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Anti tornado

Feb 24-25th Severe Weather

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NAM much better representation of the low level wind fields as I noted yesterday. I would discount the GFS's highly veered low level flow, the Euro is closer to the NAM in this respect.

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Much more backed low level flow and better representation of the thermodynamics on the NAM

21z at DTW is pretty damn impressive to be honest.

CxETfug.png

 

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2 minutes ago, Hoosier said:

Ideally would like to see less than 180 at the surface given the flow aloft, but might have to make do.

Here's the Indianapolis area at 18z.

2017022118_NAM_072_39.84,-85.96_severe_ml.png

Look just east of there at 21z, it gets better.

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28 minutes ago, Stebo said:

Look just east of there at 21z, it gets better.

Compared to the GFS, the NAM looks like it has more of a pressure trough extending southward... even a secondary surface low that tries to get going in Michigan.  I'm sure that is helping the low level wind fields. 

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1 minute ago, Hoosier said:

Compared to the GFS, the NAM looks like it has more of a pressure trough extending southward... even a secondary surface low that tries to get going in Michigan.  I'm sure that is helping the low level wind fields. 

Yeah once you get to 00z it helps back the flow over us and into Ohio.

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GFS prefrontal zone is a bit more southerly this run, still having an issue with the low occluding back over Wisconsin though.  I will say this though, a nice dry line is showing up that surges northeast after 15z into the region.

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Well, whatever happens, it is impressive to see the NAM with CAPE over 1000 well into lower MI.  I'm sure that is near the upper end of what happens at this time of year.

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51 minutes ago, Hoosier said:

Well, whatever happens, it is impressive to see the NAM with CAPE over 1000 well into lower MI.  I'm sure that is near the upper end of what happens at this time of year.

Mind you this only off of soundings for DTX but yeah get ready to fall out of your chair when you see the chart below. cape.png

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Just now, cyclone77 said:

Wow, no 1000J/kg soundings in March?  That's crazy.  

Taking point locations probably limits it a bit (as it does with any sounding climatology) since I know the Dexter day had like 3000 J/kg SBCAPE in parts of Michigan, but regardless, climo wise we're talking some pretty unusual stuff, assuming it verifies. Notably, this is with a warm sector that isn't as moist as it could be thanks to that ULL in the SE.

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4 minutes ago, cyclone77 said:

Wow, no 1000J/kg soundings in March?  That's crazy.  

Yeah I was floored when I saw that, especially considering a couple of major events occurred in March, 3/20/76 and 3/27/91 also Dexter tornado back in 2012.That is the one issue with sounding climo, it misses in between 12/00z. Though one would have to imagine that an event would come along and have that much SBCAPE at 00z for either month.

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Just now, andyhb said:

Taking point locations probably limits it a bit (as it does with any sounding climatology) since I know the Dexter day had like 3000 J/kg SBCAPE in parts of Michigan, but regardless, climo wise we're talking some pretty unusual stuff, assuming it verifies. Notably, this is with a warm sector that isn't as moist as it could be thanks to that ULL in the SE.

Yeah imagine if we had dew points in the low 60s, good lord.

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2 minutes ago, Anti tornado said:

GDPS FWIW. lol 

Screen Shot 2017-02-21 at 7.02.10 PM.png

If we were to get moisture pooling along the boundaries, it wouldn't surprise me to see a few locations near 60 on dew points.

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3 hours ago, Hoosier said:

Ideally would like to see less than 180 at the surface given the flow aloft, but might have to make do.

Here's the Indianapolis area at 18z.

2017022118_NAM_072_39.84,-85.96_severe_ml.png

You guys can have the severe/tornadic stuff if you want.  While they are impressive to see, keep them away from here!

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I accidentally posted this on a different thread, but anyway, from what it seems, I believe there definitely will be severe weather on 2/24, but I don't think it would be as strong as some severe events we have seen so far this year.

sfcwind_mslp.conus.png

This definitely shows a storm system moving through however...

 

ehi01.conus.png

The energy helicity doesn't look to promising at the moment. Usually values above 1.5 pose a more dangerous situation but these values are mainly 1-1.5.

 

 

stp.conus.png

Lastly, the significant tornado parameter is decently low in the same area currently. I'd say looking at the situation right now, when the severe weather outlooks are released, there will be mainly a marginal risk and maybe a slight.

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4 minutes ago, Braden43 said:

I accidentally posted this on a different thread, but anyway, from what it seems, I believe there definitely will be severe weather on 2/24, but I don't think it would be as strong as some severe events we have seen so far this year.

sfcwind_mslp.conus.png

This definitely shows a storm system moving through however...

 

ehi01.conus.png

The energy helicity doesn't look to promising at the moment. Usually values above 1.5 pose a more dangerous situation but these values are mainly 1-1.5.

 

 

stp.conus.png

Lastly, the significant tornado parameter is decently low in the same area currently. I'd say looking at the situation right now, when the severe weather outlooks are released, there will be mainly a marginal risk and maybe a slight.

This area hasn't even seen any severe weather yet this year, and the main threat of this event is damaging wind, due to low cape, high shear situation

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Model consistency has to be taken into account at this point. It really truly looks like a strictly QLCS event. I wouldn't be surprised at a few spin ups....but classic supercells look unlikely at this point. 

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4 hours ago, WestMichigan said:

You guys can have the severe/tornadic stuff if you want.  While they are impressive to see, keep them away from here!

All this hoopla over a line of showers and 10 minutes of lightning. Storms this time of year are usually a single line that blows though in 20 minutes.

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Although I do see a threat for locally damaging winds and brief QLCS/embedded tornadoes, I don't see Friday as any significant severe event. The analogs are lackluster and very few of them show any severe reports north of the Ohio River. 

It's really too early in the season for much of a warm front threat with this type of setup and the signal for any prefrontal discrete storms is poor, at best. I suppose given the shear you could have some line segments with a strong/marginally severe wind threat, if storms do form ahead of the cold front. 

Analog guidance WRT 1+ severe report:

image.png

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Welp, didn't expect an enhanced risk this early, though their discussion hits everything very thoroughly.

 Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CST Wed Feb 22 2017

   Valid 241200Z - 251200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL AND
   NORTHERN INDIANA INTO NORTHWESTERN OHIO AND FAR SOUTHERN LOWER
   MICHIGAN...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   SOUTHERN LOWER MICHIGAN AND MUCH OF THE OHIO VALLEY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   One or more bands of strong to severe thunderstorms are forecast
   across the southern Great Lakes and Ohio Valley on Friday and Friday
   night.

   ...Synopsis...
   A mid-level trough/low is forecast to move from the middle MO Valley
   eastward to the western Great Lakes and OH Valley and assume a
   neutral to slightly negative tilt.  As this occurs, a belt of strong
   and cyclonically curved 500-mb flow is forecast to intensify in
   excess of 100-kt over the OH Valley late Friday night.  A surface
   low near the MO/IA border will develop northeastward into northern
   Lower Michigan as a warm front to its east advances northward.  A
   cold front near the MS River around midday Friday will sweep
   eastward across the OH and TN Valleys by daybreak Saturday.  

   ...southern Great Lakes and Ohio Valley...
   Low-level moisture is forecast to slowly increase on strong
   southerly flow with boundary-layer dewpoints forecast to range 52-58
   degrees F.  Although cloud cover will retard strong surface heating,
   cooling mid-level temperatures to around -19 degrees C will
   contribute to weak buoyancy (ranging from 250-1000 J/kg MUCAPE)
   within the northward expanding warm sector during the day.  As
   strong forcing for ascent (DCVA) approaches and overspreads the
   western parts of the area, a band of thunderstorms will likely
   develop and intensify.  Strong effective shear around 50 kt will act
   to organize updrafts and strengthening 700-mb flow to the 55-60 kt
   range will contribute to cold pool's organization and upscale
   growth. Downward momentum transport via damaging winds are the
   predominant severe risk.  However, some forecast soundings show
   relatively moist low levels with strong 0-1 km shear in excess of
   25-30 kt.  A tornado risk may develop with the maturing squall line
   and/or pre-frontal supercell(s) that eventually merges with the
   line.  A gradual weakening in buoyancy by the early to mid evening
   into the overnight will likely lead to a lessening in the
   damaging-wind risk as storms rapidly move east and northeastward
   after dark.

   ...TN and southern Appalachians...
   Storm development over this region will likely be inhibited by an 
   initially capped warm sector until stronger 500-mb height falls
   arrive towards evening.  Model guidance suggests a squall line will
   zipper southward into parts of TN as shear profiles strengthen. 
   Damaging winds will be the primary threat.

 

9gDkZ1E.gif

 

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14 minutes ago, Stebo said:

Welp, didn't expect an enhanced risk this early, though their discussion hits everything very thoroughly.

 Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CST Wed Feb 22 2017

   Valid 241200Z - 251200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL AND
   NORTHERN INDIANA INTO NORTHWESTERN OHIO AND FAR SOUTHERN LOWER
   MICHIGAN...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   SOUTHERN LOWER MICHIGAN AND MUCH OF THE OHIO VALLEY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   One or more bands of strong to severe thunderstorms are forecast
   across the southern Great Lakes and Ohio Valley on Friday and Friday
   night.

   ...Synopsis...
   A mid-level trough/low is forecast to move from the middle MO Valley
   eastward to the western Great Lakes and OH Valley and assume a
   neutral to slightly negative tilt.  As this occurs, a belt of strong
   and cyclonically curved 500-mb flow is forecast to intensify in
   excess of 100-kt over the OH Valley late Friday night.  A surface
   low near the MO/IA border will develop northeastward into northern
   Lower Michigan as a warm front to its east advances northward.  A
   cold front near the MS River around midday Friday will sweep
   eastward across the OH and TN Valleys by daybreak Saturday.  

   ...southern Great Lakes and Ohio Valley...
   Low-level moisture is forecast to slowly increase on strong
   southerly flow with boundary-layer dewpoints forecast to range 52-58
   degrees F.  Although cloud cover will retard strong surface heating,
   cooling mid-level temperatures to around -19 degrees C will
   contribute to weak buoyancy (ranging from 250-1000 J/kg MUCAPE)
   within the northward expanding warm sector during the day.  As
   strong forcing for ascent (DCVA) approaches and overspreads the
   western parts of the area, a band of thunderstorms will likely
   develop and intensify.  Strong effective shear around 50 kt will act
   to organize updrafts and strengthening 700-mb flow to the 55-60 kt
   range will contribute to cold pool's organization and upscale
   growth. Downward momentum transport via damaging winds are the
   predominant severe risk.  However, some forecast soundings show
   relatively moist low levels with strong 0-1 km shear in excess of
   25-30 kt.  A tornado risk may develop with the maturing squall line
   and/or pre-frontal supercell(s) that eventually merges with the
   line.  A gradual weakening in buoyancy by the early to mid evening
   into the overnight will likely lead to a lessening in the
   damaging-wind risk as storms rapidly move east and northeastward
   after dark.

   ...TN and southern Appalachians...
   Storm development over this region will likely be inhibited by an 
   initially capped warm sector until stronger 500-mb height falls
   arrive towards evening.  Model guidance suggests a squall line will
   zipper southward into parts of TN as shear profiles strengthen. 
   Damaging winds will be the primary threat.

 

9gDkZ1E.gif

 

Did not expect ENH this early either, but I'd have to think that lack of extensive warm sector convection on the preceding day is playing a role.  There are potential failures but pretty high confidence in the setup not getting screwed up by that.

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By looking at the soundings for Northwest Ohio, starting to think that a hail risk could be possible as well for Friday. This would be especially true with initial development.

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NAM 4 KM sounding in southern indiana.... 

 

NAM 4 KM is likely out in lala land but for **** and giggles it has a few pre-frontal supercells and bowing line segments....

nam4km_2017022212_060_38.8--86.71.png

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