Quincy Posted May 9, 2013 Share Posted May 9, 2013 May is here and the severe weather season is starting to get underway. It's been off of a relatively slow start nation-wide, but as Wiz mentioned, there could be some convective activity today. Radar has been lighting up over and around Long Island. Perhaps the first legitimate shot, albeit a relatively marginal one, could come into the Northeast by Saturday. Pump up the warm sector and dew-points into at least the lower 60's with some instability aloft and we could see some isolated severe weather on Saturday. Wind shear may not be as high as one would like to see, but CAPE and LI values could support isolated severe storms. I'd imagine the highest probability for such activity would be northwest of I-84 and more-so as one moves westward into New York state and Pennsylvania. Link to comment Share on other sites More sharing options...
Tstorm723 Posted May 9, 2013 Share Posted May 9, 2013 Sun coming out here...feeling better about the chance of thunder today. Hope we can rock n roll a few times in the next couple of days. Link to comment Share on other sites More sharing options...
Quincy Posted May 10, 2013 Author Share Posted May 10, 2013 Saturday still looks like it could get interesting, especially towards western Mass. and western Conn. Haven't looked at anything new since last night, except for the 6z NAM simulated radar, which shows a few cells firing by mid/late afternoon. Let's hope we can get a few hours of sunshine to break through the clouds and destabilize the atmosphere. SPC is not impressed. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted May 10, 2013 Share Posted May 10, 2013 Looks wild tomorrow FTW SATURDAY...EXPECT SHOWERS AND SCT THUNDERSTORMS TO MOVE ACROSS SNE AS THELOW LEVEL JET SHIFTS EAST. HAVE LIKELY POPS ALL ZONES BUT FOCUSFOR SHOWERS/TSTMS FOR SE NEW ENG WILL LIKELY BE LATE SAT/SATEVENING. INTERESTING SITUATION FOR SAT AFTERNOON AHEAD OF THECOLD FRONT AS DECENT MID LEVEL JET LEADS TO 0-6KM SHEAR VALUESGREATER THAN 40 KT DEVELOPING IN THE INTERIOR COINCIDENT WITHCAPES OF 500-1000 J/KG. INSTABILITY IS THE WILDCARD AS CLOUDCOVER MAY LIMIT INSTABILITY AND MID LEVEL LAPSE RATES AREMARGINAL WHICH WOULD LIMIT SEVERE WEATHER POTENTIAL.HOWEVER...MODEL CROSS SECTIONS INDICATE SOME THINNING OF THEMOISTURE WHICH COULD LEAD TO SOME BREAKS OF SUNSHINE THUSINCREASING INSTABILITY. HEAVY DOWNPOURS IS THE MAIN THREAT...BUTCANT RULE OUT POTENTIAL FOR SEVERE WEATHER IN THE INTERIOR IFMORE INSTABILITY IS REALIZED. THIS BEARS WATCHING. EXPECTED TEMPSWILL REACH THE LOW/MID 70S AWAY FROM THE COAST Link to comment Share on other sites More sharing options...
CoastalWx Posted May 10, 2013 Share Posted May 10, 2013 Looks wild tomorrow FTW SATURDAY... EXPECT SHOWERS AND SCT THUNDERSTORMS TO MOVE ACROSS SNE AS THE LOW LEVEL JET SHIFTS EAST. HAVE LIKELY POPS ALL ZONES BUT FOCUS FOR SHOWERS/TSTMS FOR SE NEW ENG WILL LIKELY BE LATE SAT/SAT EVENING. INTERESTING SITUATION FOR SAT AFTERNOON AHEAD OF THE COLD FRONT AS DECENT MID LEVEL JET LEADS TO 0-6KM SHEAR VALUES GREATER THAN 40 KT DEVELOPING IN THE INTERIOR COINCIDENT WITH CAPES OF 500-1000 J/KG. INSTABILITY IS THE WILDCARD AS CLOUD COVER MAY LIMIT INSTABILITY AND MID LEVEL LAPSE RATES ARE MARGINAL WHICH WOULD LIMIT SEVERE WEATHER POTENTIAL. HOWEVER...MODEL CROSS SECTIONS INDICATE SOME THINNING OF THE MOISTURE WHICH COULD LEAD TO SOME BREAKS OF SUNSHINE THUS INCREASING INSTABILITY. HEAVY DOWNPOURS IS THE MAIN THREAT...BUT CANT RULE OUT POTENTIAL FOR SEVERE WEATHER IN THE INTERIOR IF MORE INSTABILITY IS REALIZED. THIS BEARS WATCHING. EXPECTED TEMPS WILL REACH THE LOW/MID 70S AWAY FROM THE COAST No. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted May 10, 2013 Share Posted May 10, 2013 No. Not for you to be sure Link to comment Share on other sites More sharing options...
CoastalWx Posted May 10, 2013 Share Posted May 10, 2013 Not for you to be sure Meh tomorrow unless we have a ton of sun. Winds are good though. Link to comment Share on other sites More sharing options...
CT Rain Posted May 10, 2013 Share Posted May 10, 2013 NAM hodograph for 21z tomorrow near OXC. Fairly long and if you wind up with some channeled southerly flow you actually have a bit of clockwise curvature in the 0-1km level. Link to comment Share on other sites More sharing options...
free_man Posted May 10, 2013 Share Posted May 10, 2013 Not for you to be sure Link to comment Share on other sites More sharing options...
ct_yankee Posted May 10, 2013 Share Posted May 10, 2013 Anybody have any information about the tornado in Stoughton, MA. yesterday? I've heard it described as a cold air funnel that touched down, but the pictures and video I've seen sure look like there was a mesocyclone involved. I could see on radar that there was enough shear to generate some localized areas of strong vorticity embedded in yesterday's convection, I wonder if this tornado wasn't a direct result of that. Edit: OK, I see this was already discussed a bit in the banter thread, which of course I didn't read (hey, it's got "boring" right in its title, what can I say). Would still like more info on this event, however. Link to comment Share on other sites More sharing options...
Quincy Posted May 10, 2013 Author Share Posted May 10, 2013 I'll be doing an analysis/recap of the Stoughton tornado later on (this weekend due to my schedule), but here are some approximate severe weather values at 4 p.m. in the vicinity, a little bit before the tornado spun up:STP: 0.312 (Significant Tornado Parameter)SPC: 1.0 (Supercell Composite)MLCAPE: 500 J/kg Shear: 27kt (Effective Bulk)SRH: 60 m2/s2 (Helicity)MLLCL: 700m (LCL height) Two things that jump out... 1. Shear was relatively low compared to historic events for eastern Mass. 2. Favorable LCL height, as it was relatively low. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted May 10, 2013 Share Posted May 10, 2013 Damaging day tomorrow Link to comment Share on other sites More sharing options...
Quincy Posted May 10, 2013 Author Share Posted May 10, 2013 Damaging day tomorrow Could be, but the threat in your neck of the woods is very marginal. Have to head west to increase the potential... Link to comment Share on other sites More sharing options...
weatherwiz Posted May 10, 2013 Share Posted May 10, 2013 What's quite intriguing is both the NAM/GFS develop a fairly strong S/W (with the NAM being the strongest) late tomorrow afternoon which passes from SW to NE over CT. Certainly a feature which could really enhance lift/shear/helicity. The big question is (as always) how much instability we can develop. Looking at soundings across the region, I think there is enough dry air within the column to where we will have some sunshine across the area. I'm not sure if we will see widespread convection at this point, however, I think we see see a few broken squall lines and perhaps a few discrete cells. Wet microbursts would certainly be a possibility given the look of the profile but hail would certainly be a possibility as well given low freezing levels. If the models are correct with that s/w depiction and that ends up being 3-5 hours faster then I think the situation could be a tad more interesting, especially with potential for rotating storms. Link to comment Share on other sites More sharing options...
CoastalWx Posted May 10, 2013 Share Posted May 10, 2013 Cold air funnels need little shear...have some boundaries in place combined with lift and there ya go. Link to comment Share on other sites More sharing options...
weatherwiz Posted May 10, 2013 Share Posted May 10, 2013 Cold air funnels need little shear...have some boundaries in place combined with lift and there ya go. Usually pretty rare though to see them make contact with the sfc Link to comment Share on other sites More sharing options...
CoastalWx Posted May 11, 2013 Share Posted May 11, 2013 Usually pretty rare though to see them make contact with the sfc Sometimes it just takes a little instability and shear when you have low LCLs like that. There was definitely a hint of a weak inflow notch in some of those pics. Link to comment Share on other sites More sharing options...
weatherwiz Posted May 11, 2013 Share Posted May 11, 2013 Sometimes it just takes a little instability and shear when you have low LCLs like that. There was definitely a hint of a weak inflow notch in some of those pics. While the setup was not a text book set-up, when you really look at how things were set up, even locally...the conditions did favor the potential for that kind of activity. This is why I'm really becoming to favor heavily localized conditions and small scale factors over large scale patterns and the large scale synoptic setup. Sure the large scale is much more important when it comes to wide spread severe but localized severe is just as important, especially around here. Link to comment Share on other sites More sharing options...
weatherwiz Posted May 11, 2013 Share Posted May 11, 2013 From BUF this afternoon Link to comment Share on other sites More sharing options...
CoastalWx Posted May 11, 2013 Share Posted May 11, 2013 While the setup was not a text book set-up, when you really look at how things were set up, even locally...the conditions did favor the potential for that kind of activity. This is why I'm really becoming to favor heavily localized conditions and small scale factors over large scale patterns and the large scale synoptic setup. Sure the large scale is much more important when it comes to wide spread severe but localized severe is just as important, especially around here. There isn't any real terrain there..just a general 200' elevation. There may have been a little seabreeze interaction as well..or some sort of weak diffuse boundary. Something to generate helicity. If there is one thing storms love, it's boundary helicity where they can gobble that up like pac man. Anyways, cool little storm. I know exactly where that area is as I grew up near there in Brockton.Luckily a little spinner and that's it. Link to comment Share on other sites More sharing options...
weatherwiz Posted May 11, 2013 Share Posted May 11, 2013 There isn't any real terrain there..just a general 200' elevation. There may have been a little seabreeze interaction as well..or some sort of weak diffuse boundary. Something to generate helicity. If there is one thing storms love, it's boundary helicity where they can gobble that up like pac man. Anyways, cool little storm. I know exactly where that area is as I grew up near there in Brockton.Luckily a little spinner and that's it. Could it have been sea-breeze though? I would think, especially this time of year it would have actually lead to a more stable environment. I left for Boston about 1:00-ish so I didn't really get to look at any data but when I left CT it was very cloudy and when I got near Worcester and points NW there was much more sun...perhaps it was a differential heating boundary that escalated things? Differential heating boundaries can really provide a great focal point for svr. Link to comment Share on other sites More sharing options...
Quincy Posted May 11, 2013 Author Share Posted May 11, 2013 There isn't any real terrain there..just a general 200' elevation. There may have been a little seabreeze interaction as well..or some sort of weak diffuse boundary. Something to generate helicity. If there is one thing storms love, it's boundary helicity where they can gobble that up like pac man. Anyways, cool little storm. I know exactly where that area is as I grew up near there in Brockton.Luckily a little spinner and that's it. Here's a look at the SFC-3km helicity...just enough in the right place: Link to comment Share on other sites More sharing options...
CoastalWx Posted May 11, 2013 Share Posted May 11, 2013 There may have been more mesoscale processes too. I honestly didn't really pay attention, but I know Logan had a wind from 070 while in SE MA it was more like 120. Link to comment Share on other sites More sharing options...
weatherwiz Posted May 11, 2013 Share Posted May 11, 2013 Thanks for posting that! 150 0-3 is all you need for a weak spin-up...especially if you can get a decent core which can tap into that and there is little to disrupt the updraft Link to comment Share on other sites More sharing options...
Quincy Posted May 11, 2013 Author Share Posted May 11, 2013 Thanks for posting that! 150 0-3 is all you need for a weak spin-up...especially if you can get a decent core which can tap into that and there is little to disrupt the updraft The mean helicity value for historical tornadoes (grid centered over central/eastern Mass.) is 155 and there have been multiple cases with values between 110 and 155. Having the LCL's so low certainly helped. Well below the mean for past events. Link to comment Share on other sites More sharing options...
weatherwiz Posted May 11, 2013 Share Posted May 11, 2013 Yeah LCL's are also pretty crucial (and sometimes underrated) when it comes to TOR's Link to comment Share on other sites More sharing options...
CoastalWx Posted May 11, 2013 Share Posted May 11, 2013 Yeah LCL's are also pretty crucial (and sometimes underrated) when it comes to TOR's LCLs are very important. Link to comment Share on other sites More sharing options...
weatherwiz Posted May 11, 2013 Share Posted May 11, 2013 LCLs are very important. Hell, we see in the Plains where synoptically an event looks great for tornadoes but LCL's are too high and damaging winds dominate the event. Link to comment Share on other sites More sharing options...
Quincy Posted May 11, 2013 Author Share Posted May 11, 2013 NAM/SREF keeps speeding things up and I'm not sure that gives us enough time to break out. We'll see though. I imagine it will very much be a nowcast type of deal. Link to comment Share on other sites More sharing options...
ct_yankee Posted May 11, 2013 Share Posted May 11, 2013 The 3z RAP is showing some really nice parameters for central CT tomorrow afternoon: CAPE of 1500, 1k SRH >200, that's more than sufficient for rotating storms and yes, tornadoes. Not sure that I buy those numbers, but it certainly indicates that the day holds potential. Those kind of numbers being progged this close to the event definitely gets my attention. Link to comment Share on other sites More sharing options...
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