thewxmann Posted April 7, 2011 Share Posted April 7, 2011 Like I mentioned before, relying on the NAM for convective initiation is a terrible idea at this time frame. Hell, it's not even that great inside 24 hours most of the time. Then again, there are few models that can do it well (the 4km NMM isn't bad). There's definitely enough going on Sat. afternoon/ early evening to get convection rolling, including some synoptic forcing (height falls and strengthening/backing LLJ) and a convergence boundary or two. And you'd better believe those winds will back ahead of the dryline on Sunday, especially near a bulge. Live by the models... die by the models. I am defin not using NAM for convective initiation verbatim. However, when I look at the H7 temps progged and the overall delay of the system (with s/w energy not arriving till after 0Z), I become extremely doubtful of the prospects of initiation. And I do not live/die by the models. I know 1) models tend to overdo dewpoints by a few degrees in cases where deep BL mixing happens, and 2) models consistently underdo H7 temps by a couple of degrees. If this occurs again (which is likely), it would be that much more difficult to get storms to initiate. Link to comment Share on other sites More sharing options...
thewxmann Posted April 7, 2011 Share Posted April 7, 2011 I'm nowhere close to dismissing any day out of the Fri-Sun period at this point, but I do have to admit, it's funny how defensive certain people get when a conservative/pessimistic viewpoint is presented. I just always get the feeling here that, all else being equal, pessimistic opinions get you less leeway from criticism than bullish ones. Talking about potential scenarios and what "could happen" is fine, but remember, that works both ways. If you're willing to gloss over posts on a highly-caped day about how the triple-point "could" be prolific if something manages to break the cap, you shouldn't have any complaints when someone mentions how the cap "could" be stronger than anticipated on a day everyone's excited about, either. I haven't seen that many angry posts, haha. Thanks for the defense though. I try to balance optimism and pessimism whenever I can (not trying to do have purely one side of the viewpoint). This time, however, I cannot see how storms can initiate on Saturday, based on the data I have now... which is mainly composed of NAM/GFS outputs. Sure they suck at times but I don't have much better guidance besides them and the ECM, the latter of which I don't have good maps for. Link to comment Share on other sites More sharing options...
Stebo Posted April 7, 2011 Share Posted April 7, 2011 I am defin not using NAM for convective initiation verbatim. However, when I look at the H7 temps progged and the overall delay of the system (with s/w energy not arriving till after 0Z), I become extremely doubtful of the prospects of initiation. And I do not live/die by the models. I know 1) models tend to overdo dewpoints by a few degrees in cases where deep BL mixing happens, and 2) models consistently underdo H7 temps by a couple of degrees. If this occurs again (which is likely), it would be that much more difficult to get storms to initiate. This might be the case in late spring/summer events, but I have to disagree with early spring events like this one. Link to comment Share on other sites More sharing options...
csnavywx Posted April 7, 2011 Share Posted April 7, 2011 I haven't seen that many angry posts, haha. Thanks for the defense though. I try to balance optimism and pessimism whenever I can (not trying to do have purely one side of the viewpoint). This time, however, I cannot see how storms can initiate on Saturday, based on the data I have now... which is mainly composed of NAM/GFS outputs. Sure they suck at times but I don't have much better guidance besides them and the ECM, the latter of which I don't have good maps for. Add the SREF in, it does a very decent job, and the mean removes much of the bias of the individual members. Each of the main model suites that go into the SREF has its own strengths and weaknesses, but generally speaking, it will outperform the deterministic models as a whole up until we get into the very short term. Link to comment Share on other sites More sharing options...
Kevin Askew Posted April 7, 2011 Share Posted April 7, 2011 Since being introduced to SREF, Ive base alot of region targets on it and have been paying off well every time Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 Memphis "THERE APPEARS TO BE LITTLE IF ANY THREAT OF TORNADOES WITH THIS EVENT." I am surprised a NWS Office would say that with decent event forecast for Sunday. Although conditions may not be favorable for tornadoes - anytime you have a strong squall line with segments and bows - you run the risk of tornadoes. ILX on the other hand discusses the increased tornado possibility: BY MIDNIGHT SUNDAY NIGHT...STRONG TO SEVERE STORMS SHOULD BE ACTIVE IN OUR CWA. MODEL DIFFERENCES CREATE SOME UNCERTAINTY AS TO WHERE THE MAIN FOCUS WILL BE. THE GFS HITS THE SOUTHEAST COUNTIES THE HARDEST...WHILE THE ECMWF PROGRESSES STORMS FROM THE NW BEFORE MIDNIGHT ACROSS THE NORTHERN COUNTIES AFTER MIDNIGHT. WILL KEEP LIKELY POPS IN ALL COUNTIES FOR NOW...BASED ON THE STRENGTH OF THE SYSTEM AND ALL THE INSTABILITY PARAMETERS THAT ARE COMING TOGETHER. VGP INDICES SHOW HIGH ROTATIONAL POTENTIAL FOR THE STORMS...WITH TORNADOES POSSIBLE. IT IS STILL VERY EARLY YET...BUT SUNDAY NIGHT COULD HAVE A PERIOD OF SEVERE WEATHER IN CENTRAL IL. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 And LOT: IT IS ALSO STILL A LITTLE TOO FAR OUT TO IRON OUT THE DETAILS FOR SEVERE SPECIFICS...BUT IT ALMOST FEELS LIKE THERE IS NO NEED TO LOOK AT SEVERE INDUCES WHEN WE MAY HAVE 65+ TD'S AT THE SFC...14+ TD'S AT H85 WITH 40+ KT WINDS...70+ KT AND INCREASING WINDS AT H5 AS A NEGATIVELY TILTED CLOSED AND COLD CIRCULATION PUSHES EAST. JOKING ASIDE...WE ARE STILL ON THE ORDER OF 3 DAYS OUT AND ANY SMALL SHIFT CAN HAVE A BIG IMPACT ON WHAT WILL PAN OUT. THAT SAID...IT IS STILL LOOKING LIKE IT WILL BE AN EVENING SEVERE EVENT THAT MAY LINGER INTO THE OVERNIGHT HOURS. THE TROUGH THAT WILL BE TRIGGERING ALL OF THE WEEKEND ACTION IS PRESENTLY NOTED ON WATER VAPOR IMAGERY CARVING SOUTH THROUGH ACROSS THE WESTERN CONUS AND INTO SOUTHERN CALI THIS AFTERNOON...AND IS PROGGED TO SLOWLY LIFT THROUGH THE FOUR CORNERS THESE NEXT FEW DAYS. MORE DETAILS TO FOLLOW IN THE COMING SHIFTS... Link to comment Share on other sites More sharing options...
Ed Lizard Posted April 7, 2011 Share Posted April 7, 2011 Only difference is that we're in early April and not late June. It's generally much easier to break capping inversions this time of year due to the fact that baroclinicity (and its resultant synoptic forcing/preconditioning) hasn't waned, and can be paired with other sources of forcing on the mesoscale in addition to diabatic heating. In the summer, you typically have to rely on daytime (diabatic) heating and a boundary alone to do the work for you. Not so sure, I noticed this a few days ago with the regional spectral, and today it is a different model family, checking it because I'm going to an outdoor event near Dallas tomorrow night, and all the model families in the 15Z SREF are dry except for one, and in that one, every perturbation shows the isolated storms developing. The means include an entire family of outliers. GIGO situation? Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 I'm really hoping things change a little bit for Saturday because I would love to make this a 2 day chase rather than just Sunday Link to comment Share on other sites More sharing options...
prinsburg_wx Posted April 7, 2011 Share Posted April 7, 2011 from DVN SUN-SUN NGT... INGREDIENTS APPEAR TO BE IN PLACE RESEMBLING MILLER TYPE B SYNOPTIC PATTERN (CLASSIC TORNADO OUTBREAK) ESPECIALLY TO OUR WEST AND SOUTHWEST... WITH POTENT AND PROGRESSIVE MID LEVEL SHORTWAVE TAKING ON SOMEWHAT OF NEGATIVE TILT ALONG WITH 130+ KT CYCLONIC CURVED JET EMERGING INTO PLAINS BY EVE... AND DEEPENING SFC LOW WITH ASSOCIATED COLD AND WARM FRONTS AND THERMAL ADVECTIONS. GENERAL SUGGESTION IS BROKEN LINE OF DISCRETE SUPERCELLS DEVELOPING BY MID-LATE PM FROM SOUTHWEST IA THROUGH EASTERN KS/WESTERN MO... EASTERN OK AND NORTHEAST TX WHERE BEST TORNADO POTENTIAL WILL EXIST IN STRONGLY SHEARED ENVIRONMENT. MOTION VECTORS GENERALLY PARALLEL TO FRONT EXCEPT ON SOUTHERN FLANK THROUGH OK INTO TX WHERE SHOWN TO BE MORE PERPENDICULAR AND THUS CELLS MAY STAY DISCRETE MUCH LONGER THERE... WHILE NORTHERN HALF WITH PARALLEL MOTIONS WOULD SUGGEST IN TIME EVOLUTION TO LEWP OR SQUALL LINE RACING EWD ACROSS CWA SUN NGT WITH MAINLY LARGE HAIL AND DAMAGING WIND THREAT THOUGH RISK OF TORNADO IF STORMS CAN REMAIN DISCRETE LONGER THAN CURRENTLY SUGGESTED. BEGAN RAMPING UP POPS SUN AFTN IN THE FAR WEST AND RAISED POPS TO CATEGORICAL ALL AREAS SUN NGT. FAST MOVEMENT OF LINE SHOULD CUT DOWN ON PCPN AMOUNTS WITH GENERAL 0.25 TO 0.5 INCH. HOWEVER... WITH SWLY 850 MB FLOW MAY SEE CONTINUED DEVELOPMENT IN AREAS ALL NGT AND SO POTENTIAL FOR LOCALIZED HIGHER AMOUNTS AROUND 1-1.5 INCHES. Link to comment Share on other sites More sharing options...
TimChgo9 Posted April 7, 2011 Share Posted April 7, 2011 I have been following this pretty closely. Kind of figuring we are going to see something on Sunday,. My question, or concern, really, is if there is any storms that form in IA and move to the east overnight on Saturday, depending on timing, what are the chances of an overnight MCS through N IL/S WI that leaves behind a lingering cloud cover, that doesn't clear out quickly, or completely. How dependent is this system on day time heating ahead of the front? We are progged for upper 70's/low 80's for Sunday. I would imagine if any serious cloud cover is left behind, temps won't reach those levels. If the overnight MCS-leaving-subsidence-in-it's wake pans out (and it happened a few times last year) I would imagine the threat would be ratcheted down somewhat, at least for the N IL/S WI area.. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted April 7, 2011 Author Share Posted April 7, 2011 I have been following this pretty closely. Kind of figuring we are going to see something on Sunday,. My question, or concern, really, is if there is any storms that form in IA and move to the east overnight on Saturday, depending on timing, what are the chances of an overnight MCS through N IL/S WI that leaves behind a lingering cloud cover, that doesn't clear out quickly, or completely. How dependent is this system on day time heating ahead of the front? We are progged for upper 70's/low 80's for Sunday. I would imagine if any serious cloud cover is left behind, temps won't reach those levels. If the overnight MCS-leaving-subsidence-in-it's wake pans out (and it happened a few times last year) I would imagine the threat would be ratcheted down somewhat, at least for the N IL/S WI area.. Not always the case, sometimes you will get an MCS to go through during the morning hours and we clear out rapidly in the afternoon. June 5th last year being an example as well as 8/4/08, along with other times. You can also get that MCS to leave out a boundary or two to focus convection later in the day. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 Not always the case, sometimes you will get an MCS to go through during the morning hours and we clear out rapidly in the afternoon. June 5th last year being an example as well as 8/4/08, along with other times. You can also get that MCS to leave out a boundary or two to focus convection later in the day. Link to comment Share on other sites More sharing options...
wisconsinwx Posted April 7, 2011 Share Posted April 7, 2011 I have been following this pretty closely. Kind of figuring we are going to see something on Sunday,. My question, or concern, really, is if there is any storms that form in IA and move to the east overnight on Saturday, depending on timing, what are the chances of an overnight MCS through N IL/S WI that leaves behind a lingering cloud cover, that doesn't clear out quickly, or completely. How dependent is this system on day time heating ahead of the front? We are progged for upper 70's/low 80's for Sunday. I would imagine if any serious cloud cover is left behind, temps won't reach those levels. If the overnight MCS-leaving-subsidence-in-it's wake pans out (and it happened a few times last year) I would imagine the threat would be ratcheted down somewhat, at least for the N IL/S WI area.. Well, considering it sounds like the Sunday threat for those areas will be pretty late in the day/evening as well, I figure as long as it clears out by mid-morning Sunday, there should be enough daytime heating to allow the current forecast to occur, am I correct? Link to comment Share on other sites More sharing options...
jdrenken Posted April 7, 2011 Share Posted April 7, 2011 ILX on the other hand discusses the increased tornado possibility: BY MIDNIGHT SUNDAY NIGHT...STRONG TO SEVERE STORMS SHOULD BE ACTIVE IN OUR CWA. MODEL DIFFERENCES CREATE SOME UNCERTAINTY AS TO WHERE THE MAIN FOCUS WILL BE. THE GFS HITS THE SOUTHEAST COUNTIES THE HARDEST...WHILE THE ECMWF PROGRESSES STORMS FROM THE NW BEFORE MIDNIGHT ACROSS THE NORTHERN COUNTIES AFTER MIDNIGHT. WILL KEEP LIKELY POPS IN ALL COUNTIES FOR NOW...BASED ON THE STRENGTH OF THE SYSTEM AND ALL THE INSTABILITY PARAMETERS THAT ARE COMING TOGETHER. VGP INDICES SHOW HIGH ROTATIONAL POTENTIAL FOR THE STORMS...WITH TORNADOES POSSIBLE. IT IS STILL VERY EARLY YET...BUT SUNDAY NIGHT COULD HAVE A PERIOD OF SEVERE WEATHER IN CENTRAL IL. It's amazing how little VGP indicies get noticed. All you hear about is the standard EHI, SRH, etc. Link to comment Share on other sites More sharing options...
jdrenken Posted April 7, 2011 Share Posted April 7, 2011 Not always the case, sometimes you will get an MCS to go through during the morning hours and we clear out rapidly in the afternoon. June 5th last year being an example as well as 8/4/08, along with other times. You can also get that MCS to leave out a boundary or two to focus convection later in the day. This is what we are hoping for! Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 From Gino earlier this morning: Based on the current model runs, I think Sunday has High Risk potential and depending who's working the outlook desk, maybe even Saturday farther west. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted April 7, 2011 Author Share Posted April 7, 2011 From Gino earlier this morning: Based on the current model runs, I think Sunday has High Risk potential and depending who's working the outlook desk, maybe even Saturday farther west. I can see sunday being a high risk but not saturday. Maybe a MDT on saturday but we'll see how the models trend in the next 24hrs. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 Obviously none of this matters if we don't get initiation - but here is Cape & SRH 0-3 KM for Saturday Evening Link to comment Share on other sites More sharing options...
Thundersnow12 Posted April 7, 2011 Author Share Posted April 7, 2011 The 18z GFS continues to show CI occuring saturday evening. Link to comment Share on other sites More sharing options...
jdrenken Posted April 7, 2011 Share Posted April 7, 2011 Interesting from Little Rock LOW LEVEL MOISTURE DOES NOT APPEAR TO BE SUFFICIENT ENOUGH TO SUPPORT TORNADOES... What do they want...80 degree dew points? Link to comment Share on other sites More sharing options...
jdrenken Posted April 7, 2011 Share Posted April 7, 2011 Is this the one from Facebook someone mentioned a day or so ago? He created a poll 15 hours ago with that wording on his FB. Link to comment Share on other sites More sharing options...
TheWeatherPimp Posted April 7, 2011 Share Posted April 7, 2011 Is this the one from Facebook someone mentioned a day or so ago? Correct - from his facebook this morning. Link to comment Share on other sites More sharing options...
VAwxman Posted April 7, 2011 Share Posted April 7, 2011 I haven't seen that many angry posts, haha. Thanks for the defense though. I try to balance optimism and pessimism whenever I can (not trying to do have purely one side of the viewpoint). This time, however, I cannot see how storms can initiate on Saturday, based on the data I have now... which is mainly composed of NAM/GFS outputs. Sure they suck at times but I don't have much better guidance besides them and the ECM, the latter of which I don't have good maps for. I hope you didn't take my post as harsh, as that was definitely not my intention. You're a good poster, but do tend to almost always play conservative. That will win more battles than being perma bullish though in general. And besides all that, I'm with you in seeing limitations on tornado potential, assuming nothing changes. Best potential to me would be with anything that might root in the BL initially Sat night and the initial cells Sunday afternoon / evening. Link to comment Share on other sites More sharing options...
Srain Posted April 7, 2011 Share Posted April 7, 2011 ^ kudos for chiming in... Link to comment Share on other sites More sharing options...
csnavywx Posted April 7, 2011 Share Posted April 7, 2011 Interesting from Little Rock LOW LEVEL MOISTURE DOES NOT APPEAR TO BE SUFFICIENT ENOUGH TO SUPPORT TORNADOES... Odd, I would've thought they would be more concerned about solar shielding via thick STJ cirrus down that way. Link to comment Share on other sites More sharing options...
Fred Gossage Posted April 7, 2011 Share Posted April 7, 2011 What do they want...80 degree dew points? There are more important things related to boundary layer moisture quality for tornadoes... than surface dewpoints alone. The moisture needs to be deep and rich enough to not mix out so much so that a layer of convective inhibition (whether it's a capping layer or not, CIN and cap are different), that would prevent storms from being surface-based. Link to comment Share on other sites More sharing options...
Thundersnow12 Posted April 7, 2011 Author Share Posted April 7, 2011 The RDK sounding for saturday evening off the 12z NAM still looks sexy with some impressive turning and parameters but still 88 j/kg of CIN at 0z. Link to comment Share on other sites More sharing options...
jdrenken Posted April 7, 2011 Share Posted April 7, 2011 There are more important things related to boundary layer moisture quality for tornadoes... than surface dewpoints alone. The moisture needs to be deep and rich enough to not mix out so much so that a layer of convective inhibition (whether it's a capping layer or not, CIN and cap are different), that would prevent storms from being surface-based. Thanks Fred. I knew that CIN was progged to be high, or low depending on how you look at it....it was just weird to see that wording with 65-70 degree dew points. Link to comment Share on other sites More sharing options...
CUmet Posted April 8, 2011 Share Posted April 8, 2011 There are more important things related to boundary layer moisture quality for tornadoes... than surface dewpoints alone. The moisture needs to be deep and rich enough to not mix out so much so that a layer of convective inhibition (whether it's a capping layer or not, CIN and cap are different), that would prevent storms from being surface-based. That's certainly true, but the moisture depth doesn't appear to be much of an issue for Sunday. Link to comment Share on other sites More sharing options...
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