Don't dumb it down

The Outbreak of 27-28 April 2011 was incredible. Incredible loss of life in a relatively high population density area, amazing damage to what we believe are sturdy structures, amazing long track tornadoes, some incredible supercell storms, incredible LIVE coverage of the tornadoes, and an incredible number of warnings, and a pretty good warning lead time performance for the weather service.

What I also find incredible is the disconnect between the linkage of science and society as it pertains uniquely to journalism. I will not pretend I am a journalism expert. I am not. So take the following with a grain of salt.

What makes a great story are personal details. Something the reader can relate to and understand. As if they were there, reliving the story with themselves as the subject of the story. There is implied intelligence here. This human story does not require anything more than what happened and how did you feel and what was going through your mind. This gives that sense of being there only without the mystery of what happens next. The spoiler was probably the title, and the fact that a person was interviewed means they survived.

To add to the story writers like to add facts for perspective. They look for all kinds of facts. They ask the experts and then they modify the words for effect sometimes losing all coherence. They like to add words like rare and extreme.

Then they add their own perspective. They cite their experience of why they are qualified to offer an opinion. Read that sentence carefully. There is only one. Assess if they are truly qualified to make a statement. It is usually obvious. If you ask a wrongologist, they would remind you that the writer is like the coyote chasing the road runner off the cliff (not having fallen yet). They keep writing because they are on a roll and havent taken stock of where they are. Then they realize. They look down and fall.

I have read a number of articles where the writer just hasn't realized. Then they make statements which seem plausible but wouldnt stand up to a thorough review by a subject matter expert. Remember the experts? They are interviewed first. The editor has the last say. Think he/she is a scientist?

The disconnect is in the presentation of "dumb-downed" science. The public may not understand everything about the science, but surely they are capable of learning. We need a more educated public. A more educated public is quicker to adapt. They are harder to confuse. They are privy to the "inside" information ("inside" will fade away when everyone knows the information). They are more likely to prepare because the risk is that much more understandable, that much more real, and that much more on their radar (pun unintended).

I like when people on TV say things like: "We are not used to this like people on the Great Plains." Thanks. I accept your accolades. You just insulted all your listeners. You told me that other people are more prepared, more accepting of the risk, more in tune with the violent weather risk. You also admitted publicly that you haven't done enough to prepare your listeners for that dreadful day.

Ask any survivor if they are used to being in a tornado that is ravaging their lives. The people are used to warnings and watches. They believe they are at risk, rightfully so, but usually are not directly at risk. Tornadoes tend to be small. That is one aspect of the problem. Big mile wide tornadoes are somewhat rare and also somewhat weaker on average, a fact I still find surprising. (I await that data being published in a peer reviewed journal.)

Not all stories or opinion pieces are bad though. I have read quite a few amazing stories, seen even more on TV. The father and son who left their mobile home to seek shelter face down in a ditch. The apparent life saving act was a tree falling on them to keep them anchored to the ground before it was lifted off of them by the tornado trying to suck them up. I guess the word is getting out to the mobile home folks, even if it is a relative few. This was the 2nd such story I read where people left their mobile home and sought refuge in a ditch. Others who stayed in theirs, were not so lucky.

****
Was this event rare? Rare in the once every generation rare. In terms of the meteorology it was certainly unique to have so many supercells producing long lived, long track tornadoes. The violence of those tornadoes was certainly not rare, but the number of them that were violent in a high population density area could perhaps be described as rare.

The EF5 in MS received the following description from the NWS Storm Survey: "appliances and plumbing fixtures in the most heavily damaged area were shredded". That to me is rare, having not been a storm surveyor, but only because I too think that the safest place to be in a house without a shelter or basement is the bathroom. Where all the pipes essentially reinforce the walls at least in a small area.

I should also refer you to this blog: http://stormeyes.org/wp/ for more perspective on this outbreak. It was well worth the time.

Supercell buffet

It appears that parts of Iowa, near Mapleton and points east and southeast were hit hard by 3/4 mile wide tornado (according to the storm reports).  The storms took a while to develop and mature but sure enough once that cell crossed into Iowa it was going nuts. Here's why:

1. The instability was high, up around 3600 J/kg and moisture was 13.6 g/kg through a deep layer.
2. The low level shear was 27 knots and the bulk deep layer shear was 62 knots.
3. The hodograph is a classic quarter circle up to 6 km.

Of course the other storms in Nebraska were prolific splitting supercells, with the left mover racing north.  A very impressive supercell buffet. This area was highlighted well by SPC, despite the NSSL WRF having nothing in this area today. This was also despite a relatively good forecast by the same model for events last night in the Ohio River Valley. The cloud simulation looked good too, but perhaps the resolution was just too coarse to really capture the boundary layer processes responsible for convective initiation of relatively small thunderstorms.

UPDATE: Sounding image obtained from SPC, and radar image from College of DuPage (http://cod.weather.edu)

Chasing supercells

Pretty good chase day today. Any chase day is a great day, but this was good because it ended my absence on the Plains after roughly 4 years. It culminated in a splitting supercell with near tennis ball size hail in a marginal low level shear environment, but favorable bulk shear environment.

Hard to say what the issue with convection initiation was, but most of the updrafts that initiated at least marginal vertical cumulus growth seemed to tilt and then result in small turrets on the top. The clusters of clouds that did manage to grow finally did so after 2200 UTC, and by 2300 UTC we had a nice storm to chase at least from its radar presentation. The base was elevated a bit but a clear updraft bell had formed, and when we drove north on I35 to stay ahead of it, noticed pretty good size hail on the ground. Maybe 2-3 inches in diameter, low-density. I even found some that had split in half so you could see the rings. Most of the hail in the grass was unbroken, but the stuff that had hit the pavement was easily smashed.

The model scenario played out fairly well. A moisture pool was left over from the late afternoon mixing of the dryline further south. Last nights NSSL WRF simulation had 1 storm form west of Tulsa and I took this to be a positive sign that CI was probable. Of course the model had some pretty high moisture values so that was a concern. However, afternoon observations indicated that dew points would hold near 64 F. Of course the low level shear was weak as was the SRH, but the bulk shear was up around 20 m/s. Plenty good for supercells, but not so good for tornados.

The focus for initiation was along a convergence zone in Northern Oklahoma that would eventually redevelop rapidly north, at least in model land. I will have to investigate if this actually occurred.  I think its worth investigating from the modeling standpoint, especially the structure of the boundary layer that led to the mixing out event further south but kept enough moisture further north.

The storm we were on is to the east-northeast  of WDG on the image below at the time tennis ball hail was falling while we were on I-35.

Glad to be back chasing storms...

Uncertainty cont.

I have been able to examine the NSSL-WRF, 00 UTC and 12 UTC NAM this morning.
With regard to the trough that is forecast to be the major player, it is likely that significant severe will break out colocated with the strong forcing along the triple point, in the dry punch into MO, and then another round even later in AR.

The main uncertainty lies in OK, where my hopecast suggests storms could try to break out along the dryline. The problem is that it occurs just around 22-23 UTC when the wind profile might be considered terrible for tornadoes. The wind profiles in general become more favorable further east and later on putting the tornado threat into AR but the window for discrete supercells appears to be small. Rather a squall line of some type will form with probably the chance for embedded supercell structures.

Further south however, there are better wind profiles, but the cap is somewhat stronger. The 00 UTC NSSL-WRF forms a squall line there as indicated by the synthetic satellite imagery.

I don't have a good intuitive feel for what may occur given some of the wind profiles I have seen. I do think the overnight models will struggle as they are typically too far east with any convection. They also struggle to produce individual storms ... will only produce storms in stronger forcing. The resolution of the models, the tendency to produce weaker lapse rates, etc all contribute to the storm bias. That said, the main threat appears to Normans east (Tulsa area and north), northwest (along the triple point), and southeast (secondary dry punch). There is still a chance for central OK. It all depends on if any storms attempt to go up along the dryline, which ultimately depends on the relative balance between the depth of moisture in the warm sector and the cap strength.

I am hoping that LMN and OUN will launch 21 UTC soundings, and maybe 18 UTC soundings so we can really examine the wind profile evolution as well as the cap. This will be a good case for analysis either way as it is a strong forcing case that is highly dependent on mesoscale details that our models may not get correct.

Severe weather potential

Interesting forecast shaping up for tomorrow evening. Somewhat strong trough will move into OK tomorrow bringing with i the chance for significant severe weather to central and eastern OK and continuing eastward overnight.

The more certain portion of the forecast is the later period late Sunday night when it appears probable that a severe MCS/squall line will tear up parts MO, AR, LA again. I think its likely as more time will allow for more moisture to advect northward in what amounts to me to be an odd linkage between a pre-existing low level jet well east of the effects of the trough and the trough. The apparent phasing of the two will occur later sunday evening. These highly dynamic environments lead to some interesting MCSs.

The early part of the threat in central OK is less certain. To me, at the moment, the most interesting part of the forecast is that the features of interest appear to slow down before entering it the Plains, then speed up once they do. This makes for a confusing scenario. The prominent features I see this morning are the dryline in western OK, the dryline warm front intersection in NW OK, and the rather strong 700 hPa cold advection over the dryline all at 00 UTC. Now, I have no idea what to expect in this type of slow then fast large scale regime. This fact alone adds uncertainty for my limited experience of significant severe weather in OK during Feb.

What is not clear is if the cold advection aloft will be enough to remove the cap, and if the instability will be large enough to be realized. We just had some rain followed by cold temperatures, and soil water fractions are high apparently. The last 10 and 30 day rainfall maps show that western OK is dry and eastern OK has seen around 2+ inches. So it is possible that strong sensible heating will take place on Sunday in areas that are drier ahead of the dryline. Will this actually matter? I will tell you on Monday.

The other major issue is how the dryline and shear align. At the moment the mean wind for sunday evening appears to be from the SW and the dryline is oriented more north-south. This angle difference will allow storms to move off the dryline. The shear vector should also orient itself across the dryline but the magnitude of that angle will be very important to storm mode.

I guess my inclination at this moment are that all the necessary ingredients can be found, it will be a matter of how they come together and when that will occur and for how long. For now, at least, it is important to get that moisture screaming northward. I could use a good storm chase.

A lot will change. But I think there is a chance for supercells. I am uncertain where convective initiation will occur, and where severe storms will get going, and what that initial mode will be. I will evaluate the Short range ensemble Forecast (SREF) when the 15z run becomes available later this afternoon.  Really this is just me getting my thoughts ramped up ... otherwise known as situational awareness.

Supercell formation observation

I have seen a number of supercell initiations this year and it occurred  to me that there is a distinction between a pure supercell initiation and a cluster of cells conglomerate supercell initiation. What do I mean?

Earlier this year in OK and way back in Nov 2005, dryline or near boundary initiation of supercells follow what appears to be a very linear low level reflectivity storm structure. From there these storms take time to evolve classic supercell structure at least in the low levels. (mental note: is this shear-instability dependent?)

This other mode evolves differently. Multiple, close proximity storms initiate and seemingly "merge" or form a conglomerate. The pictures to the left illustrate this process. The southernmost storm in the cluster appears to dominate. The one tornado was reported around 2200 UTC.

It is odd, but it appears that "upscale" growth occurs via merging. The assumption I have been using without explicitly stating it, is that supercells appear to need to reach a critical size to become productive in terms of tornadoes. I wonder what the supercell size distribution is, but from what I have observed via radar, it can not be a wide distribution, and I wonder if the tornadic supercells fit neatly into a portion of the middle of that distribution. A certain size might be necessary to withstand shear, and may be dependent on the shear-instability relationship.

Another issue is how crazy it is to have all those storms to the north produce very little wind or hail reports while no more than 2 counties south you have a supercell. This is a weak example of that, but there are many scenarios where storms are in a similar environment, yet only a few random cells are rotating. Maybe this is size related, or more in line with Markowski and Richardson's work, in which locally the SRH is very different via different hodographs or storm motions or both.

post storm analysis

Well my gut telling me that south central OK would be the best play wasn't quite correct.

The second initiation of convection to the south near Lawton just took forever to congeal into a supercell after many many mergers of smaller storms. The hint is that the cap was too strong, or the shear was too strong for the minimal instability being released. This would suggest that the stronger dynamical forcing to the north was a key factor in the rapid transition from small cells into bigger supercells.

The shear though was also questionable at FWD , despite 200 SRH, only the lowest km had significant hodograph curvature. aloft the hodograph was a straight line. At OUN, within some sort of convection, the hodograph was much larger and curvature much more pronounced.

The observed 500 hPa frontal zone was pretty much in contact with the main supercell of the day and had a pretty good connection to the initiation in southern OK. V2 soundings might shed light on this .

Overall I am not sure what to think of an event like this. The soundings to the north in OK appeared to be uncapped and the shear great. Tornado production was similar to the day before ... apparently present but most short lived. Moisture was present, SRH was high, BRNSHR was in the 10-80 range, and the hodographs all had good curvature.

To the south, there was a cap, perhaps weaker forcing until much later, hodographs were curved by trended to be more straightline (window of opportunity was shorter to the south perhaps), but the instability was greater. I did notice that the southern supercells, had outflow attached to them. So perhaps the mid level dryness enhanced cold pool strength. This case has lots of interesting questions.

dynamical devil

The dryline bulge is in western Oklahoma somewhat removed from the 500 hPa frontal zone as seen in water vapor imagery. However the circulation about this front has resulted (or speculated to have resulted in a narrow moist tongue over the proximate location of the dryline in OK.

I expect CI to be imminent, and perusal of vis sat imagery confirms the presence of a cumulus field in western OK. Not sure if the remnant outflow boundary is really a front or if the nocturnal MCS simply cooled and clouded over the northern portion of the front. Thus, not sure if this front is very active....or if it will truly be a focus for CI.

Vis imagery wave clouds would indicate that it is still relatively stable in Central and southern OK.

First echos on the dryline at 18:56 strengthened by 19:14 UTC. Looks like convection is right on time.

The devil is in the dynamics

A nice little potential outbreak today for OK and North TX. Complicated situation as the night time MCS moves away from OKC, with no outflow boundary clearly visible. The low level cloud field is eerily similar to previous days. The complications are that the elevated mixed layer is well into the area, and the 500 hPa frontal zone is already through AMA. Surface convergence will be there to the north but it may be the dynamics that sets this thing off.

The cap is the big player and the models favor this opinion. NCAR ARW run from last night says multiple periods of initiation to the north, remniscent of May 10, again occurring earlier in the 18-19 UTC time frame. Then later on initiation occurs along a dryline boundary (around 22 UTC) before growing upscale. NSSL ARW run is a lot different probably because of the poor precipitation forecast it produced to the west of the MCS. So too much precipitation to the west virtually ensures that a subsequent trigger for new convection occurs earlier.

Both models agree that initial development will be scattered but not isolated. Thus storm interactions and outflow development may hinder chances at discreet, cyclic tornadic supercells. Today may be a tail-end Charlie kind of day.

The models are not very different with the dryline, but it appears the 500 hPa front is much stronger in NCARs run...though i have no proof since the NSSL run does not make available fields aloft...however the CI that occurs in NCARs run appears associated with the 500 hPa frontal circulation. This is inconclusive however because the 850 RH field is near saturated as well. Breaking the cap is easier when the PBL top becomes saturated.

If I were chasing today, I would try to be south of OKC, probably in Norman. Wait to see how the cap holds to the north and if early storms stay isolated and discreet go for them. Then haul ass south later in the day as the next wave of CI occurs along the 500 hPa front. Otherwise south and east of Norman. The show should start by 19-20 UTC either way...3 hours from now.

Not sure of the tornado potential. Yesterday appeared to be ripe for tornados, yet the pictures and reports indicate short lived but strong tornados. Nice supercells on radar, though. wonder if the shear profiles were not ideal enough. The shear profiles from NCARs model at OUN at 21-23 UTC appear good enough, so this may be a right time right place scenario...brief window is implied. To the north it is less certain since storms may be on the warm front. I am still hedging my bets southward of OKC ...

Post storm wrap up

Wild day. 37 reported tornados. maximum hail size of 4.25". Max reported wind gust to 100 mph.
Looks like a number of fatalities have occurred as well.

Well forecast event by SPC. The uncertainty was well forecast at 1200 and 1300 Day 1 outlooks:
1. Initial storms would take time to organize thus Initiation area would be removed from maximum tornado risk.
2. moisture return would not be an issue.

BUT, the 1630 UTC update suggested that 21 UTC would be the new initiation time. Doubt crept in. Even to go as far as to say that central and southern OK would be capped and that models were over-aggressive. The 2000 UTC update re-instated the aggressive coverage southward based on the satellite data: cumulus cloud field developed in advance of and in proximity to the dryline.

What was not well forecast was the timing of CI. SPC was calling for a 18-19 UTC CI in SW KS, with another bout further south into OK by 21-22 UTC then further south into central and southern OK. The focus was on the cap and favorable moisture return.

Indeed the actual event sequence began like SPC said: SW KS near DDC for 2nd and 3rd storms in a bunch at 18 UTC. The storms appeared further SE into OK to the northwest of WWR by 1850 UTC and another east southeast of Gage and a few weak storms further south. These storms never really got going though they were players later when they merged with the northern storm ... that storm became tornadic after those mergers though it isnt clear they were the cause.

Now heres where the forecast goes awry. The dryline has not been dogged by storms. It was still going strong. At 2000 UTC a weak storm complex was near JWG. It almost dies, then out of nowhere re-intensifies into a nasty linear looking supercell. Much like the Nov 2005 Ames tornadic supercell or really much like high shear supercells.

By 2100 UTC a new batch of weak storms in advance of the dryline form and these quickly become supercellular in a cluster. The dryline is far removed from these storms. Much further south more storms get going, more likely previously involved storms with the dryline down there. Between these 2 areas another loan supercell formed and merged with the OUN cluster. This rogue supercell seemingly merged into the southern side of the northern supercells and that was in Norman or close by. differential storm motion for some reason on that storm.

New storms form off the dryline by JWG and move northeast to form a more linear looking cluster. By 2142 more storms form on the dryline to the west of OUN. This cluster appeared to form a line before devolving or maybe evolving into nasty hook echo supercells. Quite spectacular.

The supercells came in waves, seperated by time and/or space in clusters. They were at times poorly spaced but productive, and well spaced and spectacular. We saw the whole range of high shear supercells. More importantly we saw that the model forecast paradigm broke down. The soundings launched by vortex2 will be invaluable to assessing the environment on this day. This will be one of the most studied days in VORTEX2.

Big cities under the gun

Wichita and Oklahoma city are under tornado warnings and basically in between. A number of large tornado reports have come out, amidst the very brief 30s to 3 minute variety. The supercells have shown all kinds of high shear characteristics today.

The most crazy is a left mover split that eventually produced tornado warnings in kansas off the woodward storm. It crept in behind another storm, and then that one went tornadic as well. The woodward or likely a variant of it, because it merged with at least two other storms (of linear shape and very weak reflectivity speaking).

and the reports are coming out fast. You actually have to wonder what the impact of having a great weather dept. at OU has done for safety in Oklahoma. If there are storms you can bet like 30-60 chasers will be out combing the plains for tornados, and some of them will be relaying information back to the NWS. This doesnt prevent damage, but it should make people more aware of tornados and there warnings.

and the tornado warnings come out

Couple of reported tornados in what looks like a set of massive circular blobs which was the most continuous feature associated with the shortwave trough.

DDC initial storm just got its act together. Possible hook and strong rotation noted on radar. It appeared the evolution of such storms were very typical of high shear environments ... stretched out along the mean wind until repeated bouts of deep convection upshear culminated in protecting the storm.

This is also the case for the woodward storm though it got going later and split with the left mover not moving very far off yet. The main tornadic portion of the cell appeared to be linear! it now has a kidney bean shape with reflectivity over 65.

Situation is still somewhat chaotic between these two nice storms. no warnings and there appears to be no organization with them which is strange.

Dew points up to 68-70 in OK just west and south of OKC. Despite that the storms south of the woddward storm just cant get going. They are struggling. would love to see the sounding from OUN, as there might be a stronger cap in place which would protect OUN till later tonight.

FWD sounding was strongly capped. so was DDC though I will have to review the radar data at 1715 to see which air mass was being sampled, environment of low level storm.

Nice outflow in CO.

1st big storm went up by DDC in advance of the dryline along a cloud street. ci took 20-25 minutes. appears to have a second storm on its flank over the same initiation area. This area is where the winds have stayed from the southeast with dew points near 61 in DDC.

Storms that were ongoing associated with the low actually became tor warned first. DDC storms and initiation zippered along the dryline south still not doing much.

Cumulus cloud field sprang up in OK in apparent advance of the dryline where temperatures have gotten to 90 F with dew points into 20's. The structure of the cloud fields kind of resembles the model bulges in dryline position especially the NCAR ARW run from 00 UTC last night valid at 18 UTC. Indeed the OKMESONET says the dryline is in OK...what a surge that was...but probably not given the station spacing down there.

Northeast storm motion on these initial cells especially down into the woodward region. I am starting to think that a round 2 may be likely as the drying evident in water vapor imagery over the western TX panhandle increases and indicates that is the base of the shortwave trough. in advance of this feature is a secondary line of moisture evident on vis imagery which I believed to be part of the main dryline, but it may behind the surface dryline and may overtake the dryline in a few hours. This paradigm indicates a 2nd bout of CI as the forcing coincides with the dryline boundary...I am out on a limb here.

afternoon update

Indeed the severe weather risk areas migrate towards SW KS in advance of the surface low. Per my thinking in the previous post, storm initiation is indeed being forecast earlier. The dryline is really beefing up with dew points dropping down to near 10 F and surface winds sustained to nearly 35-40 mph with gusts to 50-60.

Current sat trends indicate multiple "cloud streets" though not of the fine scale variety behind the dry line. This indicates to me that low precip supercells may be the initial mode, however the speed at which the shortwave is progressing suggests that by the time CI does occur, they may be right in the moisture plume which argues against the low precip mode.

However, the linear banding of the cloud features at this point points to a more linear development mode. One wonders if this early convection, if it gets going, will be round 1 followed by round 2 of supercells later in the afternoon. Still more cloud lines popping up now near rthe dryline at 1715 UTC.

Waiting for 18 UTC sounding for DDC...maybe another hour or so before it appears on line if they launched at 1710 UTC like I hope they did. I also expect one from AMA at 18 or 21 UTC and one at OUN at 20 or 21 UTC. Hopefully the ARM site at LMN will also launch a few.

Dryline just went by Liberal KS, 82 over 45 this hour, was 75 over 59. Interesting that the dryline appears to be making north easterly gains into KS but not strong easterly surges in the panhandle ... recent trends indicate it is moving but not as fast further to the south. Will have to watch the progression.

Max dewpoints in OK up to 68 in the south, still holding strong at 65 in the plume to the north.

CI iminent along a line from the TX-OK border North to DDC in the next hour and a half over the OK panhandle.

The morning update

Much to my surprise, the moisture is returning with dew points up to 60 in OKC at 15 UTC with a 65 just south into TX in the narrow plume of moisture to the west of FWD. It looks like the moisture is deep at FWD on the sounding from this morning. The shear is already large and there is no reason to suspect it will diminish. The hodographs are large and semi-circular from 0-3km.

Currently though there is a deep low cloud deck with indications of wave clouds. This corresponds nicely with OUN's sounding and low level stable layer. The water vapor imagery continues to indicate a dry intrusion aloft is setting up from MAF to OUN to Tulsa. The dryline itself is already in place at AMA, and should be moving rather quickly with the arrival of the shortwave in the next few hours. Convective initiation should occur according to the data prior to 21 UTC and possibly as early as 19 UTC if I have done my wave phase speed analysis correctly.

Presumed 700 hPa cold advection is already occurring into the TX panhandle. BIG question is when will the cloud cover break up over Oklahoma, and where it will recede long enough for temperatures to climb. If the clouds hold strong, which is in doubt, then where they do break up will determine the locations, at least partly, for CI. Sounds like May 3rd all over again.

East moving storms with right movers to the south-southeast. Gonna be a long day for some folks in Oklahoma. And SPC and I are of the same opinion ... maximum threat over a limited window of time. As per my discussion last night, the rightfully acknowledge the limited span of the best thermodynamics and rightfully acknowledge that the shear may be too strong such that storms may need time to fully organize. Thus the CI forecast location is somewhat removed from the maximum tornado risk area. I still wonder though if the environment is really conducive to long track tornados.

I think the answer is yes, but I wouldnt be surprised if a few storms go up, put down a tornado, then proceed to do nothing more that put down very large hail.

Also the nature of the straightline hodograph over the CI area might be conducive to splitting supercells initially. At least a portion of the northern end of the CI area may rapidly transition to an MCS.

ARW run from NCAR indicates that CI will occur by 20 UTC, and I would guess is probably an hour or two late given the use of the MYJ PBL scheme. But it does indicate that the threat area for more isolated storms along the dryline will be further south into Oklahoma. But once storms like these get going in the model there is no telling how correct it is given the bad mass fluxes at this scale (3 km). Suffice it to say the model is trending towards my line of thinking.

Clouds starting to thin over SW OK ... game on. First batch of CI I forecast for east of Liberal KS. If I were chaing today I would be in Oklahoma City east side waiting for data until 1pm.

Potentially dangerous situation tornado watchboxes should be the norm today.

May 10 the forecast for tornadoes?

It isn't rare to have a day 2 moderate risk for the central plains including OK and KS. It is rare to see a moderate risk during VORTEX2 operations ;) . The prevailing wisdom is that if you put 100 vehicles and 400 scientists and 8 radar trucks in the Plains ...ain't nuthin' going to happen.

So I thought I would get in on the forecast action.

Broad scale specifics from the NAM model: a sfc low races out of CO tonight across southern KS and moves into northeast KS by tomorrow night. This feature is due to a pretty sharp shortwave trough at 500 hPa (about half way up in the atmosphere in terms of mass) which gives the appearance of a negative tilt into tomorrow. Note that the flow around this trough (the jet streak too) is cyclonically curved. The jet streak itself is actually located across OK and TX panhandle. The jet streak at 300 hPa is located further north and there is a hint that the flow aloft will be anticyclonic in nature across southern Oklahoma.

Players in Convective initiation: The warm from will be a breeding ground for all kinds of convection tonight into tomorrow evening. The dryline will be a major player as it punches into Oklahoma City. BUT the shear appears to be oriented perpendicular to the boundaries ... a sign that storms should start and possibly remain discreet.

The odd things I see:
The motion is fast for the shortwave aloft, and thus the moisture return may be in question ... moisture takes time to be transported in great quantities. 0500 UTC data in Texas show 60's creeping into the TX panhandle but dew points only 50 at OKC and DFW. Hi-res NSSL model is consistent through 6 hours with observed data. Models are indicating this to be the case ... that only low to mid 60's with high temperatures near 83 will be possible, though behind the dryline it may hit 90.

NSSL model also indicating the low may stall. Operational models may be aggressive in bringing this system out. Complicating factor is the system to the NW that drops in behind, and system to the east which seems to not move too much. Hard to know since the jet aloft to the rear of the shortwave is not fully ashore.

Day 1 outlook updated to reflect a high risk. Can't argue against that. Models are all producing favorable parameters for Oklahoma tornados. This is easy to forecast maximum risk where all parameters come together nicely. However, as a chaser, where would you want to be knowing:
1. fast storm motions
2. seemingly moisture limited to the east (from the limited model runs I have seen)
3. complicated cloud forecast
4. complicated surface low and dryline evolution and thus placement.

It appears SPC is playing up the moisture (to 70 F) with temps in the mid 80's, and heavily favoring the track of the midlevel jet (rightfully so).

The BIG question is what kind of supercells will be the norm? low precip, high precip, or classic? If low precip come off the dryline how will they evolve in the face of ridiculous shear (40 meters per second) and a somewhat strong cap which is sure to come out given the steady fetch from ABQ?

I have to wonder if there will be early storms in KS that get into OK and further complicate this situation with outflow boundaries. There doesn't appear to be a whole lot of limiting factors the models are picking up on, so the devil is in the details ... morning models will be key as well as the radar and moisture progress on the soundings.

High risk is warranted but there is more going on here. May 3rd 1999 comes to mind in terms of an OKC to Tulsa outbreak. Needless to say I will have the radar looping tomorrow.

High risk for Day 3

The high risk certainly verified today. Looks like either a few tornadic supercells were out prowling around or 1 cyclic tornadic supercell was about laying down multi-state sorts of damage. Cant wait to see the damage survey. I wish you well Yazoo City (and all the other cities/people affected ) in your recovery efforts.

Today was a story all about large hodographs despite what can only be considered to be marginal instability (in general) but still enough to be dangerous.

Situational awareness needed to be much higher for the average citizen out there today. I cant blame the people as much as I might want to. The High and Moderate Risk areas for today was LARGE; 4 and 6 states respectively. The event was ongoing in the morning, with multiple waves of severe weather expected.

The first tornado report was listed 2.5 hours after the convective outlook was issued. We all need to be better equipped to explain and communicate the risk. Its a serious business we are in. We dont just provide information for the average person to consume. We provide meteorological information from which a serious number of people make decisions.

From the local TV and radio coverage disseminating NWS warnings, to emergency managers trained to respond to a crisis, to the fire and police department who are also trained to monitor (in a limited role) and respond. By what do real people need to know?

This phenomena is distinct. It is short lived locally (5 to 90 minutes). Can occur in waves or epsiodes. They can be misleading. One storm can be tornadic and depending on your position can come "out of nowhere", be right in front of you for 10 minutes, or appear to be suddenly upon you though you didnt think it was that close. The local motion of the storm and the tornado may be different. The storm itself may not be that visible.

So:
1. should you travel during the storm? Check the radar. Read about the people who had their kids in the car and were caught in the storm as power lines and trees pummeled them. They claimed taking the kids out of the carseat was a good idea when they hid inside the car. A tree hit them apparently damaging the car where one child would have been. I dont want to know what would have happened if the car became airborne in that situation.

2. should you flee the storm and drive somewhere else? No. Read the article about the people who drove to the family restaurant to hide in the freezer. They ended up in the restaurant ... in their car ...thrown by the tornado they were trying to hide from.


If you are out, stay put. its easier to find shelter where you are than to relocate and find shelter.
If you are home, the basement of a well built house, or a bathroom on the lowest floor s the best option (not necessarily safe though; remember we are talking about tornado's ... they make cars fly far).

The day after tornado season started

An interesting severe weather day. Big threats for supercells in multiple regions.

The models gave us false impressions of the cap. This is a case for extensive numerical modeling of a null event in Nebraska and Kansas. The water vapor imagery combined with multiple soundings available for analysis make this case worthwhile to explore numerically.

The instability and moisture were well predicted. It appears the shear was well predicted. The timing in the NSSL and NCAR WRF models was too early and too widespread. I want to say that the models ejected the long wave trough out too quickly...but is a few meters per second really too quickly in phase speed? Or perhaps the models did not capture the vorticity evolution on the back side of this large rossby wave?
anyway the cap issue is nicely shown by the Topeka sounding (where the action was predicted by 21-00 UTC.
Note the low level cloud layer. There appeared to be shallow cumulus. Does parcel theory collapse when a cloud layer is already present? To speculate is poor science, but ideas emerge from speculation. Perhaps the cloud layer is so dynamic (entrainment at the PBL top, less than well mixed below) that parcels can only emerge or organize with the thermodynamics of the cloud layer. In that case, a parcel lifted from the cloud layer would immediately have convective inhibition.

Dr Adam Houston has published some work indicating that the lapse rate above the LCL and LFC might be very important here as well. The steeper the better which is not really observed on this sounding. Another factor may very well be the path that parcels take. That is the forcing for ascent locally may not have been favorable despite the PBL circulations.

Clearly though, the dry layer alofyt at TOP was associated with a dry intrusion of very limited extent as the inversion is not present just 4 hours later at any station. water vapor loops indicate the invsersion may have been present from 1845 to 2045 and was weakening. It was oriented north to south ... probably why SGF showed only a hint of it and why it wasnt seen elsewhere.

As the event unfolds now, Iowa and Nebraska are just now seeing the late evening initiation I was expecting if the afternoon stuff didnt go. I have some anecdotal evidence that when the warm front in Iowa is involved, chances are the cap holds until night time. I wish I could explore that issue further.

Not too much actual severe weather to report on. 8 tornado reports in 4 states.

Tornado season is upon us

Some quick facts. Today marked the latest day in the year where a moderate risk of severe weather was forecast by SPC. Interesting enough, the MOD risk was not forecast until the 20 UTC update.

Overall, the NSSL WRF model did pretty well from what I can see. It was spotty and sluggish but the put the idea out there that small scale convection was possible.

The result: 31 local storm report tornadoes.

The hodographs were nicely curved today and the moisture got into eastern Colorado. The low level cloud cover kept dew point depressions low (low lcl heights) near the warm front. There were a number of splitting supercells in very close proximity to other supercells which did not split. At the very least, my perception tells me they were supercells but it is possible that supercells were not the only organizational mode out there today.

I dont know what to make of the deep low level cloud layer at OUN. The OKC ASOS showed the overcast skies but did not that much moisture really pour into Oklahoma today? Preliminary analysis says yes since FWD reported similar low level moisture observations almost of the tropical variety.

In fact, in searching through the soundings, the elevated mixed layer was surprisingly far south in Brownsville and still weak in DRT. Not really sure what to make of that factoid. Then again I wasnt following this event very closely.

anyway, here are the pics. Wish I was out there chasing. The Plains of Colorado is some nice empty country.

supercells

I have been thinking about severe weather for my work. I have always been curious about supercells because the characteristics I have observed have been so varied. Everything from the cloud structure and radar appearance to the location of tornado (or tornado's).

What I find even more interesting is that they tend to evolve rapidly. They evolve because of a changing environment (vertical wind shear, CAPE, moisture and moisture depth). But there are also those weird days, where in a similar environment, they develop differently. In a few cases I would surmise this has occurred because some boundary has been influencing the storms.

But a paper I read hinted that there are two types of these supercells distinguished by front vs rear precipitation relative to the updraft. There are some solid objections to this line inquiry based on the known and documented differences between so-called classic supercells and Low precipitation supercell tornado threats. However, a taxonomy is only useful if the storms have a certain structure and that structure leads to some predictable behavior.

While a taxonomy appears to be worthwhile to describe these varied characteristics, what are we really trying to achieve with it?
1. Operational radar recognition of the supercell and tornado threat.
2. A conceptual model of these storm types, including their life cycle evolution.
3. Explain why some supercells produce tornado's and why some do not; why some produce many and others produce 1; why some have a predictable location of tornado occurrence and others have multiple.
4. Address: Why do tornadic supercells differ so little from non-tornadic supercells?



These challenging questions are why, once again, the VORTEX2 field project will be operating in the Great Plains this year. Hopefully a new round of data collection will offer some insights into these fascinating and destructive storms.