2024 Tornado Season

[WeatherArc]

The Winchester, Indiana tornado has been preliminary rated a high end EF3 with winds of 165+ mph, making it the strongest tornado of the year so far.

A NWS QRT has been dispatched to survey the building to see if it deserves an upgrade to EF4

Looking forward, it seems all extended range models are picking up a period of troughing around the end of march, if this was meant to be the least active month i think we may be in for quite the tornado season. 

2 dates seem to be the most probable for potential severe weather, the 25th and 26th. Have shown up repeatedly for past 5 GFS runs.

Im also watching the period around march 30-april 3rd, right at end of GFS range however multiple past runs have shown a deep trough digging down. 

Edited March 16 by WeatherArc

[AndrewHamm]

Planning a trip to Tornado Alley this spring. When would be my best chances for tornadoes? My two possible times are either April. 21-May 1 or from May. 6-15. I know things should get started in late April, but I am wondering if I should go later in May to have a better chance. Thanks!

[Ben Sainsbury]

 AndrewHamm Hi mate! It's really anyone's best guess at this point. With an early terminating El Nino, it looks like an active season is likely which is good, however even within an active season you will inevitably have quiet periods.

I have attached the latest long-range CFS forecast for April and May below:

Obviously, these need to be taken with a huge pinch of salt but they currently suggest above average rainfall across our typical chase region, however there is a greater consensus for significantly above average rainfall for May. Now this would suggest that May is potentially the better month to go this year, however should April start off very dry, the CFS could be indicating a very active end of April. 

Personally, confidence is just a little higher for the May 6-15 period vs April 21-May 1 imo. Both periods look good at this point, but that's not to say there won't be some quieter spells within the months of April and May.

 

Edited March 17 by Ben Sainsbury

[WeatherArc]

Late march continues to have that look, some issues with moisture return but if they can be fixed that is quite the impressive trough/setup.

 AndrewHamm Personally, i would go with May 6-15th, all seasonal models have been going with an active may plus it is the best month for tornadoes in the plains in general. Good luck out there!

[AndrewHamm]

 Ben Sainsbury  WeatherArc Thank you both very much!

 

[WeatherArc]

The sounding of all time 

Never change NAM

[WeatherArc]

We now have a 15% severe area for Sunday night in the plains.

To be honest, if it wasn't for the system in the Gulf sucking up the moisture a few days before this would be a significant outbreak with all sig hazards. 

If your looking for a high-end plains outbreak this is pretty much exactly what you look for and need.

 

A powerful negatively tilted trough ejecting out of the Rockies with significant divergence aloft, the left exit region of the jet streak also seems to be favourably placed over the plains. 

The only real problem with this trough is with the northern extent, north of the Kansas border there is little midlevel shear, so more veer back in hodographs to the north. However, the Oklahoma portion looks relatively good, the strong flow aloft should help lift and cool any cap. 

Strong Lee cyclogenesis leading to a rapidly deepening (984mb) surface low that will accelerate  (55 knot+) the lower level jet. Furthermore the LLJ is strong throughout the day, meaning storms can immediately tap into it when they form and don't have to wait for sundown, where a cap can quickly develop after surface heating is lost. The winds in the LLJ are also backed, meaning they come from the south rather than the south-west, this should hopefully prevent any dry air being pulled in. 

 

However, the problem here is moisture, an El Nino gulf system will pull moisture away on Friday night, this means that despite the strong wind fields the GFS suggests dewpoints will likely only be in the mid to upper 50s in Oklahoma and low 50s in Kansas. This leads to a lack of instability away from the dryline.

Still, with such a good looking trough and wind fields anything could happen. I see that many on twitter are already talking about how favourable this day looks kinematics wise , it just depends what the thermos look like on the day of the event. I mean this is completely counting on global models being completely right on the dewpoint and temperatures, which they never are. We could well see an uptrend or downtrend in severity as we go forward and CAMS come into range,  I've seen mid 50s dewpoints be upgraded to mid 60s in the space of 32 hours before as more accurate data and cams come into range. 

Another point is that we are now in late March, moisture return is much easier than it was a few weeks ago. Interested to see how this set-up evolves over next 48 hours. 

 

[WeatherArc]

NAM into range, think its safe to say if we were dealing with dewpoints 5 degrees higher we would be dealing with a classic tornado alley high-end outbreak.

Lapse rates are very steep, this could well mitigate some of the problems with moisture. 

Once the trough ejects out of the rockies a surface low develops and rapidly deepens to almost 980mb, this creates an intense 55-65 knot low level jet. 

The strength of the upper level winds and the positioning of the trough/jet streak makes me think we shouldnt have any issues lifting the cap. 

The only real con with this setup is the moisture, everything else is pretty perfect. 

Regardless of what actually happens in Sunday this is one of the most favourable troughs/setups ive seen in the plains for quite a while. Getting trough ejections like this is pretty rare but if we see anymore of these in April or May with better moisture i think the plains are in for a an active year. 

Edited March 21 by WeatherArc

[WeatherArc]

Alongside Sunday, Monday night also has my interest across Louisiana and Mississippi. 

Our trough will continue its ejection across the US, strong south westerly flow over the deep south region. Good divergence aloft with the 300mb jet streak nosing into the region. Not the most zonal flow so discreteness of cells can be questioned but still a decent look for severe weather in the deep south.

Surface low (positioned over Iowa) weakens to 993mb but still has a strong accompanying LLJ of around 55-60 knots.  3km SRH over 400m2 across the target area.

Now the problem right now shown in models is instability, however im not convinced this will be so much of an issue for a few reasons

Very good low level moisture (likely being underdone by NAM) being advected into target zone with a pretty large warm sector for any discrete supercell to take advantage of, we know the NAM has a cool bias so surface temps could well reach into the mid-upper 70s across southern Louisiana and low 70s into Arkansas.

Lapse rates, this is why this setup has gotten my attention, many models are showing pretty decent (6.5+) lapse rates being advected into the south, as ive said before the biggest problem with south east setups is the lack of decent lapse rates leading to messy convection, still some uncertainty of how far inland the higher levels will go but looks fairly decent. 

Something else i want to point out is the EML on all soundings at around 500mb, could really work in steepening lapse rates while also aiding discrete development. Low level lapse rates dont look great but i suspect this is due to the NAMs cool surface bias. 

Another reason our instability is so low is the prediction that the warm sector will be completely clouded over, could well happen but we wont know till we can look on satellite monday morning, also the EML could aid to clear some of this out by slightly mixing the dewpoints out. 

Sheer vectors are pretty parallel to boundary, may be an issue with cells firing then immediately going linear. Although if we get warm sector development it shouldnt be an issue.

 

CAMS should be getting into range of this event in the next 48 hours, one to watch. 

Sunday looks pretty much the same since last post, not much to note at the minute apart from NAM 3km wants to fire storms across the dryline but they only last for 1-2 hours before they just run out of instability and moisture, severity all dependent on our dewpoints really. Going to wait for actual surface observations to come in.

 

[The Tall Weatherman]

The Setup tomorrow in Oklahoma and Kansas looks good in terms of the kinematics and subtle details but what this setup lacks is moisture and instability. Storms may struggle to mature with the meagre Cape and dew points(50F) but if any of them manage to pull out of the mud we may have strong tornado producers on our hands. The sounding reveals weak capping and an alarmingly curved hodograph with 0-1 km SRH exceeding 400 m2s-2 !

The SPC have labelled a 5% risk for tornadoes around the Central/western Oklahoma and the southern areas of Kansas.

 

[WeatherArc]

 The Tall Weatherman I think we will get storms to fire on the dryline but the question is will they do anything before they move off it, storms will be moving over 60mph.

Regardless, whatever happens could be a good case study on high shear low cape environments, will be interesting to see if such strong shear can sustain updrafts in a very hostile thermodynamic environment.

Still 30 hours out though, could well see last minute moisture upgrades.

[WeatherArc]

Monday still interests me, if you look at the 12z vs 18z 3km nam there's clearly a trend towards a more powerful trough with the core placed further south.

LLJ goes bonkers, 80 knots+ of flow in places. 

Good dewpoints in place, i would like it if our warm sector wasn't as pinched/was much larger though, surface temps likely being undercooked due to cool bias. 

Lapse rates look decent on nam but still general lack of instability across warm sector. 

Soundings from across the warm sector show this issue, good shear with meagre instability. 

EML at 700mb noted.

Low level lapse rates iffy, cells would really struggle in this environment but still think day needs watching, esp for any instability uptrends

[WeatherArc]

11z HRRR 

Tracks a supercell  down the I44 corridor and straight into Moore/OKC metro 

All the trends today have been uptrends, increasing storm coverage, increasing moisture, increasing warm sector/instability and decreasing storm speeds. 

Id probably expect a SPC upgrade imminently if these trends continue.

 

Edited March 24 by WeatherArc

[WeatherArc]

Just an absolutely classic observed sounding from Oklahoma city

Make the dewpoint and temp 15 degrees higher and this could be a sounding taken before a major tornado outbreak in May. 

Edited March 24 by WeatherArc

[The Tall Weatherman]

This event later will have a very conditional tornado threat as the SPC highlighted but with soundings like this taken outside the OKC metro it looks like we could potentially have a strong tornado tonight. Right-moving shear munching beasts look likely !

[WeatherArc]

Well, yesterday completely busted. Dryline was way out west and storms fired early in the day without cape or that much shear to tap into. 

Onto today, enhanced risk in Louisiana and Mississippi

 

10% hatched risk for strong (EF2+ tors) although storm mode remains uncertain, however with how strong the shear is even a QLCS could produce significant spinups. 

Just going over past 5 HRRR runs sbcape defo has uptrended, gone from around 500-1200 in some spots, with how strong the shear is today any robust updraft could really be an issue.

SRH in our target area will widely be above 500m2 with some spots reaching over 850m2. A very strong (60-90 knot) LLJ will develop.

Looking at satellite there does appear to be some unforecasted clearing ongoing, could help our event out a little.

Soundings from the warm sector at around 00z

Sounding from warm sector from 03z

 

Looking at forecasted reflectivity we can see our squall is pretty broken with windows for discrete cells, the longevity of those cells is a bit iffy though, especially given bad low level lapse rates and cape, we have had scenarios in the past where the shear is so strong and theres so little cape the updrafts just get ripped apart. 

Important to watch trends over the next few hours, yesterday models pulled our dryline 100 miles west in the space of 4 hours.

Edited March 25 by WeatherArc

[WeatherArc]

Reeds live, still not 100% about today but even if we dont get discrete cells to fire that convective line will produce tornadoes.

Lapse rates rn arent great, might cause problems but we will see. 

Edited March 25 by WeatherArc

[WeatherArc]

CFS hour 636 anyone? 

 

[WeatherArc]

Large day 5 15% issued by the spc

CSU MLP guidance is also highlighting a large area of severe weather with the equivalent of a moderate risk being shown for northern Arkansas/southern Missouri. 

Some trends within the last 24 hours with the system causing this risk, the initially positively tilted trough has developed an individual shortwave that has started to become more negatively tilted over last few runs. Strong jet streak (100+ knots) noses into the target area. 

This leads to a much stronger mass response, strengthening the low level jet. 

Unlike our previous system, absolutely no problems with moisture. Big warm sector with dewpoints in the mid to upper 60s. 

A dryline stretches from northern Kansas to the Texas coast, additionally a shortwave seems to move through the area. Both could act as discrete cell initiators. 

Strong lapse rates swinging around the southern side of the jet, if these can overlap the areas of best instability and shear i certainly think severe weather is probable.

GEFS guidance pretty much the same, maybe a little more east.

Still waiting for nam and other cams to get into range to get better idea of what could happen but all severe hazards are possible. 

D6 15% also in place for portions of Ohio, Kentucky, Tennessee, Alabama and Missouri. 

[WeatherArc]

Still lots of uncertainty in models this morning,  all to do with how the trough phases and the amplification of the jet. 

However CSU MLP guidance continues to highlight high severe probabilities, very close to showing its equivalent of a high risk 

NAM will come out in about half an hour and 3k NAM tomorrow, should hopefully give us some more confidence in the ceiling of the outbreak, at the moment i would say large hail will be the main threat due to weak low level jet. 

[WeatherArc]

Day 3 enhanced risk now in place for parts of Oklahoma, Kansas and Missouri.

Main hazard should be large hail although a tornado cant be ruled out, CAMS still not in range so difficult to say the exact ceiling of this event. 

After this severe risk passes there should be a short quiet period before another trough rolls in around the 9th, all ensembles and models support this outcome at the moment.

 

From initial looks the 06z paints a very favourable picture of a negatively tilted trough with strong mass response across Oklahoma and Kansas, moisture could be an issue but we are so far out its pretty difficult to say. 

GEFS also supports this. Interested to see how this one evolves. 

Will try to do an update on mondays risk when better cams get in range, the tornado side of the risk does not look that impressive right now though. 

[WeatherArc]

I see the nams had a few too many shots of vodka tonight  you just cant hate the absolute random outputs this thing comes out with. 

All other models have absolutely no low level shear

 

Look at the 3cape values lmao

 

Fires a supercell off the dryline bulge in south Oklahoma. 

Very, very large hail threat monday night. Any tor risk will be completely down to if we can get more of a low level jet (unlikely) or mesoscale mergers. 

 

Edited March 30 by WeatherArc

[WeatherArc]

Tuesday has now been upgraded to an enhanced risk, due to recent model trends i am becoming increasingly concerned with the threat of strong-violent tornadoes.

  
The NAM shows this environment the best, hodographs like that combined with large low level instability is never a good thing.

I know events shouldn't be compared 3 days out but the 1965 palm Sunday outbreak does have quite a few familiarities to this setup, something to watch

 

Failure modes should be stressed, positioning and strength of surface low critical to whether we see a tornado outbreak or not, furthermore until cams come into range storm mode is uncertain.

Where the warm front sets up will also be pretty important. 

Still, very potent looking setup. 

 

Edited March 31 by WeatherArc

[WeatherArc]

Yeah this could be an issue. 18z nam 3km gives a pretty high end environment across parts of Kentucky, Ohio and Indiana. 

 

 

Considering the nams linear storm bias, tuesday looks very potent at the moment. 

 

Edited March 31 by WeatherArc

[WeatherArc]

18z 3k nam also brings a pretty juiced environment to Oklahoma, likely overdoing it but interesting to note.

 

Edited March 31 by WeatherArc