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andyhb

May 7th-9th Severe Weather Episodes

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Looking like another severe event of some sort is on the horizon here (magnitude obviously TBA) with SPC highlighting Day 5 in the High Plains. Looking like some sort of upsloping event in CO/W KS/W NE is possible on Saturday given the slow progression of an upper low out of the SW and moderate southwesterly flow aloft. Main question will likely be moisture return given the initial scouring by E Coast troughing Day 3-4. As I mentioned in the other thread though, we are getting to the time of year where moisture advection tends to occur quite quickly once trajectories are established.

 

This brings us to Sunday and Monday, where flow at all levels (degree of VBV/etc. to be determined of course) strengthens across the Southern Plains as the systems ejects slowly eastward and a couple of embedded shortwaves rotate around its periphery. Moisture should become more robust by this time and should offer the possibility of a reasonably stout, perhaps multi-day threat should things fall into place (lapse rates look excellent once again). In any case, it's good to see a period that was once looking pretty ugly show some signs of life as we approach mid May.

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Moisture return really isn't projected to be that bad on Saturday and looks decent for High Plains standards early in May. The Euro, for a second run in a row, shows mid-50s dew-points across the panhandles and western Kansas with dews into the lower 60s all the way into southwestern Nebraska. Details are still TBD, but I will take a 55 Td in that area anytime in the spring.

 

As mentioned, the pattern looks fairly favorable and the models have been generally consistent with this time-frame. Given a focus on Texas/Oklahoma/Kansas for a string of days in May, this setup certainly has my attention. I wouldn't be surprised if additional risk outlines are added in the next day 4-8 convective outlook.

 

I'm planning on Saturday being the first in a string of chasing opportunities, which will be very welcomed after a slow week.

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Really liking Sunday/Monday (depending on timing) and possibly even both... Likely will see southwesterly flow aloft at H5, atop a moist and moderately unstable environment. VBV may be an issue, but not going to be focused on specifics like that yet. LLVL wind fields look like they'll be good for the most part. Lots will change.

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Moisture will be a tough sell Saturday. It doesn't take a lot out west, but I expect LCLs to be a major issue. CO will probably still manage to get it done somewhere, somehow, though. :lol:

Sunday sure looks like the main show on the Plains, whatever that may consist of. The large-scale similarities to last Tuesday, along with virtually all forecast soundings, suggest it's not a matter of whether we get VBV, but how bad it is. Ironically, it wouldn't take much at all to top Tuesday's event in terms of legit supercell tornadoes, though - I can see Sunday pulling that off pretty easily, if a few factors break the right way. As flawed as Tuesday looked beforehand, I'm surprised it failed so spectacularly and there weren't at least 1-2 decent tornadoes before linear mode took over.

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Moisture will be a tough sell Saturday. It doesn't take a lot out west, but I expect LCLs to be a major issue. CO will probably still manage to get it done somewhere, somehow, though. :lol:

Sunday sure looks like the main show on the Plains, whatever that may consist of. The large-scale similarities to last Tuesday, along with virtually all forecast soundings, suggest it's not a matter of whether we get VBV, but how bad it is. Ironically, it wouldn't take much at all to top Tuesday's event in terms of legit supercell tornadoes, though - I can see Sunday pulling that off pretty easily, if a few factors break the right way. As flawed as Tuesday looked beforehand, I'm surprised it failed so spectacularly and there weren't at least 1-2 decent tornadoes before linear mode took over.

 

 

Which part of the plains are we looking at?

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Which part of the plains are we looking at?

 

Way too early to say definitively, but current guidance suggests the area centered on C KS into C/W OK for Sunday.

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Moisture will be a tough sell Saturday. It doesn't take a lot out west, but I expect LCLs to be a major issue. CO will probably still manage to get it done somewhere, somehow, though. :lol:

Sunday sure looks like the main show on the Plains, whatever that may consist of. The large-scale similarities to last Tuesday, along with virtually all forecast soundings, suggest it's not a matter of whether we get VBV, but how bad it is. Ironically, it wouldn't take much at all to top Tuesday's event in terms of legit supercell tornadoes, though - I can see Sunday pulling that off pretty easily, if a few factors break the right way. As flawed as Tuesday looked beforehand, I'm surprised it failed so spectacularly and there weren't at least 1-2 decent tornadoes before linear mode took over.

 

Funny enough the best tornadoes of Tuesday seemed to happen between 8:30 PM and 10 PM in Grayson County (N TX) as a supercell interacted with the approaching squall line from the west. While only rated EF0/EF1 visually speaking they looked impressive - especially for a QLCS situation. Can't say I was too sorry that Tuesday busted in Central Oklahoma but of-course three days later we had issues anyway. Don't know if you still live at The Links/Greens in Norman but if so we live in the same complex. 

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Apparently it's too much to ask this year to get a setup with >200 m2/s2 0-1 km SRH E of the dryline...

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Apparently it's too much to ask this year to get a setup with >200 m2/s2 0-1 km SRH E of the dryline...

Nothing is set in stone yet... (-; Still early May, but it is irritating. Last ten days (somewhere in that time frame) of May looks active at least, if this doesn't produce much.

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Nothing is set in stone yet... (-; Still early May, but it is irritating. Last ten days (somewhere in that time frame) of May looks active at least, if this doesn't produce much.

Last 10 days of may will change 20 times between now and then :\

I'm out of town starting Sunday, back thursday, then out of town all the following week...my chase season is likely over :(

Maybe we'll get something in early June.

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Funny enough the best tornadoes of Tuesday seemed to happen between 8:30 PM and 10 PM in Grayson County (N TX) as a supercell interacted with the approaching squall line from the west. While only rated EF0/EF1 visually speaking they looked impressive - especially for a QLCS situation. Can't say I was too sorry that Tuesday busted in Central Oklahoma but of-course three days later we had issues anyway. Don't know if you still live at The Links/Greens in Norman but if so we live in the same complex. 

 

That's true - I shouldn't discount the warm sector activity to the SE, even though it was never a focus for most of us leading up to the event. Same thing goes for Friday. Also, funny you mention The Links... been here forever, but I'm finally leaving in a few weeks, actually. Enjoy Wally World for me. ;)

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Yea no kidding. The 0Z GFS doesn't change that. 

 

Weakening leftovers basically.

 

Story of the season so far.

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For Sunday, the 04/00z ECMWF has: a sharp dryline with decent (low-mid 60s) low-level moisture, a 996 mb sfc low over NW KS, strongly backed sfc winds, southerly H85 LLJ at 30-40 kt, minimal early-day convection, and a 110 kt jet streak at H2 nosing right into NW OK at 00z. Hard to ignore, even though the large-scale pattern is wonky and VBV is almost inevitable to some degree. Much hype and disappointment ahead do I sense, yes...

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SPC added a pretty large D5 for Sunday across the central and southern plains... Looks like it could be an I-35 special, still lots to figure out. But the 12Z GFS looked pretty sweet, maybe a bit too fast of timing for the main S/W, would probably see relatively early initiation. But besides that, by 00Z we see some relatively impressive LLVL wind fields,

much better than Tuesday at least, with~200-250+ m2/s2 0-1KM SRH, and a ~40kt LLJ... Critical angle to the dryline is basically perpendicular (90-degrees) on several soundings from S KS to S OK... Not that much VBV on the soundings this run... But that potential problem will have to be addressed later on. Regardless, a 50-70kt H5 jet core overspreading a moist and unstable environment characterized by mid-60s DPs, and 2000+J/KG MUCAPE by late afternoon/early evening, will result in numerous severe thunderstorms capable of all severe hazards.

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DDC mentioned in their AFD this morning the dryline could be deeper in their area given the evapotransportation from recent rains. FWIW, DDC just had their wettest April on record.

 

SPC added a pretty large D5 for Sunday across the central and southern plains... Looks like it could be an I-35 special, still lots to figure out. But the 12Z GFS looked pretty sweet, maybe a bit too fast of timing for the main S/W, would probably see relatively early initiation. But besides that, by 00Z we see some relatively impressive LLVL wind fields,
much better than Tuesday at least, with~200-250+ m2/s2 0-1KM SRH, and a ~40kt LLJ... Critical angle to the dryline is basically perpendicular (90-degrees) on several soundings from S KS to S OK... Not that much VBV on the soundings this run... But that potential problem will have to be addressed later on. Regardless, a 50-70kt H5 jet core overspreading a moist and unstable environment characterized by mid-60s DPs, and 2000+J/KG MUCAPE by late afternoon/early evening, will result in numerous severe thunderstorms capable of all severe hazards.

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Initial look at the 00z MPAS for Saturday in NW KS/CO near the triple point was pretty stout, and yeah the 12z GFS was quite an eyebrow raiser for Sunday. Definitely liking the strength of the ejecting 500 mb max (deep layer shear should be in relative abundance) and the level of convergence along the dryline, although I don't think the 12z Euro was quite as favorable as the run last night.

 

I almost like the fact that this thing looks to be slightly positive tilted since it will run less of a chance of VBV in the mid/upper levels in a shorter wavelength regime.

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Still eyeing Saturday, which now has the potential to feature isolated severe along a frontal boundary from north-central/northeastern Kansas into Missouri.

 

The 12z Euro muscles out 1500-2000 J/kg SBCAPE over portions of far eastern Colorado and western Kansas by Saturday afternoon. For the threat into the lower Missouri Valley, the Euro shows low to mid-60s dews, so moisture shouldn't be much of an issue there. 

 

Beyond that, the Euro continues to look favorable for Sunday along and west of I-35. For Monday, the wind fields get dislodged east of the better instability and the setup could be over more unfavorable terrain, so at least at this point, the Monday setup is looking more messy.

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ICT/OUN/DDC all talking about a significant severe event being possibles not Sunday in their latest AFDs. ICT seems to think moisture may be an issue on Sunday, but not sure that I agree with that really at all given the output by the GFS/Euro.

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ICT/OUN/DDC all talking about a significant severe event being possibles not Sunday in their latest AFDs. ICT seems to think moisture may be an issue on Sunday, but not sure that I agree with that really at all given the output by the GFS/Euro.

 

 

 

What are they saying?  

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What are they saying?

really just that a higher-end severe event is looking possible on Sunday afternoon and evening, with tornadoes being a possibility. But that a lot of details still have to be worked out, so it is too early to determine specifics, just that it is something to watch given the dynamics in place.

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:axe:

 

Further context please, like where this was taken (I'm assuming it was up on the warm front/triple point on Saturday evening in CO, NE or KS).

 

Really beginning to like that setup there. I'm almost certain the GFS is capping things off too quickly and mid-upper 50s dews can really do some work in that area when combined with such strongly backed flow in the low levels.

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Def a warm front sounding.

Storm motions across the boundary are concernin .

 

Euro has a 35-40 kt SSE LLJ in the TX Panhandle at 00z Sunday, something the GFS does not have. SW/WSW flow aloft on top of that is a heck of a lot of veering in the lowest 6 km...but moisture looks like junk that far south.

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That lat/lon is near Oberlin KS, near the triple point, Saturday afternoon. It's pretty close to the highest EHI point on the NAM at that point in time. It is starting to look like this area will have a higher tornado potential Saturday. And you know, some sort of severe weather will find a way to happen in Colorado.

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Not that it's overly meaningful, but #1 and #4 analogs for Sunday are pretty good: 4/14/12 and 5/3/99. I don't expect that to happen, but it's interesting.

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A little mystified by the SPC saying sups on Sunday will be high based. While LLVL moisture quality may not be superb like it was for Tuesday, LCLs still are going to be below 1000m for the most part...

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A little mystified by the SPC saying sups on Sunday will be high based. While LLVL moisture quality may not be superb like it was for Tuesday, LCLs still are going to be below 1000m for the most part...

 

I was wondering the same thing while reading that.

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