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July 26-27 Severe Threat


Hoosier

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Something tells me that this MIGHT (although unlikely) be another derecho event.  Not sure if it'll turn out that way, though.  Could be rough for cities such as Peoria, Illinois and Indianapolis, Indiana.  Which, a matter of fact, Peoria has escaped major severe weather so far this year.  That could end tomorrow, though...

 

EDIT: One really sad fact is that NWS Lincoln does not yet have SAILS installed. :(

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So sometimes the 4km NAM nest is an overachiever, but that MCS it is simulating looks pretty mean as it tracks into Indiana. It looks like it wants to peak the MCS right around the Indianapolis area with 850mb winds of ~100 kts. The MCV is clearly depicted on its UH product.

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Moderate risk on new day 1.

 

 

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
1257 AM CDT SAT JUL 26 2014  
 
VALID 261200Z - 271200Z  

 
...THERE IS A MDT RISK OF SVR TSTMS LATE THIS AFTERNOON INTO  
TONIGHT...MAINLY ACROSS MUCH OF CENTRAL ILLINOIS THROUGH CENTRAL AND  
SOUTHERN INDIANA...BUT THIS INCLUDES AT LEAST PARTS OF THE GREATER  
ST. LOUIS...INDIANAPOLIS...LOUISVILLE AND CINCINNATI METROPOLITAN  
AREAS...  
 
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK  
AREA ACROSS MUCH OF THE MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS...  
   
..SUMMARY
 
 
SEVERE STORMS...SOME ACCOMPANIED BY VERY LARGE HAIL...LOCALLY STRONG  
WIND GUSTS AND A COUPLE OF TORNADOES ARE EXPECTED TODAY INTO TONIGHT  
ACROSS PARTS OF THE MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS. ONE  
OR MORE ORGANIZED CONVECTIVE CLUSTERS CAPABLE OF GENERATING SWATHS  
OF POTENTIALLY DAMAGING WINDS MAY EVOLVE LATE THIS AFTERNOON AND  
EVENING ACROSS MUCH OF CENTRAL ILLINOIS INTO CENTRAL AND SOUTHERN  
INDIANA...PERHAPS REACHING THE CENTRAL APPALACHIANS BY LATE TONIGHT.  
   
..SYNOPSIS
 
 
WHILE BLOCKING APPEARS LIKELY TO REMAIN PROMINENT WITHIN THE  
WESTERLIES ACROSS THE HIGHER LATITUDES OF NORTH AMERICA...MODELS  
INDICATE UPPER TROUGHING EITHER SIDE OF THE HIGH CENTER OVER  
INTERIOR NORTHERN CANADA WILL BEGIN TO UNDERGO AMPLIFICATION DURING  
THIS PERIOD. AS THIS OCCURS...SUBTROPICAL RIDGING IS EXPECTED TO  
BUILD NORTHWARD THROUGH MUCH OF THE NORTHERN INTERMOUNTAIN REGION  
AND ROCKIES...AND THE CLOSED LOW...NOW UNDERCUTTING THE CANADIAN  
HIGH...SHOULD DIG SOUTHEASTWARD ACROSS THE CENTRAL CANADIAN/U.S.  
BORDER AREA.  
 
CONSIDERABLE SPREAD LINGERS WITHIN THE VARIOUS MODEL ENSEMBLE OUTPUT  
CONCERNING THIS LATTER DEVELOPMENT...BUT THE 12Z ECMWF AND 21Z NCEP  
SREF ENSEMBLE MEANS SUGGEST THAT THE REMNANT UPPER LOW/TROUGH  
PROBABLY WILL NOT REACH THE UPPER MIDWEST UNTIL LATE THIS EVENING OR  
OVERNIGHT. WHILE THE MAIN TRANSITION TO STRENGTHENING AND  
INCREASINGLY CYCLONIC MID-LEVEL FLOW MAY NOT OCCUR UNTIL WELL AFTER  
DARK ACROSS THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...DEEP  
LAYER SHEAR WILL BE MORE THAN SUFFICIENT FOR ORGANIZED CONVECTIVE  
DEVELOPMENT AS WEAK MID-LEVEL HEIGHT FALLS COMMENCE WITHIN THE  
NORTHWEST FLOW REGIME PRECEDING IT.  
 
BENEATH A REMNANT PLUME OF VERY WARM AND CAPPING ELEVATED MIXED  
LAYER AIR ALONG THE SOUTHERN EDGE OF THE STRONGER NORTHWEST  
FLOW...LOW-LEVEL MOISTENING SHOULD CONTINUE ACROSS THE LOWER  
MISSOURI/MIDDLE MISSISSIPPI VALLEYS INTO THE OHIO VALLEY. THIS IS  
EXPECTED TO CONTRIBUTE TO STRONG DESTABILIZATION SUPPORTIVE OF  
INTENSE CONVECTIVE DEVELOPMENT AND THE FOCUS FOR THE PRIMARY SEVERE  
WEATHER POTENTIAL TODAY.  
 
WEST SOUTHWESTWARD ALONG AN INITIAL SURFACE FRONT ADVANCING  
SOUTHWARD INTO THE CENTRAL PLAINS...SEVERE WEATHER POTENTIAL APPEARS  
LOWER DUE TO STRONGER LINGERING MID-LEVEL INHIBITION AND WEAKER  
SHEAR. HOWEVER...ISOLATED STRONG/SEVERE STORM DEVELOPMENT MAY NOT  
BE OUT OF THE QUESTION NEAR OR SHORTLY AFTER PEAK HEATING.  
OTHERWISE...CONDITIONS MAY ALSO BECOME AT LEAST MARGINALLY  
SUFFICIENT FOR STRONG/SEVERE STORM DEVELOPMENT IN RESPONSE TO THE  
EVOLVING UPPER PATTERN...ACROSS PARTS OF THE UPPER GREAT LAKES  
REGION THIS AFTERNOON THROUGH TONIGHT...AND PERHAPS AS FAR EAST AS  
THE LOWER GREAT LAKES/UPPER OHIO VALLEY AND CENTRAL APPALACHIANS BY  
LATE TONIGHT.  
 
MEANWHILE...MONSOONAL MOISTURE ACROSS THE HIGHER TERRAIN OF THE  
SOUTHERN PLATEAU INTO CENTRAL AND SOUTHERN ROCKIES WILL AGAIN  
SUPPORT CONSIDERABLE THUNDERSTORM ACTIVITY TODAY AND TONIGHT.  
   
..MIDDLE MISSISSIPPI INTO LOWER OHIO VALLEYS
 
 
CONVECTION ALLOWING MODEL GUIDANCE DOES NOT PROVIDE CLARITY FOR THIS  
FORECAST...OFFERING A RATHER BROAD RANGE OF POSSIBLE SOLUTIONS.  
HOWEVER...A FAIRLY CONSISTENT SIGNAL HAS BEEN EVIDENT IN THE NAM AND  
ECMWF...AMONG OTHER MODEL OUTPUT...SUGGESTING THAT POTENTIAL EXISTS  
FOR THE EVOLUTION OF ONE OR MORE ORGANIZED MESOSCALE CONVECTIVE  
SYSTEMS ACROSS PORTIONS OF THE MIDDLE MISSISSIPPI THROUGH LOWER OHIO  
VALLEYS DURING THIS PERIOD. GIVEN THE AFOREMENTIONED ENVIRONMENT  
CONDITIONS ANTICIPATED ACROSS THIS REGION BY LATE  
AFTERNOON...CONFIDENCE IS FAIRLY HIGH THAT A SIGNIFICANT SEVERE  
WEATHER EVENT WILL BE REALIZED.  
 
ALONG/NORTH AND NORTHEAST OF AN AXIS OF STRONG SURFACE HEATING  
ACROSS CENTRAL MISSOURI INTO CENTRAL ILLINOIS...MOISTENING BENEATH  
THE AXIS OF STEEPEST MID-LEVEL LAPSE RATES WILL CONTRIBUTE TO LARGE  
CAPE...BEFORE INHIBITION GRADUALLY ERODES. PROBABLY AIDED BY  
FORCING ASSOCIATED WITH LOWER/MID TROPOSPHERIC WARM  
ADVECTION...INITIATION OF STORMS MAY OCCUR PRIOR TO 21Z ACROSS PARTS  
OF SOUTHERN IOWA AND NORTHERN MISSOURI. INITIALLY DISCRETE...A FEW  
SUPERCELLS APPEAR POSSIBLE WITH THE POTENTIAL FOR VERY LARGE  
HAIL...PERHAPS TORNADOES...BEFORE ACTIVITY GRADUALLY CONSOLIDATES  
INTO AN ORGANIZING MESOSCALE CONVECTIVE SYSTEM AND DEVELOPS  
SOUTHEASTWARD ACROSS CENTRAL ILLINOIS AND CENTRAL/SOUTHERN INDIANA  
THROUGH THE EVENING.  
 
ALTHOUGH MORE UNCERTAIN...AS INITIAL ACTIVITY CONTINUES TO SPREAD  
TOWARD THE CENTRAL APPALACHIANS OVERNIGHT...FORCING ASSOCIATED WITH  
THE DIGGING UPSTREAM IMPULSE MAY SUPPORT RENEWED CONVECTIVE  
DEVELOPMENT ALONG THE TRAILING OUTFLOW BOUNDARY ACROSS THE MIDDLE  
MISSISSIPPI VALLEY. AT LEAST SOME GUIDANCE SUGGESTS THAT THIS COULD  
EVOLVE INTO ANOTHER SOUTHEASTWARD PROPAGATING MESOSCALE CONVECTIVE  
SYSTEM...IN AN ENVIRONMENT THAT SHOULD REMAIN CONDUCIVE TO THE  
PRODUCTION OF STRONG...POTENTIALLY DAMAGING WIND GUSTS.  
 
..KERR/SMITH.. 07/26/2014  

 

post-4544-0-35181900-1406354456_thumb.gi

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Good mention of the outflow generation in the D2/3 for Sunday. Increasing low level shear (which is already forecast to be sufficient for tornadoes) within this environment is simply asking for trouble. Moisture has been pretty easy to come by especially east of the MS River this year so I have little doubt that will be a problem.

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I find this very interesting.  Day 1...Approx 6.5 million peeps under moderate risk, 2.2 million under slight risk.   Day two 3.2 Million under moderate risk, 98.5 million under slight risk.  Adding them up quickly, roughly 110 Million under either a slight or moderate risk.  While I believe it may have happened before, Has anyone seen this type of set up in late July???

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I find this very interesting.  Day 1...Approx 6.5 million peeps under moderate risk, 2.2 million under slight risk.   Day two 3.2 Million under moderate risk, 98.5 million under slight risk.  Adding them up quickly, roughly 110 Million under either a slight or moderate risk.  While I believe it may have happened before, Has anyone seen this type of set up in late July???

 

There's over 22 million in the slight risk today.

 

Honestly, with the region at risk, I'm coming up blank in terms of previous setups like this one at this time of year. NW flow events are nothing new this time of year, but rarely do you see a trough this strong basically smack dab in the middle of when the jet is usually weakest (and a death ridge dominating the upper level pattern over the central US).

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I find this very interesting.  Day 1...Approx 6.5 million peeps under moderate risk, 2.2 million under slight risk.   Day two 3.2 Million under moderate risk, 98.5 million under slight risk.  Adding them up quickly, roughly 110 Million under either a slight or moderate risk.  While I believe it may have happened before, Has anyone seen this type of set up in late July???

 

 

I think you misplaced the decimal point there.  It's showing 22 million in the day 1 slight risk.

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I think you misplaced the decimal point there.  It's showing 22 million in the day 1 slight risk.

 

At any rate, I would think this set up would be more common during late spring, early fall.  But with the death ridge centered over the four corners region, and a very strong upper level low dropping in, it really does flatten out the ridge.  While a north west flow is somewhat common like Andy said,  the strength of the H5 low is very impressive indeed.

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Some hailers this morning, slipping by to my southwest. 1" reported in Covington (Fountain County). Cell still warned as it passes to the west of Indy.

 

Looks like most of the recent model guidance has tonight's action to the south of LAF. I guess I shouldn't be surprised by that. :lol:

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New day 1 outlook.

 

 

 

 

 

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK  
0748 AM CDT SAT JUL 26 2014  
 
VALID 261300Z - 271200Z  

 
...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR  
CENTRAL IL INTO CENTRAL/SRN INDIANA...  
   
..THERE IS A SLGT RISK OF SVR TSTMS FROM ERN NEB TO WRN WV
 
 
   
..SUMMARY
 
 
SEVERE STORMS...SOME ACCOMPANIED BY VERY LARGE HAIL...DAMAGING GUSTS  
AND A COUPLE OF TORNADOES ARE EXPECTED LATER THIS AFTERNOON INTO  
TONIGHT FROM EASTERN NEBRASKA TO PARTS OF THE MIDDLE MISSISSIPPI AND  
LOWER OHIO VALLEYS. THE MOST CONCENTRATED RISK AREA SHOULD BE THIS  
EVENING INTO TONIGHT FROM CENTRAL ILLINOIS INTO CENTRAL AND SOUTHERN  
INDIANA...WHERE ONE OR MORE ORGANIZED THUNDERSTORM CLUSTERS COULD  
PRODUCE SWATHS OF DAMAGING WINDS. THE DAMAGING WIND RISK COULD  
REACH AS FAR AS SOUTHERN OHIO AND NORTHERN KENTUCKY OVERNIGHT.  
   
..ERN NEB TO OH/KY THIS AFTERNOON THROUGH TONIGHT
 
 
A CLOSED MIDLEVEL LOW OVER SRN SK THIS MORNING WILL BEGIN TO MOVE  
SEWD TOWARD THE UPPER MS VALLEY BY EARLY SUNDAY...WHILE  
STRENGTHENING FLOW ALOFT OVERSPREADS THE MID MS AND LOWER OH VALLEYS  
IN THE EXIT REGION OF A 60-90 KT MID-UPPER JET STREAK ON THE SRN  
PERIPHERY OF THE CLOSED LOW. A SURFACE LOW REFLECTION OF THE UPPER  
WAVE WILL DEVELOP SEWD FROM SE MB TO NRN WI AND WRN UPPER MI...WHILE  
A REMNANT LEE CYCLONE TRANSLATES EWD FROM NE KS ACROSS NRN MO IN  
ADVANCE OF AN MCV OVER N CENTRAL KS. A CORRIDOR OF LOW-MID 70S  
BOUNDARY LAYER DEWPOINTS WILL EXPAND EWD TODAY ACROSS THE CORN BELT  
FROM ERN NEB TO IL/INDIANA...BENEATH THE EWD EXTENSION OF A WARM  
ELEVATED MIXED LAYER. THE MOISTURE AND STEEP LAPSE RATES...IN  
COMBINATION WITH DAYTIME HEATING...WILL SUPPORT STRONG BUOYANCY  
/MLCAPE OF 3000-4000 J PER KG/ IN CONJUNCTION WITH EFFECTIVE BULK  
SHEAR OF 45-55 KT.  
 
FORECAST SOUNDINGS ARE FAVORABLE FOR SUPERCELLS GIVEN THE STRONG  
BUOYANCY AND LONG HODOGRAPHS WITH STRONG DEEP-LAYER VERTICAL SHEAR.  
IT APPEARS THAT THE INITIAL CONVECTION MAY FORM ALONG THE SYNOPTIC  
WIND SHIFT ENTERING SE SD AND NE NEB THIS AFTERNOON...ON THE SRN  
FLANK OF THE MORNING ELEVATED STORMS. STORM COVERAGE IS A BIT  
UNCERTAIN INVOF ERN NEB/WRN IA...BUT ANY STORMS THAT FORM WILL  
LIKELY BECOME SEWD-MOVING SUPERCELLS WITH AN ATTENDANT RISK FOR  
ISOLATED VERY LARGE HAIL AND DAMAGING WINDS INTO THIS EVENING.  
 
FARTHER E...SEPARATE STORMS ARE EXPECTED TO DEVELOP BY LATE  
AFTERNOON/EVENING ACROSS CENTRAL IL...IN ADVANCE OF THE REMNANT MCV  
THAT IS EXPECTED TO ACCELERATE EWD FROM NRN KS THIS MORNING IN  
RESPONSE TO STRENGTHENING FLOW ALOFT. THIS CONVECTION WILL ALSO BE  
IN AN ENVIRONMENT FAVORABLE FOR SUPERCELLS WITH VERY LARGE HAIL AND  
DAMAGING WINDS...AS WELL AS SUFFICIENT LOW-LEVEL MOISTURE AND SRH  
FOR A COUPLE OF TORNADOES. UPSCALE GROWTH INTO ONE OR MORE BOWING  
SEGMENTS IS EXPECTED TONIGHT ACROSS IL/INDIANA WITH AN INCREASING  
RISK FOR SWATHS OF DAMAGING WINDS. THE CLUSTERS WILL THEN MOVE  
ESEWD THROUGH EARLY SUNDAY...REACHING SRN OH AND NRN KY WITH A  
DAMAGING WIND RISK OVERNIGHT. THE EVOLUTION OF THE STORMS OVERNIGHT  
AND THE MAGNITUDE OF THE DAMAGING WIND RISK IS SOMEWHAT IN  
QUESTION...SINCE THE SYNOPTIC WAVE IS STILL LOCATED FAR TO THE  
NW...AND THE GREATEST STRENGTHENING OF MIDLEVEL FLOW WILL OCCUR  
WITHIN THE MDT RISK AREA THE LAST 3-6 HOURS OF THE FORECAST PERIOD.

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