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Feb 24-25th Severe Weather


Anti tornado

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4 minutes ago, Hoosier said:

Looks like a couple rounds possible on Friday... prefrontal and then farther back closer to the cold front.  As far as imby, timing will be important as a quicker solution would basically put the entire threat farther east.

Do you think supercells before the front arrives is a good chance (like the 4K NAM has been advertising) is possible, or more wishful thinking.

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The secondary low feature along the front is now showing on both 4/12km NAM, on the GFS in the pressure fields though the wind fields are erroneously veered and on the Euro where it is closer to the NAM but still slightly veered at the surface. The Euro would be the compromise between the two. The big takeaway is that the potential of a secondary low is becoming real and this has a potential of locally backing the winds and enhancing the tornado potential.

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12 minutes ago, Stebo said:

That would be a great sounding for April even into early May.

Have to see if it actually gets that warm that far north, but it looks possible as most of the precip initially will be near/north of the retreating warm front.  Any breaks or thinning in the clouds during the day, along with just the advection process could allow for temps near those levels.

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Here's a sort-of-analogous example of a low-CAPE derecho, with shear that is much higher than average. Trees were knocked down by winds all over Ohio, March 9, 2002. I was there. It only rained for about 2 minutes, but there were trees down in my town anyway. Preceding conditions at ILN sounding at 12z showed SRH of 471 m2/s2. So SRH may have been over 300 m2/s2 at the time of the derecho. http://www.spc.noaa.gov/climo/reports/020309_rpts.html

Mar_9_2002_1945z_midwest_radar.gif

sfc_020309_12.gif

500_020309_12.gif

 

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I agree with the hail threat as mentioned earlier, these are some pretty steep mid level lapse rates we're seeing. My concern with tornadoes isn't so much the ingredients, as much as it is how setups like this often lead to messy storm modes. We see it all the time where it's hard with so much forcing aloft to get that classic supercell with so much stuff firing at once before it all congeals into a line


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It will be interesting to see if the NAM is onto something. 18z RGEM is 100-150 farther SW with the surface low, but still shows upper 50s dews reaching the IN/MI border. Caveat: low level winds more veered to SW/SSW.

The appearance of a notable prefrontal trough will make a big difference in the tornado potential. Without it, anything beyond a gusty squall line seems unlikely. With it, a fairly unusual late February severe threat could materialize. 

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Have to remind myself that it's only February.

 

Really a lot having to come together this far north... like today, fog and low level clouds were anticipated to clear out by 11AM. It's now six hours later and the low clouds and fog are still holding strong. Got no where near our projected high of 68°. I feel like this will be the case (atleast this far north) again on Friday due to loads of GOM moisture pooling northward (dewpoints in the upper 50's and even 60's in February is very impressive), even then a gusty line of quick moving storms would be likely in these parts. Looks like areas to the south really have a better chance of clearing out and getting unstable.

 

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36 minutes ago, Quincy said:

It will be interesting to see if the NAM is onto something. 18z RGEM is 100-150 farther SW with the surface low, but still shows upper 50s dews reaching the IN/MI border. Caveat: low level winds more veered to SW/SSW.

The appearance of a notable prefrontal trough will make a big difference in the tornado potential. Without it, anything beyond a gusty squall line seems unlikely. With it, a fairly unusual late February severe threat could materialize. 

Yeah, the prefrontal activity should make or break this from a tornado perspective (not that something couldn't occur closer to the front).  Even so, don't have tremendous directional shear and some of the hodos I've seen have a little bit of a kink, which will need to be monitored.

Winter tornadoes in the Ohio Valley aren't really rare, but it's a lot more unusual the closer you get to I-80 and northward.  This is a pretty unusual setup though for this time of year in the sense that we are not really having to race against time to get a massive northward moisture flux before the system moves out... the moisture is pretty much already in the area.  All this with a partial obstacle in that cutoff low down south, as has been discussed.  Pretty remarkable. 

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10 minutes ago, IllinoisWedges said:

Digging NC Indiana as of now. 

Not a bad spot. 

Just to give an idea of what we're up against as far as climo, here are some charts of severe frequency in the IWX cwa. Almost no activity in February, but this only covers the period from 1980-2010.

hail_month.png

 

wind_month.png

 

tor_month.png

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4 minutes ago, tornadohunter said:

Sounding out of south central michigan.....incredible for Feb 

I think that's north of the warm front with the near-surface inversion there. Soundings from south of the WF generally in the K'zoo/Battle Creek/Jackson area look pretty decent though on the 18z NAM. The Euro seems to be way undershooting the rest of the models with the moisture, I'd be interested to see its verification with dewpoints since the upgrade last year because it seems to me that it has ended up lowballing quite a few events in this respect since then (was particularly noticeable in May last year).

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6 minutes ago, andyhb said:

I think that's north of the warm front with the near-surface inversion there. Soundings from south of the WF generally in the K'zoo/Battle Creek/Jackson area look pretty decent though on the 18z NAM. The Euro seems to be way undershooting the rest of the models with the moisture, I'd be interested to see its verification with dewpoints since the upgrade last year because it seems to me that it has ended up lowballing quite a few events in this respect since then (was particularly noticeable in May last year).

Like this

2017022218_NAM_051_42.34,-84.65_severe_ml.png

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20 minutes ago, cyclone77 said:

Thought about maybe heading out east to chase this setup if things continued to look better.  Looked at a few soundings and saw the 50-60kt storm speeds, and was like naaaa.  

I don't blame you. I'm liking just to the west of MBY as a starting place. I don't want to blink as they race by or I'll miss it.

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