June 1, 2012 - Severe Thunderstorms/Tornadoes Event

[2010 extreme]

Measured three full inches with the whole event. Also had some crazy wind that between 2:45 -3:00 that knocked out power for awhile. Last time a storm did that was 7/4/06.

[tornadotony]

By DC area standards it was still a solid event I just don't know where they got the 10-15% stuff. I suppose 10% might have at least been passable. You can only take so much from parameters etc. It was pretty apparent early that even with the WF draped across the area anything near there would be brief and transient. I will say there was more discrete activity than I might have expected. It just might be about impossible to get a sizable tornado outbreak there numberswisw other than tropical.

The mass hysteria needs to stop one way or another. At some point no one will take the met community seriously. Part of the problem is that the day of or the day prior is not when people will learn at their best. Throwing around terms and ideas people don't understand from SPC etc doesnt do much good.. Neither does bowing completely to their forecast. They are by far the best in the biz but I truly believe they don't do as well with severe events east of the Apps. Local knowledge is key..

I'm gonna have to disagree with you on this particular case. SPC's forecasts were completely warranted today (and those who know me know that I'm no SPC junkie). In fact, the verified instability/shear combination observed on the 17z sounding would normally be enough for a rather sizable tornado event. IMO, what likely happened today was that the updrafts got a little moisture loaded, which can counteract upward vertical motion, which would in turn reduce stretching of vorticity and subsequent likelihood of tornadogenesis. Obviously some storms still succeeded (and a couple did so in pretty significant fashion), but not as many as even I would have expected. Truth be told, we don't have a good handle on how to forecast when this sort of thing becomes an issue. Yeah, we know it tends to occur in environments that are more saturated through a column. But because the atmosphere is a continuum, we don't have specific PWAT values or anything of that sort really to diagnose the "breakpoint," if you will, of when this either is or isn't a problem. There are several events in the past that I can think of (the Suffolk tornado in 2008 being of them) with similar environments to today that were a good bit more prolific in verification than today's event will likely be. As a forecaster, today towed a fine line. It had serious potential, and for that, SPC forecasted what they did. Nobody should blame them.

[Ellinwood]

I'm gonna have to disagree with you on this particular case. SPC's forecasts were completely warranted today (and those who know me know that I'm no SPC junkie). In fact, the verified instability/shear combination observed on the 17z sounding would normally be enough for a rather sizable tornado event. IMO, what likely happened today was that the updrafts got a little moisture loaded, which can counteract upward vertical motion, which would in turn reduce stretching of vorticity and subsequent likelihood of tornadogenesis. Obviously some storms still succeeded (and a couple did so in pretty significant fashion), but not as many as even I would have expected. Truth be told, we don't have a good handle on how to forecast when this sort of thing becomes an issue. Yeah, we know it tends to occur in environments that are more saturated through a column. But because the atmosphere is a continuum, we don't have specific PWAT values or anything of that sort really to diagnose the "breakpoint," if you will, of when this either is or isn't a problem. There are several events in the past that I can think of (the Suffolk tornado in 2008 being of them) with similar environments to today that were a good bit more prolific in verification than today's event will likely be. As a forecaster, today towed a fine line. It had serious potential, and for that, SPC forecasted what they did. Nobody should blame them.

So what you're saying is the parameters were there, but the parameters weren't there.

[Ian]

I'm gonna have to disagree with you on this particular case. SPC's forecasts were completely warranted today (and those who know me know that I'm no SPC junkie). In fact, the verified instability/shear combination observed on the 17z sounding would normally be enough for a rather sizable tornado event. IMO, what likely happened today was that the updrafts got a little moisture loaded, which can counteract upward vertical motion, which would in turn reduce stretching of vorticity and subsequent likelihood of tornadogenesis. Obviously some storms still succeeded (and a couple did so in pretty significant fashion), but not as many as even I would have expected. Truth be told, we don't have a good handle on how to forecast when this sort of thing becomes an issue. Yeah, we know it tends to occur in environments that are more saturated through a column. But because the atmosphere is a continuum, we don't have specific PWAT values or anything of that sort really to diagnose the "breakpoint," if you will, of when this either is or isn't a problem. There are several events in the past that I can think of (the Suffolk tornado in 2008 being of them) with similar environments to today that were a good bit more prolific in verification than today's event will likely be. As a forecaster, today towed a fine line. It had serious potential, and for that, SPC forecasted what they did. Nobody should blame them.

Well it's good to hear your opinion even if I don't agree fully. Though in the end I'd understand them being cautious. That however does not deal with the larger issue. I guess it's good to overwarn millions of people to save potentially a handful of lives but I just don't see it as a great way to get the point across. Though honestly even after 2011 I think that tornado concerns almost always verge on hysteria. Even in a high risk your odds of getting hurt or killed are extremely low. If there was better overall preparedness etc it would not have to be like it is. I think it does the community a disservice... and from someone who has probably more social science knowledge than weather knowledge I don't think I'm just being a troll by saying these things.

[cmichweather]

I'm gonna have to disagree with you on this particular case. SPC's forecasts were completely warranted today (and those who know me know that I'm no SPC junkie). In fact, the verified instability/shear combination observed on the 17z sounding would normally be enough for a rather sizable tornado event. IMO, what likely happened today was that the updrafts got a little moisture loaded, which can counteract upward vertical motion, which would in turn reduce stretching of vorticity and subsequent likelihood of tornadogenesis. Obviously some storms still succeeded (and a couple did so in pretty significant fashion), but not as many as even I would have expected. Truth be told, we don't have a good handle on how to forecast when this sort of thing becomes an issue. Yeah, we know it tends to occur in environments that are more saturated through a column. But because the atmosphere is a continuum, we don't have specific PWAT values or anything of that sort really to diagnose the "breakpoint," if you will, of when this either is or isn't a problem. There are several events in the past that I can think of (the Suffolk tornado in 2008 being of them) with similar environments to today that were a good bit more prolific in verification than today's event will likely be. As a forecaster, today towed a fine line. It had serious potential, and for that, SPC forecasted what they did. Nobody should blame them.

Before the forecast was made the first wave of activity hadn't initiated, without that initial activity we would of had a much more unstable environment for the prefrontal trough activity and the CF. I think the initial activity really limited the potential of the event but say that initial wave is weaker and more spread out you have a very dangerous situation with the low lcl's, low level helicity, and instability. It was a great outlook and you really aren't that far away from one of these storms really taking advantage of that low level environment.

[Ian]

Before the forecast was made the first wave of activity hadn't initiated, without that initial activity we would of had a much more unstable environment for the prefrontal trough activity and the CF. I think the initial activity really limited the potential of the event but say that initial wave is weaker and more spread out you have a very dangerous situation with the low lcl's, low level helicity, and instability. It was a great outlook and you really aren't that far away from one of these storms really taking advantage of that low level environment.

One thing about American in particular is everyone lives by uppermost potential. It's a simple fact that in most situations it does not happen that way. I guess the new thing in the NWS and larger community is to scare people into action but I strongly believe it will come back to bite them one day. Somehow forecasting widespread tornadic activity in one of the most heavily populated regions in the country that largely fails to materialize is better than playing things down a bit. It's peculiar to me. And you can't always just fall back on "well it could have been so much worse if just this and this and this happened."

[brettjrob]

Tough break today. From a traditional ingredients-based forecasting standpoint, I think the expectation of at least several tornadoes in the central MA was warranted. The only big mitigating factor was simply climo. Pushing back hard against climo in the forecasting process rarely pays off, yet those rare times it does are often the most critical to public safety. For that reason, saying "it's DC, they should've seen this coming" isn't really productive. Perhaps anyone saying that would've taken the same dismissive stance the morning of the 1953 ORH event or Memorial Day 1985 in OH/PA, then? (Not to say today looked just as impressive as those setups, but still).

Tony's hypothesis seems as good as any, to me. I noted the poor mid-level lapse rates as a concern when I first examined the setup, but I have to say, from experience forecasting for more tornado-prone areas, it normally wouldn't be a dealbreaker in the presence of such strong and well-configured low-level shear. It's not like we were trying to squeeze tornadic supercells out of 400 J/kg MLCAPE as is sometimes the case with overhyped high-shear east coast events; total buoyancy (CAPE) was modest but sufficient, even by Plains standards. Therefore, I assume the vertical distribution of that buoyancy and perhaps even the overabundance of mid-level moisture were significant inhibitors to robust supercells (their radar presentation looked more like what you'd expect in a ~400 J/kg environment -- small in both the horizontal and vertical with < 40k ft. tops, etc.)

Re: SPC: I find it really hard to fault them for anything today. I could understand complaints of inducing unnecessary panic if they'd gone 15% hatched or PDS Tornado, but they held back from both. In fact, the 50/30 probs on the eastern watch struck me as a deliberate consideration of climatology, as I'd expect more like 70/40 for the same environment in IL or KS. Any overhyping that occurred was farther down the chain of communication, IMO.

[real]

I think it may be better to over-warn, especially in this area. While tornadoes are rare, and destructive or life-threatening ones are like a once a decade event around here, they do occur. And considering the sort of region we live in, don't think people would necessarily react to a standard tornado warning unless the message was beat into their heads all day it should be taken seriously. What happens that one time a tornado does happen to just touch down on the Beltway at rush hour or move through Arlington County? It wouldn't even have to be on the ground long to tear up like five or six apartment complexes in less than a mile if such a thing were to happen.

[tornadotony]

So what you're saying is the parameters were there, but the parameters weren't there.

Sort of. A trained person looking at deep layer shear, CAPE (especially 0-3km CAPE which is the most important CAPE for tornadogenesis), and low-level shear on the 17z sounding should be thinking low-topped tornadic supercells, especially for regions nearer to the warm front which would feature slightly higher SRH. But perhaps, given the moisture loading of the sounding, more low-level shear than what would normally be considered required for a low-topped supercell tornado outbreak might be necessary to counteract the negative effects of moisture loading as they relate to updraft intensity.

A paper was just published back in March regarding this subject, where Lerach and Cotton from CSU look at low-level moisture, CCN, and CAPE, and relate the variables to tornadogenesis. The abstract can be viewed here:

http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-11-043.1

[Ian]

Tough break today. From a traditional ingredients-based forecasting standpoint, I think the expectation of at least several tornadoes in the central MA was warranted. The only big mitigating factor was simply climo. Pushing back hard against climo in the forecasting process rarely pays off, yet those rare times it does are often the most critical to public safety. For that reason, saying "it's DC, they should've seen this coming" isn't really productive. Perhaps anyone saying that would've taken the same dismissive stance the morning of the 1953 ORH event or Memorial Day 1985 in OH/PA, then? (Not to say today looked just as impressive as those setups, but still).

Since I'm sure this is at least slightly directed at me.. my reasoning for "downplaying" was not all climo. I spend a lot of time researching patterns to learn how to better forecast. I know what big DC tornado patterns are.. this one was close, but it had issues as far as I was concerned all along. I never bash the NWS or SPC and I did not here either. However, as someone who will never attempt to be an SPC forecaster or something I can of course speak a little more freely than perhaps you or tornadotony.

I will say again this ended up a little more than I expected and perhaps because I thought the WF would end up further north of what it did. Not to mention I probably didnt look at it as heavily as I would have if I was not out in the Plains.

[real]

Not to mention, despite pretty awful traffic around DC as the storms moved through, how many more people stayed home and off the roads because they heard the hype?

[cmichweather]

One thing about American in particular is everyone lives by uppermost potential. It's a simple fact that in most situations it does not happen that way. I guess the new thing in the NWS and larger community is to scare people into action but I strongly believe it will come back to bite them one day. Somehow forecasting widespread tornadic activity in one of the most heavily populated regions in the country that largely fails to materialize is better than playing things down a bit. It's peculiar to me. And you can't always just fall back on "well it could have been so much worse if just this and this and this happened."

I'm saying at the time of forecast the worst case was still on the table, this was a very potent upper level system with respectable height falls and nice jet divergence and a nice low level environment. Everything was on the table for a moderate risk event, if they had only a slight risk and the initial wave hadn't contaminated the environment and that storm near DC or Baltimore had produced you'd see posts about how the spc had failed in alerting the public to the risk. To be honest a slight risk isn't going to alert the public to the threat this had a very high upside in relation to severe weather. For this area and what was on the table at the time of issuance I think it was the right call.

[tornadotony]

Well it's good to hear your opinion even if I don't agree fully. Though in the end I'd understand them being cautious. That however does not deal with the larger issue. I guess it's good to overwarn millions of people to save potentially a handful of lives but I just don't see it as a great way to get the point across. Though honestly even after 2011 I think that tornado concerns almost always verge on hysteria. Even in a high risk your odds of getting hurt or killed are extremely low. If there was better overall preparedness etc it would not have to be like it is. I think it does the community a disservice... and from someone who has probably more social science knowledge than weather knowledge I don't think I'm just being a troll by saying these things.

If I were to criticize anything today, it would be the number of TORs that went out on some really marginal signatures. But then again, we've had events around here with not nearly as good of parameter spacing that have dropped EF2s along what looked like simple shear zones at the leading edge of a squall line, so I still can't really fault the NWS for wanting to take the more liberal approach to warnings today, especially when the I-95 corridor kinda became a supercell railroad track.

[cmichweather]

If I were to criticize anything today, it would be the number of TORs that went out on some really marginal signatures. But then again, we've had events around here with not nearly as good of parameter spacing that have dropped EF2s along what looked like simple shear zones at the leading edge of a squall line, so I still can't really fault the NWS for wanting to take the more liberal approach to warnings today, especially when the I-95 corridor kinda became a supercell railroad track.

Agreed they did seem a bit trigger happy on the warnings, some of the storms looked nice on radar but didn't have evident strong meso's or were indicative or a tornadic storm but the environment did give them the benefit of the doubt.

[Ian]

If I were to criticize anything today, it would be the number of TORs that went out on some really marginal signatures. But then again, we've had events around here with not nearly as good of parameter spacing that have dropped EF2s along what looked like simple shear zones at the leading edge of a squall line, so I still can't really fault the NWS for wanting to take the more liberal approach to warnings today, especially when the I-95 corridor kinda became a supercell railroad track.

In the end it's not worth a long argument. I have a lot of respect for you, Brett and others as forecasters in this area. I probably tend to downplay more than I should in some cases and realize that. Though I actually have a pretty good record so whatever. Not to mention I know mark (Ellinwood) knows his stuff too and he was not screaming from the rooftops at any point.. And I don't think it was purely because we are out of town.

[brettjrob]

Since I'm sure this is at least slightly directed at me.. my reasoning for "downplaying" was not all climo. I spend a lot of time researching patterns to learn how to better forecast. I know what big DC tornado patterns are.. this one was close, but it had issues as far as I was concerned all along. I never bash the NWS or SPC and I did not here either. However, as someone who will never attempt to be an SPC forecaster or something I can of course speak a little more freely than perhaps you or tornadotony.

I will say again this ended up a little more than I expected and perhaps because I thought the WF would end up further north of what it did. Not to mention I probably didnt look at it as heavily as I would have if I was not out in the Plains.

No, I understand your concerns and I won't hesitate in saying the 15% contour wasn't a good forecast, subjectively (in hindsight, of course). I won't discount your experience and research as a local, either. Oddly, I've noticed that a lot of times eastern setups that look suspiciously Plains-like will underperform; it's almost as if a different shear configuration is ideal there vs. here. When you're staring at large, looping hodographs and backed boundary-layer flow, though, it's hard to discount potential simply on that notion -- right or wrong. (Just off the top of my head, I can imagine one reason these "classic Plains" hodos underperform is because the relatively backed mid-level flow could correspond to greater mid-level moisture advection vs. a more veered profile overall -- i.e., W to NW flow might be more "mandatory" for big events there).

[tornadotony]

In the end it's not worth a long argument. I have a lot of respect for you, Brett and others as forecasters in this area. I probably tend to downplay more than I should in some cases and realize that. Though I actually have a pretty good record so whatever. Not to mention I know mark (Ellinwood) knows his stuff too and he was not screaming from the rooftops at any point.. And I don't think it was purely because we are out of town.

Oh I don't think this is an argument. Instead, I think it's a discussion that has to be had. Overall, I, along with SPC/NWS, generally busted today in forecasting this event. There's no use in trying to forecast if you don't learn from mistakes. I don't have as much experience with the mid atl region as you or Mark have.

[thewxmann]

No, I understand your concerns and I won't hesitate in saying the 15% contour wasn't a good forecast, subjectively (in hindsight, of course). I won't discount your experience and research as a local, either. Oddly, I've noticed that a lot of times eastern setups that look suspiciously Plains-like will underperform; it's almost as if a different shear configuration is ideal there vs. here. When you're staring at large, looping hodographs and backed boundary-layer flow, though, it's hard to discount potential simply on that notion -- right or wrong. (Just off the top of my head, I can imagine one reason these "classic Plains" hodos underperform is because the relatively backed mid-level flow could correspond to greater mid-level moisture advection vs. a more veered profile overall -- i.e., W to NW flow might be more "mandatory" for big events there).

Yeah I think in general, the further east you go, the "ideal" configuration becomes increasingly veered from the "ideal" configuration in the Plains. For instance, westerly to WNW flow in the eastern U.S. helps with EML advection, and while backed low-level flow is essential for Plains events, this is not as important for areas east of the Mississippi, since they don't have as many issues with low-level moisture mixing out.

[thewxmann]

I wasn't really able to watch today's event, but the parameters were pretty impressive. I think Tony has the right idea here, in that there was too much moisture through the column, and so essentially, the lack of an EML limited updraft acceleration. Then again the whole College Park, MD event in 2001 and 4/27 last year had similar setups in the MA. So who knows. There's so many "higher-order" corrections to our current models that we simply don't have a grasp on.

[WEATHER53]

The pictures from Greenbelt/Beltsville/College Park-I was freaking there i about piss*ed myself. The rotation, desendening funnel lime cloud-All There/ I am right there!!

[thewxmann]

One thing about American in particular is everyone lives by uppermost potential. It's a simple fact that in most situations it does not happen that way. I guess the new thing in the NWS and larger community is to scare people into action but I strongly believe it will come back to bite them one day. Somehow forecasting widespread tornadic activity in one of the most heavily populated regions in the country that largely fails to materialize is better than playing things down a bit. It's peculiar to me. And you can't always just fall back on "well it could have been so much worse if just this and this and this happened."

Or, you could look back a year ago, when SPC had a 5% tor risk out, and NWS belatedly issued a tornado warning for the EF3 that tore through Springfield, MA, and everybody was on their case. I don't know if overforecasting is better, but it's certainly not worse.

[baroclinic_instability]

To sit back and call an SPC bust is ridiculous. I was less than enthused with some of the local office warnings, however.

[Hoosier]

All these ideas being bantered about are part of what make this board great. Earlier I was thinking how the thermodynamic environment was kinda reminiscent of what you often see with a landfalling tropical system (warm/moist low levels, crappy mid level lapse rates etc). Some of those events have been rather prolific tornado producers even with instability values that don't jump off the page. Maybe Tony is onto something about needing stronger shear than what you'd think in these very high PW setups.

[gymengineer]

It's not just about tornadoes though in terms of the 'hype' machine on both the media and on here. Even on our College Park and La Plata days, a tiny proportion of the total population actually experienced violent weather. During the Ivan outbreak, if you weren't directly in the path of one of the tornadoes, you probably didn't see anything particular noteworthy.

The expectations for this event were enormous-- that there would be cells ahead of the line dropping tornadoes, and then *everyone* would get crushed by the squall line. Just looking back in history, there are very few events that produce area-wide, but some of the posts almost implied the unrealistic expectation that they *would* see severe weather based on the parameters.

[Amped]

I'll wait until the damage is surveyed tomorrow to call it a bust. If I decde it is, I'm entitled to my opinion.

[Disc]

Great video. Excellent choice in siting

Thanks. I had this spot in mind all day if anything started moving in. Since this overlook faces west it would be perfect and it ended up being a much better shot than I thought.

[weatherwiz]

I agree with Tony regarding the column being a little too moist. Last night when looking at the soundings I was a bit worried about this b/c the water loading here in the mid-levels cuts back on the amount of instability through the column which makes it a bit more difficult to achieve "Fat" Cape profiles. Unfortunately I wasn't able to make it down there (long story) or didn't get the chance to watch things unfold but looking at archived mesoanalysis data Ncape values only seemed to be around 0.1 to 0.15 which is suggestive of rather skinny Cape profiles. This was also mentioned in this thread but 500mb winds weren't as impressive as they really could have been...and the speed/directional shear from 700-500mb was decent but could have been better. Also, since there was a quite a bit of convection around there could have been alot of updraft disruptions with storms fighting each other. And as Jim mentioned, mlvl lapse rates were pretty awful which cuts back on upward parcel acceleration as well.

Anyways though this really was not a bad event for that area and a pretty crazy system to see this time of year with nearly fall-like dynamics.

[Ian]

Or, you could look back a year ago, when SPC had a 5% tor risk out, and NWS belatedly issued a tornado warning for the EF3 that tore through Springfield, MA, and everybody was on their case. I don't know if overforecasting is better, but it's certainly not worse.

In the end the SPC argument is probably somewhat academic. In most cases the issues are with the media and local forecasters and how they use SPC data with an audience that doesn't get it. However, I don't completey understand how one event gets a 15% and another gets a 5% yet the 5% produces more tornadoes etc. Take KS last Friday. It was pretty clear there was a high chance of tornadoes even if a small area and it got a general 5%.

[Ian]

To sit back and call an SPC bust is ridiculous. I was less than enthused with some of the local office warnings, however.

I dunno if anyone called it an outright bust. Plus with probability forecasts you can always weasel out of any responsibility.

[weatherwiz]

In the end the SPC argument is probably somewhat academic. In most cases the issues are with the media and local forecasters and how they use SPC data with an audience that doesn't get it. However, I don't completey understand how one event gets a 15% and another gets a 5% yet the 5% produces more tornadoes etc. Take KS last Friday. It was pretty clear there was a high chance of tornadoes even if a small area and it got a general 5%.

There seem to be alot of cases where storm mode isn't quite clear or it's not quite clear what will happen after storm initiation. Unless you're dealing with a situation where you virtually have a line of supercells where just about every supercell seems to produce it can be very hard to gauge the situation.

How they also determine it probably also depends on past setups and such...don't they take alot of that into account or something?