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nsrobins

Multiday severe risk Midwest to E Conus July 13th-15th

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An unseasonably moist and unstable set-up looks likely to develop from IA east and south through Monday - Wednesday next week. All severe threats including significant tornados are likely.

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Some detail now on spatial distribution of risk for Monday with SPC pinning a 10% hatched over most of IL. The instability can't be doubted (some output has in excess of 5K worth max cape by 20Z), but there is no definitive tor level shear that I can see (edit: always check before posting. There is infact a decent 500mb flow over backed surface central IL) but I think what's driving the risk is finer mesoscale level (OFBs) so if I was chasing I'd be watching the MCS and the associated outflow. Still the Potential exists tonight for a few strong tornados

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HRRR has shifted the greatest sig supercell risk north towards the Chicago metro area from 21Z, plonking a discrete cell right over Chicago itself.

This is being closely monitored I would think, and should parameters consolidate in the next few runs I wouldn't be surprised to see a conditional HIGH risk being introduced given the population density at threat.

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HRRR has shifted the greatest sig supercell risk north towards the Chicago metro area from 21Z, plonking a discrete cell right over Chicago itself.

This is being closely monitored I would think, and should parameters consolidate in the next few runs I wouldn't be surprised to see a conditional HIGH risk being introduced given the population density at threat.

Would that be the first of the year if it did go to HIGH 

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Would that be the first of the year if it did go to HIGH 

According to SPC archive there have been no HIGH risk days so far 2015. The last HIGH risk was 3rd June 2014. There have also been no PDS issued in 2015 as far as I know. Am happy to be corrected.

Anyway, hasn't happened yet but don't be surprised in an upgrade is considered for this evening.

 

The next SPC output is due 13.00Z. Given another HRRR run showing cells on the very N boundary of the current MDT risk, an adjustment north in area is likely to include the whole Chicago metro region.

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Well what do I know?! SPC update has shifted the risk area SOUTH and Chicago Metro now only Slight zone.

These guys know what they're doing for sure but they must be totally dismissing the HRRR and NAM4K ppn output.

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I have no reputation for identifying storm initiation but am hoping to acquire one through this escapade (sic. Red Dwarf).

 

Storm mode sig supercells initiating on OFB in wake of earlier MCS in a line Joliet, IL to Lafayette, IN from 20.30Z this afternoon.

Potential for long-track tornado it the cell roots to the boundary.

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I have no reputation for identifying storm initiation but am hoping to acquire one through this escapade (sic. Red Dwarf).

 

Storm mode sig supercells initiating on OFB in wake of earlier MCS in a line Joliet, IL to Lafayette, IN from 20.30Z this afternoon.

Potential for long-track tornado it the cell roots to the boundary.

is that 20.30 US time mate

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is that 20.30 US time mate

That will be 21.30 BST. All charts and official data is normally quoted in universal or Zulu time (GMT).

I see skies have cleared nicely now in the target zone and heating is taking place. Given such a rich unstable environment initiation will occur in about three hours, although some cells have already developed in N MO and these will drift east slowly.

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Reed timmer just tweeted Cape values will be 6000 + ..Tornado risk later

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Cape values are already 4.5-5K in the region.

The gun is primed and the trigger is about to be released - insane instability will be unleashed very shortly as the last of the CIN erodes.
I like the fact SPC have now adjusted back North as per my previous thoughts. Surface obs show the OFB fairly nicely - more of a front actually looking at dps from SW to NE across IL. Any cell riding this boundary ESEwards will tap into locally enhanced helicity that threatens a strong tornado. Later this evening the wind threat takes over and a damaging derecho could well develop.

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Quality HD stream from Brett Adair just now. Cell looks very likely.

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Quality HD stream from Brett Adair just now. Cell looks very likely.

 

Yep,just watching that one neil,he needs to do a right turn out of that hail though.

 

edit:must of listened to me.

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Kansas twisters on a photogenic cell,looks nice

 

post-16960-0-87133000-1436833308_thumb.p

 

it was T warned,lets see how she goes.

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Confirmed reports of tornado touching down 12 miles NW of Lafayette

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Not much to add in postscript.

It has been the theme of this season - set-ups that look classic for tornadic supercells end up delivering a mush-fest of wind and hail. The instability was not in question here, but the directional shear was marginal and cells needed to tap into a boundary to utilise any additional shear was on offer and it didn't happen.
At one point a chaser drove past a field of wind turbines and said 'they should turn those on to get these things spinning'.

Still, another notch in the 'tornadic totum pole' of experience lol.

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Just watching chasers on that SE Manhattan cell and it is kicking out some pretty lively lightning

 

post-16960-0-62321200-1437006157_thumb.p

 

what a beast

 

post-16960-0-41116600-1437006407_thumb.p

 

 

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