tombo82685 Posted July 4, 2012 Share Posted July 4, 2012 FWIW that screwy rap model has 9-9.5 low lapse rates this afternoon. Watching the convection in northwest pa again today will see what it does today. today holds a better chance than last night ever did. Timing is better now and the instability is also greater. Just need that trigger. Link to comment Share on other sites More sharing options...
Engine2211 Posted July 4, 2012 Share Posted July 4, 2012 There were years (1998) where we had two derechos pass pretty close to the region -- one caused the severe outbreak that dropped a F3 in Berks County, second was the Labor Day event. '98 makes up for the years where we don't get any at all. http://en.m.wikipedia.org/wiki/Late-May_1998_tornado_outbreak_and_derecho#section_6 I found this article to be interesting. I remember that storm as the worst lightning I had ever seen, even here in jersey. We were without power for a day and nearby large trees were taken down in a very localized area. No tornados though. But that kind of event must be a once every 20 years. Link to comment Share on other sites More sharing options...
Parsley Posted July 4, 2012 Share Posted July 4, 2012 http://en.m.wikipedia.org/wiki/Late-May_1998_tornado_outbreak_and_derecho#section_6 I found this article to be interesting. I remember that storm as the worst lightning I had ever seen, even here in jersey. We were without power for a day and nearby large trees were taken down in a very localized area. No tornados though. But that kind of event must be a once every 20 years. Strongest non-hurricane winds I ever witnessed. Unforgettable. Link to comment Share on other sites More sharing options...
Maximum lawman Posted July 4, 2012 Author Share Posted July 4, 2012 today holds a better chance than last night ever did. Timing is better now and the instability is also greater. Just need that trigger. Definitely better, still not great. Link to comment Share on other sites More sharing options...
SmokeEater Posted July 5, 2012 Share Posted July 5, 2012 Day 3 slight risk for the entire area, excluding southern Delaware on Saturday. Link to comment Share on other sites More sharing options...
Rainshadow Posted July 5, 2012 Share Posted July 5, 2012 There were years (1998) where we had two derechos pass pretty close to the region -- one caused the severe outbreak that dropped a F3 in Berks County, second was the Labor Day event. '98 makes up for the years where we don't get any at all. The destruction in Lyons was sadly midwestern with that tornado. We nearly had a chance a couple of days later, but the air mass did not recover in time. That Labor Day event was more in prime time, how more people were not killed, hurt, IDK. That one too started near Chicago. Link to comment Share on other sites More sharing options...
Maximum lawman Posted July 5, 2012 Author Share Posted July 5, 2012 SPC a little more bullish than Mt Holly, on the edge of see text today and tomorrow, slight risk day 3 and 4 (when was the last Day 4?). In other news, it sucks to be outside. Link to comment Share on other sites More sharing options...
stormspotterlive Posted July 5, 2012 Share Posted July 5, 2012 GFS really supports that day 4 risk and also looks to make day full of boundaries out of it at the shore where it is showing the strongest convection. The Nam is saying it will be more so of an overnight event Saturday night into Sunday morning with the front slowing down here. I would think with 100 degrees on Saturday and limited clouds we would see very high instability. Link to comment Share on other sites More sharing options...
NaoPos Posted July 5, 2012 Share Posted July 5, 2012 GFS really supports that day 4 risk and also looks to make day full of boundaries out of it at the shore where it is showing the strongest convection. The Nam is saying it will be more so of an overnight event Saturday night into Sunday morning with the front slowing down here. I would think with 100 degrees on Saturday and limited clouds we would see very high instability. The problem is, the higher the temps, (100+) the dp's are gonna drop. Gonna have to walk a fine line with temps and dp's Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted July 6, 2012 Share Posted July 6, 2012 out of the area but here is a pic i captured over ABQ late this afternoon, much needed rain for the west Link to comment Share on other sites More sharing options...
Parsley Posted July 6, 2012 Share Posted July 6, 2012 out of the area but here is a pic i captured over ABQ late this afternoon, much needed rain for the west Sweet! Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted July 6, 2012 Share Posted July 6, 2012 Sweet! yeah it was cool watching it develop 2 more pic's showing the development of that 1st pic, ok, back to philly topic Link to comment Share on other sites More sharing options...
MGorse Posted July 6, 2012 Share Posted July 6, 2012 yeah it was cool watching it develop 2 more pic's showing the development of that 1st pic, ok, back to philly topic Holy funnel cloud!! Seriously though, cool pic. Link to comment Share on other sites More sharing options...
SmokeEater Posted July 6, 2012 Share Posted July 6, 2012 Funny, SNE subforum is saying the best threat looks to be in our backyard on Saturday, NYC subforum is saying the best looks to be across SNE. Which is it? lol Link to comment Share on other sites More sharing options...
Parsley Posted July 6, 2012 Share Posted July 6, 2012 Oh, when you come back to Quakertown, your yard is going to look like that first picture Link to comment Share on other sites More sharing options...
MGorse Posted July 6, 2012 Share Posted July 6, 2012 Funny, SNE subforum is saying the best threat looks to be in our backyard on Saturday, NYC subforum is saying the best looks to be across SNE. Which is it? lol It could end up being Sunday down here as the front may be slower. Link to comment Share on other sites More sharing options...
Thunder Road Posted July 6, 2012 Share Posted July 6, 2012 GFS really supports that day 4 risk and also looks to make day full of boundaries out of it at the shore where it is showing the strongest convection. The Nam is saying it will be more so of an overnight event Saturday night into Sunday morning with the front slowing down here. I would think with 100 degrees on Saturday and limited clouds we would see very high instability. This isn't directed at you really, it's more for everyone. I need to dispel this notion that higher temperatures = higher CAPE, because at a certain point that's no longer true. So let's first look at what CAPE (or Convective Available Potential Energy) is. CAPE is the area between a parcel path and the environmental temperature curve on a Skew-T diagram. Essentially, it is a measure of buoyancy, and it can be computed by a taking a relatively speaking simple integral. Here's an example sounding. The time and place are irrelevant. To calculate CAPE, first find your LCL (Lifted Condensation Level). Your LCL is the level at which your parcel would saturate if it was lifted mechanically (i.e. from a cold front, dry line, seabreeze, upslope flow on the windward side of a mountain, etc., and not from simple buoyancy). An LCL is somewhat ideal, in that it assumes your parcel is cooling at the Dry Adiabatic Lapse Rate (which is a constant, 9.8 C/km) and that it is moistening at another constant rate, known as the Mixing Ratio. Therefore, from the surface, you're parcel would parallel a Dry Adiabatic Lapse Rate line (sometimes known simply as a "Dry Adiabat") until it crosses the line that is parallel to your Mixing Ratio line starting from your surface Dew Point. Below, you see gold lines representing these two imaginary lines, and a purple dot for your LCL. From there, your parcel saturates (aka a cloud forms) and it stops following the DALR. It now cools at a different lapse rate, known as the Moist Adiabatic Lapse Rate (the long-dashed line on a TwisterData Skew-T, not a constant; rather, it increases with height because temperature cools with height in the troposphere and cooler air can't hold as much moisture as warmer air can, hence the change in that rate.) Following the Moist Adiabats, your now-saturated parcel crosses the Environmental Temperature curve, which means it is now buoyant. In other words, warm air rises, and he parcel is warmer than the surrounding, so it rises. The cream colored area is your CAPE. So where am I going with all this? Some people assume that hotter weather is more unstable. But there are two reasons why that's not necessarily true. First, in the low levels (generally below 850 mb): Very hot weather and strong incoming solar radiation will tend to "mix out" your moisture. This is why, in the sounding below (from the Philly area for Saturday afternoon) you see surface temperatures greater than 40 C (104 F) and your temperature curve generally paralleling your Dry Adiabt. Meanwhile, you're "mixed out" all the way up to about 875 mb, as seen by your Dew Point curve paralleling your Mixing Ratio lines. Therefore, if you were to compute your LCL, you'd find it is all the way up at 700 mb! That means cloud bases would be above 3100 m (or about 10,200 ft). That is very detrimental to severe weather chances. It also reduces your CAPE, because there is less area between your Environmental Temp and your Parcel Path since your starting point for that region is so high to begin with. When you see Low Level Lapse Rates getting above 9 C/km, you might think that is really good (because hey, 8 is better than 7, so 9 must be better than 8, right?), but in reality, low level lapse rates approaching 9 C/km or especially 9.5 C/km means that your moisture is mixing out. Makes sense, because lapse rates close to the DRY lapse rate mean that moisture is mixed out and your air is DRY. Second, in the mid levels: Remember that this is a hot air mass, and that it's not just surface temps that are unseasonably warm. If your Environmental Temp isn't cooling quickly, then your CAPE area will also be thin (as well as higher up). So your CAPE is reduced in that way as well. So the sounding with a surface temp of ~86 F is actually MORE unstable than the sounding with a surface temp of ~104 F. Neat, huh? Link to comment Share on other sites More sharing options...
MGorse Posted July 6, 2012 Share Posted July 6, 2012 Nicely done! Link to comment Share on other sites More sharing options...
SmokeEater Posted July 6, 2012 Share Posted July 6, 2012 Day 2 and 3 slight risk now, for most of the area. Day 3 has a 30% contour for extreme SE PA, South Jersey and Delaware. Saturday sounds marginal, looks like Sunday could be a big day in areas that don't need it. We've got so many damaged trees that are about to go down its ridiculous, I'm afraid even a 30-40 mph wind will cause a ton of damage down here at this point. Link to comment Share on other sites More sharing options...
phlwx Posted July 6, 2012 Share Posted July 6, 2012 0z runs -- EC says next-to-no storms on Sunday for the region...GFS has stuff by 18z Sunday. NAM develops activity by 21z but higher chances/qpf west/south. Hi res NAM has a supercell working into PA and fizzles it north of Harrisburg late Saturday night. Gotta break the cap to get anything to fire. I wouldn't be surprised if it takes until Sunday evening to get anything of substance around here. Link to comment Share on other sites More sharing options...
dryslotted Posted July 6, 2012 Share Posted July 6, 2012 Nicely done! Agreed, nice post TR. Someone is paying attention in class! Link to comment Share on other sites More sharing options...
tombo82685 Posted July 6, 2012 Share Posted July 6, 2012 0z runs -- EC says next-to-no storms on Sunday for the region...GFS has stuff by 18z Sunday. NAM develops activity by 21z but higher chances/qpf west/south. Hi res NAM has a supercell working into PA and fizzles it north of Harrisburg late Saturday night. Gotta break the cap to get anything to fire. I wouldn't be surprised if it takes until Sunday evening to get anything of substance around here. i could def see a screw zone somewhere from northern del to abe... storms will fire sat up north then work south. once to dark they should start to weaken which prob be around the pocs then it will continue south the front and storm refire on sunday somehwere around the philly area or just south. Link to comment Share on other sites More sharing options...
Parsley Posted July 6, 2012 Share Posted July 6, 2012 i could def see a screw zone somewhere from northern del to abe... storms will fire sat up north then work south. once to dark they should start to weaken which prob be around the pocs then it will continue south the front and storm refire on sunday somehwere around the philly area or just south. For the most part.......that has happened quite a bit this summer. Places like the Hudson Valley, southern New England and Long Island have gotten rocked....same with Maryland and South Jersey...maybe it's destined to happen again..........or not Link to comment Share on other sites More sharing options...
stormspotterlive Posted July 6, 2012 Share Posted July 6, 2012 Might be a heavy rain fall threat with the storms per Nam providing we get the capping the break on Sunday it is spitting out 2+ pw values for an 18 hour period. Kphl actually has pw values 2+ for 24 hours. Also south of the city per Nam the front is a bit slower and does not clear till Monday afternoon. Link to comment Share on other sites More sharing options...
Thunder Road Posted July 7, 2012 Share Posted July 7, 2012 SPC has all of us north of the Mason-Dixon line in a 30% Wind for tomorrow. Despite the higher probs, they don't sound overly enthusiastic. They focus mainly on NE PA, N NJ, and the Hudson Valley in the disco. ...NORTHEAST/UPPER OH VALLEY... A COMPLEX SEVERE SETUP IS ANTICIPATED WITH RELATIVELY NARROW OVERLAP OF THE MOST FAVORABLE KINEMATIC PARAMETERS WITH THE BEST THERMODYNAMIC ENVIRONMENT AMIDST A WEAKLY FORCED LARGE-SCALE PATTERN. A CLUSTER OF ELEVATED TSTMS MAY BE ONGOING AT 12Z OVER PORTIONS OF THE LOWER GREAT LAKES...THAT WILL PROBABLY WEAKEN AS IT EVOLVES E/SEWD DURING THE MORNING HOURS. STRONG HEATING SHOULD RESULT IN TEMPERATURES REACHING INTO THE MIDDLE TO UPPER 90S IN THE WARM SECTOR...WHILE MODEST LOW-LEVEL WLYS AID IN ADVECTING RICHER BOUNDARY LAYER MOISTURE FROM THE MIDWEST. WITH MID/UPPER-LEVEL LAPSE RATES NOT EXPECTED TO BE STEEP...CONSENSUS OF GUIDANCE SUGGESTS BUOYANCY WILL BE WEAK FROM THE HUDSON VALLEY INTO SRN NEW ENGLAND. HOWEVER...STRONGEST MID-LEVEL FLOW WILL BECOME CENTERED IN THIS REGION...TO AROUND 50 KT AT 700 MB BY 21Z. ALTHOUGH CONVERGENCE ALONG THE FRONT AND PRE-FRONTAL TROUGH MAY REMAIN WEAK...WIDELY SCATTERED TSTMS SHOULD FORM DURING THE AFTERNOON. WITH STEEP LOW-LEVEL LAPSE RATES AND MODERATE TO STRONG DEEP-LAYER SHEAR...MULTICELL TO SUPERCELL STRUCTURES ARE PROBABLE...ESPECIALLY ACROSS PA INTO FAR SERN NY AND NJ. HERE...THE GREATEST POTENTIAL FOR A SMALL MCS WITH EMBEDDED BOWING SEGMENTS SHOULD EXIST WITH PRIMARY RISKS OF DAMAGING WIND AND SEVERE HAIL. Link to comment Share on other sites More sharing options...
RobbTC Posted July 7, 2012 Share Posted July 7, 2012 New watch is out and its north of us Link to comment Share on other sites More sharing options...
dryslotted Posted July 7, 2012 Share Posted July 7, 2012 New watch is out and its north of us The 12z HRRR supports this, though it brings a decent line NW->SE through most of the area btwn 8-10PM tonight... Link to comment Share on other sites More sharing options...
phlwx Posted July 7, 2012 Share Posted July 7, 2012 ^ need the line to backbuild more to its west...otherwise it's Jersey and maybe Easton/Poconos that get in on it. Link to comment Share on other sites More sharing options...
Quakertown needs snow Posted July 7, 2012 Share Posted July 7, 2012 Landing at phl at 4pm so let's keep it clear till then Link to comment Share on other sites More sharing options...
RobbTC Posted July 7, 2012 Share Posted July 7, 2012 Updated Day 1 text DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1126 AM CDT SAT JUL 07 2012 VALID 071630Z - 081200Z ...THERE IS A SLGT RISK OF SVR TSTMS FROM OH INTO SRN NEW ENGLAND AND THE MID ATLANTIC STATES... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MS VALLEY TO THE OZARKS... ...OH INTO SRN NEW ENGLAND AND MID ATLANTIC STATES... A BAND OF STRONG/SEVERE STORMS HAS INTENSIFIED ALONG THE SRN EDGE OF A MCS MOVING ESEWD ACROSS WRN/CENTRAL NY. THIS IS OCCURRING ALONG THE NRN GRADIENT OF AN EML PLUME/CAPPING INVERSION THAT HAS SPREAD EWD INTO THE MID ATLANTIC REGION. VISIBLE IMAGERY SHOWS BREAKS IN CLOUDS AHEAD OF THE CONVECTIVE SYSTEM FROM PA INTO NJ AND SERN NY WHICH SHOULD PERMIT STRONG DIABATIC HEATING AND DESTABILIZATION TO OCCUR IN THE PRE-STORM ENVIRONMENT...WITH SBCAPE REACHING 2000-2500 J/KG THIS AFTERNOON. THE ACTIVITY IS IMMEDIATELY SOUTH OF A STRONG WNWLY MID/UPPER LEVEL JET...AND WITH AREA VAD PROFILES INDICATING 40-50 KT FLOW ABOVE 3-4 KFT AGL FROM NRN PA INTO SRN NY...FAST STORM MOTION AND STEEPENING LOW LEVEL LAPSE RATES WILL ENHANCE POTENTIAL FOR DAMAGING WIND GUSTS TO OCCUR INTO THE EVENING HOURS. ALTHOUGH CAPPING APPEARS TO BE STRONGER WITH WWD EXTENT INTO OH...INTENSE DIABATIC HEATING AND WEAK CONVERGENCE ALONG A SWD SAGGING FRONT WILL RESULT IN GRADUAL WEAKENING OF THE CAP. THIS WILL PROVIDE POTENTIAL FOR ADDITIONAL STORM DEVELOPMENT THIS AFTERNOON NEAR THE FRONT WHERE THE AIR MASS WILL BE VERY UNSTABLE /MLCAPE REACHING 2500-3500 J PER KG/. WNWLY FLOW ALOFT OF 25-30 KT WILL RESULT IN SUFFICIENT VERTICAL SHEAR FOR A FEW MULTICELL CLUSTERS/LINEAR SEGMENTS TO FORM...WITH STRONGER STORMS CAPABLE OF PRODUCING DAMAGING WIND GUSTS AND POSSIBLY SEVERE HAIL. Link to comment Share on other sites More sharing options...
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