Quincy Posted October 3, 2013 Share Posted October 3, 2013 Lol, every time I see those posted, the first word (or more appropriately, question) that immediately enters my head afterwards is "Why?"It's not a perfect algorithm. I've seen 15% contours and no tornadoes at all. For me I like to see the overlap between helicity, strong shear and CAPE at a glance. Do you think the threat zone is significantly different than where the bullseye is? Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 It's not a perfect algorithm. I've seen 15% contours and no tornadoes at all. For me I like to see the overlap between helicity, strong shear and CAPE at a glance. Do you think the threat zone is significantly different than where the bullseye is? What I meant was the seemingly nebulous change last year that made this product a lot less telling than it used to be when it came to predicting significant tornadic events, namely the lowering of several of the parameter levels needed when calculating the index. Link to comment Share on other sites More sharing options...
Quincy Posted October 3, 2013 Share Posted October 3, 2013 What I meant was the seemingly nebulous change last year that made this product a lot less telling than it used to be when it came to predicting significant tornadic events, namely the lowering of several of the parameter levels needed when calculating the index.Ah, the CAPE threshold is low and 1500m LCL is silly.The SigTor parameter is basic and not perfect either, but here's where the SREF nails the highest values at 00z Sat. 5 on that scale is pretty high. Link to comment Share on other sites More sharing options...
cyclone77 Posted October 3, 2013 Share Posted October 3, 2013 What I meant was the seemingly nebulous change last year that made this product a lot less telling than it used to be when it came to predicting significant tornadic events, namely the lowering of several of the parameter levels needed when calculating the index. Didn't they tweak it again this year? Haven't looked at it very much, but I remember last year after they tweaked it the values were way higher than shown above for even marginal events. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 00z GFS paints a significant threat near and east of the SLP across a large portion of Eastern NE and IA (0-3 km SRH is anywhere from 250-500 m2/s2 across essentially the entire region) by 00z with SCP maxing out in Eastern NE including the Lincoln and Omaha metro areas. There also appears to be some warm frontal action earlier on in N IA and perhaps S MN. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 Didn't they tweak it again this year? Haven't looked at it very much, but I remember last year after they tweaked it the values were way higher than shown above for even marginal events. They still look the same to me at least concerning the MLCAPE/MLLCL thresholds. Link to comment Share on other sites More sharing options...
brettjrob Posted October 3, 2013 Share Posted October 3, 2013 Such a high ceiling, but I'm beginning to see another potential mode of failure after trying to visualize trends: the trough is increasingly pinched off with a several-contour closed low, especially on the NAM. Ironic, given my concern was a positive-tilt mess by Friday a few days ago. I can envision a scenario where the best dynamics and even kinematics get held back west of the warm sector until late, then a squall line goes up. Such a tremendous environment to work with, though. Anxiously awaiting SWODY2. Link to comment Share on other sites More sharing options...
Ian Posted October 3, 2013 Share Posted October 3, 2013 The numbers seem less meaningful but the highlighted zone is generally fine IMO given what goes into the product. Some events it sucks. One issue on highest end might be smallish area and limited time for highest impact. Would be nice if the cap went tomorrow heh. Link to comment Share on other sites More sharing options...
tornadotony Posted October 3, 2013 Author Share Posted October 3, 2013 Such a high ceiling, but I'm beginning to see another potential mode of failure after trying to visualize trends: the trough is increasingly pinched off with a several-contour closed low, especially on the NAM. Ironic, given my concern was a positive-tilt mess by Friday a few days ago. I can envision a scenario where the best dynamics and even kinematics get held back west of the warm sector until late, then a squall line goes up. Such a tremendous environment to work with, though. Anxiously awaiting SWODY2. I don't know...right now, the GFS and NAM both initiate by 21z, with what would likely end up being devastating results. Even if it held off until sundown, I'm not 100% sold it would linear (ref. 4/9/11)... This system does not sit well with me. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 Such a high ceiling, but I'm beginning to see another potential mode of failure after trying to visualize trends: the trough is increasingly pinched off with a several-contour closed low, especially on the NAM. Ironic, given my concern was a positive-tilt mess by Friday a few days ago. I can envision a scenario where the best dynamics and even kinematics get held back west of the warm sector until late, then a squall line goes up. Such a tremendous environment to work with, though. Anxiously awaiting SWODY2. One thing that isn't present this time with the closed low is an awry vertical wind profile (specifically upper level backing), which is a big plus. Link to comment Share on other sites More sharing options...
Jim Marusak Posted October 3, 2013 Share Posted October 3, 2013 the areas I would definitely flag for day 2 slight risk would be from KAQP to KSTP in MN, KEAU to KMRJ WI, then most if not all of Iowa, from KUIN to KSGF in MO, to areas east of US 81 in NE and KS, and US 81 from KYKN to KBKX. mod risk, if they wanted to go with it, I would say i-90 in MN to US 61 in WI, KDBQ to KSDA in IA, and 30 mi either side of I-29 from KFSD to KAFK. that;s just a first guess. feel free to make adjustments as you see fit. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 the areas I would definitely flag for day 2 slight risk would be from KAQP to KSTP in MN, KEAU to KMRJ WI, then most if not all of Iowa, from KUIN to KSGF in MO, to areas east of US 81 in NE and KS, and US 81 from KYKN to KBKX. mod risk, if they wanted to go with it, I would say i-90 in MN to US 61 in WI, KDBQ to KSDA in IA, and 30 mi either side of I-29 from KFSD to KAFK. that;s just a first guess. feel free to make adjustments as you see fit. Not too sure they'll throw in a moderate yet (despite the apparent high potential), considering the differences in primary area affected between the various guidance. Link to comment Share on other sites More sharing options...
Jim Marusak Posted October 3, 2013 Share Posted October 3, 2013 true, but i sort of placed it where it would be the most likely warm sector, as I am extrapolating attm. I know things will change. but that sticks out to me as the higher danger area, if anywhere. I have to admit, areas north of RGK and RWF I am tentative on for even slight risk. but attm, I'll keep it in there until the warm front settles into place. but I-90 looks fairly likely for me in MN attm. Link to comment Share on other sites More sharing options...
tornadotony Posted October 3, 2013 Author Share Posted October 3, 2013 Not too sure they'll throw in a moderate yet (despite the apparent high potential), considering the differences in primary area affected between the various guidance. I'd slap a moderate from Council Bluffs to Austin/Albert Lea since that area seems pretty primed to be slammed no matter whether the NAM or GFS timing wins out. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 I'd slap a moderate from Council Bluffs to Austin/Albert Lea since that area seems pretty primed to be slammed no matter whether the NAM or GFS timing wins out. True, there is a region there that seems to be overlapped between the two solutions. Link to comment Share on other sites More sharing options...
Quincy Posted October 3, 2013 Share Posted October 3, 2013 00z RGEM is in range and has sped up. Low is in south-central NE by 18z Friday with some storms firing along the warm front in IA. (18z RGEM had the low in eastern CO) The focus point looks like IA/MN border (RGEM) and a secondary line with the cold front moves through after 00z, but looks relatively weak. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 00z RGEM is in range and has sped up. Low is in south-central NE by 18z Friday with some storms firing along the warm front in IA. (18z RGEM had the low in eastern CO) The focus point looks like IA/MN border (RGEM) and a secondary line with the cold front moves through after 00z, but looks relatively weak. GGEM counterpart is essentially right in line with the GFS with the SLP in northeastern NE by 00z Saturday. Link to comment Share on other sites More sharing options...
MnWeatherman Posted October 3, 2013 Share Posted October 3, 2013 You haven't seen a sounding like that since then. The event I keep picturing is 3/29/98, the Comfrey and St. Peter >1 mi wide wedges, only the parameter space is even more impressive. The ceiling for this event is terrifying IMO, especially for an area where this kind of threat is out of season right now. This is the same day that popped into mind a few days ago. Scary to think about. NAM continues to nudge northward, and the 00z GFS shows this trend as well. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 New D2 stays slight (clearly leaning away from the NAM, and also considering the undercutting possibility) but... DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1246 AM CDT THU OCT 03 2013 VALID 041200Z - 051200Z ..THERE IS A SLGT RISK OF SVR TSTMS ACROSS ERN NEB...IA SRN MN...WI...NWRN MO...ERN KS...NWRN OK... ..SYNOPSIS LATEST GUIDANCE FROM THE GFS AND ECMWF MODELS SUGGESTS A SLOWER EVOLUTION TO THE UPPER TROUGH THAN COMPARED TO THE MORE AGGRESSIVE NAM MODEL WHICH IS FARTHER E WITH THE COLD FRONT AND DEEPER WITH THE UPPER LOW VALID AT 00Z. FOR THIS OUTLOOK...THE SLOWER SOLUTION IS PREFERRED. DURING THE DAY...LOW PRESSURE IS FORECAST TO DEEPEN OVER WRN KS AND INTO CNTRL NEB...WITH A NEARLY STATIONARY BOUNDARY FROM FSD/SUX EWD ACROSS NRN IA OR SRN MN AND INTO WRN WI. THIS BOUNDARY WILL BE REINFORCED BY EPISODES OF RAIN AND STORMS THROUGHOUT THE PERIOD...BUT MAY RETURN SLIGHTLY AS A WARM FRONT AHEAD OF THE DEVELOPING LOW. SEVERE STORMS WILL BE POSSIBLE IN ASSOCIATION WITH THIS FRONT WELL AHEAD OF THE MAIN SYSTEM. BY LATE AFTERNOON...A STRONG COLD FRONT WILL EXTEND SWWD FROM THE ERN NEB LOW...INTO CNTRL KS...NWRN OK AND THE TX PANHANDLE. A RAPIDLY DEVELOPING SQUALL LINE IS EXPECTED...WITH THE MOST INTENSE STORMS FROM ERN NEB INTO IA...AND PERHAPS SRN MN BY EVENING. ..ERN NEB...IA...SRN MN...WRN WI SCATTERED THUNDERSTORMS MAY BE ONGOING ALONG THE WARM FRONT EARLY WITH A THREAT OF HAIL. DEPENDING ON HOW MUCH RAIN FALLS ALONG THE FRONT...IT COULD MODULATE ITS LATITUDINAL LOCATION. HEATING WILL OCCUR S OF THE FRONT...WITH MODERATE INSTABILITY DEVELOPING. AS THE UPPER TROUGH NEARS...SHEAR PROFILES WILL INCREASE...WITH LARGE LOOPING HODOGRAPHS NEAR THE WARM FRONT. THIS WILL CONDITIONALLY FAVOR SUPERCELLS WITH LARGE HAIL AND A FEW TORNADOES. THE GFS AND EURO BOTH HAVE STRONG CONVECTIVE SIGNALS ACROSS NRN IA...FAR SRN MN...AND SWRN WI DURING THE AFTERNOON...SUGGESTING CLUSTERS OF SEVERE STORMS ARE PROBABLE. MEANWHILE TO THE SW...A LOW PRESSURE TROUGH WILL DEEPEN AHEAD OF A STRONG COLD FRONT WITH SFC LOW CENTER ACROSS ERN NEB BY 21-00Z. GFS SHOWS CLASSIC LOADED GUN TYPE SOUNDINGS OVER ERN NEB AHEAD OF THE LOW...WITH STRONG CONVERGENCE AND DEEP MIXED LAYERS JUST W OF THE FRONT AT PEAK HEATING. WITH LARGE HODOGRAPHS AND STRONG FORCING...THE AREA FROM ERN NEB INTO CNTRL IA APPEARS TO HAVE THE GREATEST THREAT OF TORNADIC SUPERCELLS. IF THE COLD AIR SURGES QUICKER THAN FORECAST...A MORE LINEAR STRUCTURE COULD RESULT...BUT WITH EMBEDDED ROTATION AND LEWPS CAPABLE OF SIGNIFICANT STRAIGHT LINE WINDS. A MODERATE RISK COULD BE ISSUED IN LATER OUTLOOKS AS PREDICTABILITY OF THIS SYSTEM INCREASES. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted October 3, 2013 Share Posted October 3, 2013 12z NAM painting even more instability now in the warm sector over 50-60kts of shear Link to comment Share on other sites More sharing options...
Quincy Posted October 3, 2013 Share Posted October 3, 2013 NAM continues to impress, wonder if NWS/SPC caves a bit...I could see a MOD risk for Day 2 this afternoon, especially if the GFS is even the slightest bit more impressive. Link to comment Share on other sites More sharing options...
Jonbo Posted October 3, 2013 Share Posted October 3, 2013 For once I can look into chasing within the central/Northern Iowa area. Thank you for all the information and insights into this very interesting event about to unfold. Link to comment Share on other sites More sharing options...
Quincy Posted October 3, 2013 Share Posted October 3, 2013 For once I can look into chasing within the central/Northern Iowa area. Thank you for all the information and insights into this very interesting event about to unfold. We'll keep following it. I'm new to the area and will be heading into the same general vicinity as you tomorrow. We can all learn from each other! Link to comment Share on other sites More sharing options...
ZackH Posted October 3, 2013 Share Posted October 3, 2013 Looking like we will possibly have up to 3 cars going out from UND if things stay constant. Early cloud cover and the large scale forcing potentially creating a convective mess near the low and WF are my two biggest fears. If storms can stay relatively isolated near the TP then the environment is looking extremely impressive. Link to comment Share on other sites More sharing options...
thewxmann Posted October 3, 2013 Share Posted October 3, 2013 Given that the NAM is now within its 36 hr range, and that it shows the cold air surging forward the fastest, I'll have to concede and jump on the NAM bandwagon now. Link to comment Share on other sites More sharing options...
JoMo Posted October 3, 2013 Share Posted October 3, 2013 Day 2 mod is up. 45% hatched area up there as well. Link to comment Share on other sites More sharing options...
Quincy Posted October 3, 2013 Share Posted October 3, 2013 Moderate Risk text: ..THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF IA/SOUTHERNMN......THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MIDWEST/UPPER MSRIVER VALLEY TO THE SOUTHERN PLAINS......SYNOPSIS...AN AMPLIFYING UPPER TROUGH/ASSOCIATED POLAR JET CURRENTLY OVER THEGREAT BASIN/CENTRAL ROCKIES IS EXPECTED TO TURN MOREEAST-NORTHEASTWARD AS IT REACHES THE NORTH-CENTRAL PLAINS/UPPERMIDWEST ON FRIDAY...ALTHOUGH SOME TIMING/PLACEMENT DIFFERENCES DOSTILL EXIST REGARDING THE UPPER TROUGH/FRONTAL LOCATIONS. IN ADVANCEOF A NORTHEASTWARD-MOVING SURFACE LOW...A WARM FRONT WILL GRADUALLYSPREAD NORTHWARD ACROSS THE MIDDLE MO VALLEY/UPPER MIDWEST/UPPER MSRIVER VALLEY...WHILE A COLD FRONT ACCELERATES SOUTHEASTWARD ACROSSTHE CENTRAL AND SOUTHERN PLAINS THROUGH FRIDAY NIGHT....MIDDLE MO VALLEY/UPPER MIDWEST/UPPER MS RIVER VALLEY...INITIALLY...ELEVATED TSTMS ARE LIKELY TO BE ONGOING NEAR/NORTH OFTHE WARM FRONT...WITH SOME LINGERING POTENTIAL FOR SEVERE HAIL EARLYIN THE PERIOD WITHIN A CORRIDOR FROM EASTERN NEB/IA INTO OTHER PARTSOF THE UPPER MS RIVER VALLEY. THIS CONVECTION COULD MODULATE THENORTHWARD-ADVANCEMENT OF THE WARM FRONT DURING THE DAY. STRONGHEATING WILL OTHERWISE OCCUR SOUTH OF THE WARM FRONT AND TO THE EASTOF THE ADVANCING COLD FRONT...WITH MODERATE INSTABILITY /2000+ J PERKG MLCAPE/ DEVELOPING ACROSS THE WARM SECTOR /OUTSIDE OF ANYPOTENTIAL OUTFLOW/. HEIGHT FALLS/INCREASING FORCING FOR ASCENT WILLOCCUR IN ASSOCIATION WITH THE APPROACHING UPPER TROUGH...WITHLOW-MID LEVEL SOUTH-SOUTHWESTERLY WINDS STEADILY INCREASING OVER THEREGION THROUGH FRIDAY NIGHT...ACCENTUATED BY 500 MB SOUTHWESTERLYWINDS INCREASING TO 80-95 KT FRIDAY NIGHT.THE MOST PROBABLE/CERTAIN FOCUS FOR DEEP CONVECTIVE DEVELOPMENT ANDASSOCIATED SEVERE POTENTIAL FRIDAY AFTERNOON/EVENING WILL LIKELY BEFOCUSED NEAR/EAST OF THE SURFACE TRIPLE POINT...INCLUDING AREAS FROMEASTERN NEB/SOUTHEAST SD INTO IA AND SOUTHERN MN/SOUTHWESTWI...ALTHOUGH THIS FOCUS COULD BE SHUNTED A BIT SOUTH PENDING EARLYDAY OUTFLOW/EFFECTIVE WARM FRONTAL LOCATION. THE EXACT EXTENT OFSTORM COVERAGE NEAR THE COLD FRONT AND WITHIN THE WARM SECTOR IS ABIT UNCERTAIN. BUT IN GENERAL...NEAR/JUST SOUTH OF THE WARM FRONTAND AHEAD OF THE SURFACE LOW IS WHERE LARGE LOOPING HODOGRAPHS ANDSUPPORT RISK FOR SUPERCELLS INCLUDING LARGE HAIL AND TORNADOES /ONEOR TWO POSSIBLY STRONG/ SHOULD BE MAXIMIZED...WITH POTENTIAL FORDAMAGING WINDS AS WELL. Link to comment Share on other sites More sharing options...
nwburbschaser Posted October 3, 2013 Share Posted October 3, 2013 They don't bring up the cold front issue in that update which is a good sign. Link to comment Share on other sites More sharing options...
thewxmann Posted October 3, 2013 Share Posted October 3, 2013 They don't bring up the cold front issue in that update which is a good sign. I'm not sure why though, as it will certainly be an issue south of the immediate triple point area. (If I were chasing I would definitely stay north of I-80.) Actually the more I think about it the similarities to 3/29/28 are uncanny, maybe shifted a bit south to straddle the IA-MN border. Link to comment Share on other sites More sharing options...
andyhb Posted October 3, 2013 Share Posted October 3, 2013 I'm not sure why though, as it will certainly be an issue south of the immediate triple point area. (If I were chasing I would definitely stay north of I-80.) Actually the more I think about it the similarities to 3/29/28 are uncanny, maybe shifted a bit south to straddle the IA-MN border. You mean 3/29/98? Link to comment Share on other sites More sharing options...
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