Thursday, April 17, 2014
A small snowstorm is headed for Maine and will begin by sunrise Wednesday. This storm will ride along a very tight temperature contrast that is just to our south. On Monday, Portland nearly hit 60F and shattered the former high temperature for the day. As a cold front moved through yesterday temperatures were brought back to levels more typical of January, but still not very cold. Now, warmer air will try to move back north and combine with the cold air over us to create a very weak and fast moving storm.
When I say fast-moving, the jet stream that is carrying the storm system is moving at nearly 200 mph at 30,000 feet over New England. The rapid flow of the jet stream will keep the storm from becoming very strong and providing much accumulation. Nonetheless there is enough moisture with this system that several inches of snow is likely across southern and central Maine from York to Bangor and west to ski country. Far northern Maine will not see much if any snow from this system.
The heaviest amounts of snow look to fall just away from the coast where the snow will be lighter and therefore able to pile up a bit. Along the water, the snow will be wetter and more compressed. There may be some mixing of rain east of Portland along the immediate coastline. However, I expect the bulk of the precipitation to fall as snow and not rain. The entire system is gone Wednesday evening and that sets up a nice day Thursday. A quick shot of arctic air arrives Friday but then it turns less cold for the weekend. Next week the real cold air you might have heard about arrives and temperatures will run below normal. Tuesday, many areas inland and in the mountains will stay near zero much of the day.
Patriots Sunday Another blast of cold air will be headed for New England Sunday. The timing of the arrival of this air is not definite so it may be that we are just chilly for the game and not windy with low wind chills. Give me a few more days to evaluate the weather for the game. First thinking is that temperatures will be falling during the game with a gusty wind.
Overall pattern shift As usual, winter has not been affecting the country evenly. For the past week, the west and the southwest have been significantly colder than normal. From San Francisco to Tuscon, Arizona frost and freeze warnings are up and farmers are concerned about damage to their crops. In the east, from Florida to Maine, temperatures were running up to 20F degrees warmer than you would expect in the middle of January and much of the snow has melted. Now, we are watching the pattern slowly undergo a change which is bringing some colder air east of the Mississippi and into New England. The big question is, just how cold will it become next week?
Stratospheric Warming Let's do a quick lesson in meteorology. I want to talk about how warming high above the earth can actually create cooling down here where we live. To understand this phenomena you have to remember the atmosphere is like a layer cake. The layer closest to the ground is called the troposphere and is where most of our weather occurs. Just above that is the tropopause and that is the dividing layer before you get to the stratosphere, the next layer up. The stratosphere is also where the ozone is located. The ozone keeps that layer somewhat warmer than it would be without ozone as the ozone traps some of the sun's ultraviolet light from reaching the earth below. Even with this warming, it is still very cold at 50-80 below zero! Another aspect of the stratosphere is that there is a whirlpool of spinning air up there called the polar vortex. This vortex is also three dimensional and extends to the ground. While temperatures in the stratosphere are very cold, sometimes, in a matter of days, temperatures can suddenly spike and become warmer. Now, warmer up there might mean going from 80 below zero to a balmy 35 below zero, but that increase is dramatic and significant. This phenomena is known as sudden stratospheric warming (SSW). This warming can change the way the winds blow in the stratosphere and create changes in the troposphere below. One way these change manifest themselves is by bending the jet stream beneath the warming. These changes can also affect ocean currents, ice flow and water temperatures. The jet stream will buckle and allow the cold air over the arctic to spill south. One problem is that it is difficult to forecast the exact location of the buckling wave and thus the eventual penetration of the cold air south. These SSW events, when they happen, produce a cooling somewhere at the surface about 75% of the time. Another problem is that our computer models have a difficult time with this phenomena and the accuracy in forecasting the extent and intensity of the resulting cold isn't as good as the general day to day forecasts. The last SSW event, a couple of week ago, most likely helped create the recent extreme cold over parts of the United Kingdom and the cold across the southwest United States. End of January There are still indications of more blasts of arctic air entering the United States throughout January. Later next week another round of SSW is predicted. You can see this prediction on the image below. The result may or may not be additional blasts of cold arctic air which end up on this side of the world or perhaps affect parts of Europe or Asia. More on this in the coming days. Gardening this week I have a new video to show you this week on moving a tree. You might think big deal, right? However, the tree that got moved was done so without hurting any roots. They used something called an air tool to blow the dirt away and then lift the tree to its new home. Check it out. 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.comTweet
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.