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August 10 Severe Weather


Chicago Storm
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Watch coming for SW MI/IN.

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 Mesoscale Discussion 1456
   NWS Storm Prediction Center Norman OK
   0228 PM CDT Mon Aug 10 2020

   Areas affected...Portions of southern Lower MI into northern/central
   IN and far northwestern OH

   Concerning...Severe potential...Severe Thunderstorm Watch likely 

   Valid 101928Z - 102100Z

   Probability of Watch Issuance...95 percent

   SUMMARY...A substantial severe wind threat will likely increase this
   afternoon across parts of southern Lower Michigan and into
   northern/central Indiana with a line of storms moving quickly
   eastward. A Severe Thunderstorm Watch will be needed.

   DISCUSSION...A bow echo will continue moving rapidly eastward across
   northern IL and far southern WI this afternoon while producing
   widespread damaging winds of 70-100 mph. The airmass across southern
   Lower MI and northern/central IN continues to destabilize this
   afternoon, with surface temperatures having warmed into the mid to
   upper 80s, and surface dewpoints in the low to mid 70s. Steeper
   mid-level lapse rates observed on the 18Z ILX sounding have likely
   spread over at least the western portions of southwestern MI and
   western IN. Resultant MLCAPE of 2000-3500 J/kg and around 25-30 kt
   of effective bulk shear will likely support the maintenance of the
   severe bow echo as it moved eastward across these areas this
   afternoon and early evening. Severe wind gusts, some 75+ mph, will
   likely produce numerous to widespread damaging winds, and a tornado
   or two cannot be ruled out with circulations embedded within the
   line. This substantial severe wind risk is expected to increase
   within the next couple of hours, and a Severe Thunderstorm Watch
   will be issued to address this threat.

   ..Gleason/Grams.. 08/10/2020

 

mcd1456.gif

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Feels like a WWA during a Blizzard, but might get a watch here :lol:

 

mcd1457.gif.7cddb498ab86aa5d28e6fafc9b23a284.gif

 

Quote

Mesoscale Discussion 1457
   NWS Storm Prediction Center Norman OK
   0238 PM CDT Mon Aug 10 2020

   Areas affected...Much of Missouri...far Eastern Kansas...and
   Southern Illinois

   Concerning...Severe potential...Watch possible 

   Valid 101938Z - 102145Z

   Probability of Watch Issuance...60 percent

   SUMMARY...A few multi-cell clusters should develop this afternoon,
   with damaging winds/hail possible. Trends will be monitored for
   possible watch issuance across parts of the region.

   DISCUSSION...Regional satellite/radar trends show a variety of
   convective development processes occurring across the region. 

     1) An early morning band of severe convection continues to move
   northeastward into northeast Missouri, where outflow from the
   ongoing MCS has largely stabilized the atmosphere. These storms may
   end up merging with the MCS across this area into central Illinois,
   where MLCAPE of 3000-4000 J/kg resides. 

     2) A persistent band of elevated convection from northwest
   Missouri into southeast Kansas is beginning to show signs of rooting
   into the boundary layer. This uptick in intensity is also evident in
   visible satellite. This trend appears to pose the greatest
   short-term threat.

     3) Boundary layer cumulus is developing across south-central
   Missouri amid strong diabatic heating (temperatures in the low 90s
   F) and rich low-level moisture (dew point temperatures in the low to
   mid 70s F). This process has yielded MLCAPE of 2500-3000 J/kg.

   Given the widespread destabilization that has occurred, and the
   convective trends noted, convection should become more widespread
   throughout the afternoon. Despite ample instability, winds aloft are
   generally weak, with only about 20 kt of effective bulk shear
   present, with perhaps some enhancement near the MCS in central
   Illinois. Thus storms should form into a few mutli-cell clusters,
   posing a threat damaging winds and large hail. Convective trends
   will be monitored for potential watch issuance this afternoon.

   ..Karstens/Grams.. 08/10/2020

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...PAH...ILX...LSX...SGF...EAX...TSA...TOP...ICT...

   LAT...LON   36799475 37959571 40179296 40118766 36938868 36609234
               36799475 

 

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BULLETIN - EAS ACTIVATION REQUESTED  
TORNADO WARNING  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE  
243 PM CDT MON AUG 10 2020  
  
THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A  
  
* TORNADO WARNING FOR...  
  SOUTHEASTERN WINNEBAGO COUNTY IN NORTH CENTRAL ILLINOIS...  
  SOUTHERN BOONE COUNTY IN NORTH CENTRAL ILLINOIS...  
  
* UNTIL 345 PM CDT.  
      
* AT 243 PM CDT, A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO  
  WAS LOCATED OVER ROCKFORD, MOVING EAST AT 25 MPH.  
  
  HAZARD...TORNADO AND HALF DOLLAR SIZE HAIL.  
  
  SOURCE...RADAR INDICATED ROTATION.  
  
  IMPACT...FLYING DEBRIS WILL BE DANGEROUS TO

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Possible tornado near Rockford

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The National Weather Service in Chicago has issued a

* Tornado Warning for...
  Southeastern Winnebago County in north central Illinois...
  Southern Boone County in north central Illinois...

* Until 345 PM CDT.
    
* At 243 PM CDT, a severe thunderstorm capable of producing a tornado
  was located over Rockford, moving east at 25 mph.

  HAZARD...Tornado and half dollar size hail.

 

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1661262462_day1otlk_2000(1).gif.f7f863a76e09958de12ab061946d1234.gif

 

Quote

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0238 PM CDT Mon Aug 10 2020

   Valid 102000Z - 111200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS NORTHERN
   ILLINOIS...SOUTHEAST WISCONSIN...NORTHWEST INDIANA...FAR SOUTHWEST
   LOWER MICHIGAN...

   ...SUMMARY...
   A derecho producing significant damaging winds will persist across
   much of northern Illinois and possibly far southern Wisconsin, and
   into northern Indiana and southern Lower Michigan this evening.

   ...Northern IL...southeastern WI...northern Indiana...southwestern
   Lower Michigan...
   A Derecho will continue east across northern Illinois, at speeds
   around 60 mph. Many reports of 60-80 mph winds have been recorded
   along with a few over 100 mph as it moved across Iowa and crossed
   the MS River, with some areas experiencing long duration of severe
   winds over 50 kt.

   The environment remains favorable ahead of the Derecho as
   temperatures continue to warm. Modified midday soundings show steep
   midlevel lapse rates and MLCAPE over 3000 J/kg. This will prove
   sufficient to maintain a severe wind threat through the Chicago
   area, including northwest Indiana and parts of Lower Michigan.

   For more information see mesoscale discussions 1455 and 1456.

   ..Jewell.. 08/10/2020

 

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BULLETIN - EAS ACTIVATION REQUESTED
Tornado Warning
National Weather Service Chicago/Romeoville
255 PM CDT Mon Aug 10 2020

The National Weather Service in Chicago has issued a

* Tornado Warning for...
  Northern Boone County in north central Illinois...

* Until 345 PM CDT.

* At 255 PM CDT, a severe thunderstorm capable of producing a tornado
  was located near Loves Park, moving northeast at 30 mph.

  HAZARD...Tornado.

  SOURCE...Radar indicated rotation.

  IMPACT...Flying debris will be dangerous to those caught without
           shelter. Mobile homes will be damaged or destroyed.
           Damage to roofs, windows, and vehicles will occur.  Tree
           damage is likely.

* This dangerous storm will be near...
  Candlewick Lake and Timberlane around 305 PM CDT.
  Poplar Grove around 310 PM CDT.
  Capron around 320 PM CDT.

Other locations impacted by this tornadic thunderstorm include
Caledonia.

 

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2 minutes ago, luckyweather said:

I don’t have a wx station, so no tangible data to share - I’m in NE Winnebago County and just my obs - the wind hasn’t materialized here. Gusty but garden variety gusty.

The wind core is south of you and not really part of the main convective line, it's a bit removed.

 

image.png.344ad7654d96a04f4a1c7d280260a5e8.png

 

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strongest winds on the leading edge are associated with microscale bows and are more isolated. note the stronger/longer duration winds are associated with lighter precip, indicative of the downward motion associated with the descending rear inflow jet (blue areas in velocity on the right-most image). 

derecho.thumb.jpg.36a841e7db49986c0bf985aea5e89a8c.jpg

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Been watching this elsewhere and that is absolutely an historic derecho for Iowa. Extreme high end gusts (and a lot of them), the duration of damaging winds, it tracking through the most densely populated corridor in the state.

Not sure I've ever seen such a duration of 100+ kt returns with any single derecho as I saw with that (from both the DMX and DVN radars). I'd have to imagine some of the reports from outside the bigger cities like Cedar Rapids, Iowa City, and Des Moines are going to be frightening. Particularly in the region along US 30 and I-80 between Des Moines and Cedar Rapids (Tama, Marshalltown) and also NW of Des Moines near Madrid. Can't imagine what Iowa State and the UI campuses look like right now, but I'd imagine it's something along the lines of a war zone.

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