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April 8-10 Severe threat


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I'm a bit surprised that the severe threat is almost entirely out of Iowa, when a few of the models seemed to be slowing down the surface low.

 

 

Terrible forecast.  If it ends up being right, it won't be for the right reasons.  Ongoing convection will have totally screwed eastern IA is the only way this forecast works out IMO.

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Terrible forecast.  If it ends up being right, it won't be for the right reasons.  Ongoing convection will have totally screwed eastern IA is the only way this forecast works out IMO.

I agree, unless the surface low speeds up and moves past us by the time storms develop.  Thinking I'll still probably go chase, or at least spot, mainly because I won't have to go far to do it.

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Shocked to see eastern IA is pretty much excluded from anything at all. Completely disagree with that.

Good thing it'll be updated again at 13z. Was also surprised with the shift east. The NAM soundings were cited in the outlook but then the 00z NAM solution and a lot of other guidance seemed to be discarded.

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I don't often criticize forecasts publicly, but there's a level of nonsensicalness to this outlook.  I don't at all understand the reasoning for shifting the western edge of the outlook east when the trend all day long has been to develop intense convection farther and farther west to start.  I can kind of see leaving it at enhanced for now (though tornado probs should completely be 10%), but the changes made to this outlook from the previous outlooks make zero sense.

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I don't often criticize forecasts publicly, but there's a level of nonsensicalness to this outlook.  I don't at all understand the reasoning for shifting the western edge of the outlook east when the trend all day long has been to develop intense convection farther and farther west to start.  I can kind of see leaving it at enhanced for now (though tornado probs should completely be 10%), but the changes made to this outlook from the previous outlooks make zero sense.

Yes I completely agree, especially near the low and maybe in eastern MO/AR as well.

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Good thing it'll be updated again at 13z. Was also surprised with the shift east. The NAM soundings were cited in the outlook but then the 00z NAM solution and a lot of other guidance seemed to be discarded.

 

This, I'm seeing inflated parameter space all across eastern IA on the 00z NAM for 18-21z and possibly beyond. I don't want to start speculating on this kind of stuff, but it seems like he didn't even look at a good part of the model suite (like you mention) when doing this outlook, or he went almost straight to what it was showing at 00z Friday.

 

As far as the probs go, I could easily see a 10% tor (although I can understand wanting a bit more certainty with mesoscale/leftover convection/etc.), but the whole business with the location is rather baffling.

 

I think it also needs to be emphasized that the reports from today were concentrated on the western edge of the risk areas (aside from the earlier stuff), which indicates the trough was likely a bit slower than many model forecasts.

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From the brand new NSSL.  Cape is still very impressive in eastern IA at 4pm.  Certainly not gonna be a marginal risk in this area at peak heating lol.

 

2h80k8g.jpg

Agreed, I'm fully expecting the 13z outlook to push the risk back to at least the quad cities, if not farther back towards Iowa City & Cedar Rapids and points eastward unless any new information comes out that says that shouldn't be the case.

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From the brand new NSSL. Cape is still very impressive in eastern IA at 4pm. Certainly not gonna be a marginal risk in this area at peak heating lol.

2h80k8g.jpg

Heh, and right near the surface low too. If there's any question with storm mode, it'll probably be the farther east you go (though I think it'll be mainly discrete across much of LOT), but initiation in eastern IA is basically a lock for discrete.
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This, I'm seeing inflated parameter space all across eastern IA on the 00z NAM for 18-21z and possibly beyond. I don't want to start speculating on this kind of stuff, but it seems like he didn't even look at a good part of the model suite (like you mention) when doing this outlook, or he went almost straight to what it was showing at 00z Friday.

 

As far as the probs go, I could easily see a 10% tor (although I can understand wanting a bit more certainty with mesoscale/leftover convection/etc.), but the whole business with the location is rather baffling.

 

I think it also needs to be emphasized that the reports from today were concentrated on the western edge of the risk areas (aside from the earlier stuff), which indicates the trough was likely a bit slower than many model forecasts.

The GFS doesn't even have the front reaching the river until 00z.  I just don't understand this.

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Won't take much warming tomorrow to get destabilization either. Temperatures ranging from the mid 60s to low 70s south of the front in Illinois here at 06Z. These will easily warm a minimum of 5 degrees even with overcast. 5 degrees = sufficient. 10 degrees = boom!

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The GFS doesn't even have the front reaching the river until 00z.  I just don't understand this.

Check the 4km SPC-WRF. It is really the only model that shows nothing in Iowa, it also has most areas in IA/IL/IN/MI not getting unstable at all. It is completely on an island compared to all other guidance though.

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This, I'm seeing inflated parameter space all across eastern IA on the 00z NAM for 18-21z and possibly beyond. I don't want to start speculating on this kind of stuff, but it seems like he didn't even look at a good part of the model suite (like you mention) when doing this outlook, or he went almost straight to what it was showing at 00z Friday.

As far as the probs go, I could easily see a 10% tor (although I can understand wanting a bit more certainty with mesoscale/leftover convection/etc.), but the whole business with the location is rather baffling.

I think it also needs to be emphasized that the reports from today were concentrated on the western edge of the risk areas (aside from the earlier stuff), which indicates the trough was likely a bit slower than many model forecasts.

Excellent points. I was just confused by the outlook in general, the 00z guidance seemed to highlight the trend toward slower and thus farther west initiation in addition to what was observed likely pointing at that outcome. Gino mentioned yesterday after doing the forecast when the NAM was the slowest model by a decent bit that he thought even it may be too fast because of typical trend with these systems to be slower than progged; and as a result the highest tor probs may very well be in eastern IA and NW IL.

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Won't take much warming tomorrow to get destabilization either. Temperatures ranging from the mid 60s to low 70s south of the front in Illinois here at 06Z. These will easily warm a minimum of 5 degrees even with overcast. 5 degrees = sufficient. 10 degrees = boom!

Warming isn't really even the issue.  You have this huge reservoir of steep lapse rates courtesy an EML across most of the central United States.  If you convect in one area, you can advect steep lapse rates back in quickly, particularly with a jet streak like the one we'll have tomorrow.  Some of these lapse rates will modified overnight and into the morning with convection, but when your baseline is numerous states worth of 7.5-9 k/km, that's just hard to beat, especially in April.

 

post-97-0-42044500-1428560551_thumb.gif

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Check the 4km SPC-WRF. It is really the only model that shows nothing in Iowa, it also has most areas in IA/IL/IN/MI not getting unstable at all. It also is completely on an island compared to all other guidance.

 

By bringing a metric a*sload (scientific term I know) of junk convection across those areas I might add.

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Check the 4km SPC-WRF. It is really the only model that shows nothing in Iowa, it also has most areas in IA/IL/IN/MI not getting unstable at all. It is completely on an island compared to all other guidance.

It is on an island, and it is the only model to remote support this outlook.

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Excellent points. I was just confused by the outlook in general, the 00z guidance seemed to highlight the trend toward slower and thus farther west initiation in addition to what was observed likely pointing at that outcome. Gino mentioned yesterday after doing the forecast when the NAM was the slowest model by a decent bit that he thought even it may be too fast because of typical trend with these systems to be slower than progged; and as a result the highest tor probs may very well be in eastern IA and NW IL.

 

Another question is what does LOT do now with this, or even a better question, what does DMX/DVN do?

 

Staying with the general model slowdown and also observational data would contradict that outlook in many ways. I mean that's what I would do, but I see there's already comments on twitter/etc. of people being relieved that their areas were taken out of the risk/lowered probabilities.

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Warming isn't really even the issue.  You have this huge reservoir of steep lapse rates courtesy an EML across most of the central United States.  If you convect in one area, you can advect steep lapse rates back in quickly, particularly with a jet streak like the one we'll have tomorrow.  Some of these lapse rates will modified overnight and into the morning with convection, but when your baseline is numerous states worth of 7.5-9 k/km, that's just hard to beat, especially in April.

 

attachicon.giflapserate_wow.gif

 

I agree, I have been amazed by this EML for the past few days. Will be nice to see the storms finally take advantage of it tomorrow. It is hard to get high cape AND high shear east of the Mississippi, but when it does occur...look out. Tomorrow definitely has the potential for both high cape and high shear cross Illinois.

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For the most part I actually agree with his forecast.  The high resolution ECMWF has been rock solid the last couple of days with sb cape values struggling to get much higher than about 1200.  In addition to that it has also be consistent in showing unimpressive H92-H5 crossover's for the area.  I believe it has mostly elevated convection during the daylight hours.  I wish that EuroWx had MU cape maps, as I would expect those would be higher.  Where I disagree with the forecast is the winds.  I like the 30% winds but would hatch it over much of Illinois and Indiana, I believe that a 45% hatched wind forecast will come out for somewhere over this area in the morning update.

 

Once again which is right, the Euro or short term forecast models,  If the Nam and short term CAM's continue their stronger solution by 12z tomorrow morning than I would certainly go to 10%  tornado with a small area hatched, just not sure where yet.  Having said all this I have a healthy respect to the long term posters on this board.

 

Edit: The 0z ECMWF continues with its depiction of how the day unfolds.

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Another question is what does LOT do now with this, or even a better question, what does DMX/DVN do?

Staying with the general model slowdown and also observational data would contradict that outlook in many ways. I mean that's what I would do, but I see there's already comments on twitter/etc. of people being relieved that their areas were taken out of the risk/lowered probabilities.

DVN is probably in the toughest spot because if there is disagreement, becomes inconsistency with the National center's outlook and possibly confusion in the public. Would be unfortunate if some areas in IA and NW IL wake up hearing that threat has diminished, followed by shifting back west at 13z. For my office, probably status quo because almost entire CWA was kept in the ENH.

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I see the SPC moved the slight risk area 75 miles or more south here in MI. I figured that would be the case since latest model runs show no real CAPE getting up here this afternoon and evening now, with a big line of crapvection / clouds coming through this morning it will not allow any daytime heating to occur.

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Referencing my post #236 above.  This is what I said a couple of days ago over in the central western sub. It was in a answer to a chase day preceded by a long drive to get there.

 

"I wouldn't do it either, se Kansas looks good Wednesday night, but its very local IMO.  Thursday in my mind is not what many are saying, I think convection just ahead of the warm front or along it may lock the best cape values around the AR/LA/Tex area.  This seems to be reflected by the ECMWF."

 

Yesterdays storm reports, Euro seemed to have it right.  Hard to go against it for today at this time.

 

today.gif

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