Tim from Springfield (IL) Posted August 5, 2011 Share Posted August 5, 2011 Starting a new thread for next week after seeing this morning's Day 4 SPC outlook: http://www.spc.noaa....s/exper/day4-8/ Link to comment Share on other sites More sharing options...
andyhb Posted August 5, 2011 Share Posted August 5, 2011 Looking like we could possibly see a multi day severe threat from this event... Link to comment Share on other sites More sharing options...
Amped Posted August 5, 2011 Share Posted August 5, 2011 Pressure gradient across the country sucks entire country between 1004mb and 1015 MB. No surface jet in that kind of crap. Link to comment Share on other sites More sharing options...
JoMo Posted August 5, 2011 Share Posted August 5, 2011 It's not supposed to storm here in August. Link to comment Share on other sites More sharing options...
andyhb Posted August 6, 2011 Share Posted August 6, 2011 Whether anything will go up and be able to sustain itself is the question, the models still have quite a bit of variability between them... Link to comment Share on other sites More sharing options...
tornadotony Posted August 6, 2011 Share Posted August 6, 2011 Pressure gradient across the country sucks entire country between 1004mb and 1015 MB. No surface jet in that kind of crap. There's no such thing as a "surface jet." Link to comment Share on other sites More sharing options...
Powerball Posted August 6, 2011 Share Posted August 6, 2011 Well I guess we can try again Sunday for some severe weather. I would like to see a little more shear and moisture though. Link to comment Share on other sites More sharing options...
Amped Posted August 6, 2011 Share Posted August 6, 2011 There's no such thing as a "surface jet." I meant LLVL jet. Up to 900mb or so the height field usually still looks like the SLP field. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 6, 2011 Share Posted August 6, 2011 The tornado threat might be higher than I thought in southwest MN/northwest IA looking tomorrow looking at the 0z NAM. Link to comment Share on other sites More sharing options...
tornadotony Posted August 6, 2011 Share Posted August 6, 2011 The tornado threat might be higher than I thought in southwest MN/northwest IA looking tomorrow looking at the 0z NAM. Funny you mention that...I realized recently that this year is the only year that I can think of off the top of my head that has had an EF3 or greater in each month this far into the year. 1/1 2/28 3/26 4/9 4/10 4/14 4/15 4/16 4/19 4/22 4/25 4/26 4/27 5/21 5/22 5/24 5/25 6/1 7/17 Link to comment Share on other sites More sharing options...
tornadotony Posted August 6, 2011 Share Posted August 6, 2011 The tornado threat might be higher than I thought in southwest MN/northwest IA looking tomorrow looking at the 0z NAM. Also, the NAM is just brutal out there. It has the one thing that kept us in check our last couple tornado threats out here: sufficient-good mid-level (700-500mb) flow. Link to comment Share on other sites More sharing options...
andyhb Posted August 6, 2011 Share Posted August 6, 2011 Agreed, the helicities are looking more favorable than in any of the previous runs... Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 6, 2011 Share Posted August 6, 2011 Also, the NAM is just brutal out there. It has the one thing that kept us in check our last couple tornado threats out here: sufficient-good mid-level (700-500mb) flow. Ya 45kts at H7 and flags just above that is always impressive for this time of year, stronger and better 850's on the NAM leading to better low level shear and getting backed flow at the sfc creating over 90 degrees of turning from the sfc to 700mb. Link to comment Share on other sites More sharing options...
andyhb Posted August 6, 2011 Share Posted August 6, 2011 MDT risk perhaps? Link to comment Share on other sites More sharing options...
tornadotony Posted August 6, 2011 Share Posted August 6, 2011 Ya 45kts at H7 and flags just above that is always impressive for this time of year, stronger and better 850's on the NAM leading to better low level shear and getting backed flow at the sfc creating over 90 degrees of turning from the sfc to 700mb. The fact that you've 55kt anywhere between 700mb and 500mb this time of year in the warm sector environment just screams trouble...add in some dCVA and a dryline for sfc convergence...plus low LCLs...and shear vectors perpendicular to the dryline...yikes. Link to comment Share on other sites More sharing options...
tornadotony Posted August 6, 2011 Share Posted August 6, 2011 MDT risk perhaps? This time of year I'd always be wary to go mdt risk prior to 13z, even 1630z, until all mesoscale conditions (leftover systems, boundary placement) become at least somewhat clear. Mdt-risk caliber events this time of year, both wind (derechos) and tornadoes (rare but this area is the area to get them in August) are EXCEPTIONALLY dependent on mesoscale factors that are pretty much next to impossible to nail even at this timeframe. My personal opinion, if I were doing an outlook (and now with having looked at the GFS) would be a slight risk with 10% hatched tornado probabilities and 30% hatched wind and hail about near where they have the 30% on the day 2. Link to comment Share on other sites More sharing options...
andyhb Posted August 6, 2011 Share Posted August 6, 2011 Yeah, posted that before I looked at the GFS...still showing relatively strong mid level flow, however. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 6, 2011 Share Posted August 6, 2011 The fact that you've 55kt anywhere between 700mb and 500mb this time of year in the warm sector environment just screams trouble...add in some dCVA and a dryline for sfc convergence...plus low LCLs...and shear vectors perpendicular to the dryline...yikes. Also it looks like the cap is strong enough to hold off convection for awhile and the dryline tightens/convergence increases nicely once we hit late afternoon around FSD into southwest MN...storms will have no problem moving off the boundary. Once they start moving east though, instability parameters lessen though, but they should be in a pretty darn good environment atleast for awhile. Link to comment Share on other sites More sharing options...
tornadotony Posted August 6, 2011 Share Posted August 6, 2011 Yeah, posted that before I looked at the GFS...still showing relatively strong mid level flow, however. The GFS didn't change my thinking...it merely solidified it. It's slightly weaker (5kt ish). Not a big difference. And the big point to make from it is that there's no relative weakness in the midlevels. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 6, 2011 Share Posted August 6, 2011 too bad we didn't have more instability and further east or we could see a pretty good wind event continue overnight given the jet. But I would think whatever congeals will survive ateast into northeast IA/WI Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 6, 2011 Share Posted August 6, 2011 0z 4km WRF... Link to comment Share on other sites More sharing options...
cyclone77 Posted August 6, 2011 Share Posted August 6, 2011 Southwest Minnesota tomorrow. Not bad. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted August 6, 2011 Share Posted August 6, 2011 Southwest Minnesota tomorrow. Not bad. The hodograph for that area is quite impressive..a serious improvement from the 12z NAM, really strengthened sfc-850mb winds on this run. Link to comment Share on other sites More sharing options...
cyclone77 Posted August 6, 2011 Share Posted August 6, 2011 Based on the 00z guidance I'm thinking about heading to southwest Minnesota tomorrow. Haven't chased in over 2 months so I'm itching to head out. Link to comment Share on other sites More sharing options...
andyhb Posted August 6, 2011 Share Posted August 6, 2011 0z 4km WRF... Yikes... Link to comment Share on other sites More sharing options...
cyclone77 Posted August 6, 2011 Share Posted August 6, 2011 The hodograph for that area is quite impressive..a serious improvement from the 12z NAM, really strengthened sfc-850mb winds on this run. Yeah it's pretty impressive. This time of year it always seems hard to get decent winds below H7, which is sort of a turnoff for me as far as chasing. Obviously high cape/weak low-level winds can be fruitful sometimes, but I hate chasing setups with weak sub H7-8 winds. Link to comment Share on other sites More sharing options...
Chicago Storm Posted August 6, 2011 Share Posted August 6, 2011 Based on the 00z guidance I'm thinking about heading to southwest Minnesota tomorrow. Haven't chased in over 2 months so I'm itching to head out. Have an extra seat? If I can clear other obligations for tomorrow morning, I might consider heading out. Link to comment Share on other sites More sharing options...
cyclone77 Posted August 6, 2011 Share Posted August 6, 2011 Have an extra seat? If I can clear other obligations for tomorrow morning, I might consider heading out. Yeah it might be worth the trip if the NAM is to be believed. The mid-level support is very nice for this time of year. I like the Minnesota/Iowa border about 30 miles east of the SD border for a starting point based on the guidance tonight. As Tony pointed out the residual convection/clouds/boundaries may tweak that some by tomorrow though. Link to comment Share on other sites More sharing options...
andyhb Posted August 6, 2011 Share Posted August 6, 2011 5% Tornado probs. DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT SAT AUG 06 2011 VALID 061200Z - 071200Z ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS UPPER MIDWEST TO CENTRAL PLAINS... ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS LOWER GREAT LAKES/OH VALLEY REGION... ...SYNOPSIS... DOMINANT UPPER-AIR FEATURE WILL REMAIN STG ANTICYCLONE WITH CENTER DRIFTING WWD ACROSS N TX. ALTHOUGH RIDGING ACROSS SRN TIER OF CONUS WILL REMAIN STG...BELT OF WLYS WILL EXPAND SLIGHTLY SWD THROUGH PERIOD...WITH WEAK HEIGHT FALLS ALONG MUCH OF THEIR SRN PERIPHERY FROM GREAT BASIN TO MID-ATLANTIC REGION. HEIGHT FALLS ALSO SHOULD EXTEND INTO CORE OF ANTICYCLONE BY LATE IN PERIOD...WITH GREAT MAJORITY OF TOTAL OPERATIONAL/SREF MODELS LOSING 594-DAM HEIGHT CONTOUR AT 500-MB BY 7/12Z. SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER WRN DAKOTAS -- IS FCST TO MOVE EWD ACROSS ND AND PORTIONS SD TO UPPER MS VALLEY...THEN TURNING ESEWD OVER PORTIONS LS AND WI BY 7/12Z. AS THAT OCCURS...ASSOCIATED SFC COLD FRONT SHOULD MOVE NEWD FROM PRESENTLY ESTIMATED POSITION OVER EXTREME SWRN SD...DEEPENING SLIGHTLY AND REACHING NRN WI BEFORE END OF PERIOD. AT 7/00Z...EXPECT LOW OVER NERN SD/W-CENTRAL MN...COLD FRONT SWWD ACROSS CENTRAL/SWRN NEB TO NERN CO..AND TWO WARM FRONTS -- ONE FROM LOW SEWD OVER CENTRAL IA AND ANOTHER EWD OVER NRN WI. THIS FRONTAL ZONE SHOULD BEND EWD ACROSS PORTIONS CENTRAL IL TO OH...QUASISTATIONARY DURING AFTERNOON EXCEPT DRIFTING SEWD JUST SW OF WEAK FRONTAL-WAVE LOW MOVING SLOWLY EWD ACROSS NRN INDIANA/OH. ...UPPER MIDWEST TO CENTRAL PLAINS... PRIMARY SVR THREAT TODAY WILL OCCUR AHEAD OF PROGRESSIVE SHORTWAVE TROUGH...AND ALONG/AHEAD OF SFC COLD FRONT WHERE DIURNAL/DIABATIC SFC HEATING...RICH AND EVAPOTRANSPIRATIVELY ENHANCED SFC MOISTURE...AND FAVORABLE DEEP-LAYER SHEAR WILL BE JUXTAPOSED. CLOUD/PRECIP SHIELD ASSOCIATED WITH ONGOING AND/OR MORNING CONVECTION ACROSS PORTIONS ND/MN WILL MOVE EWD...REINFORCING BAROCLINICITY WITH NRN WARM-FRONTAL ZONE OVER THIS REGION AND EFFECTIVELY BOUNDING ORGANIZED SVR THREAT ON N END. REGION BETWEEN WARM FRONTS WILL CONTAIN LARGEST LOW-LEVEL HODOGRAPHS AND GREATEST RELATIVE SUPERCELL/TORNADO RISK...ALTHOUGH LONGEVITY OF FAVORABLE/SUPERCELL MODES IS IN QUESTION. SFC DEW POINTS 70S F WILL CONTRIBUTE TO MLCAPE AROUND 2000-3000 J/KG...WITH EFFECTIVE SHEAR MAGNITUDES 40-50 KT OVER PORTIONS MN...ERN SD AND NWRN IA. BAND OF TSTMS SHOULD BUILD SWWD INTO CENTRAL PLAINS BY LATE AFTERNOON. DEEP-LAYER SHEAR WILL DIMINISH WITH SWD EXTENT...BUT MORE INTENSELY HEATED/MIXED BOUNDARY LAYERS WILL SUPPORT POTENTIAL FOR TSTMS TO PRODUCE SVR HAIL/GUSTS OVER PORTIONS NEB/KS. MEANWHILE...POSTFRONTAL/UPSLOPE FLOW OVER PORTIONS NERN CO AND ERN WY WILL SUPPORT ISOLATED TO WIDELY SCATTERED AFTERNOON TSTMS IN REGIME OF STG DIRECTIONAL SHEAR AND 50-60 KT UPPER LEVEL WINDS TO AID IN ORGANIZATION. LOW-LEVEL WINDS SHOULD BE RATHER WEAK...HOWEVER...LIMITING HODOGRAPH SIZE IN ENTIRE SWATH FROM ERN WY SEWD ACROSS KS/OK. ...LOWER GREAT LAKES/OH VALLEY REGION... WIDELY SCATTERED TO SCATTERED TSTMS IN CLUSTERS AND E-W BANDS ARE POSSIBLE ALMOST ANYWHERE FROM SRN/CENTRAL PLAINS TO CENTRAL APPALACHIANS...STG/DAMAGING GUSTS BEING PRIMARY THREAT. GREATEST JUXTAPOSITION OF SUSTAINED INSOLATION...RICH LOW-LEVEL MOISTURE...WEAK CINH AND CONVECTIVE PRECIP AMONGST OPERATIONAL/SREF PROGS IS OVER SWATH FROM SRN IL EWD TO ENEWD NEAR OH RIVER. STG SFC HEATING WILL OCCUR OVER PARTS OF THIS REGION...AND IT WILL BE NEEDED TO OFFSET WEAK MID-UPPER LEVEL LAPSE RATES TO YIELD DEEPLY BUOYANT PROFILES...WITH MLCAPE 1000-2000 J/KG. RELATIVELY DENSE CONCENTRATION OF TSTMS MAY RESULT IN AT LEAST MESOBETA SCALE COLD-POOL DEVELOPMENT AND UPSCALE GROWTH FOR A FEW HOURS IN LATE AFTERNOON AND EARLY EVENING. ...ERN MT... ISOLATED TO WIDELY SCATTERED TSTMS MAY DEVELOP DURING MID-LATE AFTERNOON INVOF TROUGH AND WEAK FRONTAL ZONE EXTENDING SWD FROM SK...ASSOCIATED WITH NRN-STREAM SHORTWAVE TROUGH OVER CANADA. MRGL/RESIDUAL MOISTURE AND DIABATIC SFC HEATING WILL CONTRIBUTE TO WEAK CINH AND 500-1000 J/KG MLCAPE...AFTER PASSAGE OF SHORTWAVE RIDGING. MOST INTENSE CELLS MAY PRODUCE HAIL/GUSTS NEAR SVR LEVELS...THOUGH DEEP-LAYER SHEAR AND TSTM COVERAGE EACH SHOULD BE TOO SMALL FOR ORGANIZED SVR THREAT. ..EDWARDS/GRAMS.. 08/06/2011 Link to comment Share on other sites More sharing options...
andyhb Posted August 6, 2011 Share Posted August 6, 2011 30% Svr in new Day 3 as well. 00Z NAM verbatim would not be pretty across Central MO with the exception of possible capping (although the GFS lays off the capping much more than the NAM)... DAY 3 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0222 AM CDT SAT AUG 06 2011 VALID 081200Z - 091200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM A PORTION OF THE CNTRL PLAINS INTO THE MIDDLE MS VALLEY AREA... ...SYNOPSIS... SLOW BUT GRADUAL AMPLIFICATION OF LARGE SCALE TROUGH IN THE EAST THROUGH MONDAY WILL RESULT IN SUPPRESSION OF SERN U.S. UPPER RIDGE. OTHERWISE...SYNOPTIC PATTERN WILL REMAIN CHARACTERIZED BY BELT OF STRONGER FLOW OVER THE NRN HALF OF THE COUNTRY WITH AN ELONGATED UPPER RIDGE OVER THE SRN THIRD. SIGNIFICANT SHORTWAVE TROUGH THAT WILL MOVE THROUGH THE GREAT LAKES SUNDAY WILL CONTINUE INTO THE NERN STATES MONDAY FOLLOWED BY A STRONGER SHORTWAVE TROUGH THAT WILL MOVE INTO THE UPPER MS VALLEY MONDAY AFTERNOON. COLD FRONT WILL CONTINUE THROUGH THE NERN STATES IN ASSOCIATION WITH LEAD IMPULSE. TRAILING PORTION OF THIS BOUNDARY WILL EXTEND WWD THROUGH MO AND KS/NRN OK DURING THE LATE AFTERNOON. ANOTHER FRONT WILL ADVANCE INTO THE NRN PLAINS AND UPPER MS VALLEY IN ASSOCIATION WITH SHORTWAVE TROUGH MOVING THROUGH SRN MANITOBA AND SW ONTARIO. ...CNTRL PLAINS THROUGH MID MS VALLEY REGION... STORMS WILL LIKELY BE IN PROGRESS PRIMARILY WITHIN ZONE OF WARM ADVECTION AND ISENTROPIC ASCENT NORTH OF FRONTAL ZONE FROM PORTION OF NEB INTO MO. STORMS SHOULD SHIFT EWD AND MAY DECREASE DURING THE DAY AS THE LLJ WEAKENS. THIS ACTIVITY WILL SERVE TO REINFORCE PRE-EXISTING BAROCLINIC ZONE AS THE WARM SECTOR TO THE SOUTH DESTABILIZES WITH THE ONSET OF DIABATIC WARMING. POTENTIAL WILL EXIST FOR STORMS TO DEVELOP ALONG THIS BOUNDARY AS SURFACE LAYER WARMS AND CAP WEAKENS. A STRENGTHENING HEIGHT GRADIENT ASSOCIATED WITH SHORTWAVE TROUGH DROPPING INTO SWRN ONTARIO WILL CONTRIBUTE TO 40-50 KT EFFECTIVE SHEAR SUPPORTIVE OF SUPERCELLS AND BOWING SEGMENTS. ACTIVITY MAY EVENTUALLY EVOLVE INTO AN MCS OVER THE MS VALLEY AREA...ESPECIALLY AS THE LLJ STRENGTHENS OVERNIGHT. ...UPPER MS VALLEY AREA... AXIS OF MORE MODEST LOW-LEVEL MOISTURE WILL ADVECT NWD INTO THE UPPER MS VALLEY PRE-FRONTAL WARM SECTOR IN ASSOCIATION WITH THE PROGRESSIVE SHORTWAVE TROUGH MOVING THROUGH SRN MANITOBA. THIS WILL CONTRIBUTE TO POTENTIAL FOR 500-1000 J/KG MLCAPE DURING THE AFTERNOON. STORMS WILL LIKELY DEVELOP FROM THE UPPER MS VALLEY INTO ERN SD WITHIN ZONE OF FAVORABLE ASCENT ACCOMPANYING THE SHORTWAVE TROUGH AND ATTENDANT COLD FRONT. VERTICAL SHEAR WILL RANGE FROM 35-40 KT OVER NRN MN IN CLOSER PROXIMITY TO UPPER JET ROUNDING BASE OF IMPULSE TO BELOW 30 KT ACROSS ERN SD. A FEW STORMS MAY BECOME CAPABLE OF PRODUCING ISOLATED LARGE HAIL AND DAMAGING WIND AS ACTIVITY SHIFTS EWD TOWARD THE GREAT LAKES BEFORE WEAKENING DURING THE EVENING. WILL INTRODUCE 5% SEVERE PROBABILITIES THIS UPDATE...BUT CONTINUE TO MONITOR FOR A POSSIBLE SLIGHT RISK IN LATER OUTLOOKS. ...NERN STATES AND MID ATLANTIC... SHORTWAVE TROUGH THAT WILL MOVE THROUGH THE GREAT LAKES SUNDAY IS FORECAST TO DEAMPLIFY AS IT CONTINUES INTO THE NERN STATES. HEATING OF THE MOIST WARM SECTOR WILL LIKELY CONTRIBUTE TO 1000-1500 J/KG MLCAPE...BUT WITH WEAK MID LEVEL LAPSE RATES. SOME INCREASE IN VERTICAL SHEAR WILL OCCUR AND BECOME AT LEAST MARGINALLY SUPPORTIVE OF ORGANIZED STORMS...ESPECIALLY TOWARD THE MID ATLANTIC AREA. STORMS ARE EXPECTED TO REDEVELOP ALONG AND AHEAD OF COLD FRONT FROM PORTIONS OF ERN NEW YORK AND PA INTO THE MID ATLANTIC REGION. A FEW OF THESE COULD POSE A RISK OF MAINLY ISOLATED STRONG WIND GUSTS AND HAIL. THIS AREA WILL CONTINUE TO BE MONITORED FOR A POSSIBLE CATEGORICAL RISK IN LATER OUTLOOKS. ..DIAL.. 08/06/2011 Link to comment Share on other sites More sharing options...
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