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2024 Short/Medium Range Severe Weather Discussion


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On 3/18/2024 at 8:34 AM, nwohweather said:


How difficult was tracking this in the office? Findlay/Tiffin are in a bit of a radar hole and until they got a little more easterly it wasn’t the easiest rotation to discern

The long-tracked supercell that started near Findlay and later produced the EF-2 in Crawford and Richland Counties was actually not too bad to track all things considered. Regarding the radar coverage there, you are entirely correct. Several years ago they added a supplemental lower radar tilt on a number of 88D radars (in most cases, 0.2 or 0.3 degrees) to attempt to help give better low-level radar coverage to more areas...the CLE radar was one of those but due to beam blockage our supplemental tilt is 0.4 degrees. We turned it on as that cell developed west of Findlay and it lowered our lowest beam height from slightly over 10k feet to slightly over 9k feet :arrowhead:

Regardless of the poor radar coverage, it helped that when the cell was that far away in poor radar coverage that it was light out and we had several people looking at it. The initial Tornado Warning felt slightly flimsy...it was a marginally strong-enough couplet at 9-10k feet, and given it was a discrete supercell in an environment favorable for tornadoes (the effective sig tor parameter was 2-3 at the time) the course of least regret was to go with a TOR. Immediately after that was issued we had a trained spotter call from just west of Findlay with a persistent rotating wall cloud (definitely enough to warn on in an environment favorable for tornadoes if radar is sampling a mesocyclone with the storm). That spotter called back off and on, we also had a few other public and spotter calls as it moved across Hancock and into southwestern Seneca, were streaming county dispatches on broadcastify (law enforcement was reporting funnels and possible tornadoes), and had HAM radio operators in the office who relayed a couple of reports from other HAM radio operators out in that area. Despite the poor low-level radar coverage, we were fairly confident it was trying hard (but probably not putting down anything too strong or persistent) from just east of Findlay into southwestern Seneca County. We finally confirmed an EF-Unknown tornado from far eastern Hancock into southwest Seneca. It's possible there were brief touchdowns before and after this, but this was the area where we had multiple, firm eyewitness accounts (with roads/directions clearly listed and consistent among reports) along with multiple pictures and a video of a tornado in a field. 

We did not hear anything concrete for a chunk of time is it moved across southeastern Seneca into extreme northeastern Crawford County despite a relatively decent couplet through there (it's very sparse in there and it was starting to get pretty dark...we also found no damage in that area so it likely wasn't quite producing or was just producing very weak/brief stuff in fields). By the time it produced the EF-2 in northeast Crawford/northwest Richland the radar coverage was better (we were hitting it at <5k feet by then) and it did briefly have an intense couplet and definite TDS, which allowed us to go with "radar confirmed" wording in the warning despite still not getting any concrete reports. We were on the fence regarding going with the "particularly dangerous situation" or "large and extremely dangerous tornado wording" in the warning (which is intended for high-confidence, potentially strong ongoing tornadoes but is a level below a Tornado Emergency, which is reserved for high-confidence and likely violent ongoing tornadoes) and finally got a call from an EM, who relayed a report from a fire department of a large (they said "half mile wide" though it was more like 250 yards) tornado currently on the ground, at which point we went with the higher wording. From there the tornado quickly lifted as the storm appeared to cycle and it never produced after that. 

NOW, as for the cell behind that, responsible for the (unwarned) EF-1 tornado southwest of Jenera in Orange and Van Buren townships...that was just annoying and is very symbolic of our challenges along I-75 (especially in Wood and Hancock...the Detroit radars can help with Lucas). The storm did not look impressive at all on radar, did not produce any upstream reports of anything close to tornadic in Allen County, and then dropped an EF-1 in Hancock. We heard about it pretty quickly and issued a warning when we got multiple reports of a tornado on the ground but had already missed it. It's annoyingly common that marginal looking storms on radar west of I-75 are unwarned and don't generate reports and then all of a sudden produce reports when they hit more population along I-75. 

On 3/18/2024 at 5:58 PM, TheWeatherPimp said:

The Winchester Tornado hit very close to home (well it was my home). The house I grew up in was destroyed and my family's houses were less than 2 blocks from the tornado. They were very lucky and I feel extremely relieved. I was on the phone with them yelling at them to get in the bathrooms and cover themselves with blankets and pillows. It was nauseating. But I'm so thankful they are all okay. 

It sounds like the NWS Indianapolis has finalized the rating of the Winchester tornado as an EF3. To be honest, I truly thought they might push it over the threshold based on some of the photos I've seen but I haven't seen the damage in person and won't until later this week. 

I'm glad to hear that your family made it through but am sorry to hear about the house you grew up in. I was a little curious to see if that may get an EF-4 rating. It seemed like the only damage truly in question was the Taco Bell...the expected wind speed for that damage indicator (complete destruction of a small retail building) is 167 MPH (EF-4) but they went 165 MPH (EF-3). I had seen one or two pictures of what looked like actual bolts ripped from the foundation (which would be proper construction) but also saw several more pictures where it appeared to just be straight nails holding the building to the foundation (which will give way much quicker and don't support an EF-4 rating). I'm curious if they found legitimate construction issues with the Taco Bell (i.e. anchored with nails and not bolts) and kept it an EF-3 for that reason (perfectly valid) or if they thought the Taco Bell was well-constructed but kept it an EF-3 due to a lack of other EF-4 damage indicators (which I have more mixed feelings on, especially in a multi-vortex tornado where the strongest winds will occur in very small suction vortices). Right or wrong, it's seemingly very difficult to get a higher tornado rating if it's just one damage indicator that supports it unless the one DI is very solid, and there were other structures around the Taco Bell that weren't really in consideration for the higher rating. I try not to get caught up in the rating debate too much because ultimately it's the people who lost loved ones and/or had their lives turned upside-down that really matter, but there's uncertainty in a lot of stronger tornado ratings...I feel like the burden on proof for a higher rating is placed on the tornado when they decide the final rating when there’s uncertainty and could go either way (if that makes sense). 

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SPC's highlight is much further south, but the 12Z NAM (and most antecedent GFS runs up to this point) would certainly support a severe/:twister: threat in a narrow arc across eastern Iowa Monday afternoon. Those hodographs and 3CAPE are something else, if not for the antecedent Gulf drying, I really think we'd be staring down the barrel of another significant late March outbreak. The one thing I will say is that the surface low appears to be weakening with time on Monday; whereas last year March 31 it was deepening or at least holding steady. That might have mitigated the overall threat some in any case, but even so that's a pretty impressive profile despite the paltry on their face T/Td values. You only have to go back one more year (and in the very same state no less) to see what can happen when a setup like that overperforms.

nam_2024032212_081_42.42--91.98.png

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I'm glad to hear that your family made it through but am sorry to hear about the house you grew up in. I was a little curious to see if that may get an EF-4 rating. It seemed like the only damage truly in question was the Taco Bell...the expected wind speed for that damage indicator (complete destruction of a small retail building) is 167 MPH (EF-4) but they went 165 MPH (EF-3). I had seen one or two pictures of what looked like actual bolts ripped from the foundation (which would be proper construction) but also saw several more pictures where it appeared to just be straight nails holding the building to the foundation (which will give way much quicker and don't support an EF-4 rating). I'm curious if they found legitimate construction issues with the Taco Bell (i.e. anchored with nails and not bolts) and kept it an EF-3 for that reason (perfectly valid) or if they thought the Taco Bell was well-constructed but kept it an EF-3 due to a lack of other EF-4 damage indicators (which I have more mixed feelings on, especially in a multi-vortex tornado where the strongest winds will occur in very small suction vortices). Right or wrong, it's seemingly very difficult to get a higher tornado rating if it's just one damage indicator that supports it unless the one DI is very solid, and there were other structures around the Taco Bell that weren't really in consideration for the higher rating. I try not to get caught up in the rating debate too much because ultimately it's the people who lost loved ones and/or had their lives turned upside-down that really matter, but there's uncertainty in a lot of stronger tornado ratings...I feel like the burden on proof for a higher rating is placed on the tornado when they decide the final rating when there’s uncertainty and could go either way (if that makes sense). 

Really appreciate the in depth minute by minute analysis. Really interesting to hear what the beam heights are on a county by county basis. The remarks about I-75 is a bitter pill to swallow, high beam heights and the airport radar out of Detroit are covering the heart of a 650K metro area. Really highlights the importance of trained spotters in the Toledo area
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DMX with a great AFD write-up on all the potential impacts of the Sunday-Monday system including severe and synoptic winds. DVN/ARX seem purely concerned with snow despite the potential for the narrow instability sweet spot to set up at least partially in one of their CWAs.

Quote
Right on the heels of this lighter precipitation will be strong warm
air/theta e advection ahead of a synoptic scale system bringing much
needed precipitation to the area. This system checks a lot of the
boxes, with good kinematic and thermodynamic support throughout the
layer. Moisture also won’t be an issue, as the pacific moisture
stream mentioned earlier will phase with a developing lower level
moisture stream from the Gulf of Mexico. As the broad scale lift
helps to induce widespread precipitation, there will also be
localized FGEN support on the leading edge of the warm air advection
stream.

So what’s this all mean for sensible weather? Well, as the theta e
advection pushes into the state on Sunday morning, cooler
temperatures will initially cause moderate to heavy snowfall in
roughly the northern half of the state with rain further south.
However, as the warmer air and higher dewpoints stream north, this
snowfall will quickly flip over to rain for much of central Iowa by
mid-day Sunday. As this transition occurs, it’s possible some will
see a brief wintry mix before rain takes over completely Sunday
afternoon, although no impacts are expected due to an icy
precipitation. The warmer temperatures will arrive in northern Iowa
the latest, and therefore the highest snow totals are  expected near
the Iowa/Minnesota border and north. For those further south, snow
may initially accumulate on cooler surfaces, but rain falling on top
of snow, as well as higher temperatures and dewpoints should quickly
melt any snow on the ground. This snowfall distribution is pretty
unanimous across the current deterministic and ensemble output, as
the trend in guidance leans towards a deeper, more amplified system
pulling more warm air into Iowa sooner on Sunday, and therefore a
northern trend in the higher snowfall totals.

The fun doesn’t end after Sunday, as the surface low pivots over
eastern Kansas and Nebraska late Sunday night, then tracking through
western Iowa on Monday morning. As mentioned previously, the trend
in guidance has been towards a deepening and more amplified system,
which has slowed the low and pushed it further west, placing the
warm sector over much of central Iowa. This trend not only leads to
continued precipitation into Monday, but also poses the risk for
some stronger thunderstorms mid-day. While it is still too far out
to get too bogged down in the details, this setup looks to be your
typical early season low CAPE, high shear scenario. Models are
starting to hint at a pocket of 500 to 700+ J/kg of surface based
CAPE within the warm sector as well as more than enough shear to
produce an organized storm or two. Again, not going to dive too far
into the possibilities at this time, especially as the threat looks
somewhat conditional on how much instability is present. However,
keep the potential for severe weather in the back of your mind as we
get closer to Monday.

Finally, not to be overshadowed by the rain, snow and thunderstorm
chances this weekend, this system will also be quite wound up,
meaning tight pressure gradients and gusty winds. EPS ensemble wind
gust statistics are quite impressive, with a mean wind gust
magnitude of 35+ mph on Sunday and up to 45 mph on Monday. This is
corroborated by GFS and NAM soundings mixing up to 800 mb with 50
kts at the top of the mixed layer on Monday. NBM seems to be
handling this well for now, putting gusts over 30 kts both days and
over 40 kts on Monday. Should this trend continue through future
forecast cycles, wind headlines will likely be needed for one or
both of these days, but will hold off on that for now.&&

 

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Marginal Risk for much of our forum tomorrow.

20240325 1730 UTC Day 2 Outlook Graphic

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1228 PM CDT Mon Mar 25 2024

   Valid 261200Z - 271200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   SOUTHERN ALABAMA AND THE WESTERN FLORIDA PANHANDLE...

   ...SUMMARY...
   An isolated threat for damaging winds and a tornado or two may
   persist Tuesday along/near the central Gulf Coast, with a separate
   area of isolated strong to severe thunderstorms potentially
   developing by Tuesday afternoon across parts of the Midwest and
   southern Great Lakes.

   ...Synopsis...
   Extensive upper troughing is expected to cover the majority of the
   CONUS early Tuesday morning. Moderate to strong mid-level flow will
   extend throughout this troughing Tuesday morning, arcing
   cyclonically from the West Coast across central Mexico and the TX
   Gulf Coast, and then up the MS Valley through the Upper Great Lakes.
   Several shortwave troughs will be embedded within this large
   troughing, with the most prominent shortwave beginning the period
   over the Mid MS Valley. Expectation is for this shortwave to move
   quickly northeastward into eastern Ontario by the afternoon,
   accompanied by very strong mid-level flow (i.e. 100+ kt at 500 mb).
   Deep surface low associated with this wave is also expected to move
   northeastward from its initial position over northwest WI into
   northwest Ontario. As it does, an attendant cold front will sweep
   quickly eastward/northeastward across the Mid MS Valley, the Upper
   Great Lakes, and the OH Valley. 

   Farther south, thunderstorms will likely be ongoing early Tuesday
   morning along an outflow-reinforced cold front stretching from
   middle TN southwestward off the AL/MS coast. Steady eastward
   progression of this front is expected throughout the day, before it
   stalls over GA and the eastern FL Panhandle Tuesday evening.

   ...Southern AL into Southeast GA and the FL Panhandle...
   Ongoing convective line is expected to extend from central AL into
   coastal AL and the far western FL Panhandle early Tuesday morning.
   Moderate low-level moisture and buoyancy will be over southwest
   AL/coastal AL and the far western FL Panhandle early Tuesday, with
   some potential for damaging gusts and maybe even a brief tornado or
   two as the line moves through. An isolated severe threat may persist
   into Tuesday afternoon and continue through Tuesday night across
   southeastern AL, southwestern GA, and the FL Panhandle vicinity as
   mid to upper 60s surface dewpoints attempt to advance inland across
   these areas. However, poor lapse rates aloft and limited daytime
   heating from cloud cover should temper buoyancy, leading to a
   gradually diminishing storm intensity.

   ...OH Valley/Southern Lower MI... 
   Clearing is anticipated in the wake of the warm conveyor and ahead
   of the primary cold front across the OH Valley and southern Lower
   MI, beginning during the late morning over IL. This clearing is
   expected to allow temperatures to climb into the 60s. Low-level
   moisture will be limited (i.e. in the low 50s), but the combination
   of modest low-level moisture with temperatures in the 60s and cold
   mid-level temperatures (i.e. around -20 deg C at 500 mb) is expected
   to result in air mass destabilization and modest buoyancy. Shallow
   thunderstorms are expected to develop along the cold front as it
   interacts with this destabilized air mass, likely beginning during
   the late morning across IL before then moving eastward/northeastward
   throughout the day. Buoyancy will be modest, but robust low to
   mid-level fields will be present and the deep-layer vertical shear
   vector will oriented mostly perpendicular to the front. These
   factors suggest fast-moving storms capable of damaging gusts,
   particularly since the gradient surface wind will already be
   enhanced. A tornado or two is also possible, although the limited
   storm depth could act as a limiting factor for greater storm
   organization.

   ..Mosier.. 03/25/2024
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1 hour ago, largetornado said:

 

My whole Twitter feed is insane. So many fan-created "risk" maps that show their "dream" severe scenarios. It's hard for me to differentiate between actual SPC maps and teenage kids with their wishcasting. 

Nevertheless, it is definitely something to watch especially for the south and mid-Atlantic. 

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2 hours ago, largetornado said:

Every time Weed sees a trough on the models, he drives the social media hype train out of the station at full throttle, derails, crashes, and burns.

I remain skeptical of this timeframe due to inconsistency between models/runs. Could it turn into something big? Sure, but IMO it's just as likely at this point to be a relatively modest event with a lot of rain/general thunderstorms and some isolated severe weather.

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49 minutes ago, CheeselandSkies said:

Every time Weed sees a trough on the models, he drives the social media hype train out of the station at full throttle, derails, crashes, and burns.

I remain skeptical of this timeframe due to inconsistency between models/runs. Could it turn into something big? Sure, but IMO it's just as likely at this point to be a relatively modest event with a lot of rain/general thunderstorms and some isolated severe weather.

I'm a hurricane guy so I'm not seasoned in severe weather and I don't storm chase but these people are drooling and begging for a severe event. Spring is flying by and they're going bonkers.

It's actually quite annoying. 

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2 minutes ago, Floydbuster said:

I'm a hurricane guy so I'm not seasoned in severe weather and I don't storm chase but these people are drooling and begging for a severe event. Spring is flying by and they're going bonkers.

It's actually quite annoying. 

Well, I am a chaser and I do love severe weather, but I advocate for restraint on social media hype unless/until there is actually good model agreement/consistency for a high-ceiling threat.

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Just now, CheeselandSkies said:

Well, I am a chaser and I do love severe weather, but I advocate for restraint on social media hype unless/until there is actually good model agreement/consistency for a high-ceiling threat.

I agree, and when I see people who want tornadoes in Chicago hyping what would likely be a severe event for Arkansas and Tennessee, it's cringey. 

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2 hours ago, CheeselandSkies said:

The equinox was only a week ago, lol.

I mean "springtime" figuratively speaking. Most people consider "springtime" pretty much Valentine's Day to Memorial Day. March has flown by. 

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30% added to the D4 outlook for Monday, with most of the Southern area of the sub under a 15%. Does this mean that tomorrow's D3 outlook will more likely be slight/enhanced, or marginal/slight?day4prob.gif

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4 minutes ago, nvck said:

30% added to the D4 outlook for Monday, with most of the Southern area of the sub under a 15%. Does this mean that tomorrow's D3 outlook will more likely be slight/enhanced, or marginal/slight?day4prob.gif

The probabilities on the Day 4 and beyond outlooks don't have a direct correlation to the Day 3 and closer. The 30% zone is for all hazards. For an Enhanced risk, the wind OR hail probability has to be 30% OR the tornado probability of 10%. So it all depends on how things trend and how confident they are.

They treat the longer range outlooks a little differently than they used to. Nowadays, they'll introduce a 15% at Day 6 if they're reasonably confident in an at least 15% probability of wind or hail (slight risk) maintaining itself by Day 1. Twenty years ago, if you saw a 25% (then used for a "high-end" slight risk, what would be an Enhanced risk today, the minimum threshold for a slight risk was 15% just like now) contour on the Day 3 outlook, it implied above-average confidence in a widespread/high-ceiling threat and a good chance of a high risk popping up at some point on Day 1.

 

 

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Tuesday looks potentially volatile in the OV on the 12z GFS and Euro. 40-50 kt SW/WSW LLJ with a potent vort ejecting out of the Plains positive tilt trough. Moisture looks like a non-issue, the primary fly in the ointment looks to be the degree of veering in the surface winds, which will also be tied to the timing of the ejecting wave/potential phasing with the northern stream.

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19 hours ago, Floydbuster said:

I mean "springtime" figuratively speaking. Most people consider "springtime" pretty much Valentine's Day to Memorial Day. March has flown by. 

Well yeah, you used to live in Florida.

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Yes the 18z NAM is absolutely nasty on Tuesday. Granted, that probably won't hold, although its 500 mb setup isn't much different than the other models.

The low levels will make or break this along with prior convection from Monday.

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5 hours ago, andyhb said:

Yes the 18z NAM is absolutely nasty on Tuesday. Granted, that probably won't hold, although its 500 mb setup isn't much different than the other models.

The low levels will make or break this along with prior convection from Monday.

yep, didnt hold in the 0Z suite. However, the warm front on Monday has that look to me and the D2 outlook hits on that. 

day2probotlk_0600_torn.gif

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  • 2 weeks later...

I'm surprised they went with such a high risk. There could be alot of rainfall throughout the day Thursday helping to lower instability in the region, similar to last week. Thankfully, this is much less threatening than last week, however, the focus will be more on flooding rainfall threats.

The NWS says the severe risk is highly dependent on lingering rain and clouds through the day. I think this has a high bust potential.

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