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April 2nd - April 5th Severe Weather


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Our new website is up and running as of today, check it out. My favorite new thing is the overlays of many products on 1km sat images, almost like AWIPS

http://weather.cod.edu/index.php

you guys need a redirect from the old url for people with bookmarks.....if i didn't see your post here i would of thought you guys were down when i used my bookmark

http://weather.cod.edu/danatext.html

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True - however, a few supercells mixed in with the bunch and widespread wind damage could warrant the high. I would tend to think that the mod/high would be more for wind damage than tornadoes - with some tornadoes likely. Although to get a high risk for wind I believe it has to be 60% in the probabilities. Defin a moderate risk day shaping up.

I definitely am not in the "super outbreak" "apocalyptic outbreak" camp - and I am seeing that stuff floated around.

But definitely a strong risk for damaging winds and a few tornadoes.

I would outline the best tornado risk on Monday somewhere from Bowling Green, KY down to Nashville/Columbia, TN and then down towards Tupelo/Florence/Huntsville for the highest probabs (then perhaps a second area further south of there a bit). Although the damaging wind risk should be pretty significant over much of Kentucky/southern Indiana/southern Ohio, as well.

Not only 60% but it has to be hatched too. I think the last one for wind was on 10/26 of last year.

prob_to_cat_day1_seetext.jpg

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True - hard to get high risk on wind days - although SPC has leaned towards more mod/high risks over the last couple years (according to some of their members).

It's hard to know when to pull the trigger for them too. Back when we did the whole severe weather outlook thing with NEMAS and then later when we tried to build our own websites.... we made it a point to only do High Risk level wind probs for a serial derecho... never a progressive derecho... because there isn't a lot of rhyme or reason to differentiate a progressive derecho that would verify a HIGH or one that needs a MDT instead. We also tried to make it so that we tried to correlate wind-driven HIGH probs with days we were already going HIGH for tornadoes.... if it looked like, in addition to the tornado threat, a big serial derecho would show itself. Otherwise, we tried to lean toward a strongly-worded MDT.

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Regarding the Euro/GFS discussion--all the models on an individual basis stunk it up horribly with this event and overall pattern evolution--and honestly with the complex phasing and the very low amplitude nature of the leading IPV anomaly near the west coast-there was a huge discrepancy in the overall evolution of the wave into either a strung out full latitude positive tilt trough with an eventual cutoff low or a northern stream dominated wave--this is not a surprise. There simply is no way the models can latch on to this type of low amplitude variability so far out. I will agree with thewxmann that the Euro did well in first sniffing out a dominant leading northern stream IPV anomaly and more of a shallow cold front dominated by shallow low level cold air advection just near the surface (hence the sharp nature of the trough). CMC hinted at this for a couple runs--but it came to that conclusion in the wrong way (hence the rapid transition to a full latitude, positive tilt trough dominated by a slow moving, meandering southern stream bowling ball type low). I also agree with fredgossage that the Euro was also by far the most "bullish" with the southern stream cutoff scenario as it had a number of runs with a large bowling ball/deep cutoff IPV max sometimes as far S as the GOM as little as 3-4 days out. In the end all individual global models stunk--but as a whole--they gave us a great look into the overall variability as well as height field potential as far as day 6 out. Perhaps we have become too used to how well global models can simulate future wave patterns--but this storm was a good reminder there are certain setups where the overall amount of variability is simply higher than others.

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Regarding the Euro/GFS discussion--all the models on an individual basis stunk it up horribly with this event and overall pattern evolution--and honestly with the complex phasing and the very low amplitude nature of the leading IPV anomaly near the west coast-there was a huge discrepancy in the overall evolution of the wave into either a strung out full latitude positive tilt trough with an eventual cutoff low or a northern stream dominated wave--this is not a surprise. There simply is no way the models can latch on to this type of low amplitude variability so far out. I will agree with thewxmann that the Euro did well in first sniffing out a dominant leading northern stream IPV anomaly and more of a shallow cold front dominated by shallow low level cold air advection just near the surface (hence the sharp nature of the trough). CMC hinted at this for a couple runs--but it came to that conclusion in the wrong way (hence the rapid transition to a full latitude, positive tilt trough dominated by a slow moving, meandering southern stream bowling ball type low). I also agree with fredgossage that the Euro was also by far the most "bullish" with the southern stream cutoff scenario as it had a number of runs with a large bowling ball/deep cutoff IPV max sometimes as far S as the GOM as little as 3-4 days out. In the end all individual global models stunk--but as a whole--they gave us a great look into the overall variability as well as height field potential as far as day 6 out. Perhaps we have become too used to how well global models can simulate future wave patterns--but this storm was a good reminder there are certain setups where the overall amount of variability is simply higher than others.

This is a big factor. For the past several severe weather seasons, and especially 2006-2008, we have had numerous large situations where the medium range guidance started depicting a solution well in advance... and except for minor glitches... kept said solution with remarkable consistency on the bigger events.... for days (7-10 days in advance). 3/12/06, 4/7/06, and 2/5/08 are incredible examples. I think that by having so many of those... with different synoptic scenarios and in different global conditions... we may have become a little too accustomed to the idea that the "biggies" often telegraph their intentions well in advance. Last year, and especially this year, have proven that that is indeed not always true. :whistle:

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The Sunday setup is definitely interesting. My concern is the best instability/weaker cap is west of the better low-level wind fields. Winds below 850mb are pretty crappy over southeast Iowa/northern Missouri where the instability is the best per latest NAM. Further to the east the winds get much better over Illinois, but the temps at H7 also increase quite a bit. I would also like to see the winds at the surface and 925mb backed a bit more. Of course if the northern low is a little stronger than currently forecast that could help keep surface winds backed longer. There's still several more model runs to go until we get to this event, so there's still time for tweaking of the wind fields, etc.

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The Sunday setup is definitely interesting. My concern is the best instability/weaker cap is west of the better low-level wind fields. Winds below 850mb are pretty crappy over southeast Iowa/northern Missouri where the instability is the best per latest NAM. Further to the east the winds get much better over Illinois, but the temps at H7 also increase quite a bit. I would also like to see the winds at the surface and 925mb backed a bit more. Of course if the northern low is a little stronger than currently forecast that could help keep surface winds backed longer. There's still several more model runs to go until we get to this event, so there's still time for tweaking of the wind fields, etc.

This setup kind of reminds me of the setup we had 2 weeks ago (I believe the SREF popped a 30 for tor ingredients that day) where it was southern IA/northern MO under the gun and where the best instability was but the low-level flow was veered to crap with southeasterly flow in IL but lesser instability.

I would like to see a stronger and slower sfc low with a warm front around I-80. But then we still have the capping issues. The 0z GFS has decent instability over northern IL with southerly sfc winds but capping concerns.

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Why am I starting to get the feeling this is going to be a wasted potential event :/

Because it largely will be.

There is no significant lifting mechanism progged to help break the cap along the warm front Sunday. By Monday, I have a feeling the front will be flying east and I just don't see enough of a cap breakage ahead of the front to really allow for prefrontal supercellular convection. In order for me to buy anything, timing will have to slow significantly and the low will have to be weaker than progged. I just don't see it.

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This setup kind of reminds me of the setup we had 2 weeks ago (I believe the SREF popped a 30 for tor ingredients that day) where it was southern IA/northern MO under the gun and where the best instability was but the low-level flow was veered to crap with southeasterly flow in IL but lesser instability.

I would like to see a stronger and slower sfc low with a warm front around I-80. But then we still have the capping issues. The 0z GFS has decent instability over northern IL with southerly sfc winds but capping concerns.

Yeah I'm hoping as we get closer the higher res models keep the northern surface low a bit stronger, and hence a more backed surface flow. I just hope the stronger winds between 925mb and 700mb aren't as far east as what's shown on the NAM. Backed surface winds won't do much good with such weak winds in that range IMO.

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Because it largely will be.

There is no significant lifting mechanism progged to help break the cap along the warm front Sunday. By Monday, I have a feeling the front will be flying east and I just don't see enough of a cap breakage ahead of the front to really allow for prefrontal supercellular convection. In order for me to buy anything, timing will have to slow significantly and the low will have to be weaker than progged. I just don't see it.

Hell I am hoping it speeds up so Sunday Evening is better. At this point it looks like this thing maximizes its potential at night which is a significant limiting factor.

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Because it largely will be.

There is no significant lifting mechanism progged to help break the cap along the warm front Sunday. By Monday, I have a feeling the front will be flying east and I just don't see enough of a cap breakage ahead of the front to really allow for prefrontal supercellular convection. In order for me to buy anything, timing will have to slow significantly and the low will have to be weaker than progged. I just don't see it.

Oh, you know it's not going to be anything horrendous when Tony plays it low-key. :devilsmiley:

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I didn't say otherwise... and this is what I believe is going to happen. You said to never bet against the Euro.... and if that were true just two days ago, we'd be looking at a bowling ball Monday. Period. End of discussion. Don't make me go grab the progs to prove my point. The Euro can be wrong just like anything else can... and outside of 84 hours... it has struggled like anything else since at least December.

My bad... you are correct for sure and I misunderstood your original response. I meant to say "dont bet against to Euro when it shows a consistent solution". (Even when the GFS shows a consistent, but alternative, solution.)

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Moving on, anyone see the GFS progs for 4/8-9? Consistency is building*, and for once the GFS doesn't even show a thermonuclear cap! (A bit curious as to why not though.)

*Even Dr. No-No, which hasn't been consistent with this system, is trending towards a more interesting soln.

I have tentatively noticed it but I like to take things one system at a time, and until the Sunday/Monday thing passes, I take everything beyond it for what its worth.

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Moving on, anyone see the GFS progs for 4/8-9? Consistency is building*, and for once the GFS doesn't even show a thermonuclear cap! (A bit curious as to why not though.)

*Even Dr. No-No, which hasn't been consistent with this system, is trending towards a more interesting soln.

Pretty hard to ignore. If it wasn't 2011, I'd be jumping out of my skin. As it is, I'm calmly waiting for another bait and switch to a stall-trough-along-west-coast-then-shear-out solution. :popcorn:

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