earthlight Posted July 30, 2012 Share Posted July 30, 2012 Forecast guidance is hinting at a potential active start to the month of August in the severe weather and convection department, especially across the Northern Tier of the Central and Eastern US. A broad area of troughing over Central Canada is expected to shift eastward with time, with forecast guidance struggling (as expected at this range) with individual shortwaves and perturbations within the flow. That being said, some of the differences amongst guidance go further than that, with the GEFS mean and GFS OP being much less enthused than the OP ECMWF and ensembles in regards to a strong shortwave trough swinging south from the International Border and the N Plains, through the Great Lakes and towards Southeast Canada. Such a shortwave, if realized as the Euro suggests, would likely bring significant height falls and strong forcing to support the development of convection in the warm sector which will shift east from the Great Lakes Day 6 to the Northeast US Days 7 and 8. The general set up, though, remains too uncertain at this point..with several model differences on timing, track, strength. Link to comment Share on other sites More sharing options...
kevbo81 Posted July 30, 2012 Share Posted July 30, 2012 Excellent post as always John. A couple of observations and a question: Upton mentioned today in their discussion (latest one) the very same thing you're keying in on. It's reminiscent of the way that Thursday's storms were well telegraphed from about a week away. In fact, SPC put out a rare day 7-8 outlook, then pulled back due to uncertainty. It also looks like another short way is hot on the first one's heals. Is that so? Seems to me that the pattern may be rather stagnant, so that even the first full week of Aug has some potential as well. Link to comment Share on other sites More sharing options...
Allsnow Posted July 30, 2012 Share Posted July 30, 2012 Even though its been mostly out of the metro area.. it has been very active in nj this summer...many storms producing damage Link to comment Share on other sites More sharing options...
earthlight Posted July 30, 2012 Author Share Posted July 30, 2012 Excellent post as always John. A couple of observations and a question: Upton mentioned today in their discussion (latest one) the very same thing you're keying in on. It's reminiscent of the way that Thursday's storms were well telegraphed from about a week away. In fact, SPC put out a rare day 7-8 outlook, then pulled back due to uncertainty. It also looks like another short way is hot on the first one's heals. Is that so? Seems to me that the pattern may be rather stagnant, so that even the first full week of Aug has some potential as well. Well there is definitely a broad "threat" for storms. I don't think anything is really clear at this point...the models are all over the place. I don't expect them to issue any type of extended outlook area at this point given the big differences. But if the threat does materialize and things become more clear as we get closer to the event, then there would be similarities in the way we were able to snuff it out about a week away. Link to comment Share on other sites More sharing options...
earthlight Posted July 30, 2012 Author Share Posted July 30, 2012 The GFS trended stronger with the surface cyclogenesis but remains farther north and west from this afternoons ECMWF which was driving the upper level low over the Great Lakes with more of an easterly trajectory. Link to comment Share on other sites More sharing options...
ag3 Posted July 30, 2012 Share Posted July 30, 2012 The GFS trended stronger with the surface cyclogenesis but remains farther north and west from this afternoons ECMWF which was driving the upper level low over the Great Lakes with more of an easterly trajectory. 0z euro continues with its 12z idea of a strong closed low through the lakes. Link to comment Share on other sites More sharing options...
Weathergun Posted July 30, 2012 Share Posted July 30, 2012 See Text & 5% risk on Wednesday: Shear with the upper-level trough looks weak overall. But we have may have steep mid-level lapse rates with the cold pocket aloft: ...PARTS OF THE UPR OH VALLEY/APPALACHIANS INTO ATLANTIC COAST... AT THIS TIME...FOCUS FOR STRONGER CONVECTIVE DEVELOPMENT...OTHER THAN THE HIGHER TERRAIN...REMAINS UNCLEAR. BUT...MODELS SUGGEST AT LEAST SOME STEEPENING OF LOW/MID-LEVEL LAPSE RATES ASSOCIATED WITH THE CONTINUED EASTWARD ADVECTION OF ELEVATED MIXED LAYER AIR INTO THE VICINITY OF THE APPALACHIANS. COUPLED WITH CONTINUED LOW-LEVEL MOISTENING...MIXED LAYER CAPE AHEAD OF A WEAKENING FRONT ADVANCING INTO THE OHIO VALLEY IS FORECAST TO BECOME SIZABLE /2000 TO PERHAPS LOCALLY 3000 J PER KG/ BY WEDNESDAY AFTERNOON. ALTHOUGH NORTHWESTERLY MID-LEVEL FLOW TO THE WEST OF THE UPPER TROUGH AXIS MAY BEGIN TO WEAKEN...VERTICAL SHEAR MAY REMAIN STRONG ENOUGH AT LEAST IN POCKETS TO ENHANCE CONVECTION...AND CONTRIBUTE TO THE RISK FOR LOCALIZED SEVERE WIND AND HAIL. Link to comment Share on other sites More sharing options...
ag3 Posted July 30, 2012 Share Posted July 30, 2012 See Text & 5% risk on Wednesday: Shear with the upper-level trough looks weak overall. But we have may have steep mid-level lapse rates with the cold pocket aloft: ...PARTS OF THE UPR OH VALLEY/APPALACHIANS INTO ATLANTIC COAST... AT THIS TIME...FOCUS FOR STRONGER CONVECTIVE DEVELOPMENT...OTHER THAN THE HIGHER TERRAIN...REMAINS UNCLEAR. BUT...MODELS SUGGEST AT LEAST SOME STEEPENING OF LOW/MID-LEVEL LAPSE RATES ASSOCIATED WITH THE CONTINUED EASTWARD ADVECTION OF ELEVATED MIXED LAYER AIR INTO THE VICINITY OF THE APPALACHIANS. COUPLED WITH CONTINUED LOW-LEVEL MOISTENING...MIXED LAYER CAPE AHEAD OF A WEAKENING FRONT ADVANCING INTO THE OHIO VALLEY IS FORECAST TO BECOME SIZABLE /2000 TO PERHAPS LOCALLY 3000 J PER KG/ BY WEDNESDAY AFTERNOON. ALTHOUGH NORTHWESTERLY MID-LEVEL FLOW TO THE WEST OF THE UPPER TROUGH AXIS MAY BEGIN TO WEAKEN...VERTICAL SHEAR MAY REMAIN STRONG ENOUGH AT LEAST IN POCKETS TO ENHANCE CONVECTION...AND CONTRIBUTE TO THE RISK FOR LOCALIZED SEVERE WIND AND HAIL. 12z euro is on board for this event. Link to comment Share on other sites More sharing options...
ag3 Posted July 30, 2012 Share Posted July 30, 2012 0z euro continues with its 12z idea of a strong closed low through the lakes. 12z euro continues it's idea of a strong closed ULL driving through the northern part of the country for Sunday. On today's run, it stays a little too north of the area, but it's a very interesting pattern to keep an eye out on. Link to comment Share on other sites More sharing options...
Isotherm Posted July 30, 2012 Share Posted July 30, 2012 12z euro continues it's idea of a strong closed ULL driving through the northern part of the country for Sunday. On today's run, it stays a little too north of the area, but it's a very interesting pattern to keep an eye out on. Yeah the 12z data keeps the sfc low well north of the US/Canadian border but the pressure falls do extend swd into the Northeast along the FROPA. I'd like to see the height falls extend further south than currently depicted. Right now I'm more interested in the Wednesday convective threat as the s/w will be nearly overhead, thus stronger forcing, but the Sunday potential has plenty of time to change. Definitely an interesting pattern going forward into August. Link to comment Share on other sites More sharing options...
Isotherm Posted July 30, 2012 Share Posted July 30, 2012 Re Wednesdy, surface lifted condensation levels will be very low along with weak convective inhibition, so fairly widespread T-storm development should be expected. Sfc instability parameters aren't that impressive, but lapse rates and forcing from the short wave aloft should compensate. Severe stuff will probably be isolated, though I wouldn't be surprised to see an upgrade to slight risk by Wednesday. Sfc LCL's -- very humid/moist boundary layer will aid in increased buoyancy and widespread convection. Hvy rain producers are probable with heightened PWs. Link to comment Share on other sites More sharing options...
bluewave Posted July 30, 2012 Share Posted July 30, 2012 It looks like the storms on Wednesday will be nearly stationary with very heavy rains and possibly pulse severe. Link to comment Share on other sites More sharing options...
Isotherm Posted July 30, 2012 Share Posted July 30, 2012 It looks like the storms on Wednesday will be nearly stationary with very heavy rains and possibly pulse severe. Agreed, precipitable water value of 1.7 per that sounding. Convection that develops will drop a ton of rain, similar to what we saw on Saturday. LI's of -3 and CAPE < 1000 J/KG (around 500 actually), so meager sfc instability parameters. Severe will be short lived and pulse type as you noted. Link to comment Share on other sites More sharing options...
bluewave Posted July 30, 2012 Share Posted July 30, 2012 Agreed, precipitable water value of 1.7 per that sounding. Convection that develops will drop a ton of rain, similar to what we saw on Saturday. LI's of -3 and CAPE < 1000 J/KG (around 500 actually), so meager sfc instability parameters. Severe will be short lived and pulse type as you noted. Yeah, it may be the kind of day where convection forms right along any boundaries like the sea breezes and just trains over the same locations. Link to comment Share on other sites More sharing options...
earthlight Posted July 31, 2012 Author Share Posted July 31, 2012 Yeah the 12z data keeps the sfc low well north of the US/Canadian border but the pressure falls do extend swd into the Northeast along the FROPA. I'd like to see the height falls extend further south than currently depicted. Right now I'm more interested in the Wednesday convective threat as the s/w will be nearly overhead, thus stronger forcing, but the Sunday potential has plenty of time to change. Definitely an interesting pattern going forward into August. The trend amongst guidance over the last day or two has definitely been towards bringing the height falls and forcing a little farther south. The set up seems a little disjointed to me so one has to wonder what kind of kinematics/wind fields we would be dealing with. But, just as an illustration, the DGEX brings things decently far south (surface low is still in Southeast Canada, though) with convection through the warm sector. http://www.meteo.psu.edu/~gadomski/DGEXEAST_18z/f150.gif Link to comment Share on other sites More sharing options...
Isotherm Posted July 31, 2012 Share Posted July 31, 2012 The trend amongst guidance over the last day or two has definitely been towards bringing the height falls and forcing a little farther south. The set up seems a little disjointed to me so one has to wonder what kind of kinematics/wind fields we would be dealing with. But, just as an illustration, the DGEX brings things decently far south (surface low is still in Southeast Canada, though) with convection through the warm sector. http://www.meteo.psu...ST_18z/f150.gif Yeah, if the DGEX were to verify, that's not a terrible look. Best severe threat still in NNE, but there is some more bagginess to the height field as the s/w rolls through sern Canada. Should see plenty of convection with that set-up at least. Hopefully we'll see more positive trends in the coming days. Link to comment Share on other sites More sharing options...
Isotherm Posted August 1, 2012 Share Posted August 1, 2012 What we see to our west should occurr in our area tomorrow -- slow moving convection, mostly non-severe, but putting down a lot of water in short order. PW values are tropical for tomorrow afternoon. Look for locallized zones of 1-3" of rain where T-storms train. Link to comment Share on other sites More sharing options...
earthlight Posted August 1, 2012 Author Share Posted August 1, 2012 You can see an area of vorticity now even on the GFS, extending southward near the frontal zone from the main height falls. The setup remains pretty muddled though. I would think there would at least be a threat for organized convection despite the surface low being very far north. Link to comment Share on other sites More sharing options...
Dsnowx53 Posted August 1, 2012 Share Posted August 1, 2012 The surface low itself might be far north, but that trough and height falls and vorticity extend pretty far south. Also, the low will be sub 1000mb. That can still lead to deep enough pressures near our latitude. Link to comment Share on other sites More sharing options...
Dsnowx53 Posted August 1, 2012 Share Posted August 1, 2012 That being said, it might not be great to have to rely on something as small-scale as vorticity out ahead of the main trough for our lift. In that regard it might not be so great to have the surface low so far north. But IF we can get that vorticity to advect into our area, that should create enough lift so that the pressure trough without deep pressures is still enough. Link to comment Share on other sites More sharing options...
andyhb Posted August 1, 2012 Share Posted August 1, 2012 DAY 4-8 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0359 AM CDT WED AUG 01 2012 VALID 041200Z - 091200Z ...DISCUSSION... THE SPREAD AMONG THE MEMBERS OF THE MEDIUM RANGE ENSEMBLES IS SIZABLE FROM THE OUTSET OF THE FORECAST PERIOD CONCERNING THE STRONG SHORT WAVE TROUGH LIKELY TO BE ACCELERATING EAST OF THE CENTRAL CANADIAN/U.S. BORDER AREA...WITHIN A PERSISTENT BELT OF STRONGER WESTERLIES. HOWEVER...THERE DOES APPEAR REASONABLE CONSENSUS WITH REGARD TO THE BASIC TRENDS LIKELY TO IMPACT CONVECTIVE POTENTIAL ACROSS THE GREAT LAKES INTO THE NORTHEAST... AS CYCLOGENESIS PROCEEDS ACROSS ONTARIO AND QUEBEC THIS COMING WEEKEND. ALTHOUGH BETTER LOW-LEVEL MOISTURE INFLOW TO THE DEVELOPING SYSTEM MAY BEGIN BY SATURDAY...THE MORE SUBSTANTIVE STRENGTHENING OF SOUTHERLY LOW-LEVEL WARM SECTOR FLOW AND SHEAR MAY BE CONFINED TO PORTIONS OF ONTARIO TO THE NORTH OF LAKES SUPERIOR AND HURON. AS DEEPENING OF THE SURFACE LOW CONTINUES ON SUNDAY... STRENGTHENING OF LOWER AND MID TROPOSPHERIC FLOW FIELDS APPEARS INCREASINGLY PROBABLE AS FAR SOUTH AS AREAS TO THE EAST OF THE LOWER GREAT LAKES...PERHAPS THE UPPER OHIO VALLEY. WHILE THIS MAY NOT BE MUCH MORE THAN 30-40 KT...IT DOES APPEAR THAT LOW-LEVEL MOISTENING AND STEEPENING OF MID-LEVEL LAPSE RATES WILL BECOME SUFFICIENT FOR THE DEVELOPMENT OF MODERATELY LARGE CAPE ACROSS MUCH OF NEW YORK/PENNSYLVANIA AND PORTIONS OF ADJACENT STATES. THIS ENVIRONMENT APPEARS POTENTIALLY SUPPORTIVE OF AN EVOLVING ORGANIZED MESOSCALE CONVECTIVE SYSTEM CAPABLE OF PRODUCING CONSIDERABLE DAMAGING WIND GUSTS...PARTICULARLY AS MID-LEVEL FORCING FOR UPWARD VERTICAL MOTION BEGINS TO SPREAD EAST OF THE LOWER GREAT LAKES REGION...EITHER LATE SUNDAY OR SUNDAY NIGHT. ..KERR.. 08/01/2012 Link to comment Share on other sites More sharing options...
blizzardof09 Posted August 1, 2012 Share Posted August 1, 2012 Ok so are these storms gonna be setting up along the seebreezr front today? I know these storms are gonna be loaded with water and may be pulse severe as well. Im hoping im actually on the right side of the seabreeze front for once Link to comment Share on other sites More sharing options...
Weathergun Posted August 1, 2012 Share Posted August 1, 2012 Lapse rates look poor on 12z OKX sounding, for even a pulse severe threat. And they aren't forecast improve much. I think we see mostly showers and t-storms with just heavy rains. Link to comment Share on other sites More sharing options...
Superstorm93 Posted August 1, 2012 Share Posted August 1, 2012 SPC D5 outlook looks pretty decent. Might be something to monitor over the next couple days. Link to comment Share on other sites More sharing options...
bluewave Posted August 1, 2012 Share Posted August 1, 2012 Starting to see training of cells now as the radar lights up around the area. You can see the axis of higher PWAT's. Link to comment Share on other sites More sharing options...
bluewave Posted August 1, 2012 Share Posted August 1, 2012 Statement as of 11:27 AM EDT on August 01, 2012 The National Weather Service in Upton NY has issued an * Urban Flood Advisory for minor flooding of poor drainage areas in... Kings (Brooklyn) County in southeast New York... Richmond (staten island) County in southeast New York... western Nassau County in southeast New York... Queens County in southeast New York... * until 100 PM EDT... * at 1125 am EDT... radar showed slow moving showers and thunderstorms over the lower boroughs of New York City... with rainfall rates of 1 to 2 inches per hour. Precautionary/preparedness actions... Excessive runoff from these storms will cause flooding of urban areas... highways... streets and underpasses as well as other drainage areas and low lying spots. Be prepared to take action if the flooding threat increases... or if a Flash Flood Warning is issued. Link to comment Share on other sites More sharing options...
Sundog Posted August 1, 2012 Share Posted August 1, 2012 There's flooding in central Queens. Link to comment Share on other sites More sharing options...
Sock Puppet Posted August 1, 2012 Share Posted August 1, 2012 Under the training rain in Brooklyn. Just Plain old heavy rain Link to comment Share on other sites More sharing options...
Neblizzard Posted August 1, 2012 Share Posted August 1, 2012 The sun was out here in Elizabeth NJ for about an hour and now storms are starting to fire just to my south. Looks like the sun gave the atmosphere a jolt...will be interesting to see how active things get over the next several hours . Link to comment Share on other sites More sharing options...
bluewave Posted August 1, 2012 Share Posted August 1, 2012 Some spots picked up close to 2 in last hour. Link to comment Share on other sites More sharing options...
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