bdgwx Posted July 15, 2018 Share Posted July 15, 2018 Thursday could be interesting in terms of severe weather for at least the western parts of this subforum. Link to comment Share on other sites More sharing options...
hlcater Posted July 16, 2018 Share Posted July 16, 2018 2 hours ago, bdgwx said: Thursday could be interesting in terms of severe weather for at least the western parts of this subforum. Nice 500mb speed max here. Low levels need some work if we're looking for tornado potential, but things would probably lend themselves to at least a decent MCS as things stand now. Link to comment Share on other sites More sharing options...
bdgwx Posted July 16, 2018 Author Share Posted July 16, 2018 There is a wide variety of solutions in model land right now. Even the GFS vs GFS/FV3 is strikingly different. And for what it's worth the FV3 has better low level setup. It also keeps interest alive on Friday further east. A lot of possibilities are still on the table at this point. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 17, 2018 Share Posted July 17, 2018 You know it's bad when even Broyles can't find an excuse to introduce more than a marginal risk. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 18, 2018 Share Posted July 18, 2018 Last night's 00z NAM was a big leap toward the GFS which has been portraying a more robust severe threat over the upper Midwest on Thursday evening. Mr. B. may have to upgrade his marginal risk, at least for portions of eastern Iowa if things hold as they are. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 18, 2018 Share Posted July 18, 2018 06Z NAM continued to up the ante for eastern/northeastern Iowa with 3KM EHIs into double digits and lapse rates >7c/km at all levels. Must be modeling the early clouds/precip clearing out. Only thing I really don't like on the forecast soundings is the weak winds above 500mb. From 700 to 500mb however westerly winds are progged to be quite strong above southwesterlies at 850mb and SSW at the surface. 3K NAM shows something we haven't seen a whole lot in 2018 - a sub-1000mb surface low with surface winds that are not horribly veered in the warm sector. It does however show a primarily linear convective mode at 00Z Friday but what looks like the possibility of a discrete cell or two toward the south end near the IA/MN border. GFS meanwhile is now a little slower/further west. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 18, 2018 Share Posted July 18, 2018 New 3K much further west and less impressive with IA convective activity at 00Z Friday, but somehow has two massive supercells tracking south through central Missouri. Hurl. Link to comment Share on other sites More sharing options...
hlcater Posted July 18, 2018 Share Posted July 18, 2018 2 hours ago, CheeselandSkies said: New 3K much further west and less impressive with IA convective activity at 00Z Friday, but somehow has two massive supercells tracking south through central Missouri. Hurl. Yup. 12z suite of both the NAMs and the GFS decided that the best course of action was just to take a dump all over Iowa and move to Misery. Gross. These runs have caused me to lose a good deal of confidence in the setup. GFS moved the surface low like 200 miles. Usually a change like that this late in the game means something. EDIT: What it meant was that the GFS's evolution of the surface low is being impacted by convection tugging the low further south and east than it otherwise would be going. I'm pretty sure... Link to comment Share on other sites More sharing options...
bdgwx Posted July 18, 2018 Author Share Posted July 18, 2018 It looks to me like the low was getting a tug from being in that right entrance region of that UL jet streak up there in Canada. But, on the 12Z run you can clearly tell that it wants to fully lock onto the southern flow and drift southeast instead of northeast. That is a huge change; no doubt about it. And seeing a change like this within 36-48 hours of event will definitely get a forecaster's attention. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 18, 2018 Share Posted July 18, 2018 Hmmm, despite the curveballs from the 12Z runs SPC did upgrade to slight for the southeast and east-central parts of Iowa, which is basically what I would have done based on last night's 0z and 6z runs, and then been given pause by the 12Z runs. Lol. Link to comment Share on other sites More sharing options...
hlcater Posted July 18, 2018 Share Posted July 18, 2018 Tomorrow in that instability department hinges entirely on how robust and the longevity of overnight MCS in NE. If it's able to push well into MO(Like the NAMs suggest) then warm front gets hungup and instability is slowed significantly, not to mention remnant cloud debris. This(or something close to it) seems to be the preferred outcome of the NWS. The models that lack a robust/long lasting MCS have no problem getting the warm front NE and build 4000+ SBCAPE. Link to comment Share on other sites More sharing options...
Stebo Posted July 19, 2018 Share Posted July 19, 2018 There are some high octane soundings on the NAM 12km/3km for KY/TN on Friday. I am not sure what to make of it though, but it is at the nose of the mid level jet so could be some credibility there. Link to comment Share on other sites More sharing options...
snowlover2 Posted July 19, 2018 Share Posted July 19, 2018 New day 2 sees expansion of marginal/slight risk areas as well as addition of a small enhanced area for S IN./KY. Quote DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1227 AM CDT THU JUL 19 2018 VALID 201200Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE OHIO AND TENNESSEE VALLEYS... ..SUMMARY SCATTERED SEVERE THUNDERSTORMS ASSOCIATED WITH LARGE HAIL, WIND DAMAGE AND A TORNADO THREAT WILL BE POSSIBLE FRIDAY AFTERNOON AND EVENING ACROSS PARTS OF THE OHIO AND TENNESSEE VALLEYS. ..OHIO AND TENNESSEE VALLEYS AN UPPER-LEVEL TROUGH WILL MOVE INTO THE OHIO AND TENNESSEE VALLEYS ON FRIDAY AS AN UNSEASONABLY STRONG MID-LEVEL JET MOVES THROUGH THE SOUTHWESTERN SIDE OF THE SYSTEM. AT THE SURFACE, A LOW IS FORECAST TO MOVE EAST-SOUTHEASTWARD ACROSS NORTHERN ILLINOIS DURING THE DAY AS A COLD FRONT ADVANCES EASTWARD ACROSS THE MID MISSISSIPPI VALLEY. AHEAD OF THE FRONT, A VERY MOIST AIRMASS SHOULD BE IN PLACE WITH SURFACE DEWPOINTS IN THE LOWER 70S F. THIS SHOULD ENABLE A CORRIDOR OF MODERATE TO STRONG INSTABILITY TO DEVELOP AHEAD OF THE FRONT BY AFTERNOON. AS LOW-LEVEL CONVERGENCE INCREASES ALONG THE FRONT, THUNDERSTORMS ARE FORECAST TO FORM DURING THE EARLY TO MID AFTERNOON IN THE MID MISSISSIPPI VALLEY WITH THE STORMS MOVING SOUTHEASTWARD ACROSS THE OHIO AND TENNESSEE VALLEYS DURING THE LATE AFTERNOON AND EARLY EVENING. FORECAST SOUNDINGS FOR PADUCAH, KY, EVANSVILLE, IN AND LOUISVILLE, KY AT 00Z ON SATURDAY SHOW MLCAPE VALUES OF 2500 TO 3000 J/KG, 0-6 KM SHEAR OF 40 TO 50 KT AND STEEP MID-LEVEL LAPSE RATES. THIS ENVIRONMENT SHOULD BE FAVORABLE FOR SUPERCELLS WITH LARGE HAIL. HAILSTONES OF GREATER THAN 2 INCHES WILL BE POSSIBLE WITH THE MOST INTENSE CELLS. AS THE LOW-LEVEL JET STRENGTHENS DURING THE EARLY EVENING, 0-3 KM STORM-RELATIVE HELICITY IS FORECAST TO REACH THE 200 TO 250 M2/S2 RANGE. THIS SHOULD BE ENOUGH FOR A TORNADO THREAT WITH THE MORE DOMINANT SUPERCELLS. STORM COVERAGE IS EXPECTED TO INCREASE MARKEDLY BY EARLY EVENING AS AN MCS ORGANIZES ACROSS THE OHIO AND TENNESSEE VALLEYS. IN RESPONSE, THE WIND-DAMAGE THREAT SHOULD GRADUALLY INCREASE DURING THE LATE AFTERNOON AND EARLY EVENING AS SUPERCELLS OR BOWING LINE SEGMENTS MOVE SOUTHEASTWARD ACROSS THE INSTABILITY CORRIDOR. AT THIS TIME, THE MODELS ARE IN GOOD AGREEMENT CONCERNING FRIDAY'S SCENARIO. THE ENVIRONMENT WILL LIKELY SUPPORT A SUBSTANTIAL SEVERE THREAT ACROSS THE OHIO AND TENNESSEE VALLEYS SO THIS OUTLOOK INCLUDES AN UPGRADE TO ENHANCED RISK. ..MAXIMUM RISK BY HAZARD TORNADO: 5% - SLIGHT WIND: 30% - ENHANCED HAIL: 30% - ENHANCED ..BROYLES.. 07/19/2018 Link to comment Share on other sites More sharing options...
OHweather Posted July 19, 2018 Share Posted July 19, 2018 Yeah late Friday in the lower Ohio Valley down into TN may be interesting. NAMs in all likelihood overdone, but...sort of checking a lot of boxes on this one, so the parameter space could end up being impressive, especially for July. The GFS and NAM both have a 50+ knot 500mb jet moving over the warm sector late Friday, with at least some backing of the surface wind due to the seasonably strong surface low and anomalously deep/negatively tilted trough. Very rich low-level moisture at the surface with a remnant EML advecting in aloft could allow for strong instability. Some questions regarding ongoing clouds/convection early Friday ahead of the front, though the EML advecting in aloft and tropical airmass could allow for quick recovery if the sun comes out for any length of time. You also have to figure the low-level winds probably won't be quite as backed/strong as the NAM, though the GFS still has enough helicity and more than enough instability for something interesting. So I don't think a lack of parameters will be an issue. With pretty decent large-scale forcing for ascent in the left-exit quad of the incoming jet streak and a ton of DCAPE on model soundings, have to think upscale growth into MCS(s) with a potential significant damaging wind threat could occur pretty quickly, limiting the possible window for supercells with a very large hail/tornado risk. The exact location of where any higher threat ends up panning out could depend a bit on mesoscale details that can't really be figured at this point, but I'd certainly imagine we'll see something higher than slight out of the SPC at some point, probably on one of these day 2's. Thursday is kind of a light version of Friday's setup in IA/MO...pretty gaudy instability and decent wind fields, but not as strong as what's modeled for Friday. Link to comment Share on other sites More sharing options...
cyclone77 Posted July 19, 2018 Share Posted July 19, 2018 Kind of lol worthy that we're going to have a hard time building decent instability for tomorrow's setup over Iowa after all the extreme instability we've seen the past several weeks beneath zero wind shear. We finally get a potent little vort and can't muster jack squat for cape. #****bag2018season Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 19, 2018 Share Posted July 19, 2018 4 hours ago, cyclone77 said: Kind of lol worthy that we're going to have a hard time building decent instability for tomorrow's setup over Iowa after all the extreme instability we've seen the past several weeks beneath zero wind shear. We finally get a potent little vort and can't muster jack squat for cape. #****bag2018season 06Z 3K NAM and 09Z HRRR actually get pretty frisky with some UH streaks over eastern Iowa at 0Z Friday. Link to comment Share on other sites More sharing options...
snowlover2 Posted July 19, 2018 Share Posted July 19, 2018 Risk areas expanded south and west. Wondering if enhanced might be shifted north later as 12z NAM was showing an intense looking line of storms around 0z tomorrow night for E IN/OH. Quote Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1236 PM CDT Thu Jul 19 2018 Valid 201200Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR SOUTHERN IL/IN...CENTRAL/WESTERN KY...MIDDLE/WESTERN TN...NORTHERN MS/AL... ...SUMMARY... Scattered severe thunderstorms associated with large hail, wind damage and a tornado threat will be possible Friday afternoon and evening across parts of the MIssissippi, Ohio and Tennessee Valleys. ...Synopsis... An anomalously strong deep layer trough and associated surface cyclone are expected to move southeastward from the upper Midwest into portions of the lower Great Lakes on Friday. The surface pattern will be complicated by one or more convectively-induced outflow boundaries, with a synoptic-scale surface trough/cold front expected to progress eastward south of the surface low through the period. A stout EML will spread eastward from the southern Plains over rich low-level moisture, resulting in a volatile thermodynamic environment developing over portions of the MS/TN/OH River Valleys and the Midwest. ...MS/TN/OH River Valleys into the Midwest... A potentially significant severe thunderstorm episode is possible across portions of the MS/TN/OH Valleys and the Midwest on Friday, though considerable uncertainty remains regarding convective evolution through the period. One or more clusters of convection will likely be ongoing Friday morning, though the remnants of these clusters are expected to push east through the day, allowing for moderate-to-strong destabilization in their wake. The strongest focus for convection will be the surface trough moving through IL/IN/OH, though this area will be somewhat removed from the stronger shear and instability, especially with northward extent. Foci for convective initiation will be more subtle further south and west, but the environment will also be much more volatile, with strong instability (MLCAPE of 2500-4000 J/kg possible) and effective shear (45-60 kt) in place. Scattered thunderstorms are expected to develop during the afternoon, potentially along the trailing surface boundary and also evolving out any early day elevated convection. Initially discrete storm modes will favor large hail (potentially greater than 2 inches in diameter), along with damaging wind gusts and a tornado or two. With time, evolution into one or more upscale-growing clusters is expected into the evening. Any such clusters would be capable of producing damaging wind swaths as they propagate to the southeast. Link to comment Share on other sites More sharing options...
andyhb Posted July 19, 2018 Share Posted July 19, 2018 Could pretty easily see a moderate for wind tomorrow given the amount of instability blended with unseasonably strong deep layer shear. My question revolves around the extent of the veering with height in the lowest 6 km and whether that might curb some of the long-lived MCS potential (and possibly raise the tornado threat). Link to comment Share on other sites More sharing options...
Hoosier Posted July 19, 2018 Share Posted July 19, 2018 Relative to what we have seen for the most part this year, it looks like a setup with decent potential. Perhaps a bit unusual as well with the southward extent of the better threat. Link to comment Share on other sites More sharing options...
snowlover2 Posted July 19, 2018 Share Posted July 19, 2018 There's a tornado watch in SE IA and a handfull of tornado warnings there as well. Link to comment Share on other sites More sharing options...
Chinook Posted July 19, 2018 Share Posted July 19, 2018 7 preliminary tornado reports in IA (probably 6 individual tornadoes) Link to comment Share on other sites More sharing options...
Dustin Posted July 19, 2018 Share Posted July 19, 2018 These cells look anemic at best. What gives? Link to comment Share on other sites More sharing options...
snowlover2 Posted July 19, 2018 Share Posted July 19, 2018 4 minutes ago, Chinook said: 7 preliminary tornado reports in IA (probably 6 individual tornadoes) Pretty amazing to get tornado warnings on cells that don't look like much with the one obvious exception. Link to comment Share on other sites More sharing options...
Dustin Posted July 19, 2018 Share Posted July 19, 2018 Well as soon as I say that, the southern-most cell is looking very impressive. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 19, 2018 Share Posted July 19, 2018 Pella tornadic cell looks quite impressive, most impressive of the year for the region in fact. Wish I was under it, or that it was about 100 miles to the east-northeast. Darn work. HRRR and 3K NAM both picked up on this pretty well this morning. When they roughly agree on UH tracks it's a good bet something is going to happen in that area, too bad they don't do so more frequently. Link to comment Share on other sites More sharing options...
geddyweather Posted July 19, 2018 Share Posted July 19, 2018 #partyatIowa's The Pella, IA storm is the best looking supercell I've seen this year since the one cyclic cell up in MT/SD a few weeks ago. The cell up around Marshalltown, IA just underwent a merger and is also beginning to look robust. As to why we had some warnings with other wise anemic looking cells on radar, lots of low level shear and SRH in that region to the south/SW of the low. Not surprised that even the smallest of showers have some spin to them. Link to comment Share on other sites More sharing options...
Jackstraw Posted July 19, 2018 Share Posted July 19, 2018 The one to the north by Marshalltown starting to rev up. Link to comment Share on other sites More sharing options...
Chinook Posted July 19, 2018 Share Posted July 19, 2018 tornado report at Leighton IA. I hope nobody was hurt. Link to comment Share on other sites More sharing options...
CheeselandSkies Posted July 19, 2018 Share Posted July 19, 2018 Holy cow, Oskaloosa could be in some serious trouble before long and they're not even in the polygon yet. Actually chased in this exact same area in June 2015, the probabilities were higher that day but of course the storms kept congealing and never produced. Link to comment Share on other sites More sharing options...
snowlover2 Posted July 19, 2018 Share Posted July 19, 2018 13 minutes ago, Jackstraw said: The one to the north by Marshalltown starting to rev up. Confirmed tornado on that one now. Link to comment Share on other sites More sharing options...
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