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2013 GLOV Severe Weather Discussion


Chicago WX

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I think the midweek period could be the last severe activity in the region until at least the tail end of April if not May. Going to be plagued by eastern troughing for a while and even after it breaks down, any system that comes out initially could have problems with good moisture return.

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Some models still show the potential for a nice line of storms to develop in central Iowa tomorrow afternoon.  Cape still looks pretty meager, but with strong forcing and pretty nice shear profiles there could still be a few decent storms along the line.  If there was a little more instability/deeper moisture available a brief tornado would have been a possibility before the line consolidates, however the lack of moisture/instability ensures that won't happen. 

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02z RAP instability for 20z tomorrow.  Man it's too bad this is way too high, or this would actually be a pretty nice little setup.  Shows pockets of 1500j/kg cape over central Iowa beneath very nice shear profiles.  Unfortunately cape will probably have a hard time getting much above 500j/kg with the lack of deep moisture.  You have to go way down to southern Arkansas to find dews over 50 currently. 

 

RAP_255_2013041402_F18_CAPE_SURFACE.png

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I noticed that College of Dupage has updated their NAM model products and change their base map for the MW region. A couple of new products on there are:

 

Supercell composite

 

namMW_con_scp_084.gif

 

Sig Tornado Parameter:

 

namMW_con_stp_084.gif

 

1KM EHI

 

namMW_con_1kmehi_084.gif

 

3KM EHI

 

namMW_con_3kmehi_084.gif

 

PWAT

 

namMW_con_pwat_084.gif

 

Sim Reflectivity

 

namMW_sfc_radar_084.gif

 

Now I know you can get some of these products elsewhere but this is the first place I know of where you can get these products for free centered on this region. I for one, like the new products, now if we could get the NAM to actually have quality output that would help as well.

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I must be on crack, but I'm gonna probably head to central Iowa here in a bit.  Instability is gonna be weak to be sure, but with these shear profiles and the slightest possibility there could be just enough instability to get something decent I can't resist.  Liking the area near Iowa Falls.  Good soundings for that area, and will be on the northern area of best (relatively speaking) moisture/instability.  Could see a quick spin-up there before the line consolidates. 

 

 

Near Iowa Falls around 22z.  Just need a little more instability and this would be pretty nice.  Too close not to at least take a shot lol.

 

RAP_255_2013041414_F08_42.5000N_93.5000W

RAP_255_2013041414_F08_42.5000N_93.5000W

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SPC upgraded Iowa into the slight risk along with 2% tornado probs.  Dews are still in the 40s over most of Iowa and Missouri, so the mid-upper 50s shown on the RAP will be too high of course.  Might see a narrow corridor of 50-55 dews though immediately ahead of the front later today, and that MIGHT be just enough to encourage a little nadogenesis.  Gonna head towards Des Moines and adjust from there...

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I noticed that College of Dupage has updated their NAM model products and change their base map for the MW region. A couple of new products on there are:

 

Supercell composite

 

Now I know you can get some of these products elsewhere but this is the first place I know of where you can get these products for free centered on this region. I for one, like the new products, now if we could get the NAM to actually have quality output that would help as well.

 

Stebo, thanks for finding that on the COD web site.

 

The only other web site with the supercell composite and STP is this:

 

http://www.wxcaster.com/experimental_products.htm

 

Sometimes the SCP values are way overdone (not sure why.)

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You out there right now Cyclone and where?

 

Yeah ended up northwest of Des Moines by Perry and Boone.  First cells that went up were mildly interesting but quickly became undercut and crapped the bed.  May have got a semi-decent time lapse with the gopro.  Wasn't really expecting much, but I thought they would do a little better than they did.  Oh well, still fun to get out for the first time this year and test some new stuff I picked up over the winter.

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Too bad the Tuesday system doesn't have better moisture...

 

Well, I don't exactly need any more moisture up this way.  Not right away anyways.  Seems like I can't get severe up here anyways without first getting through a whole buttload of overrunning crapvection which is the last thing we need.  I'm through with the floods.  The mosquitoes are going to be awful as soon as it warms up.

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SPC put a slight risk out for DBQ and DVN areas for Monday.

 

 

.PARTS OF THE UPPER/MID-MS VALLEY...
AS NOTED IN THE INITIAL D2 DISCUSSION...MODEL GUIDANCE /ESPECIALLY
SREF...NAM AND GFS/ MAY BE GROSSLY OVERDONE WITH THE DEGREE OF
LOW-LEVEL MOISTURE RETURN INTO THE MIDWEST BY MON AFTERNOON.
FORECAST SOUNDINGS FROM THESE MODELS INDICATE MEAN MIXING RATIOS
REACHING 12-14 G/KG WITH MINIMAL INHIBITION PRIOR TO DEPICTED
CONVECTIVE INITIATION ALONG THE DECAYING FRONT. WITH ONLY A MODERATE
SWLY LLJ ON SUN NIGHT...AND 12Z RAOBS THIS MORNING INDICATING MEAN
MIXING RATIOS OF THAT MAGNITUDE CONFINED TO DEEP S TX AND ACROSS THE
LOWER MS VALLEY...IT APPEARS A BIT FAR-FETCHED THAT THIS AMPLITUDE
OF MOISTURE RETURN WILL BE FULLY REALIZED. IN ADDITION...THE
FRONTOLYTIC NATURE OF THE BOUNDARY ALONG WITH WAA AT 700 MB LIKELY
MAINTAINING A CAPPING INVERSION WILL PROBABLY MITIGATE DIURNAL TSTM
DEVELOPMENT TO ALONG THE LEADING EDGE OF THE CAP. THIS TYPE OF
SCENARIO APPEARS FAIRLY REPRESENTED IN 12Z CONVECTION-ALLOWING WRF
GUIDANCE. AMIDST A BELT OF ENHANCED MID-LEVEL WLYS...THIS SETUP
COULD YIELD A FEW SUPERCELLS WITH LARGE HAIL AS THE PRIMARY THREAT
DURING THE LATE AFTERNOON/EVENING IF TSTMS INDEED FORM.

 

 

 

14e87xi.png

 

 

4uynad.png

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Tennis ball sized hail being mentioned in the warning.

 

SEVERE THUNDERSTORM WARNINGILC085-300245-/O.NEW.KDVN.SV.W.0018.130430T0156Z-130430T0245Z/BULLETIN - IMMEDIATE BROADCAST REQUESTEDSEVERE THUNDERSTORM WARNINGNATIONAL WEATHER SERVICE QUAD CITIES IA IL856 PM CDT MON APR 29 2013THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A* SEVERE THUNDERSTORM WARNING FOR...  NORTHERN JO DAVIESS COUNTY IN NORTHWEST ILLINOIS...* UNTIL 945 PM CDT* AT 850 PM CDT...A SEVERE THUNDERSTORM WAS LOCATED NEAR GALENA...AND  MOVING NORTHEAST AT 30 MPH.  HAZARD...TENNIS BALL SIZE HAIL.  SOURCE...TRAINED WEATHER SPOTTERS.  IMPACT...PEOPLE AND ANIMALS OUTDOORS WILL BE INJURED. EXPECT DAMAGE           TO ROOFS...SIDING...WINDOWS...VEHICLES AND CROPS.* LOCATIONS IMPACTED INCLUDE...  COUNCIL HILL...SCHAPVILLE...SCALES MOUND...APPLE RIVER...WARREN...  GALENA TERRITORY...GUILFORD...APPLE CANYON LAKE AND APPLE RIVER  CANYON STATE PARK.
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MESOSCALE DISCUSSION 0581

NWS STORM PREDICTION CENTER NORMAN OK

0900 PM CDT MON APR 29 2013

AREAS AFFECTED...PORTIONS ERN IA...NRN IL...SRN WI.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 300200Z - 300400Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...ISOLATED/QUICKLY DEVELOPING SVR TSTM PRODUCED 2.5-INCH

HAIL REPORT NEAR DBQ AT 130Z. PER COORD W/AFFECTED WFOS...NO WW IS

BEING ISSUED YET. HOWEVER...CONVECTIVE TRENDS WILL BE MONITORED FOR

UPSCALE GROWTH THAT COULD COMPEL WW ISSUANCE...IN ENVIRONMENT THAT

SHOULD REMAIN FAVORABLE FOR OCNL LARGE HAIL FROM ANY SUSTAINED

CONVECTION.

DISCUSSION...ACTIVITY NEAR DBQ DEVELOPED NEAR DIFFUSE SFC WARM FRONT

EXTENDING WNWWD ACROSS SRN MN INTO ERN SD...AND ALSO..NEAR NERN END

OF FRONTOLYTIC WARM-FRONTAL CORRIDOR THAT EXTENDS INTO LOW OVER

CENTRAL/SWRN KS. NEARBY DVN RAOB...IN WARM SECTOR...SAMPLED STEEP

MIDLEVEL LAPSE RATES AND INCREASING LOW-LEVEL MOISTURE...WITH

ROUGHLY 1-INCH PW SUPPORTING MLCAPE 800-900 J/KG. MUCAPE FOR

INCREASINGLY MOIST PARCELS ROOTED AROUND 800-850 MB IS IN 2000-2500

J/KG RANGE...MORE REPRESENTATIVE OF RAPID INITIAL INTENSIFICATION

RATE OF CONVECTION OBSERVED SO FAR. WITH NEAR-SFC

COOLING...ACTIVITY SHOULD BE MOSTLY ELEVATED...BUT WITH POTENTIAL TO

SEND ISOLATED STG/DAMAGING GUST THROUGH SHALLOW NEAR-SFC STABLE

LAYER. MAIN CONCERN WILL BE HAIL.

SIGNALS FOR KINEMATIC SUPPORT ARE MIXED...WITH RELATIVELY WEAK

MID-UPPER WINDS LIMITING CLOUD-LAYER SHEAR. HOWEVER...LOW-LEVEL WAA

AND RELATED VEERING OF WINDS WITH HEIGHT CONTRIBUTE TO FAVORABLE

EFFECTIVE SRH AROUND 200-250 J/KG. THOUGH FIXED-LAYER SRH SHOULD

INCREASE BENEATH STRENGTHENING SWLY LLJ...NEAR-SFC DIABATIC

STABILIZATION WILL EFFECTIVELY TRUNCATE SOME OF THAT HELICITY IN

VERTICAL. EFFECTIVE SHEAR MAGNITUDE 35-40 KT IS EXPECTED TO

CONTINUE.

..EDWARDS/KERR.. 04/30/2013

 

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