TalcottWx Posted August 21, 2011 Share Posted August 21, 2011 A POWERFUL COLD FRONT WILL TRACK ACROSS THE REGION SUNDAY AFTERNOON AND NIGHT. SEVERE THUNDERSTORMS...CAPABLE OF PRODUCING DAMAGING WINDS AND HAIL...WILL BE POSSIBLE. AN ISOLATED TORNADO IS WITHIN THE REALM OF POSSIBILITIES AS WELL. IN ADDITION...HEAVY RAIN FROM THUNDERSTORMS WILL HAVE THE POTENTIAL TO PRODUCE LOCALIZED FLASH FLOODING. I think this threat extends up into western Mass and much of CT, as well... A line of fury from new england to dc Link to comment Share on other sites More sharing options...
weatherwiz Posted August 21, 2011 Share Posted August 21, 2011 Just got home and pretty exhausted but looking at some 0z model data it appears as if the best shear and strongest LLJ don't move into our area until the evening hours and by then the best instability values will be gone due to loss of daytime heating. ML lapse rates are meh and temps aloft not that cold with very little cooling so once the sun goes down instability will wane quickly. Just going to have to see how things look in the AM/early PM. Link to comment Share on other sites More sharing options...
OKpowdah Posted August 21, 2011 Share Posted August 21, 2011 If you don't have a storm shelter, build one tonight! Link to comment Share on other sites More sharing options...
free_man Posted August 21, 2011 Author Share Posted August 21, 2011 If you don't have a storm shelter, build one tonight! Maybe we should go grassroots level and start handing out flyers, to warn of the upcoming danger! Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 00z models look a little better but I still think the threat is fairly marginal in SNE. To the west across NY/NJ/E PA the threat is more substantial. It will all hinge on how much instability we can develop (models have been all over the place with this) and whether or not low/mid level wind fields strengthen before we begin to lose the best instability. Juxtaposition of shear/instability doesn't appear perfect now but that may change.... we'll see. Link to comment Share on other sites More sharing options...
free_man Posted August 21, 2011 Author Share Posted August 21, 2011 00z models look a little better but I still think the threat is fairly marginal in SNE. To the west across NY/NJ/E PA the threat is more substantial. It will all hinge on how much instability we can develop (models have been all over the place with this) and whether or not low/mid level wind fields strengthen before we begin to lose the best instability. Juxtaposition of shear/instability doesn't appear perfect now but that may change.... we'll see. I agree completely. Heavy rain could be a problem overnight? Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 The convection over W NY/W PA shows the problem as it is. Tons of clouds will roll in from this... though I think the initial round of convection falls apart. I agree completely. Heavy rain could be a problem overnight? Link to comment Share on other sites More sharing options...
moneypitmike Posted August 21, 2011 Share Posted August 21, 2011 The convection over W NY/W PA shows the problem as it is. Tons of clouds will roll in from this... though I think the initial round of convection falls apart. Well-as it stands here as the sun peeks over the hills to the east, a lot of cirrus overhead with what looks like a lower-level deck coming in about 20 miles west of here. Those may be due to the 6:30a.m. sun angle, but I don't think so. Still keeping fingers crossed for a good storm, but I'll be okay with just a good dousing as well. 58.7/57 Link to comment Share on other sites More sharing options...
Damage In Tolland Posted August 21, 2011 Share Posted August 21, 2011 Satellite shows we should have a good deal of sunshine today as it's partly/mostly sunny well out into PA and NY..so instability should be good. Looks like Tip was right about today from his post yesterday..Wild day/night ahead Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 Satellite shows we should have a good deal of sunshine today as it's partly/mostly sunny well out into PA and NY..so instability should be good. Looks like Tip was right about today from his post yesterday..Wild day/night ahead Tip said this was like 6/1. It's not like 6/1 at all. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted August 21, 2011 Share Posted August 21, 2011 Tip said this was like 6/1. It's not like 6/1 at all. Well no..the set up really isn't..though SPC does mention there's a shot at some TOR's today..but it's not as good as 6/1 Link to comment Share on other sites More sharing options...
snowNH Posted August 21, 2011 Share Posted August 21, 2011 Well no..the set up really isn't..though SPC does mention there's a shot at some TOR's today..but it's not as good as 6/1 6/1 was a 1/20 year event.. I hope no one thought tip was serious when he mentioned 6/1 Either way I had my best severe of the year on Friday when I wasn't expecting it so maybe this one will do the same.. Looks like we all get heavy rain no matter what Link to comment Share on other sites More sharing options...
free_man Posted August 21, 2011 Author Share Posted August 21, 2011 Tip said this was like 6/1. It's not like 6/1 at all. Maybe he was speaking "threat" wise rather than scientifically analogous? Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 Sunday afternoon is about as impressive in the soundings as any event this year, including June 1. Strong 70kt mid level jet punches in around the base of the trough PA/NY and punches into western zones by mid afternoon, with llv SW flow of theta-rich air, and strong diabatic heating earlier in the day. 500mb temperatures are down to -12C, which isn't extreme, but supports between moderate to severe updraft velocities for parcel rich risers. Large hail and possible tornadoes in the back-winded valleys of western Mass, CT, with linear segment straight line wind in momentum transfers combined with negative CAPE production elsewhere all look good to me. Large hail with those mid lvl temps as well. SBCAPE may approach 3,000 in a band from NW NJ to SE NJ around 2pm; at that time, a broken line with segmented severe and possible meso's embedded should be entering western zones on the nose of said jet. This situation perhaps lacks the same triggering device in that baroclinicity is not as impressive as June 1, but the timing of shear/diabatic heating and CAPE production are super-imposed similarly. Not sure of the EML look but I'm going to be evaluating that shortly. I completely disagree with that assesment... I think they are in totally different leagues. There are a lot of negatives for today. Sure I could see us going under a svr tstm or tornado watch but I doubt it's a major outbreak right now. Low end severe... quite possible. Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 Well no..the set up really isn't..though SPC does mention there's a shot at some TOR's today..but it's not as good as 6/1 Yeah I'm just worried about how much CAPE we can generate today. Link to comment Share on other sites More sharing options...
weatherwiz Posted August 21, 2011 Share Posted August 21, 2011 The SPC SREF is really hitting the severe potential hard across areas just off to our west later this afternoon and into this evening. Some of these areas include eastern PA/eastern NY and norther/central NJ with the area potentially extending into extreme western MA/CT. Across these areas the SPC SREF indicates the better potential for higher cape values (SBCapes potentially nearing or exceeding 2000 J/KG, MLcape values nearing 2000 J/KG, and MUcape values nearing or exceeding 3000 J/KG with LI values as low as -6C to -7C). Within this axis of potentially moderate instability will also exist the stronger shear values. While the SPC SREF is not very beefy with helicity values (0-3km helicity values around 100 m2s2 and 0-1km helicity values around 150 m2s2) you still have to watch for areas of increased helicity due to the warm front and winds also channeling through the valleys across PA/NY. I would think across these areas storm mode early on will be rather discrete and this is where the tornado potential will be the highest, depending on if they can reach those maximum instability values. As the activity begins to move eastward towards southern New England due to the potential for late in the day timing instability will gradually begin to weaken, however, the wind fields aloft will strengthen which should help to overcome the loss of instability a bit...at least help to maintain the storms a bit longer but they may be gradually weakening. As the activity moves towards our region any discrete storms may begin to evolve into a squall line or a series of small bowing lines; thus the greatest threat for western southern New England would be damaging winds. SPC SREF does, however, keep a very small tornado threat into southern New England well into the evening and overnight so I suppose this potential can't totally be ruled out but with the loss of much stronger instability this threat may not be all that much. Besides the severe wx threat today and/all storms will be capable of producing extremely heavy rainfall as PWAT values near 1.8'' or even higher. Given strong winds aloft storms should move rather quickly but some isolated flash flooding can't be ruled out given the juicy atmosphere and potential for extremely heavy downpours dropping alot of rain in a small amount of time. This is just going to have to be watched closely throughout the afternoon. Link to comment Share on other sites More sharing options...
TalcottWx Posted August 21, 2011 Share Posted August 21, 2011 (Thoughts from over on Mid Atl sub) Upton gung ho for a big event in their CWA. Mentions of supercells. Interesting to note that LWX lacks any mention of supercells in their CWA, surprised as I thought we would see at least for northern portions. Further north in the slight risk area, ALB says if clouds do not significantly hamper instability, severe likely. They are pushing enhanced wording. Mount Holly seems somewhat lackadaisical with the threat.. mentioning high parameters of svr, their afd wanes in comparison to the gung ho upton one however. Do I think this is a huge event for the books? No. Maybe our most memorable event locally however. But I think there will be a couple supercells this afternoon with plenty of svr reports. Well organized storms elsewhere.. and possibly a pretty awesome line of storms. Thoughts on a map: UPTON PARAMETERS REMAIN IN PLACE FOR A SEVERE OUTBREAK. 00Z NAM CAME IN A BIT HIGHER WITH THE BRN...RESULTING IN A TENDENCY TOWARDS MULTICELLULAR. SYNOPTIC LLVL DIRECTIONAL SHEAR IS LIMITED...HOWEVER AS STORMS DEVELOP ALLOWING FOR LLVL INFLOW...EXPECT THIS SHEAR TO BE ENHANCED RESULTING IN AN ENVIRONMENT MORE SUPPORTIVE OF SUPERCELLS. STERLING THE COLD FRONT OVER THE GREAT LAKES EARLY THIS MORNING WILL BUILD SOUTH AND EAST INTO PENNSYLVANIA AND THE OHIO VALLEY LATER TODAY. A WARM SOUTHWEST FLOW IS EXPECTED TO CONTINUE AHEAD OF THE FRONT ACROSS OUR AREA. DESPITE THE FRONT REMAINING TO THE NORTH...A PRESSURE TROUGH NEAR THE ALLEGHENY HIGHLANDS WILL ACT AS A LIFTING MECHANISM FOR CONVECTION TO DEVELOP WELL AHEAD OF THE COLD FRONT THIS AFTERNOON. THE WARM MOIST AIRMASS ALONG WITH SOME SUNSHINE WILL ALLOW FOR MODERATE AMOUNTS OF INSTABILITY TO DEVELOP LATE THIS MORNING AND AFTERNOON. NAM/GFS BUFKIT INDICATE ABOUT 1500 J/KG OF MLCAPE DEVELOPING THROUGHOUT THE DAY. WEAK DEEP LAYER SHEAR PROFILES WILL STRENGTHEN THROUGHOUT THE DAY AS THE UPPER-LEVEL TROUGH AXIS SLIDES EASTWARD TOWARD THE OHIO VALLEY. THE COMBINATION OF MODERATE INSTABILITY AND MODERATE DEEP LAYER SHEAR SUGGESTS THAT STORMS WILL BE CAPABLE OF PRODUCING DAMAGING WIND GUSTS AND LARGE HAIL THIS AFTERNOON. THUNDERSTORMS WILL ALSO BE CAPABLE OF PRODUCING LOCALLY HEAVY RAINFALL AND THIS COULD LEAD TO LOCALIZED FLASH FLOODING THIS AFTERNOON ESPECIALLY WHERE FLASH FLOOD GUIDANCE IS LOW DUE TO RECENT RAINFALL. LOWEST FLASH FLOOD GUIDANCE IS ACROSS BALTIMORE AND WASHINGTON WHERE ONE HOUR FFG VALUES ARE AROUND 1 TO 1.5 INCHES. SIMILAR VALUES IN FFG EXIST ACROSS PORTIONS OF THE SHENANDOAH VALLEY AS WELL. ALBANY FOR TODAY...THERE IS THE POTENTIAL FOR SOME STRONG TO SEVERE THUNDERSTORMS ESPECIALLY FROM MID MORNING THROUGH THIS AFTERNOON AHEAD OF A STRONG COLD FRONT WHICH IS EXPECTED TO DROP SOUTHEAST FROM THE EASTERN GREAT LAKES THIS MORNING REACHING THE HUDSON VALLEY LATE IN THE DAY. ML MUCAPES REACH 1000-2500 J/KG THIS AFTERNOON... H7-H5 LAPSE RATE NOT OVERLY IMPRESSIVE 5.5 TO 6.5 C/KM...0-3 KM HELICITY 100-300 M2/S2 WITH HIGHEST VALUES ON GFS AND NAM TOWARDS 00Z ACROSS THE SE TWO THIRDS OF THE FA...AND CYCLONICALLY CURVED H5 JET OF 60 TO 70 KNOTS MOVING INTO FA INDICATE THAT THE POTENTIAL CERTAINLY EXISTS FOR SEVERE CONVECTION...HOWEVER HEATING AND INSTABILITY MAY BE SIGNIFICANTLY INHIBITED BY CLOUD COVER. WILL CONTINUE TO HIGHLIGHT SLIGHT RISK POTENTIAL IN HWO AND HAVE PLACED ENHANCED WORDING IN THE GRIDS STARTING AROUND 14Z MENTIONING HEAVY RAIN...SMALL HAIL AND GUSTY WINDS. Mount Holly THE STORM PREDICTION CENTER HAS PLACED ALL OF THE MID ATLANTIC REGION IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS. WITH THE LATER TIMING, THERE SHOULD BE AMPLE OPPORTUNITY FOR DAYTIME HEATING AND DESTABILIZATION, BUT THERE CONTINUES TO BE ENOUGH LOW LEVEL MOISTURE AROUND. THIS MOISTURE, COUPLED WITH THE DAYTIME HEATING WILL CAUSE AN INCREASE IN CAPE VALUES. ADDITIONALLY, WITH INCREASING LL FLOW DURG THE AFTN AND EVENING HOURS, A WIND THREAT WILL DEVELOP AND CERTAINLY IN THIS TYPE OF REGIME, HAIL CANNOT BE RULED OUT EITHER. Link to comment Share on other sites More sharing options...
dendrite Posted August 21, 2011 Share Posted August 21, 2011 Anyone ever use the CIPS warm season site? Here's the sum of the reports from the top 15 analogs for 00z tonight. Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 Satellite and radar doesn't look good this AM. Will be interesting to see how the day unfolds from here. Link to comment Share on other sites More sharing options...
CoastalWx Posted August 21, 2011 Share Posted August 21, 2011 Anyone ever use the CIPS warm season site? Here's the sum of the reports from the top 15 analogs for 00z tonight. Not bad. The ern PA reports look on target. SREFs like areas near the south coast tonight. Perhaps this is due to stronger windshear, as they have a pocket of higher supercell probs there. maybe low LCL's too. I haven't looked too hard at tonight, so not sure if it's out to lunch, but interesting. Link to comment Share on other sites More sharing options...
CoastalWx Posted August 21, 2011 Share Posted August 21, 2011 Man WTF happened with Irene? What a center jump. My San Juan forecast fail perhaps. Ugh. Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 Not bad. The ern PA reports look on target. SREFs like areas near the south coast tonight. Perhaps this is due to stronger windshear, as they have a pocket of higher supercell probs there. maybe low LCL's too. I haven't looked too hard at tonight, so not sure if it's out to lunch, but interesting. Surprisingly the severe threat looks to extend through almost 6z on south coast. Little inversion, very low LCLs, and nicely curved hodographs and surface based instability. Very unusual around here and can only happen a month or two out of the year (with warm SSTs). Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 Man WTF happened with Irene? What a center jump. My San Juan forecast fail perhaps. Ugh. Had a feeling that may happen last night when convection went nuts north of the center... and the center initially wasn't particularly compact. By 11pm I thought things were in trouble lol. Link to comment Share on other sites More sharing options...
CoastalWx Posted August 21, 2011 Share Posted August 21, 2011 Had a feeling that may happen last night when convection went nuts north of the center... and the center initially wasn't particularly compact. By 11pm I thought things were in trouble lol. Yeah oops..lol. I didn't see anything since like 3pm yesterday. Woke up and was like WTF..lol. I went back in the tropical thread. Hopefully winds are under 45-50kts there. That's usually the threshold. Luckily still plenty of time for them to get planes out if they need to. Link to comment Share on other sites More sharing options...
CoastalWx Posted August 21, 2011 Share Posted August 21, 2011 Some of the models really try to blow up some stuff well ahead of the main line it seems. Pre-frontal trough perhaps. Link to comment Share on other sites More sharing options...
Tropopause_Fold Posted August 21, 2011 Share Posted August 21, 2011 I completely disagree with that assesment... I think they are in totally different leagues. There are a lot of negatives for today. Sure I could see us going under a svr tstm or tornado watch but I doubt it's a major outbreak right now. Low end severe... quite possible. yeah tend to agree here. not quite as warm @ the surface as 6/1 and not nearly as prolific LR-wise in the mid-levels = a skinny CAPE deal. certainly not as good a fropa/pre-frontal trough timing either. obviously a svr wind concern...and *maybe* a weak spin up given so much shear, but we don't have those ridiculous mid-west style hodographs this go around. that was such a classic environment in so many ways. Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 Yeah oops..lol. I didn't see anything since like 3pm yesterday. Woke up and was like WTF..lol. I went back in the tropical thread. Hopefully winds are under 45-50kts there. That's usually the threshold. Luckily still plenty of time for them to get planes out if they need to. I think the northward relocation was worst case scenario for the weenies. The poor thing might run the length of Hispaniola! Link to comment Share on other sites More sharing options...
CoastalWx Posted August 21, 2011 Share Posted August 21, 2011 Man that trough from 500mb on up really digs and sharpens overnight. Wow. Nice RRQ from 300-200mb too. Sometimes it's tough to get both in a similar looking position. Link to comment Share on other sites More sharing options...
CT Rain Posted August 21, 2011 Share Posted August 21, 2011 SPC has 5%/30%/30% just west of SNE down through NYC and PHL. Seems reasonable to me. Not sure how the threat evolves in these parts... but I like western areas best and maybe a rare late evening/overnight threat for the south coast? Link to comment Share on other sites More sharing options...
CoastalWx Posted August 21, 2011 Share Posted August 21, 2011 Man that trough from 500mb on up really digs and sharpens overnight. Wow. Nice RRQ from 300-200mb too. Sometimes it's tough to get both in a similar looking position. Of course what does it mean? Who knows...but just noting some decent dynamics there. Link to comment Share on other sites More sharing options...
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