Thunder Road Posted May 29, 2011 Share Posted May 29, 2011 I'm getting excited about the potential severe weather Wednesday evening, and even though t's still 3 days away I wanted to start a thread on it already. If it looks legit, please post saved images instead of hyperlinks that will auto-refresh. Thanks. SPC highlighted D5 yesterday and D4 today, which is pretty rare for the northeast. 18z NAM has good instability, >2000 J/Kg area-wide wkth pockets of >3000 J/Kg. almost no cap to speak of, half-decent vertical shear (for this area anyway) but the lower levels are a tad dry thoughts? Link to comment Share on other sites More sharing options...
am19psu Posted May 30, 2011 Share Posted May 30, 2011 I'm getting excited about the potential severe weather Wednesday evening, and even though t's still 3 days away I wanted to start a thread on it already. If it looks legit, please post saved images instead of hyperlinks that will auto-refresh. Thanks. P.S. If you are using Chrome (and why aren't you?), the imgur extension is a good one to have for using permanent hyperlinks. I'm not all that excited about this "outbreak." The best dynamics will be to our north. Link to comment Share on other sites More sharing options...
Thunder Road Posted May 30, 2011 Author Share Posted May 30, 2011 P.S. If you are using Chrome (and why aren't you?), the imgur extension is a good one to have for using permanent hyperlinks. I'm not all that excited about this "outbreak." The best dynamics will be to our north. Chrome eh? I think IE5 works fine. Ok not really. I'm partial to Firefox. And yeah clearly SPC thinks the best stuff is to our north where there's better shear, but I think we have a better shot than, say, last week. Link to comment Share on other sites More sharing options...
NaoPos Posted May 31, 2011 Share Posted May 31, 2011 Mr. Gigi writes up an excellent disco today about the convective chances for this possible event: CONTINUITY AND LATEST MODEL INFO TO DRAW A POP LINE IN THE SAND. WEDNESDAY MIGHT BE AN INTERESTING CONVECTIVE DAY PENDING A COUPLE OF PIECES FALLING INTO PLACE. FIRST BOTH THE GFS AND WRF-NMM FCST INSTABILITY ARE TOO BULLISH AS THEIR SFC FCST DEW POINTS ARE TOO HIGH (LO-MID 70S). THAT SAID THE EML SOUTH OF THE MN CONVECTION IS SUPPOSE TO REMAIN UNTOUCHED INTO WEDNESDAY AND PENDING THE MODEL OF CHOICE WE ARE FCST TO HAVE ANYWHERE FROM 6.5C/KM TO 7.5C/KM MID LEVEL LAPSE RATES. THERE ARE MODEL HINTS THAT A LEE SIDE TROF MAY FORM PRECEDING THIS FRONT AS STAT GUIDANCE FCST WINDS HAVE NOW BACKED MORE TO THE SW. STAT GUIDANCE FCST DEW POINTS ARE AWFULLY LOW ESPECIALLY GIVEN WHAT THE MODELS THEMSELVES ARE FORECASTING. A COMPROMISE SOLUTION BETWEEN SHOULD VERIFY AS THERE SHOULD BE POOLING IF A LEE SIDE TROF FORMS. ALTHOUGH WE DONT GIVE THIS STRONG WEIGHT, WE SUPPOSE SOME CLOUDINESS AND LEFTOVER CONVECTION MIGHT SLOW OUR ASCENT. BUT, THE DAYS DO NOT GET MUCH LONGER THAN THIS. THE FORECAST BULK SHEAR IS NOT THAT VIGOROUS THE FARTHER SOUTH IN OUR CWA ONE DELVES AS THE JET ALF IS FORECAST TO REMAIN NORTH AND LLVL JET WINDS THEMSELVES ARE ADEQUATE, BUT NOT ROBUST AND ALSO MAINLY NORTH. UPSHOT BECAUSE THE ISENTROPIC 850MB MOISTURE TRANSPORT IS FCST TO BE DECENT AND FCST QVEC CONVERGENCE LOOKS GOOD BETWEEN 850MB AND 500MB DURING THE HEATING OF THE DAY, WE WENT WITH HIGHER POPS THAN STAT GUIDANCE. Link to comment Share on other sites More sharing options...
Thunder Road Posted May 31, 2011 Author Share Posted May 31, 2011 the 18z GFS lost the morning crapvection Wed. 18z NAM & GFS both have >3000 J/Kg CAPE over most of the Philly area at 18z Wed. No major capping issues, although the GFS has a slight inversion around 925mb at that time. Helicity, both low-level and mid-level, is non-existent. There's about 20-25 kts of unidirectional shear, which is nice to work with but nothing that special either. The NAM's sim radar has a nice line in Chesco by 18z, then SE of Philly at 21z. The parameters are definitely there. If we have good timing, and we avoid morning crapvection, then I think we have a decent chance at some good line segments going up. Supercells probably not, since we don't have the shear. Link to comment Share on other sites More sharing options...
cast4 Posted May 31, 2011 Share Posted May 31, 2011 The EML might really enhance this threat. Link to comment Share on other sites More sharing options...
NJHurricane Posted May 31, 2011 Share Posted May 31, 2011 I expect a solid line of convection, just not sure many will see severe parameters met at this point. Link to comment Share on other sites More sharing options...
am19psu Posted May 31, 2011 Share Posted May 31, 2011 I expect a solid line of convection, just not sure many will see severe parameters met at this point. Yep, that sounds about right. Link to comment Share on other sites More sharing options...
tombo82685 Posted May 31, 2011 Share Posted May 31, 2011 i could see the early morning convection like the 6z nam is showing mucking things up later on. Link to comment Share on other sites More sharing options...
NaoPos Posted May 31, 2011 Share Posted May 31, 2011 12z Nam is in, let's take a look: Surface DP's still remain in the upper 60's, and a few pockets of low 70's. NO surprise here that this will lead to these Pwat values Now, lets look at shear. Because bulk shear has increased to about 30kts roughly, EHI has increased. Not worried about EHI values in the tornadic sense, but i wanted to show the increase in forecasted shear. ( speed shear) As you can see above, when it comes to thermo dynamics, the environment is bubbling. This could offset some issues with water loading because of the higher pwat values and modest shear. As far as morning could debris, not too much being shown on the 12z run: Around 6z, there's a little bit: But between 6z and 15z, it seems all is clear untill the squall line gets going: When it comes to the morning cloud debris, we're going to have to nowcast it. it's always a crap shoot. Link to comment Share on other sites More sharing options...
NaoPos Posted May 31, 2011 Share Posted May 31, 2011 THE EML does it's job, making sure the squall line doesn't run into prefontal activity* Link to comment Share on other sites More sharing options...
LMolineuxLM1 Posted May 31, 2011 Share Posted May 31, 2011 ...EASTERN STATES... DEEP LAYER WESTERLY FLOW AND SHEAR WILL BE STRONGEST NEAR THE COLD FRONT AS IT ADVANCES ACROSS PENNSYLVANIA AND NEW YORK INTO NEW ENGLAND DURING THE DAYTIME HOURS...BUT STRONGEST DESTABILIZATION PROBABLY WILL OCCUR WITHIN THE PRE-FRONTAL LEE SURFACE TROUGH FROM VIRGINIA INTO NORTHERN MID ATLANTIC COASTAL AREAS AND SOUTHERN NEW ENGLAND. CONDITIONS NEAR THESE SURFACE FEATURES MAY BECOME THE FOCUS FOR SCATTERED STRONG/SEVERE STORM DEVELOPMENT CAPABLE OF PRODUCING DAMAGING WIND GUSTS AND LARGE HAIL WEDNESDAY...AND CATEGORICAL/PROBABILITY LINES HAVE BEEN ADJUSTED TO ACCOUNT FOR THIS...AS WELL AS FAVORABLE OROGRAPHIC FORCING ALONG AND EAST OF THE BLUE RIDGE MOUNTAINS. Link to comment Share on other sites More sharing options...
NaoPos Posted May 31, 2011 Share Posted May 31, 2011 ...EASTERN STATES... DEEP LAYER WESTERLY FLOW AND SHEAR WILL BE STRONGEST NEAR THE COLD FRONT AS IT ADVANCES ACROSS PENNSYLVANIA AND NEW YORK INTO NEW ENGLAND DURING THE DAYTIME HOURS...BUT STRONGEST DESTABILIZATION PROBABLY WILL OCCUR WITHIN THE PRE-FRONTAL LEE SURFACE TROUGH FROM VIRGINIA INTO NORTHERN MID ATLANTIC COASTAL AREAS AND SOUTHERN NEW ENGLAND. CONDITIONS NEAR THESE SURFACE FEATURES MAY BECOME THE FOCUS FOR SCATTERED STRONG/SEVERE STORM DEVELOPMENT CAPABLE OF PRODUCING DAMAGING WIND GUSTS AND LARGE HAIL WEDNESDAY...AND CATEGORICAL/PROBABILITY LINES HAVE BEEN ADJUSTED TO ACCOUNT FOR THIS...AS WELL AS FAVORABLE OROGRAPHIC FORCING ALONG AND EAST OF THE BLUE RIDGE MOUNTAINS. This would be the 3rd 30% risk the day before an event. the previous 2 ones , the entire CWA was dropped from the 30%, and eventually, any severe chances were extremely isolated. Not due to bad forecasting, but just because of how poorly the airmass was modeled. this is looking like a legit threat though, so i believe it will hold serve. Link to comment Share on other sites More sharing options...
LMolineuxLM1 Posted May 31, 2011 Share Posted May 31, 2011 This would be the 3rd 30% risk the day before an event. the previous 2 ones , the entire CWA was dropped from the 30%, and eventually, any severe chances were extremely isolated. Not due to bad forecasting, but just because of how poorly the airmass was modeled. Dont go all sunny on my parade please. LOL Link to comment Share on other sites More sharing options...
NaoPos Posted May 31, 2011 Share Posted May 31, 2011 Mt. Holly's thoughts: THE NEXT PROBLEM IS CONVECTION. AS MENTIONED EARLIER...MODEL ARE POINTING TO THE POTENTIAL FOR A LEESIDE TROUGH TO DEVELOP LATE WEDNESDAY MORNING AND EARLY WEDNESDAY AFTERNOON JUST EAST OF THE TERRAIN. THIS COULD ACT AS A FOCUS FOR THE CONSIDERABLE AMOUNT OF INSTABILITY ACROSS THE LEHIGH AND DELAWARE VALLEYS EARLY WEDNESDAY AFTERNOON. THE FLOW JUST ABOVE THE BOUNDARY LAYER LOOKS AS THOUGH IT MAY BECOME MORE WESTERLY AT THIS TIME...POSSIBLY RESULTING IN LESS IN THE WAY OF LOW LEVEL CONVERGENCE. SO...WHILE CONVECTION IS EXPECTED TO DEVELOP AHEAD OF THE LEESIDE TROUGH (IN THE BEST SURFACE DEW POINT POOLING)...IT IS NOT CLEAR JUST HOW EXTENSIVE THE CONVECTION MIGHT BE. SYNOPTIC SCALE LIFT MAY BE HARD TO COME BY WEDNESDAY AFTERNOON...AS THE BEST JET REMAINS WELL NORTH OF THE AREA. MODIFIED MODEL SOUNDINGS SUGGEST THAT AREAS SOUTH AND EAST OF PHILADELPHIA COULD REMAIN CAPPED WELL INTO THE AFTERNOON...SO THAT THE BEST CHANCE OF CONVECTION WOULD BE NORTHWEST OF THERE. ANY CONVECTION THAT DEVELOPS WILL BE ABLE TO TAKE ADVANTAGE OF THE INSTABILITY AND INCREASING BULK SHEAR (ESPECIALLY ACROSS THE NORTH). MODIFIED SOUNDINGS SUGGEST MULTI CELLULAR WILL BE THE CONVECTIVE MODE OF CHOICE...MANIFESTING ITSELF AS LINE SEGMENTS OR SMALL BOW. THERE IS SOME INDICATION THAT...AS THE SHEAR INCREASES ACROSS THE NORTH...THAT SUPERCELL STRUCTURES BECOME POSSIBLE. HOWEVER...WHERE THE SHEAR IS BETTER...THE INSTABILITY IS LESS...SO IT MAY END UP BEING A WASH. Link to comment Share on other sites More sharing options...
cast4 Posted May 31, 2011 Share Posted May 31, 2011 I'm pretty excited about this setup. Just wish we had more shear because the CAPE and EML will be there. Link to comment Share on other sites More sharing options...
SmokeEater Posted May 31, 2011 Share Posted May 31, 2011 Quoting the REAL HM, from the NYC thread. I agree that tomorrow is the first candidate for a moderate risk from western New England to eastern PA...including NYC... I love the veering profiles amongst the EML and 40 knot mid level flow with the nicely timed FROPA. Classic Northeast severe weather outbreak! The thing that may potentially kill tomorrow south of New England may be the anticyclonic shear/general NVA with the orientation of the trough/ridge. A lot of areas may just stay capped, even with the prefrontal trough. This may not be a bad thing, because if the convection waits for the better winds to arrive and forcing, then it will likely be more severe. There is also the issue with the morning MCS potential and leftover cloud debris. However, with the first point, I think the general descent behind this feature will thin out the clouds and allow for heating. Some of these soundings are downright awesome, especially north of the area. Once something gets going in the Mid Atlantic, it will set off a chain reaction. So if something orographic happens with the prefrontal trough, that may be enough to form a cold pool that races to the coast. I am not saying that. I am just giving pros and cons for tomorrow. My personal thoughts are that we get a mod risk from E PA to western New England and a couple of areas develop. Something will get a cold pool going in the Mid Atlantic tomorrow and the dynamics will get New England to PA going. There is usually a screw zone in between but I think that NYC will be included in the northern stuff. If it has enough momentum, it could even include all of Long Island. Link to comment Share on other sites More sharing options...
LMolineuxLM1 Posted May 31, 2011 Share Posted May 31, 2011 Quoting the REAL HM, from the NYC thread. Sounds very promising, might be a good chase on my hands then tomorrow. Link to comment Share on other sites More sharing options...
NaoPos Posted May 31, 2011 Share Posted May 31, 2011 Sounds very promising, might be a good chase on my hands then tomorrow. With the capping and EML, hand in hand, there should be minimal "rounds" of severe weather. my bet for you would be pick a high point in delco, and wait for the storms to come to you. Link to comment Share on other sites More sharing options...
cast4 Posted June 1, 2011 Share Posted June 1, 2011 It looks like SPC SREF is starting to bring the shear up a bit. 30 kts should get it done. Now all we need is no early morning cloud or MCS debris. Link to comment Share on other sites More sharing options...
SmokeEater Posted June 1, 2011 Share Posted June 1, 2011 It looks like SPC SREF is starting to bring the shear up a bit. 30 kts should get it done. Now all we need is no early morning cloud or MCS debris. What would cause the moring MCS or crapvection? There's nothing at all to our west, and the MCS never formed in Michigan. There's not even that much convection left up there. Link to comment Share on other sites More sharing options...
cast4 Posted June 1, 2011 Share Posted June 1, 2011 What would cause the moring MCS or crapvection? There's nothing at all to our west, and the MCS never formed in Michigan. There's not even that much convection left up there. The NAM has something developing in the late morning hours. I don't believe it though if the EML acts as it should. Link to comment Share on other sites More sharing options...
Thunder Road Posted June 1, 2011 Author Share Posted June 1, 2011 The 0z HRRR has convection developing in DE by 14z already. Unlikely, imo, given that there will be a bit of a cap in place. Link to comment Share on other sites More sharing options...
NaoPos Posted June 1, 2011 Share Posted June 1, 2011 kinda off topic, but not really. Just wanted to point out some obs. (hot linked images, so time sesitive)... ABSOLUTELY UNREAL THERMODYNAMICS OUT THERE.. even for central plains standards: thats 4000-4500 SB cape..(surface based) 4000j of ML cape ( REDONKULOUS) 6000!! of MUCAPE.... can we saw GEWW! 1700 of downdraft cape. -12 Lifted index values... 8.5 degree mid level lapse rates nothing will pop due to the CAP/CIN in place, but still, very impressive thermodynamics attm.. Gut feeling here, but i think things will pop tomorrow. Heat wave with a fropa=fireworks... not like days where we struggle to hit 80., Link to comment Share on other sites More sharing options...
cast4 Posted June 1, 2011 Share Posted June 1, 2011 kinda off topic, but not really. Just wanted to point out some obs. (hot linked images, so time sesitive)... ABSOLUTELY UNREAL THERMODYNAMICS OUT THERE.. even for central plains standards: thats 4000-4500 SB cape..(surface based) 4000j of ML cape ( REDONKULOUS) 6000!! of MUCAPE.... can we saw GEWW! 1700 of downdraft cape. -12 Lifted index values... 8.5 degree mid level lapse rates nothing will pop due to the CAP/CIN in place, but still, very impressive thermodynamics attm.. Gut feeling here, but i think things will pop tomorrow. Heat wave with a fropa=fireworks... not like days where we struggle to hit 80., Loving those 8.5 ML Lapse Rates :scooter:Tomorrow's parameters are going to be crazy. Link to comment Share on other sites More sharing options...
NaoPos Posted June 1, 2011 Share Posted June 1, 2011 Loving those 8.5 ML Lapse Rates :scooter:Tomorrow's parameters are going to be crazy. Yep. That's our EML Link to comment Share on other sites More sharing options...
Thunder Road Posted June 1, 2011 Author Share Posted June 1, 2011 just some more NSFW weather images, courtesy of the 01z HRRR Link to comment Share on other sites More sharing options...
Thunder Road Posted June 1, 2011 Author Share Posted June 1, 2011 sim radar at 17z. Explosion right on top of Philly. Link to comment Share on other sites More sharing options...
Thunder Road Posted June 1, 2011 Author Share Posted June 1, 2011 SPC didn't go with the Moderate. 5% tornado, 30% wind, 15% hail I'm surprised. I expect they will upgrade to Moderate at 12z. Discussion cited early start to convection (15z-18z) as the main detriment, but imo, when we have 1500 J/Kg of MLCAPE at 06z, a 15z start time will still produce some good boomers Link to comment Share on other sites More sharing options...
NaoPos Posted June 1, 2011 Share Posted June 1, 2011 SPC didn't go with the Moderate. 5% tornado, 30% wind, 15% hail I'm surprised. I expect they will upgrade to Moderate at 12z. Discussion cited early start to convection (15z-18z) as the main detriment, but imo, when we have 1500 J/Kg of MLCAPE at 06z, a 15z start time will still produce some good boomers Not surprised. Good call. I think they'll wait till just before initialization to go ahead with it, if it seems right. Link to comment Share on other sites More sharing options...
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