Arnold214 Posted July 18, 2015 Share Posted July 18, 2015 NAM 4km is pretty meh on the simulated reflectivity products, but you can see it spits out a few rogue supercells in the warm sector. I think the one real plus we have going is that the steepest lapse rates overspead the area after dark, so whatever convection gets going should have the fuel to sustain. Definitely not one of those scenarios where you expect thunder to crap out with the setting sun. do i need to cancel my leave tomorrow night? Link to comment Share on other sites More sharing options...
OceanStWx Posted July 18, 2015 Share Posted July 18, 2015 do i need to cancel my leave tomorrow night? Maybe I'll come back from Loudon and go straight into severe weather ops. Still mostly potential tomorrow night, not ready to bite on the event actually happening. Link to comment Share on other sites More sharing options...
OceanStWx Posted July 18, 2015 Share Posted July 18, 2015 The NAM seems to push the steepest lapse rates off to the east around/shortly after 0z tomorrow night. I just had the chance to look at 12z GFS bufkit for BDL and it's quite intriguing...actually has lapse rates nearing 8 C/KM in the 700-550mb layer near 3z with great cape...even some slight turning evident on the hodo GFS and Euro seem to be on board regarding lapse rate advection late tomorrow. Link to comment Share on other sites More sharing options...
ma blizzard Posted July 18, 2015 Share Posted July 18, 2015 not a bad look, valid 6z overnight tmrw on the 18z GFS Link to comment Share on other sites More sharing options...
weatherwiz Posted July 18, 2015 Share Posted July 18, 2015 GFS and Euro seem to be on board regarding lapse rate advection late tomorrow. I've noticed the NAM does not seem to really handle lapse rates all that well, particularly when we're talking about the advection of steeper lapse rates. The NAM is often too aggressive in pushing the lapse rates east or weakening them. It probably has to do with the physics of the model and such and how it handles modeled convection and using that to ruin lapse rates. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 18, 2015 Share Posted July 18, 2015 Maybe I'll come back from Loudon and go straight into severe weather ops. Still mostly potential tomorrow night, not ready to bite on the event actually happening. Part of the issue too is just the timing of everything. It's highly possible the timing of all the features is just too off...activity moving in before the strongest shear arrives (this is going to be the key aspect IMO with regards to the overall severe potential). If the strongest shear lacks but we have the steep lapse rates present we're probably looking at a few severe pulsers but if the strongest shear can arrive in time along with steep lapse rates present we could be looking at a little more in the way of organized severe Link to comment Share on other sites More sharing options...
OceanStWx Posted July 18, 2015 Share Posted July 18, 2015 I've noticed the NAM does not seem to really handle lapse rates all that well, particularly when we're talking about the advection of steeper lapse rates. The NAM is often too aggressive in pushing the lapse rates east or weakening them. It probably has to do with the physics of the model and such and how it handles modeled convection and using that to ruin lapse rates. Given the look of the 12km version simulated reflectivity, it generates quite a bit of convection which probably erases any lapse rates. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 18, 2015 Share Posted July 18, 2015 Given the look of the 12km version simulated reflectivity, it generates quite a bit of convection which probably erases any lapse rates. that makes sense...I guess it can't be completely discounted as a scenario but given what the GFS/Euro are displaying I am a bit more confident in this scenario not being highly likely. What I would have really liked to see was that pocket of 500mb winds >50-60 knots on the GFS remain in tact as it pushes into New England but that pocket weakens and we're looking at closer to 40-45 knots. I know some of our bigger nocturnal events not only are associated with steep lapse rates but typically I believe 500mb winds usually are in excess of 50 knots. Link to comment Share on other sites More sharing options...
OceanStWx Posted July 18, 2015 Share Posted July 18, 2015 that makes sense...I guess it can't be completely discounted as a scenario but given what the GFS/Euro are displaying I am a bit more confident in this scenario not being highly likely. What I would have really liked to see was that pocket of 500mb winds >50-60 knots on the GFS remain in tact as it pushes into New England but that pocket weakens and we're looking at closer to 40-45 knots. I know some of our bigger nocturnal events not only are associated with steep lapse rates but typically I believe 500mb winds usually are in excess of 50 knots. I mean shear isn't really that bad believe it or not, when you are looking over a deep enough layer. MCS maintenance is differentiating better by looking at those deep layers. We're talking over 70 knots based on the 18z GFS (through 0-10km). Might like to see the mid level winds a little more northwesterly if we were looking for a severe MCS, but we definitely have some players on the table for late tomorrow. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 18, 2015 Share Posted July 18, 2015 I mean shear isn't really that bad believe it or not, when you are looking over a deep enough layer. MCS maintenance is differentiating better by looking at those deep layers. We're talking over 70 knots based on the 18z GFS (through 0-10km). Might like to see the mid level winds a little more northwesterly if we were looking for a severe MCS, but we definitely have some players on the table for late tomorrow. Over 70 knots in the 0-10km layer...wow that's actually pretty darn impressive really. Definitely a good signal for an organized squall line...or like you even said maybe an MCS? I was actually just talking with someone about MCS potential tomorrow night...I wonder if we could see something like that evolve on the nose of the MLJ? EDIT: Thanks for bringing up the 0-10 km shear value...didn't look into that. I wish weather.cod would have those types of parameters listed. I know on twisterdata you can look at bulk shear values through various levels. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 19, 2015 Share Posted July 19, 2015 Speaking of deep layer shear, how do you find those values by hand through various levels? What equation do you use? Link to comment Share on other sites More sharing options...
weatherwiz Posted July 19, 2015 Share Posted July 19, 2015 Not our area but was looking at SPC SREF and noticed there was a little area of SIG TOR hatched in western NY off the lakes...with these types of setups it's not completely uncommon to have some enhancement off the lakes with lake breeze boundaries locally enhancing helicity and causing a brief spin-up or two Link to comment Share on other sites More sharing options...
OceanStWx Posted July 19, 2015 Share Posted July 19, 2015 Over 70 knots in the 0-10km layer...wow that's actually pretty darn impressive really. Definitely a good signal for an organized squall line...or like you even said maybe an MCS? I was actually just talking with someone about MCS potential tomorrow night...I wonder if we could see something like that evolve on the nose of the MLJ? EDIT: Thanks for bringing up the 0-10 km shear value...didn't look into that. I wish weather.cod would have those types of parameters listed. I know on twisterdata you can look at bulk shear values through various levels. I kind of took apart the SPC MCS maintenance parameter and looked at each part individually. Link to comment Share on other sites More sharing options...
OceanStWx Posted July 19, 2015 Share Posted July 19, 2015 Speaking of deep layer shear, how do you find those values by hand through various levels? What equation do you use? Vector subtraction, or just ask AWIPS to do it like I did. Ha Link to comment Share on other sites More sharing options...
OceanStWx Posted July 19, 2015 Share Posted July 19, 2015 Not our area but was looking at SPC SREF and noticed there was a little area of SIG TOR hatched in western NY off the lakes...with these types of setups it's not completely uncommon to have some enhancement off the lakes with lake breeze boundaries locally enhancing helicity and causing a brief spin-up or two Should be a pseudo-warm front just south of Lake Ontario. That ROC to SYR corridor is always good for a big storm. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 19, 2015 Share Posted July 19, 2015 Vector subtraction, or just ask AWIPS to do it like I did. Ha I wouldn't mind doing the math, that would be fun. Plus, I don't have AWIPS so I can't ask it lol Should be a pseudo-warm front just south of Lake Ontario. That ROC to SYR corridor is always good for a big storm. That is a great area for severe...they can get some monster looking storms. Always have to watch storms out that way when you have so many boundaries around. Link to comment Share on other sites More sharing options...
OceanStWx Posted July 19, 2015 Share Posted July 19, 2015 That is a great area for severe...they can get some monster looking storms. Always have to watch storms out that way when you have so many boundaries around. For something long tracked or significant, you really want that cooler water source to be to your north and that way it can act as a warm front. Cold water to the south sucks, because it just undercuts the updrafts and your instability ends up behind the storm rather than ahead of it. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 19, 2015 Share Posted July 19, 2015 For something long tracked or significant, you really want that cooler water source to be to your north and that way it can act as a warm front. Cold water to the south sucks, because it just undercuts the updrafts and your instability ends up behind the storm rather than ahead of it. Plus with the source to the north, if you have a stronger lake breeze occurring, it can really enhance the 0-1km shear and you have a pretty nice looking little hodo. The best s when you have one of those cells occurring that ride right along the boundary and go to town for a good period. It's pretty amazing when you look at tornado tracks across that portion of NY how many tornado tracks are pretty much exactly the same....not only path but length Link to comment Share on other sites More sharing options...
CoastalWx Posted July 19, 2015 Share Posted July 19, 2015 Definitely an interesting look regarding mid level lapse rates late day and evening. Approaching s/w with subtle height falls too. Timing isn't that great, but other factors may help limit weakening. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted July 19, 2015 Share Posted July 19, 2015 BOX not mincing words SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... ***POTENTIAL FOR SIGNIFICANT SEVERE WEATHER OUTBREAK SUNDAY EVENING WITH ISOLATED STRONG TO SEVERE STORMS POSSIBLY LASTING WELL INTO THE NIGHT*** WE HAVE TWO SIGNIFICANT ISSUES FOR THE SHORT TERM PERIOD. FIRST...SUNDAY WILL FEATURE HOT TEMPERATURES AND HIGH HUMIDITY. MAX TEMPERATURES ARE EXPECTED TO REACH THE LOWER 90S ACROSS MUCH OF THE INTERIOR. COMBINED WITH DEWPOINTS NEAR 70 DEGREES...HEAT INDICES WILL REACH INTO THE UPPER 90S ACROSS PORTIONS OF THE INTERIOR FOR A TIME SUNDAY AFTERNOON. HIGHEST VALUES IN THE 97 TO 99 RANGE EXPECTED ALONG THE CT RIVER VALLEY FROM THE SPRINGFIELD AREA ON SOUTH. THESE VALUES ARE JUST A TAD BELOW THE HEAT ADVISORY THRESHOLD. WE ARE EXPECTING NO RAIN DURING THE DAYTIME PERIOD ON SUNDAY AS A CAPPING AREA OF WARM AIR ALOFT WILL INHIBIT CONVECTION. THAT CAP...HOWEVER...WILL BEGIN TO ERODE TOWARD EVENING. SECOND...WE ARE CONCERNED THAT THE CAP WILL ERODE ENOUGH SUNDAY EVENING TO ALLOW STRONG TO SEVERE CONVECTION TO DEVELOP IN MODERATE TO HIGH INSTABILITY AND INCREASING VERTICAL WIND SHEAR. THERE LOOKS TO BE AN ELEVATED MIXED LAYER WITH MID LEVEL LAPSE RATES EXPECTED TO APPROACH OR EVEN EXCEED 7C/KM AFTER 00Z MON. MODEL CONSENSUS INDICATES THAT TOTAL TOTALS WILL RISE TO BETWEEN 50 AND 55 AND SHOWALTER INDICES BELOW -4. VERTICAL WIND SHEAR IS INITIALLY A MODEST 25 TO 30 KT IN THE EARLY EVENING BUT INCREASES TO 35 TO 40+ KT BY AROUND MIDNIGHT. THINK WE COULD SEE ORGANIZED STRONG TO SEVERE TSTM LINE SEGMENTS WITH POSSIBLY A FEW BOW ECHOES. HEAVY DOWNPOURS WITH PWATS 1.5 TO 1.8 INCHES...SOME HAIL AND PROBABLY FREQUENT LIGHTNING ARE ADDITIONAL HAZARDS FOR SUNDAY EVENING INTO SUNDAY NIGHT. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 19, 2015 Share Posted July 19, 2015 0z NAM sounding for somewhere in northern CT at 0z tomorrow...pretty damn unstable! also a little backed winds in the lowest few km...too bad shear isn't stronger Link to comment Share on other sites More sharing options...
weatherwiz Posted July 19, 2015 Share Posted July 19, 2015 NAM has some pretty good convergence over CT around 3z Link to comment Share on other sites More sharing options...
eekuasepinniW Posted July 19, 2015 Share Posted July 19, 2015 I wouldn't mind having those storms to my NW drop a little further south. Link to comment Share on other sites More sharing options...
alex Posted July 19, 2015 Share Posted July 19, 2015 Pouring in Bartlett Link to comment Share on other sites More sharing options...
Damage In Tolland Posted July 19, 2015 Share Posted July 19, 2015 As usual models are all over the place for tonight's event. Some say hammer time, some say totally dry. Hopefully mets can clear up the confusion Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted July 19, 2015 Share Posted July 19, 2015 As usual models are all over the place for tonight's event. Some say hammer time, some say totally dry. Hopefully mets can clear up the confusion Never a good sign Link to comment Share on other sites More sharing options...
Damage In Tolland Posted July 19, 2015 Share Posted July 19, 2015 Never a good sign Until mets can jump in and clarify the threat potential all we can do is hope for a huge outbreak with many, many trees down in blowdowns Link to comment Share on other sites More sharing options...
Ginx snewx Posted July 19, 2015 Share Posted July 19, 2015 Until mets can jump in and clarify the threat potential all we can do is hope for a huge outbreak with many, many trees down in blowdowns1) SEVERAL PIECES OF GUIDANCE...ESPECIALLY THE GLOBAL MODELS KEEPTHE MAIN ACTION TO OUR NORTH ACROSS NORTHERN NEW ENGLAND IN THE VICINITY OF THE MAIN SHORTWAVE. IF THIS OCCURS...ISOLATED STRONG TO SEVERE THUNDERSTORMS WILL MAINLY OCCUR NORTH OF THE MA TURNPIKE FROM LATE THIS AFTERNOON INTO THE EVENING. ISOLATED WIND DAMAGE WOULD OCCUR BUT MUCH OF THE REGION MAY END UP DRY ESPECIALLY OUR SOUTHERN ZONES. (2) MEANWHILE...SOME OF OUR MESOSCALE GUIDANCE SHOWS THIS ISOLATED ACTIVITY MERGING INTO AN MCS AND DIVING INTO PORTIONS OF OUR REGION. THIS IS CERTAINLY POSSIBLE GIVEN STEEP MID LEVEL LAPSE RATES KEEPING HIGH INSTABILITY IN PLACE WELL AFTER SUNSET. IN THESE TYPE OF ENVIRONMENTS...COMPLEXES OF THUNDERSTORMS CAN OFTEN PUSH FURTHER SOUTH THAN THE MODELS DEPICT TO AS A RESULT OF COOL OUTFLOW PUSHING SOUTH INTO A VERY UNSTABLE ENVIRONMENT. IF THIS DOES COME TO FRUITION...POCKETS OF SIGNIFICANT WIND DAMAGE WOULD BE POSSIBLE GIVEN EML IN PLACE ALONG WITH IMPROVING 0 TO 6 KM SHEAR. MODELS SHOW THE BEST SHOT AT THIS NORTH OF THE MA TURNPIKE...BUT IF AN MCS DOES GET GOING IT COULD END UP SWEEPING ACROSS THE REST OF THE REGION AS WELL. IN ADDITION...TO THE THREAT FOR POCKETS OF SIGNIFICANT WIND DAMAGE...TORRENTIAL RAINFALL MAY RESULT IN LOCALIZED FLOODING ALONG WITH DANGEROUS CLOUD TO GROUND LIGHTNING. ALL IN ALL...WE SHOULD AT LEAST BE DEALING WITH ISOLATED STRONG TO SEVERE THUNDERSTORMS. WHETHER OR NOT WE END UP WITH A SIGNIFICANT SEVERE WEATHER EVENT REMAINS TO BE SEEN...BUT WILL HAVE TO CLOSELY MONITOR THAT POTENTIAL LATER TODAY. PRIME TIME FOR SEVERE WEATHER LOOKS TO OCCUR FROM 4 PM TO MIDNIGHT...BUT ISOLATED STRONG TO SEVERE STORMS WILL REMAIN POSSIBLE THEREAFTER AS A RESULT OF STEEP MID LEVEL LAPSE RATES KEEPING INSTABILITY IN PLACE. Link to comment Share on other sites More sharing options...
weatherwiz Posted July 19, 2015 Share Posted July 19, 2015 Great write-up by BOX. They explained the few scenarios with tremendous detail. All you can really do at this stage is just really nowcast. Models really aren't going to be a big help at this point. We know it's going to be pretty damn unstable, we know lapse rates will be steep, we know shear will increase. It's all about whether activity that develops into an MCS and if so where does it track. Link to comment Share on other sites More sharing options...
Guvna Posted July 19, 2015 Share Posted July 19, 2015 From SPC overnight...new update coming in 30 minutes. THE SEVERE THREAT SHOULDEXTEND AS FAR NORTHEAST AS NEW YORK AND INTO PARTS OF NEW ENGLANDWHERE LARGE-SCALE ASCENT WILL BE STRONGER DUE TO THE APPROACHINGSHORTWAVE TROUGH. OVER THIS AREA...FORECAST SOUNDINGS SHOW SOMEDIRECTIONAL SHEAR IN THE LOW LEVELS WITH ENOUGH DEEP-LAYER SHEAR FORROTATING STORMS ACCOMPANIED BY DAMAGING WIND GUSTS AND HAIL. Link to comment Share on other sites More sharing options...
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