crownweather Posted February 17, 2011 Share Posted February 17, 2011 I am hoping to try and find a correlation between terrain & frictional effects and the formation of some tornadoes here in New England. I took a few tornado cases and overlaid a relief map on top of the tracks, even going back 50-60 years. One notable tornado that I mapped out was the 1953 Worcester, Massachusetts tornado which actually developed on the eastern shore of Quabbin Reservoir in western Worcester County; so I am wondering if the frictional effects of an already established rotating supercell between the Reservoir and the surrounding lands helped to spin up the tornado. Living here in northern Maine, I took a look at a few cases. The first case is a F2 tornado that occurred in the Allagash waterway on August 15, 1958. This tornado formed on the eastern shore of St. Froid Lake and traveled eastward from there. Two very local F0 to F1 strength tornadoes were June 18 and July 1 of 1994. June 18's tornado formed on the south side of Caribou in an area that features a 50-75 foot ravine; I believe this tornado formed in this ravine and tracked southeastward snapping a few trees and taking out a waterside at a local amusement park. The July 1 event occurred just 1/2 mile from my home and formed along a ridge line and climbed a 100-120 foot hill before taking the roof off of a barn. A picture of this tornado can be found in Tom Grazulis' supplemental to the Significant Tornadoes book. Other tornadoes that have been influenced/formed from topographic include a EF-1 tornado from May 24, 2009, http://www.erh.noaa.gov/car/News_Items/2009-05-24_item002.htm & an EF 0 tornado that tracked just south of Presque Isle on May 31, 2009 http://www.erh.noaa.gov/car/News_Items/2009-05-31_item001.htm . The main question I have now is can these events be "forecasted" even a few minutes beforehand by observing storm-relative velocity on radar overlaid onto a terrain map?? So, let's say you have a storm with a "signature" on SRV, now if I overlaid a relief map over the cell and noticed it was going over a lake (frictional) or down into a ravine/mountain (frictional effects stretching out the vortex), could we raise the probability of having a tornado to high or very high based on topography? Thanks, Rob Lightbown/Crown Weather Services Link to comment Share on other sites More sharing options...
weatherwiz Posted February 17, 2011 Share Posted February 17, 2011 Very interesting, thanks for posting! The terrain here in New England is very interesting and can at times help to influence the development of tornadic activity, and there have been plenty of cases where this has occurred. For example, one tornado, the BDL one in 1979 was also influenced by the effects of the CT Valley. As the supercell came off of Long Island sound and worked it's way northward through the valley the southerly winds really got enhanced even further and with already a decent amount of low-level directional shear in place this further added to the amount of helicity. This also holds some great merit just to our west out across NYS with the Hudson Valley and then local effects from sea-breezes and such. I think one day down the road, perhaps relatively soon something like this could be forecasted in advance...perhaps even a day before although something like this could take a little longer...this is something that I've actually tried to work on myself and hope to do for years down the road. Link to comment Share on other sites More sharing options...
tamarack Posted February 17, 2011 Share Posted February 17, 2011 Living here in northern Maine, I took a look at a few cases. The first case is a F2 tornado that occurred in the Allagash waterway on August 15, 1958. This tornado formed on the eastern shore of St. Froid Lake and traveled eastward from there. Since that event happened 18 yr before I began working in that country, I'm not real familiar with its impact. Also, its effects as seen from the river were pretty much obliterated by late 70s clearcuts on the surrounding acres. However, St. Froid Lake lies about 30 miles ENE from where the tornado crossed the Allagash, and there are very few lakes to westward - almost 30 miles to Depot Lake. I tried searching for "Allagash tornado 1958" and found little info, so I'd be quite pleased to learn more about it. In my experience, the major destructive wind events in that country have been straight-line microbursts. One flattened about 600 acres of forest between Eagle and Square Lakes on 9/30/1986, blowing trees into the north end Square and requiring salvage of nearly 10,000 cords of timber by the landowners. (That's very late for severe convective events that far north. Five years later that area had several inches of snow on 9/30.) Another in 2005 hit the same area with a narrower but longer track, starting on T15R6, then continuing across T16R6 onto T16R5, jumping the east end of Eagle Lake, and blowing down 150-200 acres including one patch of 60 acres which my agency salvaged a bit south of the lake. I've always wondered why that area just east of the town of Eagle Lake was a magnet for destructive straight-line winds. Edit, for faulty memory: The latter blowdown occurred in 2004. Due to the winter-only road system on State lands (T16R6) south of Eagle Lake, it was only discovered later in the year and our correspondence with Maine Forest Service about it took place in 2005. Most of the track of this event is quite clearly seen on Google Earth. It's visible signs begin a mile or so SE of where Rt 11 crosses the Fish River near the outlet of St. Froid Lake, then continue at North 60 degrees East for nearly 10 miles. The most NE-ly evidence I could see was just east of the open bog between Eagle and Square. Link to comment Share on other sites More sharing options...
crownweather Posted February 17, 2011 Author Share Posted February 17, 2011 Check out http://www.tornadohistoryproject.com for a wealth of track info. That's where I got the exact touchdown point for the 1958 Allagash tornado. I'll write more later... Link to comment Share on other sites More sharing options...
tamarack Posted February 17, 2011 Share Posted February 17, 2011 Check out http://www.tornadohistoryproject.com for a wealth of track info. That's where I got the exact touchdown point for the 1958 Allagash tornado. I'll write more later... Looks like a great link, thanks. I couldn't access the maps, maybe because I wasn't registered. That's now covered, though to my home e-mail so I'll need to await the confirmation there. Link to comment Share on other sites More sharing options...
wxmanmitch Posted February 18, 2011 Share Posted February 18, 2011 I'm not sure if this will be of any help, but I wrote a paper for one of my graduate classes on this very subject about 2 years ago. I have uploaded a pdf copy of the paper to my web server that you (and anyone else for that matter ) can access by clicking here. The paper primarily focuses on eastern NY and western New England, but the thinking could probably be applied to other areas in this part of the country. I examined 4 different tornado events and found that there was a tendency for increased instability and low-level wind shear in the valley locations, favoring tornadogenesis in those locations. I used NARR reanalysis data for the study, which is not the best because of its low vertical and horizontal resolution, but it is the best I could do. The correlation is likely not strong between the terrain and tornadoes, but a case can possibly be made for at least a weak correlation. In order to really examine this subject, a much larger study needs to be done with many more cases. Depending on the results of such a study, it then might be possible to prove (or disprove) a link between topography and tornadogenesis. Link to comment Share on other sites More sharing options...
AtticaFanatica Posted February 19, 2011 Share Posted February 19, 2011 This has been looked at a few times. Here are some peer-reviewed studies: http://journals.ametsoc.org/doi/full/10.1175/WAF957.1 http://journals.ametsoc.org/doi/full/10.1175/1520-0434(2002)017%3C1277:TIOTOT%3E2.0.CO;2 Link to comment Share on other sites More sharing options...
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