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2015 Short Term Severe Weather Discussion


Hoosier

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ILN is talking about some strong pulse storms and heat indices in the 100s. Strong pulse storms are pretty sweet. 

 

WITH DEWPOINTS 70 TO 75 F ON FRIDAY...THIS COMBINED WITH
WARM TEMPERATURES WILL ALLOW HEAT INDEX VALUES TO APPROACH 100
DEGREES F. CONTINUE TO MENTION HEAT HAZARD IN THE HWO.

THUNDERSTORMS ALSO RETURN TO THE FORECAST ON FRIDAY. INCREASING
MOISTURE WILL CONTRIBUTE TO INSTABILITY WHICH HAS THE POTENTIAL
TO EXCEED 2000 J/KG BY AFTERNOON. MAIN FORCING LOOKS TO AT LEAST
INITIALLY BE ACROSS THE NORTHERN CWA /SHORTWAVE/TROUGH/ BUT ITS
POSSIBLE THAT ANY CONVECTION COULD SPREAD SOUTHEAST THROUGH THE
AFTERNOON/EVENING PARTICULARLY IN THE ABSENCE OF ANY CAPPING.
WHILE SHEAR IS FORECAST TO BE WEAK...AMOUNT OF INSTABILITY /CAPE/
COULD SUPPORT SOME STRONGER STORMS.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
PERIOD BEGINS WITH LARGE SUBTROPICAL RIDGE CENTERED OVER LOUISIANA.
SHORTWAVE FROM FRIDAY WILL BE SHIFTING AWAY INTO SERN CANADA WITH
WHATEVER SEMBLANCE OF SURFACE FRONT HAVING LONG SINCE WASHED OUT
OVER THE OHIO VALLEY...LEAVING A HEALTHY PWAT AXIS /+1 SIGMA ABOVE
CLIMO/ IN PLACE. A SHARP POSITIVE TILT SHORTWAVE TROUGH WILL BE
PRESENT FROM ND BACK INTO DEEPER CYCLONE OVER IN THE INTERMOUNTAIN
WEST.

HEIGHTS WILL RISE ON SATURDAY SUGGESTING FORCING FOR ASCENT WILL BE
WEAK AND DRIVEN VIA DIABATIC HEATING OF THE EXTREMELY
WARM/ANOMALOUSLY MOIST AIRMASS. WITH TEMPS APPROACHING 90F AND
DEWPTS WELL INTO THE LOW 70S...SCT DIURNALLY FORCED CONVECTION WILL
DEVELOP NEAR AROUND PVS BOUNDARIES. LOCALLY HEAVY DOWNPOURS FROM
SLOW MOVING STORMS...PERHAPS A FEW DOWNBURSTS WILL BE PRIMARY
THREATS WITH WEAK TROPOSPHERIC FLOW.

 

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It's my hunch for the upcoming sequence that many of us will be paying much more attention to ML CAPE per tornadotony's comments on our last episode and not just surface CAPE.  Gotta make sure the energy and moisture gets up there.

Well, MLCAPE or not, the shear in the upcoming period isn't gonna be favorable for a respectable tornado threat. With that said... I dunno what else MLCAPE plays a role in because the supercells on Monday seemed to do just fine.

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With how moist the soils are...(I know that's not the end all be all)...I just see repeated bouts of well-fueled and somewhat disorganized MCSs stalling boundaries...not much chance for boundary momentum...so I will side with ALEK...fwiw

The main difference I see are similar situations to a few days ago with elevated DPs to make it feel hotter thanks in part to the oversaturated soils and the sweaty cornfields

I'd be surprised if the front gets hung up too far south this time. Really don't see Chicagoland escaping some pretty significant heat/humidity, especially early weekend (possible exception right along the lakeshore if the gradient is weak enough).
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Finally they introduced a marginal risk for tomorrow locally though I do expect a slight risk for tomorrow.

Maybe ENH if a cold pool gets going? NSSL WRF painting a nice picture for tomorrow...wouldn't be surprised if that model verifies exactly. SREF has been slowly upping precip. amounts for central Ohio with continued 3000-4000 J/kg MUCAPE. Only limiting factor is only 20-30 kts. shear. Should be interesting...

capwnd31.pngrfcslp35.png

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Maybe ENH if a cold pool gets going? NSSL WRF painting a nice picture for tomorrow...wouldn't be surprised if that model verifies exactly. SREF has been slowly upping precip. amounts for central Ohio with continued 3000-4000 J/kg MUCAPE. Only limiting factor is only 20-30 kts. shear. Should be interesting...

capwnd31.pngrfcslp35.png

I don't think we see an enhanced. Lack of appreciable shear, a well defined shortwave, and a decent cap. However it should still be a slight imo.

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Last event the warm front ended up further north and east than expected. This isn't April or May...

 

True, but the timing could be a bit slower than progged now.

 

The latest NAM runs only have us getting into the mid/upper 80s on Friday (whereas before, it had highs in the low 90s).

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I don't think we see an enhanced. Lack of appreciable shear, a well defined shortwave, and a decent cap. However it should still be a slight imo.

It's very wishful thinking...like you noted though, a SLGT appears likely. Sunday is looking like the better day with the frontal passage.

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Finally they introduced a marginal risk for tomorrow locally though I do expect a slight risk for tomorrow.

 

My issue with late tomorrow will be the subsidence cap in the wake of the morning shortwave. 

 

The low level convergence doesn't look to be nearly as impressive as with the last event, which will make it harder for any organized convection to break through the cap without a formidable shortwave.

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Now August 24 2007 Popping up on the analogs...that's a couple solid performers for LOT

This event also produced a couple tors in MI

 

It was a multi-day event in fact.

 

August 23, 2007 featured the long-lived derecho that I believe tracked from Nebraska the previous night before finally diminishing here in Detroit (though not before giving us a solid t'storm).

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My issue with late tomorrow will be the subsidence cap in the wake of the morning shortwave. 

 

The low level convergence doesn't look to be nearly as impressive as with the last event, which will make it harder for any organized convection to break through the cap without a formidable shortwave.

We will warm to near 90 tomorrow which should be enough to break the cap along with the subtle shortwave that is coming across the state in the afternoon. Mind you I don't think tomorrow is going to be some sort of outbreak of severe weather, but there could be isolated to scattered strong/severe storms.

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Decent little environment currently in SE IA and west central IL. Gradient of MLCAPE set up from PIA to DVN with backed low level flow (effective SRH of 200-400 m2/s2) and effective shear around 40 kts. Would be most interested in the cells near Burlington and Mount Union currently. They both have rather strong rotation aloft.

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We will warm to near 90 tomorrow which should be enough to break the cap along with the subtle shortwave that is coming across the state in the afternoon. Mind you I don't think tomorrow is going to be some sort of outbreak of severe weather, but there could be isolated to scattered strong/severe storms.

 

Oh I agree with the potential of isolated thunderstorms, and obviously severe weather will be a concern with any t'storm given the instability/moisture expected. I just disagree with the idea of a slight risk from the SPC, at least now. 

 

We're going to need to get temps warmer than "near 90*F" with 850mb temps expected to surge to at least 20*C late in the day for a  "slight risk" coverage of severe t'storms, given that we don't have a formidable trigger to work with.

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BULLETIN - EAS ACTIVATION REQUESTED  

TORNADO WARNING  

NATIONAL WEATHER SERVICE QUAD CITIES IA IL  

545 PM CDT THU JUL 16 2015  

 

THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A  

 

* TORNADO WARNING FOR...  

CENTRAL HENDERSON COUNTY IN WEST CENTRAL ILLINOIS...  

DES MOINES COUNTY IN SOUTHEASTERN IOWA...  

 

* UNTIL 630 PM CDT  

 

* AT 545 PM CDT...A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A  

TORNADO WAS LOCATED OVER BURLINGTON...MOVING EAST AT 25 MPH.  

 

HAZARD...TORNADO AND QUARTER SIZE HAIL.  

 

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...  

BURLINGTON AND GULF PORT AROUND 555 PM CDT.  

STRONGHURST AROUND 610 PM CDT.  

GLADSTONE AROUND 615 PM CDT.  

OQUAWKA AND BIGGSVILLE AROUND 620 PM CDT.  

ROZETTA AROUND 625 PM CDT.  

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