andyhb Posted May 7, 2015 Author Share Posted May 7, 2015 So my concerns at this point are starting to diminish. As far as low-level shear is concerned, doesn't the GFS have a low bias in these cases? Yeah, it has done this several times before, especially with a deepening low (fails to show enough of a low level wind response). NAM, as I mentioned above, continues to look like a very high end event with some truly outrageous wind profiles for May. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted May 7, 2015 Share Posted May 7, 2015 I really like the OK play on Saturday, much better shear vectors to the dryline and stronger/more favorable upper level winds as well. Link to comment Share on other sites More sharing options...
Chinook Posted May 7, 2015 Share Posted May 7, 2015 SPC upgraded to enhanced risk near TX/OK border today. Link to comment Share on other sites More sharing options...
OUGrad05 Posted May 7, 2015 Share Posted May 7, 2015 Actually, I like the fact that the heaviest convection over E OK before 12Z is much less widespread/moves out more quickly on the 12Z as opposed to previous runs. Plus, the overall evolution of the trough has been to favor a more rapid ejection and a broader, more consolidated mid-level feature, thereby greatly alleviating the veer-back-veer not just before 00Z, but also well into the overnight and early morning hours. The ECMWF and the GFS now seem to be inching toward better agreement on the timing of large-scale ascent and ejection, and the overall net trend is faster and more favorable for a significant severe outbreak on Saturday--one with a potentially long-lived threat for supercells/significant tornadoes overnight. So my concerns at this point are starting to diminish. As far as low-level shear is concerned, doesn't the GFS have a low bias in these cases? To me, what matters is the overall synoptic set-up, the improving thermodynamic prospects (at least before 18Z), and the strengthening low-level jet into the evening hours/overnight. Initiation time will still need to be nailed down, but fortunately there is ample time for change. The GFS is probably suffering from convective feedback due to WAA. The GFS is looking better but hodographs are still kinked but definitely improving. Link to comment Share on other sites More sharing options...
CUmet Posted May 7, 2015 Share Posted May 7, 2015 I favor the OK target as well, given that the veer-back-veer issue will be less pronounced down there, as well as the likely more-isolated coverage and later initiation. The eye-popping instability/shear combo over a large area would normally scream significant tornado outbreak to me, but the aforementioned veer-back-veer issue gives me quite a bit of pause. The 5/24/11 event had some veer-back-veer concerns as well, though they were more subtle than this event if I recall correctly. Things got pretty messy in N OK/S KS on that day. Link to comment Share on other sites More sharing options...
andyhb Posted May 7, 2015 Author Share Posted May 7, 2015 The 5/24/11 event had some veer-back-veer concerns as well, though they were more subtle than this event if I recall correctly. Things got pretty messy in N OK/S KS on that day. I believe this also had to do with a large amount of upper level backing north of the KS/OK stateline, since the trough was quite sharp and rather strongly negatively tilted. The trough here seems to be broadening a bit with each run, which may help improve the wind profile aloft. For the record, I also like the OK target more as of now due to the reasons you mentioned. Link to comment Share on other sites More sharing options...
Ian Posted May 7, 2015 Share Posted May 7, 2015 The northern target had veer back veer issues on April 14 2012 also. Probably other cases but remember many an unhappy NE chaser. Link to comment Share on other sites More sharing options...
tornadotony Posted May 7, 2015 Share Posted May 7, 2015 I favor the OK target as well, given that the veer-back-veer issue will be less pronounced down there, as well as the likely more-isolated coverage and later initiation. The eye-popping instability/shear combo over a large area would normally scream significant tornado outbreak to me, but the aforementioned veer-back-veer issue gives me quite a bit of pause. The 5/24/11 event had some veer-back-veer concerns as well, though they were more subtle than this event if I recall correctly. Things got pretty messy in N OK/S KS on that day. Veer-back-veer was actually far less subtle on 5/24/11. It was extreme, particularly in KS and then spreading south into OK after about 23z. OUN didn't launch a 00z sounding (for obvious reasons), but DDC gives you some idea of just how severely the flow aloft backed. Link to comment Share on other sites More sharing options...
thewxmann Posted May 7, 2015 Share Posted May 7, 2015 I'm starting to wonder whether a D2 moderate risk will be issued for tomorrow with the later D2 update this morning. Both the NAM and GFS have a favorable parameter space over a large area and the ascent from that lead impulse should be substantial enough to encourage fairly widespread initiation. Forcing is fairly diffuse too which may encourage a rather long-lived discrete mode. NAM has over 4,000 J/kg banked up against the Caprock with 45 kt at H5 at 21Z tomorrow. Should support monster hailers if nothing else. Link to comment Share on other sites More sharing options...
tornadotony Posted May 7, 2015 Share Posted May 7, 2015 Continuing with the 5/24/11 comparison for a second, besides veer-back-veer causing issues, you also had extreme upper-level difluence/divergence across the warm sector, leading to substantial upward vertical motion to help allow for widespread convection. I just don't see this degree of difluence or the degree of veer-back-veer in the shear profiles that we saw on 5/24/11 being realized with this trough. Link to comment Share on other sites More sharing options...
CUmet Posted May 7, 2015 Share Posted May 7, 2015 Veer-back-veer was actually far less subtle on 5/24/11. It was extreme, particularly in KS and then spreading south into OK after about 23z. OUN didn't launch a 00z sounding (for obvious reasons), but DDC gives you some idea of just how severely the flow aloft backed. Sorry, I meant more subtle over OK. What the NAM has is probably comparable to 5/24/11 with regard to this issue, but the GFS is much worse. Link to comment Share on other sites More sharing options...
geddyweather Posted May 7, 2015 Share Posted May 7, 2015 SPC Day 2 inbound with a large MDT spot over Wrn OK/TX panhandle Link to comment Share on other sites More sharing options...
thewxmann Posted May 7, 2015 Share Posted May 7, 2015 SPC Day 2 inbound with a large MDT spot over Ern OK/TX panhandle I think two MDTs just broke the SPC website Link to comment Share on other sites More sharing options...
geddyweather Posted May 7, 2015 Share Posted May 7, 2015 DAY 2 CONVECTIVE OUTLOOKNWS STORM PREDICTION CENTER NORMAN OK1226 PM CDT THU MAY 07 2015VALID 081200Z - 091200Z...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF NORTHWESTTX...WESTERN OK AND SOUTHERN KS......THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF THE SOUTHERNAND CENTRAL PLAINS......THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SOUTHERNAND CENTRAL PLAINS......THERE IS A MRGL RISK OF SVR TSTMS FROM SW TX TO IL......THERE IS A MRGL RISK OF SVR TSTMS ALONG THE CAROLINA COAST......SUMMARY...SEVERE THUNDERSTORMS WILL DEVELOP ACROSS THE SOUTHERN AND CENTRALGREAT PLAINS. VERY LARGE HAIL...DAMAGING WINDS...AND TORNADOES AREEXPECTED...ESPECIALLY ACROSS WESTERN OKLAHOMA....SOUTHERN/CENTRAL GREAT PLAINS...LARGE-SCALE HEIGHT FALLS WILL SPREAD INTO THE DESERT SOUTHWESTDURING THE DAY2 PERIOD AS STRONG UPPER LOW TRANSLATES INTO THE4-CORNERS REGION LATE. DIFLUENT HIGH-LEVEL FLOW WILL SPREAD ACROSSTHE SRN/CNTRL PLAINS AHEAD OF THIS FEATURE WITH SUBSTANTIAL FLOWEXPECTED TO OVERSPREAD A PRONOUNCED DRY LINE DURING PEAK HEATING.STRONG SHEAR AND FAVORABLE HIGH-LEVEL VENTING SHOULD RESULT IN ACONCENTRATED CORRIDOR OF SEVERE THUNDERSTORMS...ESPECIALLY ACROSSWRN OK.BOTH THE GFS AND NAM SUGGEST A WEAK MID-LEVEL SHORT-WAVE TROUGH WILLEJECT ACROSS THE SRN HIGH PLAINS AFTER 18Z...TRANSLATING INTO WRN OKBY 09/00Z. THIS FEATURE IS EXPECTED TO AID CONVECTIVE DEVELOPMENTALONG DRY LINE BY EARLY-MID AFTERNOON ACROSS THE HIGHPLAINS...SPREADING/DEVELOPING EWD TOWARD THE I-35 CORRIDOR BY LATEAFTERNOON. SHEAR PROFILES FAVOR SUPERCELLS AND BOUNDARY-LAYERMOISTURE...ABSENT DAY1 CONVECTIVE DISRUPTION...SHOULD EASILY ADVANCENWD TOWARD SYNOPTIC BOUNDARY THAT SHOULD ORIENT ITSELF IN AN E-WFASHION ACROSS SRN KS/SERN CO. IF MOISTURE/INSTABILITY RETURN TOTHE SYNOPTIC BOUNDARY...AS SUGGESTED BY LATEST NAM...ROBUST SEVERETHUNDERSTORMS WILL DEVELOP ALONG A FAVORABLY SHEARED BOUNDARY THATCOULD ENHANCE TORNADO POTENTIAL WITH ANY SUPERCELLS. EVENSO...DISCRETE WARM SECTOR SUPERCELLS ARE EXPECTED TO DEVELOP ACROSSTHE AFOREMENTIONED REGION OF NWRN TX...NWD TO THE SYNOPTIC FRONTWITHIN AN ENVIRONMENT SEEMINGLY FAVORABLE FOR VERY LARGEHAIL...TORNADOES...AND DAMAGING WINDS. FORECAST NAM SOUNDINGSEXHIBIT PROFILES CHARACTERISTIC OF STORMS CAPABLE OF PRODUCING HAILIN EXCESS OF 2 INCHES AND PERHAPS EVEN A FEW STRONG TORNADOES.SCT SUPERCELLS SHOULD DEVELOP/SPREAD NEWD TOWARD THE I-35 CORRIDORBY LATE AFTERNOON AS FOCUSED LLJ AIDS INFLOW. DURING THEEVENING...SEVERE CLUSTERS SHOULD EVOLVE ALONG THE E-W SYNOPTIC FRONTWHERE LLJ IMPINGES ON BOUNDARY...DARROW.. 05/07/2015 Link to comment Share on other sites More sharing options...
jameswx Posted May 7, 2015 Share Posted May 7, 2015 I'm starting to wonder whether a D2 moderate risk will be issued for tomorrow with the later D2 update this morning. Both the NAM and GFS have a favorable parameter space over a large area and the ascent from that lead impulse should be substantial enough to encourage fairly widespread initiation. Forcing is fairly diffuse too which may encourage a rather long-lived discrete mode. Good call, Andy. Link to comment Share on other sites More sharing options...
geddyweather Posted May 7, 2015 Share Posted May 7, 2015 I think two MDTs just broke the SPC website HA! Yes, just noticed that. They still need to do some coding/banner work for multi-day outbreaks. Link to comment Share on other sites More sharing options...
Wxradar 30623 Posted May 7, 2015 Share Posted May 7, 2015 Yeah they just fixed it. Link to comment Share on other sites More sharing options...
geddyweather Posted May 7, 2015 Share Posted May 7, 2015 Here we go: MESOSCALE DISCUSSION 0533NWS STORM PREDICTION CENTER NORMAN OK1252 PM CDT THU MAY 07 2015AREAS AFFECTED...SRN OK THROUGH NRN TXCONCERNING...SEVERE POTENTIAL...WATCH LIKELYVALID 071752Z - 071945ZPROBABILITY OF WATCH ISSUANCE...80 PERCENTSUMMARY...STORMS ARE EXPECTED TO BECOME BETTER ORGANIZED ANDINCREASE IN INTENSITY FROM SRN OK THROUGH NRN TX THIS AFTERNOON.LARGE HAIL AND DAMAGING WIND WILL BE THE MAIN THREATS...BUT A FEWTORNADOES CANNOT BE RULED OUT. WW WILL LIKELY BE NEEDED SOON.DISCUSSION...STORMS HAVE LARGELY EVOLVED INTO AN MCS FROM NWRN TXINTO SWRN OK AND IS MOVING SLOWLY EWD. STORM EMBEDDED WITHIN LEADINGEDGE OF MCS OVER SWRN OK IS BEGINNING TO SHOW UPDRAFT ROTATION. THESFC LAYER DOWNSTREAM FROM THIS ACTIVITY IS UNDERGOING RAPID RECOVERYAS AN OLD OUTFLOW BOUNDARY WEAKENS AND LIFTS NWD...ALLOWING RICHER/UPPER 60S F DEWPOINTS/ TO ADVECT THROUGH NRN TX AND SRN OK. MIXEDCONVECTIVE MODE WITHIN THE MCS AND GENERALLY MODEST LOW-LEVEL SHEARLOWERS CONFIDENCE IN A MORE SUBSTANTIAL TORNADO THREAT.NEVERTHELESS...DEEP SHEAR FROM 40-50 KT...A MOIST BOUNDARY LAYER ANDMODERATE INSTABILITY WILL SUPPORT EMBEDDED ORGANIZED STRUCTURESWITHIN THE MCS INCLUDING SUPERCELLS AND BOWING SEGMENTS. MOREOVER AFEW DISCRETE STORMS MIGHT ALSO DEVELOP SEPARATE FROM THE MCS. ASTHESE STORMS INTERACT WITH THE RESIDUAL BOUNDARY...ISOLATEDTORNADOES WILL BE POSSIBLE DESPITE RELATIVELY SMALL AMBIENTHODOGRAPHS. OTHERWISE...LARGE HAIL AND DAMAGING WIND WILL THE MAINTHREATS AS THIS ACTIVITY DEVELOPS EWD THIS AFTERNOON...DIAL/HART.. 05/07/2015 Bolded an interesting bit that may affect TOR potential later, but we'll see. Link to comment Share on other sites More sharing options...
*IndyMeso* Posted May 7, 2015 Share Posted May 7, 2015 Severe Thunderstorm Watch goes up and the KFDR radar goes down per NWS Chat. Yeesh bad timing there. Link to comment Share on other sites More sharing options...
Chinook Posted May 7, 2015 Share Posted May 7, 2015 Severe Thunderstorm Watch goes up and the KFDR radar goes down per NWS Chat. Yeesh bad timing there. I'm surprised TOKC didn't get slammed by damaging 70-90mph winds, as it seemed to be getting hit by a tornado at one point yesterday. Link to comment Share on other sites More sharing options...
Misstertwister Posted May 7, 2015 Share Posted May 7, 2015 Concerned dad here in edmond, ok. Anyone have any thoughts on where storms may fire first Saturday. Have outdoor activities until 4:00 in N OKC Link to comment Share on other sites More sharing options...
andyhb Posted May 7, 2015 Author Share Posted May 7, 2015 A bit concerned about the outflow/cold pool from the ongoing MCS in OK/TX messing up tomorrow. Despite the fact that it is a long way in advance, cold pools can be very stubborn, since temps/dewpoints have dropped into the low 60s/upper 50s behind that thing. That said, wherever that boundary ends up setting up could see enhanced tornado potential. Link to comment Share on other sites More sharing options...
Chicago Storm Posted May 7, 2015 Share Posted May 7, 2015 Veer-back-veer seems to have improved on the 06z/12z GFS runs, but it still seems to be breaking out an awful lot of convection before primetime on Saturday and still refuses to appreciably increase its low level shear values. The ECMWF continues to do the same as well, and that's my biggest (and really only) issue with Saturday. Link to comment Share on other sites More sharing options...
UKStormFan Posted May 7, 2015 Share Posted May 7, 2015 Cell looking good to the SW of Wichita Falls. Good stream from Tornado Tech on the TVN website currently. 4000 viewers. Link to comment Share on other sites More sharing options...
Indystorm Posted May 7, 2015 Share Posted May 7, 2015 That said, wherever that boundary ends up setting up could see enhanced tornado potential. I am concerned that cold pool might push the boundary farther east into more populated zones than originally thought. Link to comment Share on other sites More sharing options...
tornadotony Posted May 7, 2015 Share Posted May 7, 2015 A bit concerned about the outflow/cold pool from the ongoing MCS in OK/TX messing up tomorrow. Despite the fact that it is a long way in advance, cold pools can be very stubborn, since temps/dewpoints have dropped into the low 60s/upper 50s behind that thing. That said, wherever that boundary ends up setting up could see enhanced tornado potential. Yeah...no. Not unless that MCS magically backbuilds for the next 18 hours and the low-level cyclone never develops. Link to comment Share on other sites More sharing options...
andyhb Posted May 7, 2015 Author Share Posted May 7, 2015 Yeah...no. Not unless that MCS magically backbuilds for the next 18 hours and the low-level cyclone never develops. Alright, was just a thought. Link to comment Share on other sites More sharing options...
UKStormFan Posted May 7, 2015 Share Posted May 7, 2015 Only me who thought things would have caught spark a little more by this stage? Link to comment Share on other sites More sharing options...
Quincy Posted May 7, 2015 Share Posted May 7, 2015 MCS contamination. Gobbling up those semi discrete cells. North Texas is going to junk. I'm heading west to play the dryline. The environment is decent SE of Lubbock with moderate destabilization and backed low-level winds. Link to comment Share on other sites More sharing options...
tornadotony Posted May 7, 2015 Share Posted May 7, 2015 The ECMWF continues to do the same as well, and that's my biggest (and really only) issue with Saturday. I just don't know how much it'll matter. A lot of the early convection the models fire appears to be east of the main instability axis, allowing for maximum destabilization in the real zone of interest. I wouldn't discount it as a factor, but it doesn't concern me quite as much as it would in most cases. Link to comment Share on other sites More sharing options...
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