2018 Short to Medium Range Severe Thread

[OceanStWx]

14 hours ago, hlcater said:

Speaking of luck on local chases, I had been keeping a wary eye on today since yesterday evening. A boundary would provide sufficient SRH and coupled with low LCLs and quite a bit of 0-3km CAPE, it seemed like an environment capable of squeezing out a few tornadoes, especially if a storm was able to latch on to the boundary. And that is exactly what happened. All CAMs fired 1 or 2 discrete supercells on the boundary, however by 3:30 nothing had taken off and I was getting ready to write it off and go do something else. Just as I said this, a nice updraft developed and persisted, so I bit, and headed out west of Shellsburg. I arrived to a very healthy looking base and had excellent positioning for what was to follow. 

About 15 minutes later, the base started to really wrap up and it became evident that a tornado was imminent. So I called the NWS as the storm was not warned, and ended up staying on the phone with them through the duration of the first tornado relaying them information, as such I have no video(as I use my phone primarily), but I'd like to think feeding the NWS information was more helpful than video. Here's a picture of the multi vortex Shellsburg tornado. It lasted 5-7min.

It's not my office anymore, but we really do appreciate it. It's not everyone's first instinct to get the word to the people issuing warnings, and sometimes only a couple minutes lead time are necessary to save a life. 

I'm just as guilty of this as anyone. The first (only ) tornado I've seen (my avatar) I had been offered and accepted a job at DVN a month earlier, and I was so excited about the tornado that I forgot to call BOX for 45 minutes.

[cyclone77]

Looks like DVN confirmed an EF-1 on the west side of Cedar Rapids.  IIRC that storm wasn't tornado or severe warned.

[Hoosier]

Weak tornado confirmed in Chicago

 

Public Information Statement
National Weather Service Chicago IL
728 PM CDT Tue Sep 4 2018 /828 PM EDT Tue Sep 4 2018/

...NWS DAMAGE SURVEY FOR THE 09/03/18 BRIEF TORNADO ON WEST SIDE
OF CHICAGO...

.OVERVIEW...National Weather Service surveyed an area of damage
near the paths of two brief radar detected circulations from the
afternoon of 09/03/18. One circulation moved from Elmwood Park
into the Galewood neighborhood of the far west side of Chicago. No
significant damage was found in association with this
circulation, only some minor tree damage, likely the result of
winds less than 50 mph. The damage survey of the second
circulation revealed that an EF-0 tornado touched down on the west
side of Chicago, starting in the Austin neighborhood and tracking
across portions of the West Garfield Park neighborhood.

.Austin/Garfield Park Tornado...

Rating:                 EF-0
Estimated peak wind:    75 mph
Path length /Statute/:  1.7 miles
Path width /Maximum/:   75 yards
Fatalities:             0
Injuries:               0

Start date:             Sep 03 2018
Start time:             2:14 PM CDT
Start location:         3 NE Berwyn / Cook County / IL
Start Lat/Lon:          41.8693 / -87.7457

End date:               Sep 03 2018
End time:               2:18 PM CDT
End location:           5 ENE Berwyn / Cook County / IL
End Lat/Lon:            41.8770 / -87.7141

SURVEY SUMMARY: The majority of the damage was tree damage, with
the first damage noted on Arthington St just west of Cicero Ave. A
continuous path of mostly minor tree damage extended east-
northeast from this location crossing Interstate 290 near Pulaski
with the final damage noted in the park (Garfield Park) between
5th Ave and Jackson Blvd near Central Park Ave.

EF Scale: The Enhanced Fujita Scale Classifies Tornadoes into the
following categories.

EF0...Weak......65 to 85 mph
EF1...Weak......86 to 110 mph
EF2...Strong....111 to 135 mph
EF3...Strong....136 to 165 mph
EF4...Violent...166 To 200 mph
EF5...Violent...>200 mph

NOTE:
The information in this statement is PRELIMINARY and subject to
change pending final review of the event and publication in NWS
Storm Data.

$$

- Izzi

[Jackstraw]

Being underneath this ridge has really sucked.  Nice light show off to the NW the past few nights to tease.  Amazing how far off the storms were.  Had a little one this afternoon that broke out for about 15 min directly overhead.  May be a sign that the mid level cap is becoming reachable in these parts.  Think Gordon remnants will be a little more east than modeled if this pesky inversion over us can be overcome.

[hawkeye_wx]

3 hours ago, cyclone77 said:

Looks like DVN confirmed an EF-1 on the west side of Cedar Rapids.  IIRC that storm wasn't tornado or severe warned.

This was pretty darn close to my house, 0.7 miles to my nw.  I guess it's a good thing this cell veered north a bit as it approached.

[hlcater]

2 hours ago, hawkeye_wx said:

This was pretty darn close to my house, 0.7 miles to my nw.  I guess it's a good thing this cell veered north a bit as it approached.

I thought it was interesting that cell was still surface based. I thought for sure it would go elevated, guess not. 

[Hoosier]

Tornado warning Southeast Iowa.

[cyclone77]

22 hours ago, hawkeye_wx said:

This was pretty darn close to my house, 0.7 miles to my nw.  I guess it's a good thing this cell veered north a bit as it approached.

Damn that's a little too close for comfort!  Especially with no warning.

[luckyweather]

Damn that's a little too close for comfort!  Especially with no warning.

I was leaving the movie theater Monday in Machesney Park, IL and saw a guy on the side of the road with his flashers on and a skywarn sticker on the back. From inside the theater it sounded like just more of the same occasional tstorms of the past week. Was shocked to get home and find out the skywarn spotter was watching the brief tornado over Rock Cut state park, just outside the theater. Never warned and damage survey showed no damage, but I saw a spotter video and it was for sure a brief tornado.

[Hoosier]

5 hours ago, luckyweather said:

 

I was leaving the movie theater Monday in Machesney Park, IL and saw a guy on the side of the road with his flashers on and a skywarn sticker on the back. From inside the theater it sounded like just more of the same occasional tstorms of the past week. Was shocked to get home and find out the skywarn spotter was watching the brief tornado over Rock Cut state park, just outside the theater. Never warned and damage survey showed no damage, but I saw a spotter video and it was for sure a brief tornado.

 

Interesting that LOT didn't confirm it (I assume they saw the video)... often the offices will go EF0 if there's video but no damage or sometimes go EFU.

[IWXwx]

On 9/6/2018 at 12:52 PM, Hoosier said:

Interesting that LOT didn't confirm it (I assume they saw the video)... often the offices will go EF0 if there's video but no damage or sometimes go EFU.

I don't remember ever seeing an EFU.

[Hoosier]

8 minutes ago, IWXwx said:

I don't remember ever seeing an EFU.

I think it might depend on the office.  One of the Ohio offices did it for a tornado a couple years ago.

[hlcater]

17 minutes ago, IWXwx said:

I don't remember ever seeing an EFU.

Those are super common in the high plains. Where there's clearly very strong tornadoes that hit very little or nothing at all. If there's video of it or a visual confirmation, but no damage can be found, a lot of times they'll just go EFU.

[IWXwx]

1 hour ago, Hoosier said:

I think it might depend on the office.  One of the Ohio offices did it for a tornado a couple years ago.

 

1 hour ago, hlcater said:

Those are super common in the high plains. Where there's clearly very strong tornadoes that hit very little or nothing at all. If there's video of it or a visual confirmation, but no damage can be found, a lot of times they'll just go EFU.

It makes sense. NWS has to concur if video evidence is there, but with no damage off of which to make a wind speed estimation, an EFU is reasonable.

Rant warning-

The whole visual confirmation thing is a sensitive subject to me. A few years ago, we had a storm roll into Huntington in which IWX issued an SPS for small hail. The radar signature did show some weak, broad rotation. I wasn't expecting anything so I did not have a camera with me (flip phone only back then). As I set up to watch it roll through from the south side of the cell, a concentrated area of straight line winds appeared (based on debris and tree motion) with a vortex embedded within it. I had not ever witnessed that before even though I've seen a few tornadoes. I observed as insulation and sheet metal from a nearby warehouse roof was deposited around the top of a cell phone tower and could see it not being carried straight forward, but rotating as it was lifted from about 20-25' up to at least 90' when it hit the tower. Upon reporting it to NWS, my report was met with skepticism but they agreed to do a survey.

The WCM himself conducted the survey the next day and was accompanied by a hydrologist from their office and myself. Don't ask me why about the hydrologist, because I don't know. I am not a met and have had no formal training, however, while inspecting the damage path, I noticed a narrow area of what appeared to be convergence within a larger area of divergence which would coincide with what I witnessed. Most of the damage was tree damage although a multiple structures were also affected. The damage path varied from 50 to 200' wide. However, the WCM determined straight line wind damage even though I witnessed the rotation. He was the pro and I was not, so I didn't raise too big of a stink about it, but I let him know that I disagreed with his determination.  I'm not Joe Blow from the general public.

Disclaimer: The WCM and I continue to have a good working relationship which is very important in my profession.

I learned my lesson. My dash cam is always on, my phone is always by my side, as well as a Handycam in my vehicle.  Sorry for the rant, but that has stuck in my craw ever since and I had to let it out.

[Indystorm]

Sorry you had the disagreement between yourself and the WCM, Butch.  I can only imagine how many circulations/tornadoes might have been missed in prior years when no cams were available.

[snowlover2]

Looks like possible severe weather across the sub Thursday and Friday. Day 3 slight for IA/WI/extreme NW IL and parts of NW MI and day 4 15% outlined for IN/OH.

[Jackstraw]

SPC has slight Tues.  I'm ready to move forward into our mini TOR season in a few weeks.  Ultra long term fantasy land showing some signals for some fairly deep lows and a favorable storm track for the sub.  Think we're due for some decent late Oct. Nov. fast trackers.

[Indystorm]

Wouldn't it be ironic if the fall season gets fairly active given our lackluster spring?  The strength of those tornadoes in Ottawa Canada this weekend really surprised me for that location and time of year.

[Eric In NW Ohio]

11 hours ago, Indystorm said:

Wouldn't it be ironic if the fall season gets fairly active given our lackluster spring?  The strength of those tornadoes in Ottawa Canada this weekend really surprised me for that location and time of year.

Seems like many violent storms have occured in the fall of the year here in NW Ohio. The Van Wert F-4 was a November 10th event. Several other wind events have occured in October/November as well.

Eric in NW Ohio

[Hoosier]

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1224 PM CDT Mon Sep 24 2018

   Valid 251200Z - 261200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE
   AND UPPER MISSISSIPPI VALLEY INTO THE GREAT LAKES AND OHIO VALLEY...

   ...SUMMARY...
   Severe thunderstorms are possible Tuesday afternoon into Tuesday
   night across parts of the middle Mississippi and Ohio Valleys into
   the Great Lakes region.

   ...Synopsis...

   A broad synoptic upper trough currently situated from the northern
   Rockies through northern High Plains is forecast to amplify as it
   continues east into the upper MS Valley and Great Lakes Tuesday and
   Tuesday night. This feature should be accompanied by modest
   cyclogenesis over the upper Great Lakes, and by mid afternoon a cold
   front will likely extend from the developing cyclone over WI
   southwest through IA into the TX Panhandle. This boundary will
   advance east and southeast reaching the lower Great Lakes and
   extending southwest through central TX by the end of this period.
   Ahead of the primary synoptic trough a shortwave trough now over the
   TN valley will reach the northeast States early Tuesday morning. A
   warm front will develop northward through the OH Valley and into the
   Great Lakes during the day. 

   ...Middle Mississippi Valley  into the Ohio Valley and Great
   Lakes...

   Initial low-level jet associated with a northeast-ejecting shortwave
   trough will advance through the Northeast States early Tuesday
   accompanied by widespread showers and a few thunderstorms. In wake
   of this feature, modest southwesterly low-level winds will persist
   in the OH Valley warm sector contributing to northward advection of
   richer low level moisture with dewpoints rising to the mid-upper 60s
   F Tuesday morning as far north as southern portion of the Great
   Lakes. Showers and a few thunderstorms will be possible within this
   weak warm advection regime during the day. While vertical shear
   through a deep layer will be sufficient for organized storms,
   uncertainty still exists regarding the evolution of the
   thermodynamic environment given expected widespread clouds.
   Nevertheless, the advection of richer low-level moisture and a some
   cloud breaks should contribute to at least 1000-1500 J/kg MLCAPE by
   mid afternoon, with greatest boundary layer destabilization likely
   across a portion of the middle MS Valley. Winds aloft will gradually
   strengthen from the west Tuesday afternoon with approach of the
   upper trough along with an increase in the southerly low-level jet
   by early evening. Potential for organized severe storms should
   gradually increase Tuesday as deep layer winds strengthen and the
   surface layer undergoes at least modest destabilization. A few
   supercells and bowing segments may develop in warm sector, and
   additional severe storms with more linear organization are expected
   farther west across the upper MS Valley along the cold front.
   Initial primary threat should be damaging wind and possibly some
   hail, but as the low-level jet strengthens by late afternoon or
   evening, the threat for a few tornadoes should also increase.
   Activity will spread east through the OH Valley and Great Lakes
   region during the evening and into the overnight. Given
   uncertainties related to evolution of the thermodynamic environment,
   will maintain general 15% probabilities this outlook, but an upgrade
   to higher probabilities will be considered in day 1 updates across a
   portion of this region.

   ...MAXIMUM RISK BY HAZARD...
   Tornado:   5%     - Slight
   Wind:     15%     - Slight
   Hail:     15%     - Slight

   ..Dial.. 09/24/2018

 

[Chinook]

If you look only at the NAM significant tornado parameter tomorrow, it would seem there's a respectable chance of tornadoes or severe wind in northern Indiana and northwest Ohio. Convection-allowing models are getting more consistent in showing convection occurring in Illinois near 00z. That may be the area of most severe weather.

[Hoosier]

Speed shear looks pretty good. Directional shear is not that great overall, but there's some, especially in the lowest km and especially out ahead of the cold front.  

[Jackstraw]

KIND sounding tomorrow evening

[Hoosier]

That would work.  And the lowest level on there looks a tad backed compared to the 12 km NAM.

[nwohweather]

A little concerned about the atmosphere getting worked over tomorrow, but this is a textbook NW Ohio fall tornado day shaping up if we can avoid too much precipitation 

[Stebo]

A couple things. 1. The wind shear is already in place in the lower levels. The moisture is plentiful and only getting better through the night. 2. The wind fields only get better from here on going into tomorrow especially notable is the strengthening of the LLJ through the day tomorrow. 3. The caveat to tomorrow will be insulation but if that is greater than expected the instability will go up quickly.

[Hoosier]

Yeah, definitely a bit concerned about a junky warm sector.   But that IND sounding above managed to have in excess of 2000 J/kg CAPE with just 74/72.

[Hoosier]

Not sure how many people are aware or how long this has been the case, but COD has the 00z, 06z, 12z, 18z runs of the HRRR to 36 hours.

[Hoosier]

5% tornado area in IN/nw OH/far southern MI

 

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1256 AM CDT Tue Sep 25 2018

   Valid 251200Z - 261200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE MIDDLE
   MISSISSIPPI VALLEY INTO THE OHIO VALLEY AND SOUTHERN GREAT LAKES...

   ...SUMMARY...
   Severe thunderstorms are possible this afternoon into tonight across
   parts of the middle Mississippi and Ohio Valleys into the southern
   Great Lakes region.

   ...Synopsis...
   A mid-level trough moving into the Black Hills this morning will
   amplify during the period as a 90kt 500mb speed max develops by
   early morning Wednesday over Lake Michigan.  The positive to neutral
   tilt of the mid-level trough suggests cyclogenesis over the western
   and central Great Lakes will remain modest compared to autumnal
   climatology.  A cold front will extend southwestward from the
   developing low over WI southeast KS and into the TX Panhandle. This
   boundary will advance east and southeast reaching the lower Great
   Lakes and extending southwest through central TX by the end of this
   period.  A weak disturbance over the central Appalachians will move
   into the Northeast during the day.  A warm frontal zone will develop
   northward through the OH Valley and into the Great Lakes during the
   day.

   ...Middle Mississippi Valley into the Ohio Valley and Great Lakes...

   A warm/moist conveyer is forecast over the OH Valley as southerly
   low-level flow is maintained during the day across IN/OH into
   southern Lower MI.  A moisture-rich airmass will gradually
   destabilize during the day but strong heating will likely be limited
   by extensive cloud cover and intermittent showers at least through
   the early afternoon.  Models show upper 60s to near 70 degrees F
   dewpoints across this broader region to the east of the cold front
   over the MS Valley.  MLCAPE is forecast to range from 750-2000 J/kg
   with a relatively deep moisture profile.  As the mid/upper-level
   disturbance approaches from the west, deep layer vertical shear will
   support organized storms.  The primary uncertainty this forecast is
   the magnitude of destabilization centered on the area of northern IN
   and the hodograph structure.  The latest NAM and some of the
   convection-allowing models show southerly surface winds and some
   enlargement to the low-level portion of the hodograph during the
   22-03Z period, whereas the GFS and ECMWF exhibit smaller hodographs.
   This would have a consequential effect on the potential for
   low-level mesocyclone development from discrete storms forecast by
   some of the convection-allowing models.  A conditional risk for a
   few tornadoes appears centered over northern IN and surrounding
   portions of states.  Later during the evening, thunderstorms are
   forecast to move through the southern Great Lakes states coincident
   with the front.  The risk for damaging winds may continue as storms
   move east during the overnight as a southwesterly LLJ strengthens
   over the OH Valley/lower Great Lakes.

   Farther west, thunderstorms will likely develop near the front
   during the afternoon with upscale development eventually expected
   across northern IL during the evening.  Damaging winds are the
   primary hazard with this activity.  A couple of storms may develop
   into western MO and southeast KS during the early evening.  An
   isolated hail/wind threat may accompany the stronger storms before
   this activity diminishes during the evening hours.

   ..Smith/Squitieri.. 09/25/2018

[hawkeye_wx]

The storms are already pretty frisky-looking out in central Iowa, despite no heating.  Even here in CR, we've been socked in with clouds all morning so our heating may be minimal.  There's more sun and heating in the Burlington to QC area.

Quote

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1024 AM CDT Tue Sep 25 2018

.UPDATE...
Issued at 1005 AM CDT Tue Sep 25 2018

Severe Potential: Looks as though elevated convection will begin
to overtake the warm sector and become rooted in the BL. This
should occur shortly before noon and likely just west of the CWA.
Overall convection speed will slow down and begin to move into our
area. This will give time for CAPE to build this afternoon across
the CWA. Synoptic models show that shear doesn't support
tornadogenesis, due to SW sfc winds. It appears that a sfc wave is
forming across SW IA. This wave will back winds, much like the
HRRR shows. I believe that we will have a tornado threat from any
mesovortex that develops. I also believe that shear will be
greater than what synoptic models forecast due to this low. As far
as severe parameters go, tend to favor CAM solutions related to
shear. Severe threat for winds to 70 mph, hail and tornadoes
remains for the area.