andyhb Posted July 17, 2013 Share Posted July 17, 2013 That's insane! I've always wondered about this with jet quadrants... This is the 18z GFS run for 0z Sunday and you can see the ULJ streak and with us in the right entrance region enhancing lift...obviously the closer you are to the jet max the stronger the forcing but how far away do you really have to be before you technically aren't in the quadrant or to where it doesn't play a factor? Usually you want to be in the left-front or right-rear (or in impressive cases, both, with a departing and arriving jet streak) quadrants of the upper level jet to maximize divergence and lift, although other factors can mute this factor out. Having strong upper level winds intensifies 0-8 km shear for storm organization and longevity (at times just as important as 0-6 km bulk shear). Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted July 17, 2013 Share Posted July 17, 2013 Nice model porn this far out Link to comment Share on other sites More sharing options...
weatherwiz Posted July 17, 2013 Author Share Posted July 17, 2013 Usually you want to be in the left-front or right-rear (or in impressive cases, both, with a departing and arriving jet streak) quadrants of the upper level jet to maximize divergence and lift, although other factors can mute this factor out. Having strong upper level winds intensifies 0-8 km shear for storm organization and longevity (at times just as important as 0-6 km bulk shear). This I understand...my question was about how far away from the jet do you have to be to where it doesn't enhance lift? for example, in the image I posted above, at what distance away from the ULJ will it have no affect on? Like would lift still be enhanced over say CT/RI/eastern MA or over much of SNE at all given the best UL winds are well back across SE Canada Link to comment Share on other sites More sharing options...
heavy_wx Posted July 17, 2013 Share Posted July 17, 2013 That's insane! I've always wondered about this with jet quadrants... This is the 18z GFS run for 0z Sunday and you can see the ULJ streak and with us in the right entrance region enhancing lift...obviously the closer you are to the jet max the stronger the forcing but how far away do you really have to be before you technically aren't in the quadrant or to where it doesn't play a factor? Basically, there has to be a significant increase in the wind speed along the trajectory of air parcels moving in the right entrance region. If the air parcels are too far from the jet max, they will not accelerate much and won't turn towards lower heights, leading to little diveregence at that level. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 17, 2013 Author Share Posted July 17, 2013 Basically, there has to be a significant increase in the wind speed along the trajectory of air parcels moving in the right entrance region. If the air parcels are too far from the jet max, they will not accelerate much and won't turn towards lower heights, leading to little diveregence at that level. Thanks!!! This is a question I always had and just never asked it. Link to comment Share on other sites More sharing options...
CoastalWx Posted July 17, 2013 Share Posted July 17, 2013 Thanks!!! This is a question I always had and just never asked it. Jet streaks have a lot of mesoscale things going on which lead to areas of lift. The right entrance region is really what can give us all the fun in winter too. You can get weak forcing from right exit region too, but not in all cases and it has to be a balance of forces to allow lift. Link to comment Share on other sites More sharing options...
It's Always Sunny Posted July 17, 2013 Share Posted July 17, 2013 Good question, Paul. I think SNE will be okay but if I wanted to nit-pick I'd prefer that jet streak to be a bit further SE to get us in that 50-60 kt range. Link to comment Share on other sites More sharing options...
eire015 Posted July 17, 2013 Share Posted July 17, 2013 Interestingly, Rose et al. (2003) found that the majority of tornadoes occurred in the exit region of the jet streak. The most occurred in the left exit region as expected where there would be good divergence aloft, but a surprising number (at least to me) occur in the right exit region (especially on outbreak days) where upper-level convergence would be expected. In fact there were much more tornadoes there than the right entrance region of the jet streak on outbreak days. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 17, 2013 Author Share Posted July 17, 2013 Thanks everyone for the responses to my question! Looking at the 0z GFS you can certainly see a definite EML plume (maybe not the strongest) comes overhead during the overnight hours on Friday into Saturday morning, this either weakens or moves off-shore and lapse rates decrease slightly and CIN really decreases as well. This could be either due to the fact that the GFS has some early morning crap coming through or it wants to develop activity early on. Bufkit soundings to show precipitation as early as 10 AM-1PM for some. The GFS also has a major increase in theta-e out ahead of the front/prefrontal trough and this could allow for dewpoints to really spike up close to 70F or perhaps even a few ticks higher. While mixing may be strong which would normally mi dewpoints down, if the theta-e advection is as strong as the GFS shows, it's going to be tough to really mix out the dews. The GFS does show dews up near 70F and graphic output is developing SBcapes of 3000-4000 J/KG across much of CT/MA along with LI values which look to be as low as -8C to 9C. It also looks like we may see multiple rounds of t'storms, one with the prefrontal trough and then another line later on towards late evening or early overnight out ahead of the actual cold front. Early on with the prefrontal trough, if winds go more south than southwest that could increase 0-2km shear values which would increase the potential for some supercells, however, given the mainly unidirectional flow aloft the convective mode should be predominately linear. If we were to be looking for widespread significant severe weather potential, you'd like to see some stronger winds aloft. Currently, winds in the 700-500mb layer are generally around 35-40 knots. You would probably want to see winds around 700mb closer to 35-40 knots with winds at 500mb in the 50 to even 60 knots range. With that said, forecast soundings do give an inverted-v look with some drier air centered between about 800-600mb so that could certainly increase downdraft potential. With all this, widespread significant wind damage is probably not very likely but we could see a decent cluster of wind damage. While there will be good vertical shear and quite possibly steep lapse rates and elevated helicity levels, freezing levels appear to be on the higher side so it will be difficult to achieve large hail, however there could be several reports of small hail with a few severe hail reports mixed in, especially if we do develop any supercells. Something else to watch for is some very heavy rains across far eastern MA and the Cape as the front looks to slow/stall somewhat over this area and a weak wave of low pressure develops...could be quite rainy there overnight into a good part of Sunday. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 17, 2013 Author Share Posted July 17, 2013 Looked at the 6z NAM for hah's since it's finally in range and boy does it have a funky skew-t Link to comment Share on other sites More sharing options...
It's Always Sunny Posted July 17, 2013 Share Posted July 17, 2013 Here is the 2nd half of the Day 4 summary from the SPC earlier this morning: MODELS/ENSEMBLES ARE IN GENERALLY GOOD AGREEMENT IN DEPICTING THEAMPLIFICATION OF THE UPPER TROUGH AND SUBSEQUENT DEMISE OF THESTRONG ANTICYCLONE CURRENTLY ENCOMPASSING MUCH OF THE MIDWEST ANDEAST. MID LEVEL HEIGHTS ARE FORECAST TO FALL BY AS MUCH AS 240M BYSAT ACROSS IND/OH WHERE THE UPPER HIGH IS CURRENTLY CENTERED.VIGOROUS/SEVERE TSTMS CAN BE EXPECTED AS LIFT ALONG THE FRONTAL ZONEACTS ON VERY WARM AND MOIST AIR FROM OH TO NEW ENGLAND DURING THEDAY SAT. STRENGTHENING WIND FIELDS WILL SUPPORT BANDS OR LINES OFSTORMS SPREADING ESEWD WITH DAMAGING WINDS BEING THE PRIMARY SEVEREWEATHER HAZARD. Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted July 17, 2013 Share Posted July 17, 2013 always feels fruitless to me to try and delve into the details of severe potential in SNE more than about 24 hours out. of course, this is a weather board so if you can't talk about it here, where can you? there are just so many unfocused important details that make a huge difference. any concern about frontal timing? Link to comment Share on other sites More sharing options...
It's Always Sunny Posted July 17, 2013 Share Posted July 17, 2013 always feels fruitless to me to try and delve into the details of severe potential in SNE more than about 24 hours out. of course, this is a weather board so if you can't talk about it here, where can you? there are just so many unfocused important details that make a huge difference. any concern about frontal timing? I think timing looks pretty good right now actually. All the models appear to be on the same page, now that the NAM is in range. What are your thoughts? Link to comment Share on other sites More sharing options...
Brian5671 Posted July 17, 2013 Share Posted July 17, 2013 what's the timing of the front Saturday? Link to comment Share on other sites More sharing options...
It's Always Sunny Posted July 17, 2013 Share Posted July 17, 2013 what's the timing of the front Saturday? Should be passing through western New England mid afternoon which is perfect. Link to comment Share on other sites More sharing options...
CT Rain Posted July 17, 2013 Share Posted July 17, 2013 always feels fruitless to me to try and delve into the details of severe potential in SNE more than about 24 hours out. of course, this is a weather board so if you can't talk about it here, where can you? there are just so many unfocused important details that make a huge difference. any concern about frontal timing? Euro looks pretty early - at least with QPF depiction. I'll be interested on Friday lol Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted July 17, 2013 Share Posted July 17, 2013 I think timing looks pretty good right now actually. All the models appear to be on the same page, now that the NAM is in range. What are your thoughts? honestly i've hardly looked. now that it's inside 4 days i've started to give timing some thought. the only thing that caught my eye was the appearance of some sort of pre-frontal trough/wind shift on the euro passing through SNE midday...and, correspondingly, the deeper low-level moisture directly over SNE at 18z and pretty far offshore by 00z. made me wonder if that's going to screw things up with regard to timing by robbing the atmosphere a bit after midday. but...just one of many details that won't be known for a while. Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted July 17, 2013 Share Posted July 17, 2013 honestly i've hardly looked. now that it's inside 4 days i've started to give timing some thought. the only thing that caught my eye was the appearance of some sort of pre-frontal trough/wind shift on the euro passing through SNE midday...and, correspondingly, the deeper low-level moisture directly over SNE at 18z and pretty far offshore by 00z. made me wonder if that's going to screw things up with regard to timing by robbing the atmosphere a bit after midday. but...just one of many details that won't be known for a while. come to think of it, that timing would actually be pretty good for my neck of the woods...lol Link to comment Share on other sites More sharing options...
weatherwiz Posted July 17, 2013 Author Share Posted July 17, 2013 As long as the prefrontal would come through like after 2 that would be fine. Some of our bigger events have occurred along the pre frontal rarer than the front itself Link to comment Share on other sites More sharing options...
Baroclinic Zone Posted July 17, 2013 Share Posted July 17, 2013 Euro looks pretty early - at least with QPF depiction. I'll be interested on Friday lol I like Friday as well. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted July 17, 2013 Share Posted July 17, 2013 I like Friday as well.I believe he meant he'd start to have interest for Saturday on Friday Link to comment Share on other sites More sharing options...
CT Rain Posted July 17, 2013 Share Posted July 17, 2013 I like Friday as well. We're way too capped. 700mb temps are +13 over all of New England... that's probably wayyyyy too much. Link to comment Share on other sites More sharing options...
It's Always Sunny Posted July 17, 2013 Share Posted July 17, 2013 As long as the prefrontal would come through like after 2 that would be fine. Some of our bigger events have occurred along the pre frontal rarer than the front itself I think as long was we get some sort of forcing around that time we'll be good to go, whether it's the pre-frontal, or the actual front itself. Like Tropopause_Fold was saying, we just hope nothing is robbed. Link to comment Share on other sites More sharing options...
Baroclinic Zone Posted July 17, 2013 Share Posted July 17, 2013 We're way too capped. 700mb temps are +13 over all of New England... that's probably wayyyyy too much. For severe, yes, but for rains I like Friday with the front sagging thru. Link to comment Share on other sites More sharing options...
Baroclinic Zone Posted July 17, 2013 Share Posted July 17, 2013 I believe he meant he'd start to have interest for Saturday on Friday Yes, I agree on this. Sat into Sun looks best for severe, Link to comment Share on other sites More sharing options...
dryslot Posted July 17, 2013 Share Posted July 17, 2013 Saturday here Link to comment Share on other sites More sharing options...
forkyfork Posted July 17, 2013 Share Posted July 17, 2013 the gfs is more bullish with lapse rates than the nam... a nam outcome would be boring Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted July 17, 2013 Share Posted July 17, 2013 the gfs is more bullish with lapse rates than the nam... a nam outcome would be boring euro 7h-5h LRs are <6C/km Link to comment Share on other sites More sharing options...
forkyfork Posted July 17, 2013 Share Posted July 17, 2013 euro 7h-5h LRs are <6C/km Link to comment Share on other sites More sharing options...
It's Always Sunny Posted July 17, 2013 Share Posted July 17, 2013 the gfs is more bullish with lapse rates than the nam... a nam outcome would be boring A NAM outcome wouldn't produce jack...4.5-5.5 FTL. Where are you viewing GFS lapse rates? Bufkit? A/W? I know you can if you subscribe to this forum but I'm just seeing if you can view lapse rates elsewhere. Link to comment Share on other sites More sharing options...
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