will have a snowy day in many areas Friday and rain along parts of the coast. This could be a large storm, but it could also still turn out to produce just a few inches so stay tuned.

Why so hard?
What the models are having a hard time forecasting is what is called a 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, or northern one and the subtropical jet or 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.
split flow.png
Blizzard of 1978.png
New information
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 8:30 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.

Gardening this week
This week I wanted to share a video that shows a very unique water garden. This particular water garden contains many different varieties of fish. While you might not have the space for something this elaborate, you can mimic some of the elements on a smaller scale.

I'd love to hear your thoughts on this blog or any others. Please follow me on Twitter at @growingwisdom and check out my latest videos at GrowingWisdom.com

This blog is not written or edited by Boston.com or the Boston Globe.
The author is solely responsible for the content.

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About the author

David Epstein has been a professional meteorologist and horticulturalist for three decades. David spent 16 years at WCVB in Boston and currently freelances for WGME in Portland, ME. In 2006, More »
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