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Convective Thread


weatherwiz

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13 minutes ago, OceanStWx said:

Good grab there. 

It's almost like sometimes updrafts can constructively merge, where the more northward moving cell just ahead of the more southeastward moving cell can enhance the counter-clockwise rotation of the SE mover.

I'm guessing the southern storm had 2 peaks... one prior to that first image when it ingested the outflow boundary from the line (Poughkeepsie had golf balls) and then again as the merger began and we see that ZDR column shoot up and tornadogenesis occured. A bit of extra stretching and some enhanced SRH due to storm scale stuff. Pretty cool. 

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12 hours ago, CT Rain said:

What is interesting is that spectrum width really spiked for those 2 SAILS scans with the tornado... was quite a bit lower before and after. 

For lower power radars, high spectral width is often problematic, especially for tornadoes, because quite often an SQI filter is applied to the data.  Tornadoes often are occurring in an area of relative lower power return at least compared with the FFD region.  Wide spectrum + weak returns is very often filtered out altogether as noise... I have advocated for abandoning SQI filters altogether for that reason actually.   It's especially bad in small tornadoes when the entire rotation might fall into one or two radials, or in the dead center of a larger tornado. 

Even strong rotating updrafts can be problematic, though in that case your SNR is usually higher at least which partially compensates for the wide spectral width. 

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16 minutes ago, radarman said:

For lower power radars, high spectral width is often problematic, especially for tornadoes, because quite often an SQI filter is applied to the data.  Tornadoes often are occurring in an area of relative lower power return at least compared with the FFD region.  Wide spectrum + weak returns is very often filtered out altogether as noise... I have advocated for abandoning SQI filters altogether for that reason actually.   It's especially bad in small tornadoes when the entire rotation might fall into one or two radials, or in the dead center of a larger tornado. 

Even strong rotating updrafts can be problematic, though in that case your SNR is usually higher at least which partially compensates for the wide spectral width. 

That's interesting and definitely makes sense. 

It was interesting watching the difference between ENX and OKX. The former was closer (by about 10nm) but was shooting through that big hail core before it got to the inflow region where all the rotation was. Definitely wasn't sampling it very well... probably some TBSS issues? OKX had a much cleaner view and you could see the strong rotation that initially was pretty small (only a few bins). 

SW definitely was the one thing that showed a jump at the time of tornadogensis during the cell merger. 

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8 hours ago, CT Rain said:

That is incredible stuff!!  Excellent analysis.  I agree too that the storms just have interacted just the right way to briefly locally enhance the low-level shear.  The observation though with SW and ZDR with tornadogenesis is fantastic stuff.  It's amazing what dual pol can do 

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1 hour ago, weatherwiz said:

ughh greatest potential may be just a tad too far west to be worth going for given the setup :(

Yeah it's not a slam dunk, but I think somewhere just N of AVP could see something decent. NCAR ensemble likes a few stronger cells through that area, and the SREF has a nice bullseye just about BGM.

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8 minutes ago, OceanStWx said:

Yeah it's not a slam dunk, but I think somewhere just N of AVP could see something decent. NCAR ensemble likes a few stronger cells through that area, and the SREF has a nice bullseye just about BGM.

Some of those hodographs are actually quite nice looking. Lapse rates are garbage with WAA in mid-levels.  One thing to have crap mid-level lapse rates but it's another to have WAA.  I feel though all we need is a few hundred J of 0-3 km cape though given shear.  

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4 minutes ago, weatherwiz said:

Some of those hodographs are actually quite nice looking. Lapse rates are garbage with WAA in mid-levels.  One thing to have crap mid-level lapse rates but it's another to have WAA.  I feel though all we need is a few hundred J of 0-3 km cape though given shear.  

Forecast lapse rates are garbage, but as you say the hodographs are nice. So it will only take a little bit of sun. Keep an eye on the overnight convection.

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4 minutes ago, OceanStWx said:

Forecast lapse rates are garbage, but as you say the hodographs are nice. So it will only take a little bit of sun. Keep an eye on the overnight convection.

That could really screw thighs up too.  This is a tough call b/c I would have to pick my friend up in NH which I would do tonight.  Guess we'll see how 18z models look 

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23 minutes ago, weatherwiz said:

That could really screw thighs up too.  This is a tough call b/c I would have to pick my friend up in NH which I would do tonight.  Guess we'll see how 18z models look 

I am gun shy about lapse rates after 6/6/10. I'll toss even favorable setups with good shear without LR in excess of 7. 

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29 minutes ago, Hoth said:

I am gun shy about lapse rates after 6/6/10. I'll toss even favorable setups with good shear without LR in excess of 7. 

Lapse rates are certainly helpful but that's typically more so for widespread outbreak type events.  Severe weather and tornadoes can still happen without the presence of steep lapse rates but it's tough to get widespread significant severe without an EML/steep lapse rates.  

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Might be worth it to keep an eye on that thunderstorm cluster skirting the Can/border with ND as this ridge begins it's well advertized fabled bulge toward and through the upper OV.

That set up with stronger mid and upper air geostrophic wind components whizzing by over top in latitude is MCS city, and any renegade convection that taps into a focused sw gradient pipe at 850 would probably evolve pretty quickly into an organized system.  The GFS has been sending vorticity shrapnel over the arc of the ridge for days; could be some indication of convective presentation/or triggers.. not damping them out meaning less suppression for anything that gets going along.

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The upcoming pattern is real nice for getting some EML plumes into here...in fact, we should see a few to begin the upcoming work week.  It's unfortunate though we can't do much with them.  I definitely do agree we do have to watch for some MCS potential...especially northern New England.  Speaking of convecton though I've seen several folk on twitter targeting Tuesday as a "big day" and I have no clue why.  Maybe they're thinking the backdoor will spark stuff off but BDCF's aren't known for producing severe wx (they can but its rare) and widespread severe.  Non-existent height falls, weak vort. max, we're capped and NW flow throughout troposphere.  

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meh.  Think we'll see a few storms around...they could become quite strong strong and briefly reach severe limits.  Think lack of convergence will limit things and might remain a bit more capped...unless we get the decent s/w support.  Models though are insane with dewpoints...GFS has upper 70's and NAM low 70's.  Think both are wAY overdone and that's leading to insane cape and which is why models spitting out alot of convection.  

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You can see the main boundary entering NW-N Maine on high res vis imagery as a series of parallel bows in the low level cloud - they typically do hash like that ... 

Meanwhile a decayed(ing) MCS is moving E through lower Ontatio and there's some evidence of a terminating outflow extended west-east near BUF - east of Syracuse..  Trigger? 

We are full sun here and amply heating..  I am not sure what the mechanical forcing looks like, but just on the surface ... the DPs being regionally up into the low to mid 60s with temps already nearing the upper 80s can't be a bad sign for generating in situ CAPE.  

 

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Does anyone else find this a little odd.  It's mid 80's over mid 60's dews with fairly steep lapse rates but mesoanalysis doesn't even have 500 J  of MLcape and barely 1000 J SBcape and LI only like -1C to -2C. Ncape values are pretty darn nothing though so cape profile is really skinny but I find it hard to believe those parameters are that low given the environment...

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Nevermind lol...completely forgot it was just before 10:20 and the sfc obs updates before mesoanalysis (which updates around 10:22) and now that it's updated the parameters look more like you would expect them too.  We do have mainly westerly and even somewhat northwesterly sfc winds though so I would expect dews to mix down to the lower 60's...if not like 59-60 in some spots.  This will decrease CAPE a bit...or lower threshold.  Not that it matters much really...don't think the forcing is all that great today which is why I think we see mainly isolated convection.  Doesn't mean any storm won't become strong to marginally/briefly severe though. 

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41 minutes ago, Damage In Tolland said:

Don't think we do. LR blow.

congrats SE Mass.

Theta-e ridge popping into WNE now. Should get most areas into the 1500-2000 J/kg range before fropa just based on the heat/humidity combo alone despite meh lapse rates.

There's actually decent -10 to -30C CAPE, so can't rule out hail, though we'll need a pretty robust updraft considering how high the freezing levels are. Then of course the wet microburst potential. PWATs are up there.

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I don't think I'd say the lapse rates are meh though. 700-500mb lapse rates are between 6.5 C/KM and 7 C/KM with 2-6km lapse rates up around 7 C/KM.  What will be interesting though is to see what wins out...theta-e ridge pushing in which would increase dewpoints or the W to NW surface flow which would mix dews out.  Models seem to want to increase the dews but I'm not so sure that will work.  Guessing we will mix somewhere between 5500' and 6000' today where dews are about 57-59F.  Not terrible but definitely some drier air to mix down.  I was thinking we would eventually see dews drop to maybe 60-61F but I guess I could see them perhaps around 63-64F.  Anyways though with 90F temps, dews into at least the lower 60's and steep lapse rates instability certainly isn't the problem today...my thing is just with models overdoing dews they're overdoing cape and overdoing convection but I think short-term mesoscale models are picking up on the actual dews and are coming more realistic with convection

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