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6/19-6/23 Severe Weather Risk


Jim Martin

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First warning of many to come for our area in the next 30 hours. Just for the record.

 

BULLETIN - IMMEDIATE BROADCAST REQUESTED  
SEVERE THUNDERSTORM WARNING  
NATIONAL WEATHER SERVICE DES MOINES IA  
843 PM CDT TUE JUN 21 2016  
 
THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A  
 
* SEVERE THUNDERSTORM WARNING FOR...  
EASTERN WAYNE COUNTY IN SOUTH CENTRAL IOWA...  
SOUTHWESTERN APPANOOSE COUNTY IN SOUTH CENTRAL IOWA...  
 
* UNTIL 930 PM CDT  
 
* AT 843 PM CDT...A SEVERE THUNDERSTORM WAS LOCATED NEAR CORYDON...  
MOVING SOUTHEAST AT 40 MPH.  
 
HAZARD...60 MPH WIND GUSTS AND QUARTER SIZE HAIL.  
 
SOURCE...RADAR INDICATED.  
 
IMPACT...HAIL DAMAGE TO VEHICLES IS EXPECTED. EXPECT WIND DAMAGE  
TO ROOFS...SIDING...AND TREES.  
 
* LOCATIONS IMPACTED INCLUDE...  
SEYMOUR...CINCINNATI...PROMISE CITY...NUMA AND PLANO.  
 

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Really feeling like the midday mcs will be the main show for us up north

 

 

Definitely a possibility.  Southern areas look primed but the big question is how far north the better threat gets.  Going to be the ultimate mesoanalysis/nowcast day for areas in/near the city.

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Definitely a possibility. Southern areas look primed but the big question is how far north the better threat gets. Going to be the ultimate mesoanalysis/nowcast day for areas in/near the city.

I think the main evening event is pretty much off the table up here

Just trying to salvage some daytime garden variety at this point

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Every sounding recently shown is contaminated, which means the sounding is useless. If the dew point line follows the temperature line exactly for a good portion of the forecast sounding, nothing in that area (if small) or the whole sounding is useful. The soundings do not represent what the environment will actually be.

Edit: what Hoosier posted in the post after this one is an example of an uncontaminated sounding.

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Here's one farther southeast at the same time.  Looks like some corn fed dews.

 

The environment upstream in the 00z OAX sounding and on mesoanalysis right now in E NE/W IA speaks to this kind of potential (of course with no storms to tap it). The former had a SCP over 50 and ridiculous veering with height.

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Every sounding recently shown is contaminated, which means the sounding is useless. If the dew point line follows the temperature line exactly for a good portion of the forecast sounding, nothing in that area (if small) or the whole sounding is useful.

 

That seems legit, but how much can one rely on this? It'd be nice to have an idea at a quick glance instead of pulling up forecast reflectivity.

A lot of the UH swaths posted look like they're north of the warm front. Are they truly north of it, or riding the front and still drawing in the good air?

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The 0Z 4K NAM really doesnt have a "classic" MCS on it for tomorrow night, has multiple line segments some with bowing and hits IL/MI/IN/OH, including you Alex.

 

 

It's elevated.

 

If that.

 

MUCAPE gradient doesn't get any further NE than a Milwaukee - Findlay, OH line (let alone the gradient for surface-based CAPE).

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Izzi evening update

 

....

AREA FORECAST DISCUSSION...UPDATED  NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  857 PM CDT TUE JUN 21 2016     UPDATE    855 PM CDT    CHALLENGING FORECAST NEXT 24 HOURS FROUGHT WITH UNCERTAINTY.  SURFACE ANALYSIS THIS EVENING HAS A WARM FRONT STRETCHING NW TO SE  ACROSS THE REGION, LOCATED ACROSS WC TO SE IL. TO THE NORTH OF THE  BOUNDARY IN OUR CWA, VERY DRY AIR MASS IN PLACE WHILE SEASONABLY  MOIST AIR MASS NEAR/SOUTH OF THE BOUNDARY. VERY MOIST AIR MASS  RESIDES NEAR THE BOUNDARY WHERE MID 70 DEWPOINTS ARE POOLING.     HAVE ALREADY SEEN SOME WIDELY SCATTERED STORMS DEVELOP IN THE WAA  REGIME JUST TO THE NORTH OF THIS BOUNDARY OVER CENTRAL IA AND  WOULD EXPECT COVERAGE AND INTENSITY OF STORMS TO INCREASE TONIGHT  AS 40KT+ LLJ RESULTS IN STRONG THETA-E ADVECTION. GIVEN THE  ORIENTATION OF THE WARM FRONT/INSTABILITY AXIS AND STEERING FLOW  LARGELY FROM THE NW, WOULD EXPECT MAJORITY OF THIS CONVECTION TO  MOVE SE INTO CENTRAL IL TONIGHT AND LARGELY MISS A GOOD MAJORITY  OF OUR CWA. SOME OF THE LIGHTER MORE STRATIFORM PRECIP ON THE  NORTHERN FLANK OF THIS CONVECTION WILL LIKELY SPREAD INTO MAINLY  OUR WESTERN AND SOUTHERN CWA AFTER MIDNIGHT.    MANY MODELS SUGGEST THAT THIS WAA DRIVEN ACTIVITY COULD FESTER  WELL INTO THE AFTERNOON HOURS WEDNESDAY ONLY GRADUALLY SPREADING  NORTH. THE LAST FEW RUNS OF THE HRRRX DEVELOP A HEALTHY COLD POOL  THAT PUSHES THE EFFECTIVE OUTFLOW AUGMENTED FRONT FAR TO THE  SOUTH...SOUTH OF I-70 EVEN BY MID-LATE WEDNESDAY MORNING. NOT  CONFIDENT THAT FRONT WILL BE THIS FAR SOUTH, BUT FIGURE WITH  CLOUDS AND PROBABLY SHOWERS AND ISOLD STORMS CONTINUING INTO THE  AFTERNOON WITH A WIND OFF THE LAKE THAT TEMPS WILL BE COLDER  TOMORROW THAN WE HAD GOING. HAVE KNOCKED TEMPS BACK SEVERAL  DEGREES OVER ABOUT THE NE HALF OF OUR CWA AND EVEN THE MID-UPPER  70S IN THE GRIDS NOW MAY END UP BEING TOO WARM (ESPECIALLY NEAR  THE LAKE).     IT IS A TIME OF YEAR THAT WARM FRONTS CAN JUMP NORTH QUICKLY, AND  THAT IS CERTAINLY POSSIBLE, ESPECIALLY GIVEN FAIRLY STRONG  SHORTWAVE AND ASSOCIATED SFC LOW FOR THIS TIME OF YEAR. IT IS  LOOKING LIKE THE MORE SUBSTANTIAL SEVERE THREAT COULD END UP  NEEDING TO BE EVENTUALLY SHIFTED SOUTH IF WAA DRIVEN CONVECTION  OVERNIGHT INTO WED MORNING IS AS EXTENSIVE AS GUIDANCE SUGGESTS.    IZZI  
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