OceanStWx Posted July 20, 2012 Share Posted July 20, 2012 Well I had another post all typed up, but Firefox had other ideas. What I was getting at was that the low level environment around this storm was rather stable. Lapse rates were better farther southwest, and CAPE was located above the near surface layer. This went into efficient hail production. Additionally, PWATs approaching 2" were efficient rain producers, leading to precip loading and downbursts. The environment just seemed to favor HP supercells, and this one was quite a specimen. The problem is that HP storms have visibility issues (all the rain) and lots of precip in areas you otherwise wouldn't expect. A water loaded RFD is going to have some locally lower LCLs, and produce a shelf cloud of its own separate from the forward flank. With rain cooled and maritime air being sucked into the storm, I think low hanging, ragged shelf clouds just had the right shape to be confused with funnels. This is the most impressive pictures I've seen so far, from CBS Boston. Great structure, with the huge precip core and layered shelf clouds. What is important to note is the large inflow tail just about dead center of the photo. That is going to lead right to the wall cloud, and if there were a funnel it would be near the base of that feature, likely tucked back behind the rain. Very difficult to spot let alone film. I just don't see a lot in the low level velocity to jump to tornado conclusions. Of course the meso aloft was ripping at this time, right about over Nahant. I think it was just too stable an environment to get this circulation down to the surface from what I see. Even once over the water it looks like the best circulation was always displaced well away from the reflectivity gradients. Link to comment Share on other sites More sharing options...
wxsniss Posted July 20, 2012 Share Posted July 20, 2012 Awesome analysis OceanSt, much appreciated. Agree, even the SRV snapshot I posted from 2:29pm (25 minutes after the velocity images you have above) had best circulation well east of the best reflectivity gradients. I wonder if visible satellite imagery might have evidence of a meso over Nahant while the best reflectivity gradients are still over Lynn/Saugus. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted July 20, 2012 Share Posted July 20, 2012 Great writeup Oceanst Link to comment Share on other sites More sharing options...
dryslot Posted July 20, 2012 Share Posted July 20, 2012 Well I had another post all typed up, but Firefox had other ideas. What I was getting at was that the low level environment around this storm was rather stable. Lapse rates were better farther southwest, and CAPE was located above the near surface layer. This went into efficient hail production. Additionally, PWATs approaching 2" were efficient rain producers, leading to precip loading and downbursts. The environment just seemed to favor HP supercells, and this one was quite a specimen. The problem is that HP storms have visibility issues (all the rain) and lots of precip in areas you otherwise wouldn't expect. A water loaded RFD is going to have some locally lower LCLs, and produce a shelf cloud of its own separate from the forward flank. With rain cooled and maritime air being sucked into the storm, I think low hanging, ragged shelf clouds just had the right shape to be confused with funnels. This is the most impressive pictures I've seen so far, from CBS Boston. Great structure, with the huge precip core and layered shelf clouds. What is important to note is the large inflow tail just about dead center of the photo. That is going to lead right to the wall cloud, and if there were a funnel it would be near the base of that feature, likely tucked back behind the rain. Very difficult to spot let alone film. I just don't see a lot in the low level velocity to jump to tornado conclusions. Of course the meso aloft was ripping at this time, right about over Nahant. I think it was just too stable an environment to get this circulation down to the surface from what I see. Even once over the water it looks like the best circulation was always displaced well away from the reflectivity gradients. Great explanation, The possibility was there but looks like it never materialized Link to comment Share on other sites More sharing options...
weatherwiz Posted July 20, 2012 Author Share Posted July 20, 2012 Fantastic write-up there! Link to comment Share on other sites More sharing options...
free_man Posted July 20, 2012 Share Posted July 20, 2012 Some great storm structure photos out there from yesterday. Unfortunately, the piece of evidence that is getting touted as a funnel cloud near Lynn has me a bit skeptical. It is awfully shaky video, that is very zoomed in (no idea of storm structure and position). Can I say it isn't a funnel, no. Can I say it is a funnel, no. But to me it looks awfully like a low hanging, ragged shelf cloud. The shaking makes it very hard to determine potential rotation. I followed it, drove through storm in Medford/Somerville, and followed it again down through Charlestown and Everett. Around 2-3 miles away, plenty of video and pics. It was a scud. lol However, imo there was a developing wall cloud (perhaps not clearly defined) prior to moving offshore- and obviously the sweet shelf and overall structure. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted July 20, 2012 Share Posted July 20, 2012 Nice pic BIrv Link to comment Share on other sites More sharing options...
CoastalWx Posted July 20, 2012 Share Posted July 20, 2012 Thanks for those images Chris. Awesome breakdown. Dual Pol is a really cool feature, I'm actually trying to push that to mets that may not be as familiar with it at work...mostly the older guys. It's a good tool to see if hail is moving towards a client hub. Link to comment Share on other sites More sharing options...
ct_yankee Posted July 20, 2012 Share Posted July 20, 2012 Those pictures are awesome, but also very typical. In my experience this is exactly the kind of supercell one sees most often around here in SNE. Almost always we get these big HP beasts that make it difficult to see whether there’s any low level rotation in the storm or not, because the wall cloud or funnel, if they exist at all, are going to be rain-wrapped. And the storm motion can be so fast that the best you can usually hope for in a chase is a single intercept, hopefully timed just right to put you somewhere near the inflow notch. What one usually sees at that point is precisely what most of these pictures show: a big, mean, usually ominous looking curving RFD shelf cloud, frequently layered and/or striated, and often with ragged and sometimes funnel-like scud hanging below it. Where the RFD shelf curls back into the main updraft, the place one would look for any wall cloud or funnel, there’s usually just a vague intimation of low clouds lurking within a black precip core that could be hiding almost anything. Very cool to look at, but these supercells rarely produce tornadoes, and when they do you can almost never see it unless you’re very close and very lucky - or on occasion very unlucky. Link to comment Share on other sites More sharing options...
CoastalWx Posted July 20, 2012 Share Posted July 20, 2012 If that cell intercepted the seabreeze front, I bet it would have done some interesting things. It was rooted just above it. Link to comment Share on other sites More sharing options...
Turtle Posted July 20, 2012 Share Posted July 20, 2012 A sudden 63 mph Nw gust in a squall is certainly going to take some trees down anywhere. The definition for squall is a brief, intense gust of wind as I learned it in college. Here's a definition that fits closely to what I remember... squall (skwôl) A brief, sudden, violent windstorm, often accompanied by rain or snow. A squall is said to occur if a wind having a sustained speed of 40 km (25 mi) per hour lasts at least 1 minute and then decreases rapidly. See also squall line. The American Heritage® Science Dictionary Copyright © 2005 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. Found this on thefreedictionary.com . Very interesting. You can probably see an instantaneous gust to 55 knots and not see much damage. If you start getting 30-45 seconds of it you're going to start getting damage. Also some of these gusts can be quite isolated. It's conceivable 50+ knot gusts were spread out over a large portion of the airport and there were few trees to actually damage. Exactly, Ryan. It can hit a small area and not last long at all. Agree with this. --Turtle Link to comment Share on other sites More sharing options...
Turtle Posted July 20, 2012 Share Posted July 20, 2012 I noticed that the NWS evaluation of the microburst in Arlington was not posted here. Saw some questions about this...so here it is: PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE TAUNTON MA 257 PM EDT THU JUL 19 2012 ...MICROBURST /STRAIGHT LINE WIND DAMAGE/ CONFIRMED IN ARLINGTON...MIDDLESEX COUNTY MASSACHUSETTS... LOCATION...ARLINGTON IN MIDDLESEX COUNTY MASSACHUSETTS DATE...JULY 18, 2012 ESTIMATED TIME...6 PM EDT ESTIMATED MAXIMUM WIND SPEED...70 TO 80 MPH PATH LENGTH...APPROXIMATELY 1 MILE * FATALITIES...0 * INJURIES.....0 * THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS STORM DATA. ...SUMMARY... THE NATIONAL WEATHER SERVICE IN TAUNTON MA HAS CONFIRMED A MICROBURST /STRAIGHT LINE WIND DAMAGE/ IN ARLINGTON... MIDDLESEX COUNTY MASSACHUSETTS ON JULY 18, 2012. A NATIONAL WEATHER METEOROLOGIST SURVEYED THE DAMAGE IN ARLINGTON THIS MORNING AND CONFIRMED NUMEROUS TREES WERE DOWNED BY STRAIGHT LINE WINDS WITH THE FOCUS OF THE DAMAGE CENTERED OVER EASTERN PORTIONS OF ARLINGTON. THIS INCLUDES THE INTERSECTION OF MASSACHUSETTS AVENUE AND BROADWAY EASTWARD TO ROUTE 16...THE CAMBRIDGE CITY LINE. IN ADDITION... MULTIPLE HOMES AND AUTOMOBILES WERE DAMAGED BY DOWN TREES. THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT WEATHER.GOV/BOX. FOR REFERENCE... A MICROBURST IS A STRONG AND RELATIVELY SMALL AREA OF RAPIDLY DESCENDING AIRSTREAM BENEATH A THUNDERSTORM. A MICROBURST IS DIFFERENTIATED FROM A COMMON THUNDERSTORM DOWNDRAFT BECAUSE THE WINDS IT PRODUCES HAVE THE POTENTIAL TO CAUSE DAMAGE ON OR NEAR THE GROUND. SURFACE WIND DAMAGE PATTERNS HAVE SHOWN THAT WHETHER THE WINDS ARE STRAIGHT OR A LITTLE BIT CURVED ...THEY TEND TO SPREAD OUT OR DIVERGE CONSIDERABLY AS THEY REACH THE SURFACE. CONVERSELY DAMAGE PATTERNS RESULTING FROM A TORNADO GENERALLY CONVERGE TOWARD A NARROW CENTRAL TRACK. IN ADDITION A MICROBURST IMPACT AREA IS TYPICALLY LESS THAN 2 1/2 MILES WIDE AND PEAK WINDS LASTING LESS THAN 5 MINUTES. MICROBURSTS MAY INDUCE DANGEROUS HORIZONTAL/VERTICAL WIND SHEARS...WHICH CAN ADVERSELY AFFECT AIRCRAFT PERFORMANCE AND CAUSE PROPERTY DAMAGE. STRAIGHT-LINE WINDS ARE GENERALLY ANY WIND THAT IS NOT ASSOCIATED WITH ROTATION...USED MAINLY TO DIFFERENTIATE THEM FROM TORNADIC WINDS. $$ NOCERA I'm on vacation, so I have no idea who went out to investigate this. As for the Lynn/Saugus/Nahant storm, I have no idea. Upon the first viewing of the video the other day, I thought it was really cool and looked like it may have had rotation. However, after reading all the comments and, most importantly, viewing the video again, it could have been anywhere in that storm. I still don't know what time it happened (was there a time stamp?). I liked Chris' review of this event, and can understand the ambiquity on this cell. Again, on vacation, so have no clue what Glenn did or how he evaluated it. I do remember hearing Harvey Leonard mentioning Glenn's name on air and his (Glenn) evaluation of that video being a funnel cloud. Guess we'll never really know... --Turtle Link to comment Share on other sites More sharing options...
weatherwiz Posted July 20, 2012 Author Share Posted July 20, 2012 I'm really not all that big on Monday or Tuesday yet...seems to me like the better and more organized shear lags behind the cold front. Link to comment Share on other sites More sharing options...
Quincy Posted July 20, 2012 Share Posted July 20, 2012 A few images from the cell I intercepted in Sharon, CT on Wednesday...pretty impressive, although not as intense as some of the storms that hit portions of eastern SNE. Link to comment Share on other sites More sharing options...
CoastalWx Posted July 20, 2012 Share Posted July 20, 2012 A few images from the cell I intercepted in Sharon, CT on Wednesday...pretty impressive, although not as intense as some of the storms that hit portions of eastern SNE. I thought in the video winds were maybe 40-50 or so. I would have expected those trees to bend a lot more in 60+ winds. However, it was weird in that the sheets of rain were flying by, yet the response to the wind on those trees wasn't what I expected. Good storm regardless. Link to comment Share on other sites More sharing options...
Quincy Posted July 20, 2012 Share Posted July 20, 2012 I thought in the video winds were maybe 40-50 or so. I would have expected those trees to bend a lot more in 60+ winds. However, it was weird in that the sheets of rain were flying by, yet the response to the wind on those trees wasn't what I expected. Good storm regardless. I think in the future I'll leave my camera facing towards trees for that sort of storm. I kept shifting back and forth, so I might have missed the best. There were several trees and power lines down within a 1/4 mile of that spot. Link to comment Share on other sites More sharing options...
wxsniss Posted July 20, 2012 Share Posted July 20, 2012 Question for the mets (particularly CTRain as you might have been around when this happened in your backyard...) I'm very interested in tornadogenesis triggered by the interaction of a cell with a seabreeze boundary. I posted earlier this case study of 2 tornadoes that formed in Florida in 2003 when cyclonic shear occurred at the intersection of a seabreeze boundary and a southward moving outflow boundary: http://www.nwas.org/ej/2005-EJ6/ My question: Did this waterspout in Narangasset Bay 8/14/2008 have similar mechanics? Link to comment Share on other sites More sharing options...
JustinWX Posted July 20, 2012 Share Posted July 20, 2012 I have fairly good quality video of the approach of the shelf cloud/gust front...I was on the Lynn/Saugus line...I may have been just a hair too far north. But if anyone would like to see the video...I can put it on youtube. Link to comment Share on other sites More sharing options...
OceanStWx Posted July 20, 2012 Share Posted July 20, 2012 However, imo there was a developing wall cloud (perhaps not clearly defined) prior to moving offshore- and obviously the sweet shelf and overall structure. No doubt there was a wall cloud feature developing. Just seeing that inflow tail structure tells me there was something tucked back in there. If that cell intercepted the seabreeze front, I bet it would have done some interesting things. It was rooted just above it. Yeah, you could see the boundaries very clearly on reflectivity out west of 128. From my vantage point on the water off Seabrook, NH the cloud bases were wavy, so there was definitely a stable layer these storms were riding up over. That's probably why the wind damage was relatively isolated with that cell, until you got farther west towards Arlington. Link to comment Share on other sites More sharing options...
Ginx snewx Posted July 20, 2012 Share Posted July 20, 2012 I have fairly good quality video of the approach of the shelf cloud/gust front...I was on the Lynn/Saugus line...I may have been just a hair too far north. But if anyone would like to see the video...I can put it on youtube. yes Link to comment Share on other sites More sharing options...
JustinWX Posted July 20, 2012 Share Posted July 20, 2012 Forgive me for the "in-storm" analysis lol Link to comment Share on other sites More sharing options...
OceanStWx Posted July 20, 2012 Share Posted July 20, 2012 Question for the mets (particularly CTRain as you might have been around when this happened in your backyard...) I'm very interested in tornadogenesis triggered by the interaction of a cell with a seabreeze boundary. I posted earlier this case study of 2 tornadoes that formed in Florida in 2003 when cyclonic shear occurred at the intersection of a seabreeze boundary and a southward moving outflow boundary: http://www.nwas.org/ej/2005-EJ6/ My question: Did this waterspout in Narangasset Bay 8/14/2008 have similar mechanics? This is the surface map a couple hours before the waterspout (to avoid thunderstorm contamination of winds). Pretty weak flow, probably ideal for sea breeze formation. Looks like weak onshore flow near the coastline, but otherwise light northerly drift inland. Then you have the complicating factor of island like Jamestown and Prudence in the middle of Narragansett Bay that will distort boundaries and divert wind flow. As for an outflow boundary interaction, winds at PVD did come around to the northwest as the storm passed but I'm not sure how well defined a feature it was. The waterspout was reported to be moving northeast. Link to comment Share on other sites More sharing options...
BrianLaverty Posted July 21, 2012 Share Posted July 21, 2012 Not a big deal to most people, but this is the first time I can remember getting this much hail here... Very exciting for me. Link to comment Share on other sites More sharing options...
Quincy Posted July 22, 2012 Share Posted July 22, 2012 I am by no means a severe weather expert and I've actually already learned a lot so far this season. Anyway, I saw some highly interesting charts from midday Wednesday and notice how several of these focus on or near eastern Massachusetts... The biggest thing that jumps out at me is the effect bulk shear and how this area was in a perfect balance between CAPE and EBS. This is why the Craven Significant Severe numbers were so incredibly high. 90K in SNE? That's insane. EHI was pretty good as well and even normalizeed CAPE showed another maxima over the area. Finally, the lower two images may be the most telling... Supercell composite values of 12? That's nuts and significant tornado parameters of 3 are also huge red flags, especially for our area. Link to comment Share on other sites More sharing options...
CT Rain Posted July 22, 2012 Share Posted July 22, 2012 EML day for Tuesday gone to waste. Link to comment Share on other sites More sharing options...
CT Rain Posted July 22, 2012 Share Posted July 22, 2012 The Euro actually looks good for a few tornadoes on Friday. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 22, 2012 Author Share Posted July 22, 2012 The Euro actually looks good for a few tornadoes on Friday. Seeing you say that this far out is certainly eye opening! Agreed about Tuesday, it's time to throw in the towel. However, eastern MA could be a target again? Link to comment Share on other sites More sharing options...
OceanStWx Posted July 22, 2012 Share Posted July 22, 2012 Seeing you say that this far out is certainly eye opening! Agreed about Tuesday, it's time to throw in the towel. However, eastern MA could be a target again? I think it could be. There is enough model support to have the front not clear eastern areas until late in the day. Looking at the jet support arriving at that time, there would probably be a few strong storm even if thermodynamics were less than marginal. Link to comment Share on other sites More sharing options...
free_man Posted July 22, 2012 Share Posted July 22, 2012 The Euro actually looks good for a few tornadoes on Friday. Let's focus on the damage before the damage? ; Monday pm/night. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 22, 2012 Author Share Posted July 22, 2012 I think it could be. There is enough model support to have the front not clear eastern areas until late in the day. Looking at the jet support arriving at that time, there would probably be a few strong storm even if thermodynamics were less than marginal. I actually really like the look for eastern areas on Tuesday. One thing I'm a little concerned about is somewhat of a cap just above 700mb but forcing/lift should be enough to rid this I would think. Decent directional shear as well so maybe we could see a few discrete supercells? Would be interesting seeing a few of those interact with a sea-breeze boundary. Link to comment Share on other sites More sharing options...
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