CoastalWx Posted August 9, 2013 Share Posted August 9, 2013 The Euro definitely seems to deepen that low with falling pressures across western New England/eastern New York as the front slides east. That should keep winds backed but not sure if the strong LLJ response on the GFS/NAM is overdone or not. Obviously convective mode and amount of destabilization are still up in the air. Yeah winds still mostly S if not SSE. Link to comment Share on other sites More sharing options...
CoastalWx Posted August 9, 2013 Share Posted August 9, 2013 How accurate does the Euro tend to be with severe events compared to the NAM and GFS? Well unlike snowstorms, I feel like models usually aren't terribly far off when it comes to severe wx. You just have to watch out for possible convective feedback and overzealous LLJ as a result. However, all models strengthen the jet during the day as a weak low develops in ern NY. It's one of those things where the models all show good shear so you have multi model support for that, as well as low CAPE. It's up to the forecaster to take it from there. If you look deeper, low level CAPE in the lower 10,000ft or so is decent for stretching any updrafts. It doesn't mean tornado, but it's a signal for potential. I think shear is there, just a matter of how much we can destabilize. It might be one of those deals where a few breaks of sun and brightening gets temps to near 80 and that's all you need. Or, it could be a complete dud. I'm not one to get excited from these, but the shear caught my eye...that's darn good. Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 Well unlike snowstorms, I feel like models usually aren't terribly far off when it comes to severe wx. You just have to watch out for possible convective feedback and overzealous LLJ as a result. However, all models strengthen the jet during the day as a weak low develops in ern NY. It's one of those things where the models all show good shear so you have multi model support for that, as well as low CAPE. It's up to the forecaster to take it from there. If you look deeper, low level CAPE in the lower 10,000ft or so is decent for stretching any updrafts. It doesn't mean tornado, but it's a signal for potential. I think shear is there, just a matter of how much we can destabilize. It might be one of those deals where a few breaks of sun and brightening gets temps to near 80 and that's all you need. Or, it could be a complete dud. I'm not one to get excited from these, but the shear caught my eye...that's darn good. Yeah it looks like it will be a classic low CAPE/high shear setup. There looks like a fair amount of CAPE in the 0-3km layer... when coupled with low LCLs and high shear that's an intriguing setup. Davies 2006 is a good read. Link to comment Share on other sites More sharing options...
N. OF PIKE Posted August 9, 2013 Share Posted August 9, 2013 Mets posting non stop day before is a good sign. Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 I hope someone sees sun! Both CT tornado days this season were almost totally sunless lol Link to comment Share on other sites More sharing options...
CoastalWx Posted August 9, 2013 Share Posted August 9, 2013 Yeah it looks like it will be a classic low CAPE/high shear setup. There looks like a fair amount of CAPE in the 0-3km layer... when coupled with low LCLs and high shear that's an intriguing setup. Davies 2006 is a good read. Cpicks BTV WRF is tasty. Link to comment Share on other sites More sharing options...
CoastalWx Posted August 9, 2013 Share Posted August 9, 2013 Yeah it looks like it will be a classic low CAPE/high shear setup. There looks like a fair amount of CAPE in the 0-3km layer... when coupled with low LCLs and high shear that's an intriguing setup. Davies 2006 is a good read. Certainly is intriguing. Link to comment Share on other sites More sharing options...
joey2002 Posted August 9, 2013 Share Posted August 9, 2013 Both CT tornado days this season were almost totally sunless lol Yeah, and that Coventry/Mansfield tornado was legit... damage was minimal just because it went over such rural areas. Link to comment Share on other sites More sharing options...
N. OF PIKE Posted August 9, 2013 Share Posted August 9, 2013 Is the tor threat primarily w sne ? Link to comment Share on other sites More sharing options...
CoastalWx Posted August 9, 2013 Share Posted August 9, 2013 That is a good read. Link to comment Share on other sites More sharing options...
radarman Posted August 9, 2013 Share Posted August 9, 2013 Setup is not a spot on match, but this has some similarities to Aug 10th of last year. Another high/low day... we had some mini supercells in the morning and Southampton had damaging winds later on in a semi-training situation. Link to comment Share on other sites More sharing options...
CoastalWx Posted August 9, 2013 Share Posted August 9, 2013 Is the tor threat primarily w sne ? It actually could translate east. It's important to keep expectations in check...I wouldn't get excited for an outbreak....but there are very notable ingredients. Shear is everything in these setups. Link to comment Share on other sites More sharing options...
SnowMan Posted August 9, 2013 Share Posted August 9, 2013 How do things look for us up here in SNH? Link to comment Share on other sites More sharing options...
N. OF PIKE Posted August 9, 2013 Share Posted August 9, 2013 It actually could translate east. It's important to keep expectations in check...I would get excited for an outbreak....but there are very notable ingredients. Shear is everything in these setups. Well i dont even entertain the thought of anything inside 128, not sure if i have ever heard of ONE occuring. But s nh sw to merr valley and sw sure. Btv wrf really crushes se ny w ct s vt/wma over to south central nh and ne toward limerick maine Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 That is a good read. The Jon Davies paper? Link to comment Share on other sites More sharing options...
CoastalWx Posted August 9, 2013 Share Posted August 9, 2013 The Jon Davies paper? Yeah, well your blog too...lol. Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 Yeah, well your blog too...lol. lol thanks. Obviously there's a lot that can go wrong here but there's definitely some potential. We'll see - worth watching. I'm in the hot seat tomorrow so it may be a long last day of work b4 vacation. Link to comment Share on other sites More sharing options...
Quincy Posted August 9, 2013 Share Posted August 9, 2013 Let's compare some forecasts vs. previous analyses.(Most of the forecasts are text based, but some values had to be approximated) STP SCP MLCAPE EBS 3km SRH ML LCL Index 3.01 22 2500 48 400 1000 4.22 Springfield, Mass. June 1st, 2011 1 3.2 396 38.4 411 452 3.25 18z NAM: BAF, 18z Friday 0.21 3.2 500 40 200 500 2.79 Stamford, Conn. July 1st, 2013 0.7 2.2 800 30 180 350 2.77 18z GFS: CEF: 18z Friday 0.13 3.1 1200 25 110 600 2.43 Coventry, Conn. July 10th, 2013 For tomorrow, the GFS/NAM agree that the best overlap between CAPE and helicity/wind shear would fall near the CT/MA border. It would appear to me that a GFS solution is comparable to the previous two tornado "days" that southern New England has seen this year. The NAM on the other hand is above that and ranks fairly high. The last time a tornado case had a higher value was the mini-outbreak of July 31st, 2009. Two tornadoes in southwestern Connecticut had indicies of 3.81 and 3.83. The index is based off of a 0 to 5 scale. Based on my research of previous tornado events in SNE: <1 = Very Low probability of tornadoes <2 = Low probability 2.5 = Mean value for climo tornado cases <3 = Moderate <4 = High <5 = Very High 5+ = Historic (a 5.0 would mean every parameter is maxed out based on climo tornado cases) Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 Quincy and the severe wx parameters lol A couple things though... I'm not sure I'd lump all tornado days together. Some occur from very different synoptic setups. The "numbers" you'd expect from a classic supercell high CAPE/high shear day are very different from a closed low or near warm front high shear/low CAPE day. Also what's SCP and EBS? I don't normally look at the composite indicies because I think they can mask important details. Link to comment Share on other sites More sharing options...
weatherwiz Posted August 9, 2013 Share Posted August 9, 2013 lol thanks. Obviously there's a lot that can go wrong here but there's definitely some potential. We'll see - worth watching. I'm in the hot seat tomorrow so it may be a long last day of work b4 vacation. where are you going for vacation? Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 where are you going for vacation? Cape - leaving Saturday morning. Link to comment Share on other sites More sharing options...
Quincy Posted August 9, 2013 Share Posted August 9, 2013 Quincy and the severe wx parameters lol A couple things though... I'm not sure I'd lump all tornado days together. Some occur from very different synoptic setups. The "numbers" you'd expect from a classic supercell high CAPE/high shear day are very different from a closed low or near warm front high shear/low CAPE day. Also what's SCP and EBS? I don't normally look at the composite indicies because I think they can mask important details. I like to look at the numbers since partially since I lack the experience that many of the mets have on here with operational forecasting. I've really only closely studied severe weather for the past two summers and I'll be the first at admit there's still a lot I need to learn. Different setups yield different results. You mentioned once that there are two types of setups, the rare supercell days (like Springfield) and then the more common high shear/low CAPE. Most of the cases I've looked at have been high shear/low CAPE. SCP is the supercell composite parameter, based off of MUCAPE, SRH and bulk shear. EBS is effective bulk shear. The reason I look at those 6 parameters was that it was easy to go back and re-analyze since SPC uses those values in their charts. The mean CAPE value for 28 tornado cases in SNE was 1129. How often do we see CAPE values of 2000-3000+ with nothing significant happening? Link to comment Share on other sites More sharing options...
weatherwiz Posted August 9, 2013 Share Posted August 9, 2013 Cape - leaving Saturday morning. Oh nice! A friend of mine just went to the the last week. I'm going to Hampden Beach next weekend, can't wait! Link to comment Share on other sites More sharing options...
Quincy Posted August 9, 2013 Share Posted August 9, 2013 If the NAM is correct, we're on the extreme end compared to climo SNE tornadoes when it comes to ML LCL's and SRH. Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 I like to look at the numbers since partially since I lack the experience that many of the mets have on here with operational forecasting. I've really only closely studied severe weather for the past two summers and I'll be the first at admit there's still a lot I need to learn. Different setups yield different results. You mentioned once that there are two types of setups, the rare supercell days (like Springfield) and then the more common high shear/low CAPE. Most of the cases I've looked at have been high shear/low CAPE. SCP is the supercell composite parameter, based off of MUCAPE, SRH and bulk shear. EBS is effective bulk shear. The reason I look at those 6 parameters was that it was easy to go back and re-analyze since SPC uses those values in their charts. The mean CAPE value for 28 tornado cases in SNE was 1129. How often do we see CAPE values of 2000-3000+ with nothing significant happening? EBS - that makes sense - wasn't even thinking that. Yeah I think it's hard to look at numbers and get a really good feel because so many different setups can produce severe with different variables in place. It's tough to do. Tomorrow will be interesting - let's see how it plays out. Link to comment Share on other sites More sharing options...
CT Rain Posted August 9, 2013 Share Posted August 9, 2013 LOL - 00z NAM has a 50 knot LLJ over Hartford at 18z tomorrow. Link to comment Share on other sites More sharing options...
weatherwiz Posted August 9, 2013 Share Posted August 9, 2013 One of the toughest parts of high shear/low cape setups is generating enough buoyancy to overcome the strong shear. While strong shear is certainly great, if you don't have enough updraft support or strength, the shear overrides the updraft and the updrafts can't grow large enough to tap into and utilize those stronger dynamics. With that said, if we are able to materialize instability values tomorrow which were similar to today, there could be some storms of interest. Link to comment Share on other sites More sharing options...
weatherwiz Posted August 9, 2013 Share Posted August 9, 2013 LOL - 00z NAM has a 50 knot LLJ over Hartford at 18z tomorrow. Gotta love convective feedback Link to comment Share on other sites More sharing options...
weatherwiz Posted August 9, 2013 Share Posted August 9, 2013 The 21z SPC SREF actually has some pretty decent svr probs tomorrow afternoon Link to comment Share on other sites More sharing options...
Quincy Posted August 9, 2013 Share Posted August 9, 2013 For fun, here are two 00z NAM skew-t's. First is IJD at 18z and then BOS at 21z: Link to comment Share on other sites More sharing options...
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