Our sudden winter storms are severely impacting Boston's commuter system, and to add insult to injury we're now facing an additional 1 to 2 inches tomorrow to be followed by another foot or more next Monday night through Wednesday. We're actually running out of places to put the snow because we've received nearly our full season's total accumulation in one week rather than spread over 3 months with melts in between. Our normal season is about 4-feet average, and so far we've received about 42-inches according to one of our TV weathermen.
Because of this, there have been numerous delays, bustitutions, and outright cancelations of service on the commuter rail, heavy rail and trolley (tram) system. The problems have ranged from downed wires, frozen switches, and even a broken rail which occurred in one of the underground portions of the Green Line trolley right on the main line at rush hour. The commuter rail has suffered from delays caused by down branches, buried track, frozen switches, and signaling system issues. The surface portions of the Orange and Red Lines have also been affected due to deep snow and frozen switches, with the old Mattapan High Speed Line temporarily closed. The MHSL is actually a short stub run with renovated historic Boston PCC trolley cars from Mattapan Square to Ashmont.
http://www.mbta.com/weather/
About the weather in general and Nor'easters...
The weather pattern is normal, but a bit late. We usually start with small and medium sized storms from the middle of December then we get a few good ones in January, a few in February, then a good whopper of one in March. By then it warms up and any snow that falls melts immediately. This doesn't indicate the winter is over for us. Some areas, including where I live, have gotten snow as late as mid-April, and even some freak storms in early May. They're pretty nasty at this time because they wreck the trees, and they're usually accompanied by severe weather as well, including super cell thunderstorms, which can spawn a tornado or two, although this is a bit rare.
These storms are typical Nor'easter storms, which actually come in from the south and head up the coast. The biggest storms come in from the Great Lakes then head into the Ohio Valley where they reorganize and pick up moisture from the Gulf of Mexico. Keep in mind these storms are huge and will cover from Chicago to Missouri, with fringes as far south as Mississippi and even into Georgia and Alabama. They will then pick up the Westerly winds and head east to the Carolina coast where they pick up the warm moisture from the Gulf Stream. There they grow in size, even more than from before, and then take the ride north on the Gulf Stream which is feeding them warm moisture. Usually to get the big storms to organize and really dump a lot of snow, there's an arctic high pressure sitting over Quebec and into the Canadian Maritimes. This keeps the low from moving as it blocks it, or if it's just a bit more east, the low will follow along the outside of the storm, and ride up the side of the high pressure as it spins clockwise, like it's taking an elevator. This usually makes for a small amount of snow because the storm is pulled along quickly by the high pressure. Sometimes other low pressures will combine and sometimes weaken, or block which is a good thing. We're seeing this occur Thursday and Friday (Feb 5 & 6th) this week because of a quick moving storm settling in across New York State and moving into New England. Other times, which seems to be the case lately, the high pressure will sit above, making things cold, while some smaller storms will stay north and block the movement of a bigger storm, which causes lots of snow for us.
So what makes a Nor'easter a Nor'easter...
Keep in mind that storms are low pressure which means a storm rotates counter-clockwise. This means the air flow over the top and from the right to the left. Since the storm is out in the warmer North Atlantic, which is much warmer than the Arctic blast on land, the moisture turns to snow. If they linger, we can get a lot, but most of the storms are gone with 24-48 hours as the high pressure spins and pulls the storm away from us. Then because the air is spinning from the top of the low pressure, it comes in as a cold blast after the storm leaves because it is now pulling the cold air in behind it from that Arctic and are accompanied with very high winds.
Now for a twist... If the storm happens to cross a bit west of the region, we'll get rain and ice which usually turns to a gross wintery mix then a bit of snow. The reason for this is we're on the front side of the storm and receiving the warm moist air instead of the cold side and getting the snow. The rain will turn to snow later on after the storm heads into the colder Arctic air, giving us a frozen mess which is awful to clean up. The reason this happens is if the blocking high pressure up in Canada is too far west or is too weak to block and force the low off the coast.
So now you see why they're called a Nor'easter. The winds and snow blow in from the Northeast as the storm picks up the warm moist ocean air.
The next lesson will be on severe thunderstorms and super cells.
John
Because of this, there have been numerous delays, bustitutions, and outright cancelations of service on the commuter rail, heavy rail and trolley (tram) system. The problems have ranged from downed wires, frozen switches, and even a broken rail which occurred in one of the underground portions of the Green Line trolley right on the main line at rush hour. The commuter rail has suffered from delays caused by down branches, buried track, frozen switches, and signaling system issues. The surface portions of the Orange and Red Lines have also been affected due to deep snow and frozen switches, with the old Mattapan High Speed Line temporarily closed. The MHSL is actually a short stub run with renovated historic Boston PCC trolley cars from Mattapan Square to Ashmont.
http://www.mbta.com/weather/
About the weather in general and Nor'easters...
The weather pattern is normal, but a bit late. We usually start with small and medium sized storms from the middle of December then we get a few good ones in January, a few in February, then a good whopper of one in March. By then it warms up and any snow that falls melts immediately. This doesn't indicate the winter is over for us. Some areas, including where I live, have gotten snow as late as mid-April, and even some freak storms in early May. They're pretty nasty at this time because they wreck the trees, and they're usually accompanied by severe weather as well, including super cell thunderstorms, which can spawn a tornado or two, although this is a bit rare.
These storms are typical Nor'easter storms, which actually come in from the south and head up the coast. The biggest storms come in from the Great Lakes then head into the Ohio Valley where they reorganize and pick up moisture from the Gulf of Mexico. Keep in mind these storms are huge and will cover from Chicago to Missouri, with fringes as far south as Mississippi and even into Georgia and Alabama. They will then pick up the Westerly winds and head east to the Carolina coast where they pick up the warm moisture from the Gulf Stream. There they grow in size, even more than from before, and then take the ride north on the Gulf Stream which is feeding them warm moisture. Usually to get the big storms to organize and really dump a lot of snow, there's an arctic high pressure sitting over Quebec and into the Canadian Maritimes. This keeps the low from moving as it blocks it, or if it's just a bit more east, the low will follow along the outside of the storm, and ride up the side of the high pressure as it spins clockwise, like it's taking an elevator. This usually makes for a small amount of snow because the storm is pulled along quickly by the high pressure. Sometimes other low pressures will combine and sometimes weaken, or block which is a good thing. We're seeing this occur Thursday and Friday (Feb 5 & 6th) this week because of a quick moving storm settling in across New York State and moving into New England. Other times, which seems to be the case lately, the high pressure will sit above, making things cold, while some smaller storms will stay north and block the movement of a bigger storm, which causes lots of snow for us.
So what makes a Nor'easter a Nor'easter...
Keep in mind that storms are low pressure which means a storm rotates counter-clockwise. This means the air flow over the top and from the right to the left. Since the storm is out in the warmer North Atlantic, which is much warmer than the Arctic blast on land, the moisture turns to snow. If they linger, we can get a lot, but most of the storms are gone with 24-48 hours as the high pressure spins and pulls the storm away from us. Then because the air is spinning from the top of the low pressure, it comes in as a cold blast after the storm leaves because it is now pulling the cold air in behind it from that Arctic and are accompanied with very high winds.
Now for a twist... If the storm happens to cross a bit west of the region, we'll get rain and ice which usually turns to a gross wintery mix then a bit of snow. The reason for this is we're on the front side of the storm and receiving the warm moist air instead of the cold side and getting the snow. The rain will turn to snow later on after the storm heads into the colder Arctic air, giving us a frozen mess which is awful to clean up. The reason this happens is if the blocking high pressure up in Canada is too far west or is too weak to block and force the low off the coast.
So now you see why they're called a Nor'easter. The winds and snow blow in from the Northeast as the storm picks up the warm moist ocean air.
The next lesson will be on severe thunderstorms and super cells.
John