Erik Rasmussen's DRC Theory (chat log now inside!!!)

[Joe Guerra]

Well tonights the night, Erik popped in this morning to make sure it worked, and were all setup here

 

[Mike Peregrine]

Would someone be kind enough to archive and post this chat afterward? - I have to go into work for a couple hours right at 8:00 and will miss it unfortunately. Thanks!

 

[Joe Guerra]

Well, Eriks here now

 

[Caleb Lawrence]

Here is the chat log, folks. Erik did a great job, as did Aaron for presenting the asked questions, and George for initiating this whole thing. It was great how many people showed up, and thanks again to all who came. Great chat! I echo the sentiments of George, below this post. Thanks again Erik, Aaron, and George.

[21:03:10] <+ErikR> When we analyzed the Dimmitt (1995) storm, we saw a column of precip dangling down the back in the radar data.
[21:03:22] <+ErikR> This hangs down from the echo overhang which caps the updraft.
[21:03:29] <+ErikR> So basically it is coming down the back of the updraft
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[21:03:35] <+ErikR> But we don't know if it's in cloud, or outside
[21:03:40] <+ErikR> Hard to say.
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[21:04:00] <+ErikR> Sometimes when you look at the backsheared anvil, you see streamers of graupel/snow there taking aim on the updraft
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[21:04:14] <+ErikR> Anyway... that was unusual in itself... never before documented as far as i know.
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[21:04:36] <+ErikR> Well... Forbes saw a "dot" echo in the WSR-57 reflectivity before the xenia tornado... same thing, prolly
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[21:05:04] <+ErikR> That's how it looks often in 88D base scan data... a dot off to the right rear where you might expect a hook to form
[21:05:26] <+ErikR> This was pretty interesting... we called it a "blob echo", but "officially" it will prolly get called a Descending Reflectivity Core
[21:05:38] <+ErikR> But that's not the whole story
[21:06:14] <+ErikR> When you see these things show up in the base scan data, you VERY OFTEN see a little jetlet... locally strong outflow... right on the leading edge of the blob
[21:06:27] <+ErikR> And since the air either side of the jetlet is usually moving like inflow air, you end up with counter-rotating vortices straddling the blob.
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[21:06:47] <@Aaron_Kennedy> Note to all... if you think of a question anytime during the chat, PM it to me and I'll make sure we ask it
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[21:06:56] <+ErikR> Some of you showed BEAUTIFUL time lapse footage at the chaser convention, and if you look at this carefully, you will often
[21:06:57] <+ErikR> be able to pick out the A-C rotation on the south of the cyclonic
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[21:07:08] <+ErikR> So what's going on here?
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[21:07:24] <@Aaron_Kennedy> Well basically when you're done with the initial talk
[21:07:32] <@Aaron_Kennedy> we'll start presenting user's questions
[21:07:37] <@Aaron_Kennedy> and you get to answer them
[21:07:47] <+ErikR> It LOOKS like we form rings of horizontal vorticity around a locally strong part of the RFD that is associated with the blob
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[21:08:02] <+ErikR> And it LOOKS like the forward side of these rings, finding themselves below the updraft, get tugged violently upward, forming the
[21:08:20] <+ErikR> cyclonic AND anticyclonic vortices.... while the back side gets pressed toward the ground by the RFD.
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[21:08:50] <+ErikR> So this means the rotating that forms the tornado is PARTLY derived from the sinking vs. rising that is going on in the back of the storm, then tilted into the vertical
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[21:09:02] <+ErikR> Why don't we see more anticyclonic tornadoes?
[21:09:27] <@Aaron_Kennedy> Ok quick question to clarify
[21:09:31] <+ErikR> A bunch of the circulation that ends up being a tornado is due to the tilting of very large (streamwise) vorticity...SRH... from the inflow.
[21:09:37] <+ErikR> This favors the cyclonic vortex.
[21:09:46] <+ErikR> (My aching fingers and wrists)
[21:09:47] <@Aaron_Kennedy> Where are blobs occuring in relation to the sfc
[21:09:58] <+ErikR> OK... so that's it in a nutshell.... I see a question
[21:10:20] <+ErikR> The blob is right in the notch in the back of the updraft.... the indented part of the horseshoe
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[21:10:53] <@Aaron_Kennedy> <LauraD> What do blobs visually look like in appearance?
[21:10:54] <+ErikR> You will have a tough time making it out visually often... it's small... about a mile across... and maybe just a few more large drops than normal
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[21:11:04] <@Aaron_Kennedy> hah great timing
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[21:11:16] <+ErikR> Laura, did that answer it... you might see a bit of a rain shaft there in some cases
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[21:11:33] <@Aaron_Kennedy> Jeff Wear posted some timelapse
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[21:11:37] <@Aaron_Kennedy> of the Mulvane tornado
[21:11:46] <+ErikR> What you are more likely to notice is an abrupt advance of the clearing, and the counter-rotating cloud base vortices
[21:11:49] <@Aaron_Kennedy> you acn see a small rain shaft south of the developing rotation
[21:12:02] <@Aaron_Kennedy> cyclonic rotation that is...
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[21:12:12] <+ErikR> You all are a better judge of how often this shows up visually
[21:12:45] <@Aaron_Kennedy> <GGarf> Is "the blob" different from a "surging" RFD? If so, how are they related?
[21:12:51] <+ErikR> We sure would like to know what it looks like from the back side... to find out if it's in or out of cloud.
[21:13:27] <+ErikR> Prolly the blob is first... leading to the vortex rings aloft... then tilting happens... and the tilting of a vortex ring is a fancy way of saying that the air is starting to surge eastward behind the GF
[21:13:55] <@Aaron_Kennedy> <Chief`Skyreader> "In relation to RFD core, where would the blob be? Centered in RFD max? that is to say center of clear slot push? or on some side of clear slot/RFD?
[21:13:57] <+ErikR> In a computer simulation we ran, that's exactly what happened. It's kind of neat... there was NO SHEAR
[21:14:12] <+ErikR> in the environment of this experiment... calm air.... all we did was let rain descend at the back of an updraft.
[21:14:36] <+ErikR> And quickly the updraft turned horseshoe-shaped, and the gust front surged, and counter-rotating vortices formed
[21:15:10] <+ErikR> Good question, Chief... In the ONE case that we have good enuf data for and have analyzed, the blob is near ZERO updraft...
[21:15:12] <@Aaron_Kennedy> <LauraD> Do blobs occur only in certain types of supercells?
[21:15:23] <+ErikR> centered right between updraft and rFD, with the strongest RFD right in the back edge of the blob.
[21:15:58] <+ErikR> We have found blobbing behavior in what you might call CL and HP supercells. We have examined a few LPs, and found no blobbing
[21:16:21] <+ErikR> I might add that the blob may just be telling us that we have a small-scale, locally intense downdraft.
[21:16:38] <+ErikR> This is the sort of thing you would expect with a local column of precip... enhanced water loading, melting, evap, etc.
[21:17:07] <+ErikR> BUT/..... There are some CL tornadic supercells that produce the counter-rotating vortices without a typical blob... always some local precip back there, but not always a column
[21:17:16] <@Aaron_Kennedy> AmosM>Dr. R, do you have any preliminary sense of what factors in the larger environment might be more strongly associated with DCRs? For instance the way low-level RH values may be associated with the presence of more buoyant RFD.
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[21:17:54] <@Aaron_Kennedy> And we'll add: <AmosM> Question: Any possible relationship between DRC and the occlusion downdraft, or not enough data to know?
[21:18:36] <+ErikR> Not yet... I want to toss this to Aaron who may have looked at it more than I... I think the blob may be more EFFECTIVE at producing a tornado when it's humid, and I can elaborate on that further, but first Aaron... do you have any sense of the environment for blobs?
[21:18:48] <@Aaron_Kennedy> Not yet
[21:19:01] <@Aaron_Kennedy> we still need to build a larger case database
[21:19:04] <+ErikR> OK... let me comment on the DRC and occlusion downdraft.
[21:19:06] <@Aaron_Kennedy> of storms that do have blobage
[21:19:35] <+ErikR> Wow... I have always been troubled by the occlusion downdraft concept, to be honest. It may be quite viable, it just doesn't satisfy this soul.
[21:20:04] <+ErikR> Something VERY fascinating happened in the simulations.
[21:20:29] <+ErikR> RIght behind the vortex ring, as it got tugged east and up into the updraft, the vorticity in the ring got intensified through stretching, right?
[21:20:43] <+ErikR> That's basically the process that leads to a tornado, but it can happen horizontally as well as vertically.
[21:21:07] <+ErikR> And as the horizontal part, between the updraft and downdraft, got stretched, a locally strong downdraft about the width of the blob developed.
[21:21:20] <@Aaron_Kennedy> It is too bad this chat doesn't have a whiteboard... this topic lends itself to graphic diagrams
[21:21:27] <+ErikR> That darn thing in the simulation looks SO MUCH like what so many of us have seen... the waterfall just behind
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[21:21:32] <+ErikR> the back edge of the updraft.
[21:21:56] <+ErikR> MAYBE... that's what the occlusion downdraft really is visually and in radar obs
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[21:23:20] <@Aaron_Kennedy> Ok couple more questions involving "the big picture" at the time of blobs
[21:23:29] <@Aaron_Kennedy> <Joseph_C_Guerra> Question: In your illustration, Showing Cool and Warm downdrafts in relation to tornadogenesis, it shows that the warmer downdraft rises viloently back up, is this due to the fact that cold air sinks and hot air rises?
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[21:23:38] <+ErikR> Just to be clear, or simple simulation captured VERY MANY of the features seen in complex cloud model simulations, which leads me to ASK whether the occlusion downdraft maybe has been erroneously explained in the past.
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[21:24:34] <+ErikR> Joseph.. yes... in a nutshell... or think of it this way... the tornado cyclone would LIKE to lift the air because friction is forcing the air into it near the ground. But if it's cold, a whole lot more work must be done to lift it, and it's harder for the cyclone to intensify
[21:25:10] <@Aaron_Kennedy> <Ggarf>You have said descending reflectivity cores may be related to tornadogenesis. I
[21:25:10] <@Aaron_Kennedy> recall seeing a picture of the Hesston tornado of 1990 that showed a small rain band just
[21:25:10] <@Aaron_Kennedy> to the west-southwest of the tornado. However, at the time of the photo, the tornado
[21:25:10] <@Aaron_Kennedy> had been on the ground for ~ 40 minutes. Could DRCs also aid in the longetivity of some
[21:25:10] <@Aaron_Kennedy> tornadoes?
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[21:25:14] <@Aaron_Kennedy> Oo that came out bad
[21:25:32] <+ErikR> This idea of tornado probability, intensity, longevity etc. is from the work of Markowski, and earlier from Lance Leslie (I believe) in Australia.
[21:26:46] <@Aaron_Kennedy> <AmosM> Q: following up on Gabe's question, how do you imagine the DCRs might be altering the thermodynamics of the RFD if at all?
[21:26:49] <+ErikR> No... I understand... and I have seen the same thing. I haven't thought it through, but I'm guessing that the DRC/RFD could continue to contribute circulation as long as it's present. I have the gut feeling that many tornadoes get their initial quota of circulation, and then just gradually spin down
[21:27:01] <+ErikR> But some apparently keep getting a new dose of circulation as they go along.
[21:27:45] <+ErikR> The CRD and thermo is the million dollar question right now in my opnion. There is something that is allowing some RFDs to be intense aloft, reach the ground, and arrive there warm
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[21:28:12] <+ErikR> To be an intense RFD strongly implies that there is a lot of water loading and/or evap/melting going on aloft.
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[21:29:04] <@Aaron_Kennedy> <ef> what visual clues on radar should look for the blobs
[21:29:08] <+ErikR> But, it's apparently warming dry adiabatically near the ground. One culprit might be that the DD is being driven by the weight of a few very large drops, and hence not being cooled excessively
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[21:29:58] <+ErikR> Expect the blob to first appear aloft, right below the echo overhang at the trailing part of the storm. If the storm is close enuf to radar, you might be able to see the blob as a dot or "hot spot" in the rear-side echo appendage ALOFT FIRST.
[21:30:15] <+ErikR> They seem to descend ~ 10 meters/sec, so it takes a volume scan or two for them to show up at the base scan
[21:30:41] <+ErikR> The classic appearance, (Aaron?) is a local max in reflectivity embedded in the rear-side appendage.
[21:30:48] <@Aaron_Kennedy> ya
[21:31:01] <+ErikR> People have usually called this appendage a "hook", but in my experience, it is seldom hook-like until the gust front as surged, and the vortices have really intensified.
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[21:31:32] <+ErikR> Once it is hook-like, the storm has done its thing in terms of producing a tornado cyclone... the only question remaining is whether that will contract into a tornado
[21:32:23] <+ErikR> I want to remind everyone that a lot of what I am saying is not in the formal literature yet.... subject to a lot of scrutiny by other scientists. So your mileage may vary
[21:32:44] <+ErikR> Heh.... you DON'T WANT to know how hard it is to get this stuff published!
[21:33:08] <@Aaron_Kennedy> The red tape of science
[21:33:32] <@Aaron_Kennedy> <Joseph_C_Guerra> Where did you come up with the "Blob Echo" name?
[21:33:42] <+ErikR> There are many, many obstacles... most of which don't need to be there
[21:34:08] <@Aaron_Kennedy> And a bit more technical: <AmosM> Q: When you guys were measuring RFDs, was the DCR concept anywhere in your mind? Any chance a probe might have stumbled into one?
[21:34:29] <+ErikR> Joseph, when you see the echo in 3D, it looks like a blob descending from the echo aloft. Or a stalactite (is that the one that hangs?).
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[21:35:02] <+ErikR> We get this by doing a numerical analysis of all the tilts of 88D data to a grid, and then using visualization software to look at the 3D structure of a certain reflectivity value, like 40 dBZ
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[21:35:41] <+ErikR> The DRC was not in our minds when we were out there in VORTEX or its successors. It's pretty new in the last 18 months. But yes, I have at least one case where the cars unwittingly were in the blob.
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[21:36:12] <@Aaron_Kennedy> <Jo_n_Shane> "Do you believe there's one main type of process that leads to tornadogenesis, or do you think there's multiple processes, none of which are neccessarilty related to each other...in other words, do you believe the blob theory is touching on THE way tornado genesis occurs, or just ONE OF the ways?
[21:36:20] <+ErikR> In V2, we will intentionally sample the blobs with mobile mesonets as well as unmanned aircraft
[21:36:36] <@Aaron_Kennedy> We got a bunch of questions on Vortex II...
[21:37:00] <@Aaron_Kennedy> I figure we can finish up the blob stuff... touch vortex II, and then we have a few off topic questions
[21:37:30] <+ErikR> My sense, Jo_n_Shane, is that this is probably the MAJOR way that supercells produce tornado cyclones. ANd keep in mind that there might not always be a blob echo, but probably always a very small scale (0.5-2 mi) locally intense DD in the RFD
[21:37:31] <+ErikR> BUT
[21:38:03] <+ErikR> That only gets us to tornado cyclone... something you see visually as "rapid circulation" preferrably "right overhead".... and you will see in mobile mesonet and doppler data
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[21:38:34] <+ErikR> There may be a lot of variety in how what we call tornadoes (a visual term) come to be within the tornado cyclone
[21:39:16] <+ErikR> An interesting anecdote... to me anyway... in 1979, we were chasing the Wichita Falls storm. Near Seymour, a dark rainshaft appeared just at the back of a really wicked rotating base.
[21:39:46] <+ErikR> I thought that this was all wrong... we had been told that the base FOLLOWS the rain, not the other way around. Within minutes... a violent tornado.
[21:40:17] <+ErikR> When I looked at the picture again 25 years later, I recognized what was going on in it.
[21:40:46] <+ErikR> Next?
[21:40:50] <@Aaron_Kennedy> Ok
[21:40:53] <@Aaron_Kennedy> on too VII questions
[21:41:04] <@Aaron_Kennedy> <Ggarf>VORTEX II will have a significantly larger set of vehicles than VORTEX I. How
[21:41:04] <@Aaron_Kennedy> will logistical issues (gasoline for vehicles, etc) be handled?
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[21:41:11] <+ErikR> Wow
[21:41:48] <+ErikR> We will be doing some things differently. We will be using an ad hoc mobile digital network (WiFi?) to send graphical info to all teams
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[21:42:10] <@Aaron_Kennedy> hrm
[21:42:14] <+ErikR> I envision this to include realtime counts of the numbers of our vehicles at various service stations, etc., as well as possibly reports of restroom line length, etc.
[21:42:35] <+ErikR> We will probably be in 3-4 mini-caravans of 10-15 vehicle each. That sort of thing.
[21:42:42] <+ErikR> Next?
[21:42:59] <@Aaron_Kennedy> <AmosM> Q: Would it make sense to recruit some chasers for V2 simply to decrease traffic
[21:42:59] <@Aaron_Kennedy> density given the number of MMs planned?
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[21:43:28] <@Aaron_Kennedy> or do you grab every grad student and make full use of their stipends
[21:44:05] <+ErikR> There has been talk of outfitting chaser cars with instruments. There are pros and cons... liability being one. Another concern is that our MM mission MUST be science driven... always moving around to sample the assigned gradients, and NEVER stopping to enjoy the storm
[21:44:32] <@Aaron_Kennedy> Not sure how many chaser's would like to stick to a predetermined pattern
[21:44:33] <+ErikR> And of course the grad students... one ought to be able to be in a couple or three mms at once, right?
[21:44:58] <@Aaron_Kennedy> hah
[21:45:13] <@Aaron_Kennedy> We have several questions about the use of UAV's in Vortex II
[21:45:17] <+ErikR> We found in V1... no offence to anyone involved... that folks usually MUST stop to get video. It is too hard to resist
[21:45:53] <+ErikR> OK... first let me say that I want to be thinking with everyone here about ways to get scientifically useful video. To me, that means somehow encoding lat, lon, elevation and camera orientation into the digital stream
[21:46:19] <+ErikR> Camera orientation being azimuth, roll, and tilt to the nearest 0.1 deg or so.
[21:46:31] <+ErikR> UAVs... query away...
[21:46:48] <@Aaron_Kennedy> Have scientists talked to camera makers about including this data?
[21:47:30] <+ErikR> Not yet. I do know that there are devices that can get these data for UAVs... a small box about the size of a coffee cup in volume that cost about $5k a few years ago.
[21:47:48] <+ErikR> How to interface it to the DV data stream is another issue.
[21:48:05] <@Aaron_Kennedy> yep
[21:48:28] <@Aaron_Kennedy> As far as UAV questions.... what sort of UAVs will be used... in what quantity
[21:49:17] <+ErikR> There is a big effort underway at CU.... http://recuv.colorado.edu I think is the web page. The UAVs are roughly 2 meter wingspan.... a hardened version of a popular hobby model plane
[21:49:34] <+ErikR> They will fly 35-120 kt roughly. Somewhat hailproof. ~3 hour duration
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[21:50:15] <@Aaron_Kennedy> What sort of instrument packages will you be able to fit on them
[21:50:18] <+ErikR> And let me say that these aircraft know their position, yaw, pitch, roll, and know how to fly from one location to another on their own
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[21:50:59] <+ErikR> The idea that we will test this summer is this... a MM will be in radio contact with a UAV, sending the mm lat, lon, and pressure. The UAV will endeavor to fly to at the same lat, lon and say 50 mb lower pressure automatically
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[21:51:31] <+ErikR> Instruments... standard sonde package or better. ACtually we're looking at making our own mini-sondes for a variety of applications. And
[21:51:47] <+ErikR> we're working with NCAR to develop a device to image particles up to large raindrops and small hailstones
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[21:52:11] <@Aaron_Kennedy> like a mini cloudscope/2dc probe?
[21:52:16] <+ErikR> They could actually carry quite a bit more instrument payload... there will be an onboard generator.
[21:52:32] <+ErikR> Yep... this will be a mini 2D probe.
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[21:52:56] <@Aaron_Kennedy> <Kyle_F> you mentioned the use of airborne radars as part of VortexII. What kind of aircraft will you use for that...P-3s?
[21:52:57] <+ErikR> The precip field will be illuminated in a narrow slab by a pulsed, collimated light source.
[21:53:51] <+ErikR> It has been proposed that the NCAR/Navy Research Lab P-3 will be flown with the ELDORA radar.... there has been some discussion of adding the U Wyoming cloud radar
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[21:54:16] <+ErikR> I will be honest here, though... with seven ground-based mobile Dopplers, those will be the chief data source for Doppler analysis. One or two of these mobile radars will be dual-polarization as well
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[21:54:38] <@Aaron_Kennedy> Is there even an operational dual pol radar yet?
[21:54:42] <@Aaron_Kennedy> mobile
[21:54:43] <@Aaron_Kennedy> that is
[21:54:58] <+ErikR> It's amazing how the state of the art has changed in the last few years, thanks much to the ceaseless efforts of Josh Wurman and the recent efforts of OU/NSSL/TAMU/TTU
[21:55:32] <+ErikR> Yes, there is an X-band mobile dual-pol that usually resides in Greece, but was built here. And NSSL/OU are in the process of collaborating on another, I believe
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[21:55:54] <@Aaron_Kennedy> <ef> What states will Vortex 2 cover?
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[21:56:55] <+ErikR> V2 domain has been based on land use and road coverage... flat, agricultural, dense roads, few trees. From roughly MAF-OKC-TOP-DSM-Souix Falls-VTN-LBF-EHA-MAF
[21:57:23] <@Aaron_Kennedy> <GeorgeT> When is Vortex II scheduled to begin? And how long will the project continue?
[21:57:30] <+ErikR> By the way... V2 is a FULLY MOBILE experiment... there won't be a "home base". Home will be on the road in motels. We will set up a few maintenance depots around the Plains in case we need repairs
[21:57:46] <@Aaron_Kennedy> <MikeDinGRI>Is there any new information about the funding
[21:57:46] <@Aaron_Kennedy> status of VORTEX 2007/2008?
[21:57:55] <@Aaron_Kennedy> Last of the Vortex questions
[21:58:11] Joins: Ani ([email protected]) Clone: AdrianE [48 users]
[21:58:28] <+ErikR> V2 has been proposed for early May 2007-end of June, and the same period in 2008. Whether or not we really can go two years is up to the National Science Foundation. And there is a reasonable chance we will be asked to delay until 2008/9
[21:59:21] <+ErikR> Status... the formal experiment proposal is now in review. We should hear ~June. Then individual researchers will submit their own proposals for their own research components. Anyway... we ought to be able to announce the general go/no-go and timetable sometime this summer
[22:00:05] <@Aaron_Kennedy> Any plans for mobile phased array radar in the projecT?
[22:00:50] <+ErikR> I believe that U Mass has developed a mobile PA radar, and I would guess that perhaps Howie Bluestein will propose using it since he works closely with the UMass engineers historically
[22:01:09] <@Aaron_Kennedy> Ok... now for a few off topic questions
[22:01:16] <+ErikR> OK
[22:01:19] <@Aaron_Kennedy> <LauraD> Have you considered chasing storms in Canada to study or just for fun?
[22:02:09] <+ErikR> I'd love to chase Canada. The logistics are a bit much for V2. Someday I'll be up there incognito... the kids are now getting old enuf that I don't need to hang around the ranch so muc
[22:02:35] <@Aaron_Kennedy> <Rockwell> What do you like to do in your spare time?
[22:02:46] <@Rockwell> (assuming you have any)
[22:04:25] [@Aaron_Kennedy:#stormchase PING] 1110423871 (cloaked)
[22:04:32] <+ErikR> Heh.... I live on the Western SLope in Colorado... along the north face of the Grand Mesa. So, I have my own network of trails on my place and in the adjacent Natl Forest. I like to hike and snowshoe, x-country backcountry ski up on the Mesa, bike in the desert. I coach soccer for kids. But honestly, there isn't much spare time. I enjoy my research immensely, and my grad students keep me busy writing software tools (heh)
[22:05:02] <@Aaron_Kennedy> Some grad students are still waiting
[22:05:20] <+ErikR> We are changing you over to the 5-year plan
[22:05:26] <@Aaron_Kennedy> Ouch!
[22:05:47] <@Aaron_Kennedy> Your in trouble now
[22:05:48] <@Aaron_Kennedy> my wife saw that
[22:05:54] <+ErikR> Hah!
[22:06:08] <@Aaron_Kennedy> One last comment from a user
[22:06:19] <@Rockwell> Oh dang
[22:06:21] <@Aaron_Kennedy> Woops... net split
[22:06:27] <@Aaron_Kennedy> <Mike_H> I'd just like to state an observation I noticed(or think I did) regarding vorticies off vented steam at a corn milling plant....they are very amazing to watch how they form and when....I noticed it seemed like the biggest key to their formation was a dry environment...one day it was VERY moist...90-100%RH temps low 40s winds s 10knots....they refused to form and they are pretty common...watched and watched and watched and
[22:06:27] <@GeorgeT> net split
[22:06:29] Joins: GGarf ([email protected]) [49 users]
[22:06:29] <@Rockwell> How ironic, that server is named vortex
[22:06:33] <@GeorgeT> lol
[22:06:34] <@Aaron_Kennedy> <Mike_H> Then I started taking readings and watching to see how frequent they were and how "strong". The biggest factor seemed to be the RH. Often the steam would billow out and be tilted over horizontally by any winds. Then it would be forced to have two rotating sides with the center of this mass being "cut" up as it would spin. It would even spread as it does so until the two sides are further apart rotating by themselves.
[22:07:20] <@Aaron_Kennedy> Last chance for questions
[22:07:23] <+ErikR> Cool....are you saying they are more common/vigorous when it's dry?
[22:07:35] Aaron_Kennedy sets mode: +v Mike_H
[22:07:39] <+Mike_H> yes
[22:08:05] <+ErikR> I would speculate that this allows the edges of the steam plume to cool more than normal... increasing the horizontal vorticity of both directions of spin
[22:08:50] <+ErikR> I wonder if what I said at the start about the physics of the rotation in supercell tornadoes made any sense?
[22:09:00] <+ErikR> Did anyone wonder what the mesocyclone has to do with things?
[22:09:36] <@GeorgeT> the meso, yes. How does it fit into these new findings?
[22:09:55] <+ErikR> It doesn't, much...
[22:10:20] <+ErikR> My present opinion is that the meso is there because the inflow has large SRH... I guess we all knew that. So it is a big SRH-meter in the sky
[22:10:37] <+ErikR> I don't think a meso MAKES a tornado, like we thought for so many years
[22:10:58] <@Aaron_Kennedy> Plenty (and I mean plenty) of supercells don't produce tornadoes... or ever come close
[22:11:05] <+ErikR> It is POSSIBLE that a meso embedded in stronger winds aloft has a place at the back side with very little flow, allowing precip to descend there and creating a blob.
[22:11:06] <@Aaron_Kennedy> my chase experiences are proof of that
[22:11:51] <+ErikR> Me too. And I've seen storms WITHOUT mesos produce tornado cyclones and then tornadoes, ending up looking very classic
[22:11:51] <@Rockwell> PMFJ, but what about landspout-type tornadoes?
[22:12:14] <@Aaron_Kennedy> and <Monsoon> for Erik...does electrical charge/lightning play a role or give clues?
[22:12:18] Joins: Guest85 ([email protected]) [50 users]
[22:12:20] Quits: stwx1002 ([email protected]) (Quit: PJIRC forever!)
[22:12:54] <+ErikR> Yep... those are a different beast entirely. I don't have a good sense of how common the landspout mechanism is with supercells. It's something else we may get a chance to look at in V2. In one way, it could be the blobbing that produces the TC and gust front, and the landspout mech might take things the rest of the way
[22:13:36] <@Rockwell> Okay cool, thanks
[22:13:38] <+ErikR> Lightning... someone is baiting me here. There are some intriguing signatures in total lightning now that we're mapping it in 4D. But to my eye, they don't say a whole lot more than radar reflectivity is telling us.
[22:13:48] Quits: rdewey ([email protected]) (Quit: Leaving)
[22:14:17] <+ErikR> I was part of some experiments in the 80's that looked for anything unusual electrical near tornadoes... the Chief was our driver and inspiration... we didn't find anything. Doesn't mean it's not there... just well hidden maybe
[22:15:04] <@Aaron_Kennedy> <AmosM> Q: Since we're well enough off-topic. Some friends of mine measured RFD around the Mulvane storm 6-11-04 and found CAPE/CIN approx equivalent to ambient env. That storm was on the cool side of a boundary and I was thinking that if it had not been, the RH values would have been lower and possibly not-so-'warm' RFD would have occured. Could this mean there is more value in boundaries than simply enhanced SHV?
[22:15:23] Quits: weathernet ([email protected]) (Quit: Visit my website http://www.knology.net/~res0plht/Mi00004.htm)
[22:16:19] <+ErikR> YES! We have actually observed a peak in CAPE, a min in CIN, and a min in LCL on the immediate cool side of boundaries. SO I believe that you are right that boundaries are doing several good things for supercells, not just enhanced SRH
[22:17:21] <@Aaron_Kennedy> Finally, we have a request for any brief... interesting chase stories
[22:20:12] <+ErikR> Goodness.... I could fill volumes with interesting chase stories. But the things I've done pale in comparison to many of the things that chasers are doing these days. I guess I would take this opportunity to encourage folks not to take wild chances out there... there's always going to be another tornado, and they can be pretty enjoyable from a few tornado diameters away... no need to be in the corner region. That's one reason we're working
[22:21:31] <@Aaron_Kennedy> Well I think that pretty much concludes the formal chat
[22:21:37] <+ErikR> OK
[22:21:42] <@GeorgeT> OK, I'd like to give a big thanks to Erik for volunteering to come here and explain the DRC (among other thinngs) for us. Erik, that was an outstanding job! Also, everyone is welcome to hang around here with us as long as you want tonight and dicuss anything weather related or otherwise you'd like. Also, feel free to come back. This room is usually very active starting this time of year and lots of forecasting and other stuff goes on in here.
[22:21:47] <@Rockwell> Thank you very much, Erik
[22:21:52] <@CalebL> Yes, thank you, Erik.
[22:21:53] <@AmosM> Thanks, Dr. Rasmussen
[22:21:58] <@Rockwell> I think I speak on behalf of everyone here when I say that you're a God
[22:21:59] <@CalebL> It was very informative
[22:22:03] <+ErikR> Thanks, everyone...
[22:22:04] <+Mike_H> Yes, thanks a bunch for the time

 

[George Tincher]

I'd just like to thank everyone for making this happen. By my crude math, I counted 65 different people present tonight during the chat! That's pretty awesome turnout.

Also, a big thanks to Erik himself. He did an excellent job of explaining the DRC and what it was, how it could be identified and what it may do. He was very nice in answering questions. I'd rate his presentation A++.

Anyway, I had a blast. Feel free to provide feedback as to your experience, what you might like to see done differently in the future, etc. We may try to do these types of chats from time to time as we can find guests who are experts in particular subjects.

-George

 

[Laura Duchesne]

I really had a good time and learned some new things as well. I'd like to thank Erik for coming by tonight and I hope that he decides to stop by again sometime. I can tell he had a good time, he would occassionally through a small joke in there for a good chuckle. I would love to do this again.

 

[Jeff Miller]

well

As I am at work, I was not able to participate in the chat however I did in free time browse through the logs and will comprehensively nitpick them tonight.

Thanks a lot for posting the logs and I am sorry I was not able to be there for the largest #Stormchase chat as of yet.

 

[Gabe Garfield]

Thanks to all who organized this chat and to Dr. Rasmussen!

Gabe

 

[mikegeukes]

I would like to say thank you to Erik Rasmussen for chatting
with us for a couple of hours in the chat room, Wednesday nite,
We had 65 different people visit the chat room to listen to
Erik chat about the blob theory, and Vortex 2 project.

Once again, the chat room says thank you for your visit
Also, Aaron Kennedy for moderating the chat and George Tincher
for getting Erik to chat with us.

Mike (EF)

 

[Karen Politte]

Thank you for keeping this log. I missed the chat and didn't feel like rushing around to get to it as I wouldn't have been in the right frame of mind anyways. I printed out the above log and will greatly enjoy reading it when I have a spare minute.

KR