Monday, April 21, 2014
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.
Precipitation type is an interesting thing. There are times you think it’s cold enough for snow and it rains and times you think it’s warm enough for rain and it snows. To understand they type of precipitation we see here at the ground think about the atmosphere like a layer cake.
In the clouds, where precipitation forms is analogous to the top of the cake and the ground where the precipitation reaches is the bottom or crust (I like pie). What happens in the middle is quite critical for determining what for the precipitation will take.
Notice in the diagram below the red color represents air above freezing. In the snow situation, there isn’t any air above freezing. As the snow falls from the clouds, it’s able to make it to the ground without melting. In the other three situations, the warm air melts the snow before it reaches earth.
There’s a term some meteorologists use called “model hugging.” Basically, this means buying those models you hear so much about hook, line and sinker. The thing about the models, they are guides to what will happen in the future, not gospel.
Any model is not 100 percent correct, just ask an economist. When I forecast a storm I certainly review all the models, but ultimately I have to make the call myself. When it's three or four days before a storm, the models often are still all over the place predicting how the atmosphere will come together.
The models are amazing and it’s a wonder to me we can forecast the formation of anything 10 days in advance. Yet, they often don't have the accuracy needed for a confident forecast more than 72 hours ahead of time. This is why you hear so many "ifs" in the long range.
On a planetary scale, knowing a storm will form is important, but to get the forecast right for an area that includes Bangor to Bridgton and south to Portland, the model has to predict the track of a storm within 50 to 100 miles - otherwise the forecast won’t be accurate. The model could show a storm's track correctly 10 days in advance, but the odds are much higher it will do so two days before an event.
Welcome back to January. If the spring weather on Tuesday made you think winter was over, the howling wind and snow showers today will make you think it’s not going to end.
The mild air made quite a push westward and most of this storm fell as rain south of a line from north of Sanford to Naples, east through Lewiston/Auburn and on to the midcoast. For a time last evening the rain pushed as far west as Bridgton and Fryeburg, but then it quickly retreated east again.
Ski areas will continue to see some accumulating snow much of the day with another 3 to 6 inches. Elsewhere, 1 to 3 inches of snow could fall by mid-afternoon today. I expect a few spots in the mountains to hit the 18-inch mark or maybe even a bit more if some of the heavier bands of snow move through. This is going to extend the ski season by a couple of weeks.
The cold air remains in place through the entire day and overnight. When you get up tomorrow it will be at or below zero inland and in the low single numbers along the coast. The record low for Portland tomorrow is 2 below zero. While we won’t break that record, a low of 5 or 6 above for Friday will still make March 14 this year one of the coldest in recent memory.
As of the mid evening hours a few things have changed. The rain, as expected, is coming down along the coast. It's pushed a bit further inland than expected however. This means snowfall and sleet totals will be less than expected. As as result, the winter storm warning was downgraded to a winter weather advisory along the coast up to Rockland. I suspect areas west of Portland on a line from about Sanford to Sebago to south of August will have a tough time exceeding 4 inches of snow. When you see the accumulation maps, figure you'll be on the lower end of the range unless you are north and west of Rumford and Skowhegan.
Winter storm warnings are now posted for the foothills of Maine as well as the mountains. As you head towards the coast, winter weather advisories are posted for a mixed bag of precipitation on the way. Along the immediate coast, from about Bath southward, there are not advisories for winter weather as the bulk of the storm will be in the form of rain. That said, there will be some accumulating snow as the storm ends Thursday and advisories may still be needed along the coast.
The track of the storm for tomorrow will hug the coast. This track pulls warm air at high levels of the atmosphere and also brings warm air into the surface layers here at the ground. What this means is it will be too warm to snow along the coast, at least for a good chunk of the storm.