Tuesday, May 21, 2013
This morning we find fog advisories from Maine to the Carolinas. This is quite unusual to see nearly the entire east coast covered in fog. The reason for this is that warm air is riding up the coast and moving over the cold air and in some cases, snow at the surface. Additionally, there is very little wind to mix things up so the air becomes stuck and the fog can't move.
With melting continuing throughout the day and overnight, there will be significant snow loss especially along the coastline and into the foothills. Ski areas will also lose some of snow, but bases are quite deep and the impact should be minimal. Temperatures during this January thaw will peak Monday with 40s common across southern Maine.
We know that it is going to get colder this week, but I am not expecting any extreme cold and as a matter of fact, many areas will break freezing each afternoon. Parts of the country are seeing very cold temperatures and some of this cold is also occurring in Europe and the United Kingdom. For about two weeks we have known that colder weather was about to occur, the question has been where will the coldest of the cold happen?
Sudden 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. There is a whirlpool of spinning air up in the stratosphere called the polar vortex. This spinning system Temperatures up in the stratosphere are very cold. However, sometimes, temperatures can suddenly, in a matter of days, 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. When this warming occurs, it can change the way the winds blow up there and create changes in the troposphere below. When sudden stratospheric warming (SSW) occurs, the jet stream beneath the warming can buckle and allow the cold air over the arctic to spill south. The problem is that it is difficult to forecast the exact location of the buckling wave and thus the location of the cold air. These SSW events, when they happen, produce a cooling at the surface about 75% of the time. One of the other problems is that our computer models have a difficult time with this phenomena and so the accuracy in forecasting the extent and intensity of the cold isn't as good as the general day to day forecasts. See some of the images above that show the stratospheric warming and the vortex itself.
End of January
There are still indications of more blasts of arctic air entering the United States throughout January. I also see another possible SSW event later this month which could bring even colder air to some parts of the globe in early February. The difficult task will be in determining if the cold air ends up across Denmark, Maine or stays arcross the Atlantic in Denmark itself. 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.
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.