April 12th/13th and 15-16th Severe Weather Thread

[Thundersnow12]

Sunday with potential too on the 12z GFS along and east of I-35 and with the warm front up to I-80 in IA. Mid 60 dews up to northern MO/western IL.

[brettjrob]

Looks like our yearly OKC Tornado Outbreak is coming early this year. The chaser convergence is going to be unbelievable and apparently law enforcement is already planning to do their rolling road blocks.

Ugh... where are you hearing this? It actually wasn't even that bad for last year's outbreak, for the most part, at least in comparison to some of the 2010 days.

[scoresman]

Looks like our yearly OKC Tornado Outbreak is coming early this year. The chaser convergence is going to be unbelievable and apparently law enforcement is already planning to do their rolling road blocks.

I have seen where a caravan of chasers caused a "rolling roadblock" but have never seen law enforcement do the same..... Its dangerous enough when us yahoos get out there yet alone having the police make it worse IMHO.

[David Reimer]

Ugh... where are you hearing this? It actually wasn't even that bad for last year's outbreak, for the most part, at least in comparison to some of the 2010 days.

I've heard it from multiple local chasers who have friends in law enforcement. Apparently a crack-down is about to begin due to some chasers driving and behaving recklessly on roadways. The roadblock issue is nothing new in Oklahoma. It occurred on May 24 and November 7 last year. You can bet that OHP will have every officer available out and detouring traffic. They're actually pretty good at that on major days. I can't blame them, you and I have seen how many locals decide to go out and get close to the storm. Generally speaking, as long as you're in position, you won't have any issues because they tend to maintain a distance of about ten miles from the storm. Stay inside the moving circle and you're good!

[Superstorm93]

Sorry, but I thought this was kind of funny.

You'd think he'd have access to something other than MS paint.

"The southern Plains will continue to see an increase in severe weather the next seven days. What concerns me in the longer range is this increasing threat for tornadoes. On the map below, I outlined an area of increasing tornado threats. The key top the tornadoes will be the system that will hit California and the timing of that system into the Plains this weekend. The operational models all suggest one system that will come out Friday and stir up the storms in the Plains followed by the mother lode upper-level low this weekend. When that happens, the shear will increase and storms should become more widespread with the threat of tornadoes lasting into Monday and Tuesday. It would appear that a wild time is coming up and hopefully it will not be dangerous for folks in the Plains. "

http://vortex.accuweather.com/adc2004/pub/includes/columns/margusity/2012/590x392_04111327_severe2.png

[Gorky]

May 24th was one of the least stressful chase days I've ever had with traffic. Was it really that bad anywhere in OK? There were plenty of storms to split the chasers between and storm motions were not an issue. Many Chasers chose Central KS that day and a lot busted near the OK/KS border. It may be the weekend this time round but it's still early season so not many chasecation peeps out there

May 10th and May 19th in 2010 were horrendous but almost entirely due to more confidence of initiation over a smaller geographic area converging chasers per-initiation and faster storm speeds imo.

[brettjrob]

I've heard it from multiple local chasers who have friends in law enforcement. Apparently a crack-down is about to begin due to some chasers driving and behaving recklessly on roadways. The roadblock issue is nothing new in Oklahoma. It occurred on May 24 and November 7 last year. You can bet that OHP will have every officer available out and detouring traffic. They're actually pretty good at that on major days. I can't blame them, you and I have seen how many locals decide to go out and get close to the storm. Generally speaking, as long as you're in position, you won't have any issues because they tend to maintain a distance of about ten miles from the storm. Stay inside the moving circle and you're good!

Ah, gotcha. I didn't even notice it on either of those days, so that's a good sign. Definitely nothing wrong with keeping the clueless public away from the most dangerous part of these type of storms. (Not just the wannabe-chasers, but especially the much larger majority who are so oblivious as not to realize there's any storm at all until a wedge is filling their rearview mirror).

[JoMo]

May 24th was one of the least stressful chase days I've ever had with traffic. Was it really that bad anywhere in OK? There were plenty of storms to split the chasers between and storm motions were not an issue. Many Chasers chose Central KS that day and a lot busted near the OK/KS border. It may be the weekend this time round but it's still early season so not many chasecation peeps out there

May 10th and May 19th in 2010 were horrendous but almost entirely due to more confidence of initiation over a smaller geographic area converging chasers per-initiation and faster storm speeds imo.

That's because Joplin happened on May 22nd and the locals were scared out of their mind and they all took shelter.

[Chicago Storm]

Looks like Thur will be a no go for me, but Fri-Sun are a lock for chasing with whatever option I choose.

[David Reimer]

That's because Joplin happened on May 22nd and the locals were scared out of their mind and they all took shelter.

This is true. Traffic wasn't an issue but OHP has every road blocked within 10 miles of the El Reno Tornado by the time it moved northeast of town. Something tells me we won't be so lucky with traffic on Saturday. A non-work day combined with an April Tornado Outbreak can only mean one thing, and that's why I'll be a bit south of the main area

[Derecho!]

This is true. Traffic wasn't an issue but OHP has every road blocked within 10 miles of the El Reno Tornado by the time it moved northeast of town. Something tells me we won't be so lucky with traffic on Saturday. A non-work day combined with an April Tornado Outbreak can only mean one thing, and that's why I'll be a bit south of the main area

So what are the storm motion speeds likely to be on the various days of this event?

[David Reimer]

So what are the storm motion speeds likely to be on the various days of this event?

I honestly haven't even looked at storm speeds because I've been too busy handling some other obligations, but based on the strength of the shortwave coming in along with the wind fields I've seen, I would bet we would have storms moving at least 25 to 30 MPH, probably higher. I'm sure one of the pro mets will be able to accurately answer your question.

[andyhb]

So what are the storm motion speeds likely to be on the various days of this event?

Given the strong flow at H7 on Saturday in particular, I think the storm motions will probably be around 30-40 kts, perhaps a bit higher.

[Gorky]

Nam is showing 30kt on Saturday but wouldn't surpise me to see it pushing 40kt if the upper support arrives a bit quicker! Should be much more manageable Thursday and Friday though

[OceanStWx]

I honestly haven't even looked at storm speeds because I've been too busy handling some other obligations, but based on the strength of the shortwave coming in along with the wind fields I've seen, I would bet we would have storms moving at least 25 to 30 MPH, probably higher. I'm sure one of the pro mets will be able to accurately answer your question.

That's a pretty good estimate at this point if we're talking knots. Motions look a little faster on Saturday as opposed to the next two days.

[CUmet]

The 12z ECMWF and UKMET runs appear to have a major tornado outbreak over the Central U.S. on both Saturday and Sunday.

[soonertrey]

The 12z ECMWF and UKMET runs appear to have a major tornado outbreak over the Central U.S. on both Saturday and Sunday.

Do you have a graphic for this? I'm particularly interested in Sunday. Someone mentioned the wind profiles may be a little more linear for Sunday as compared to Saturday. Thanks in advance.

[Thundersnow12]

Right now leaning to be out chasing Sat/Sun.

[tornadotony]

It finally hit me what Saturday looks like. With the trough orientation, the extreme parameters, and the substantial warm frontal zone threat, it is awfully reminiscent of 13 March 1990.

[nwburbschaser]

Right now leaning to be out chasing Sat/Sun.

Same thing here. Going to ask for Monday off at work since I'm not sure if I will be back in time. Have to decide if I am going to leave Friday night/Early Sat to make it down to the plains, or stay more local on the warm front.

[Indystorm]

It finally hit me what Saturday looks like. With the trough orientation, the extreme parameters, and the substantial warm frontal zone threat, it is awfully reminiscent of 13 March 1990.

[Thundersnow12]

It finally hit me what Saturday looks like. With the trough orientation, the extreme parameters, and the substantial warm frontal zone threat, it is awfully reminiscent of 13 March 1990.

could even say Saturday has better moisture

[andyhb]

Anytime I see 3/13/90 brought up in a Plains svr setup, the concern really begins to rise, parameter and climo wise, there are similarities between this and 4/26/91 as well, despite the different trough setup.

[SkylerP]

The television meteorologists in Dallas keep insisting that Sunday will be the bigger day for our region. Don't know what they're basing that on. Perhaps the CAP?

[brettjrob]

A few miscellaneous thoughts about analogs:

- The H5 comparison between H+84 on the NAM vs. 13 Mar 1990 is a shockingly good match, at least over the central U.S. Downstream, ridging on the east coast is not quite as broad, suggestive of a slightly less-favorable moisture situation this time. However, it's also a month later into the season.

- The H5 comparison with 26 April 1991 does not stand up nearly as well, and I also doubt we'll quite match that day's low-level moisture.

- *If* this possible outbreak does realize its full potential, I envision it unfolding (in the roughest sense) more like one of those aforementioned days than the more recent I-35 headline events (10 May 2010, 24 May 2011). This is a much broader trough with good deep-layer directional shear extending throughout OK/KS and into NE, rather than being confined to a relatively narrow latitudinal range. The warm front should also be in play, rather than being draped in an unfavorable NW-SE orientation.

- The 13 Mar 1990 event is probably overlooked and underrated by most everyone outside the enthusiast community. If you look at the track map posted by Indystorm, all the major cities in the line of fire were spared. The immediate OKC, Wichita, Topeka, Lincoln, Omaha, and even Salina areas escaped relatively unscathed, with Hesston being the closest thing to a metro-area hit. The 26 April 1991 event was incredible in its own right, but had slightly fewer tornado reports and was more geographically confined. (This point really has little to do with Saturday; just a thought).

[SquatchinNY]

What kind of TOR threat are we looking at on THU and FRI?

[CUmet]

Do you have a graphic for this? I'm particularly interested in Sunday. Someone mentioned the wind profiles may be a little more linear for Sunday as compared to Saturday. Thanks in advance.

The free ECMWF stuff you can get off of wundermap, although it takes a while to update. Unfortunately I can't post the Accuwx pro maps. The wind fields do still look a bit funkier on Sunday, and the convection may initiate much earlier which puts some doubt into the amount of instability available. But my main point right now is that the models are starting to keep the trough intact and stronger into Sunday, so we need to entertain the possibility of Sunday being a possible outbreak day as well. Saturday is still easily the biggest threat though, and will likely remain so given the magnitude.

[tornadotony]

A few miscellaneous thoughts about analogs:

- The H5 comparison between H+84 on the NAM vs. 13 Mar 1990 is a shockingly good match, at least over the central U.S. Downstream, ridging on the east coast is not quite as broad, suggestive of a slightly less-favorable moisture situation this time. However, it's also a month later into the season.

- The H5 comparison with 26 April 1991 does not stand up nearly as well, and I also doubt we'll quite match that day's low-level moisture.

- *If* this possible outbreak does realize its full potential, I envision it unfolding (in the roughest sense) more like one of those aforementioned days than the more recent I-35 headline events (10 May 2010, 24 May 2011). This is a much broader trough with good deep-layer directional shear extending throughout OK/KS and into NE, rather than being confined to a relatively narrow latitudinal range. The warm front should also be in play, rather than being draped in an unfavorable NW-SE orientation.

- The 13 May 1990 event is probably overlooked and underrated by most everyone outside the enthusiast community. If you look at the track map posted by Indystorm, all the major cities in the line of fire were spared. The immediate OKC, Wichita, Topeka, Lincoln, Omaha, and even Salina areas escaped relatively unscathed, with Hesston being the closest thing to a metro-area hit. The 26 April 1991 event was incredible in its own right, but had slightly fewer tornado reports and was more geographically confined. (This point really has little to do with Saturday; just a thought).

The warm front is extremely in play. 12z GFS sounding for the Quad Cities Saturday evening:

[baroclinic_instability]

18Z NAM really narrows the warm sector for tomorrow afternoon. Models are still catching up to the strength and breadth of this huge surface ridge axis over the central US and the relative narrowness of the leeside trough.

[soonertrey]

The free ECMWF stuff you can get off of wundermap, although it takes a while to update. Unfortunately I can't post the Accuwx pro maps. The wind fields do still look a bit funkier on Sunday, and the convection may initiate much earlier which puts some doubt into the amount of instability available. But my main point right now is that the models are starting to keep the trough intact and stronger into Sunday, so we need to entertain the possibility of Sunday being a possible outbreak day as well. Saturday is still easily the biggest threat though, and will likely remain so given the magnitude.

Okay, thanks. I have a wedding to go to on Saturday evening so I unfortunately cannot chase that day. I'm keeping an eye out on Sunday though. I agree that early convection could be a big issue limiting instability on Sunday.