ORH_wxman Posted February 5, 2019 Share Posted February 5, 2019 I figured I would break out a new thread for this event to separate it from the general February discussion thread. This signal has been pretty clear on just about all NWP guidance for days, but given the fickle nature of icing event, it was still questionable to how it would look once we were closer. It still looks like a period of icing is going to occur for interior CT up through CNE/NNE in varying amounts starting tomorrow night (Feb 6) through Thursday night further north and it might even lag into Friday morning up north. A front moves through later today to put an end to the really mild spell we've had the past 24 hours and a robust Quebec high will filter down colder temps. However, the push isn't overly strong so it remains to be seen how far south the arctic dewpoints can filter. This event will feature the type of airmass that doesn't feel that cold before it starts....highs could even approach 40F tomorrow afternoon prior to the precip moving in. But then it should cool back down to below freezing aided by the low dewpoints. Right now, N CT into interior MA and S NH are looking pretty good for a period of glazing Wednesday night and early Thursday....places like N ORH county and into S NH could keep this going right into Thursday night....it remains to be seen how well we filter down dewpoints as the event is already underway. That will be critical in determining how quickly we latently warm to 32F. The synoptic setup us pretty typical for an icing event....note the pretty strong high to the north in Quebec stretching back to central Canada...but you can see the high "curling" around the low and almost funneling down the coast of Maine....this will try to aid in the dewpoint reduction for a time and it's actually why some of the guidance has the ice pretty close to the coastline for a while Wednesday night. Ideally you'd like to see less low pressure tyring to move up into upstate NY/ST Lawrence valley, but that is not the case here...so we wil lmostly be relying on the drain from the northeast down the coast of Maine. 1 Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 Nice synopsis, dude - "...Freezing rain and sleet, becoming all freezing rain after 8pm. Some thunder is also possible. Temperature rising to around 31 by midnight. East wind 5 to 10 mph, with gusts as high as 15 mph. Chance of precipitation is 100%. New ice accumulation of 0.2 to 0.4 of an inch possible. New sleet accumulation of less than a half inch possible...." There is a lesser known '24-hour teleconnector' between the Lakes and NE ... The Flint Tornado preceding the 1953 Worcester event fell squarely into that correlation for example.. I sense something similar to that excerpt off NWS/ORD above as approximal/applicable across the region. Though not to word precisely/necessarily .. of course. The 12z NAM is > .95" in sleet at Logan. In fact, I'd even be concerned ... that tucking might pile the cold deeper yet and we end up with that tall sleet column. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted February 5, 2019 Share Posted February 5, 2019 Give me sleet any day. Screw ice. But it looks like ice is more in the cards. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted February 5, 2019 Share Posted February 5, 2019 Hazardous Weather Outlook National Weather Service Boston/Norton MA 440 AM EST Tue Feb 5 2019 This Hazardous Weather Outlook is for northern Connecticut, central Massachusetts, eastern Massachusetts, northeastern Massachusetts, southeastern Massachusetts, western Massachusetts and northern Rhode Island. .DAYS TWO THROUGH SEVEN...Wednesday through Monday. Wednesday night into Thursday... Icing for a combination of some sleet but mostly freezing rain is forecast. Likely impacts to the Thursday morning commute. Untreated surfaces will become slick making for hazardous travel. Higher confidence away from the immediate shoreline across interior Southern New England. Greatest impact across the Berkshires and Worcester Hills. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 The importance also that this is still a fluid situation... pun is shameless, but, what I meant was, ... this could trend colder or milder... I suggest colder for the lower 200 ... 250 mb of the column though. The highest confidence aspect of this event is that the lowest resolution and cold draw/ageostrophic correction is ALWAYS in favor of the inverted sounding. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 29 minutes ago, HoarfrostHubb said: Give me sleet any day. Screw ice. But it looks like ice is more in the cards. Mixed emotions ... I've opined plenty in the past, buut, I think icing is a fascinating phenomenon... both for science and wonder, but the aesthetic specter of a trillion prisms shimmering under azure skies when the sun recommences ... defies physical description. But, that whole splendor disappears for me real, real fast when I'm standing there in a chilly living room and just about every single act in real-time we are programmed in our western civility requires electricity that I know longer have access to - including so much as a slice of toast or heating the f'n home... - the novelty of all that can go f its self. I dunno ... dystopian awe, or incalculable inconvenience ... interesting balancing act. I think at the end of the day, ..given to my age and sense of responsibility to life and home and "adulting" (... as Millenials both invented and loathe) ... I probably edge on the side of go f its self. If it stops at precisely .24" accretion, we can really have both the splendor and have the toast. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 Yeah .. still the NAM beyond 30 hours.. But, the FRH grid crude method/triangulation would pretty much squarely mean warning ice probably along the axis of roughly ASH to ORH ... and actually, in an usual circumstance related to very good timing of this event with the "freshness" idiosyncrasy of the leading polar air..the eastern side of the axis might even accrete inside the I-95 regions by some distance. Interesting... The present ice storm warning graphic at NWS/Gov situated west of ORD would be required here. We'll see what like ALL or any other guidance suggests here shortly... Link to comment Share on other sites More sharing options...
Damage In Tolland Posted February 5, 2019 Share Posted February 5, 2019 Will has pointed out many times over these types of events how models underestimate the CAD and try and warm the lower levels too much and too fast .. sometimes by 12-24 hours. Any real warming above 32 probably doesn’t happen until late Thursday or Thursday night in SNE and may never make it to CNE/ NNE. Link to comment Share on other sites More sharing options...
ma blizzard Posted February 5, 2019 Share Posted February 5, 2019 I think CAD could really hold strong through Thursday night .. question is whether temps are sub-freezing or holding in the mid 30s by then. Seems like the low passing underneath Thursday will set-up a solid drain down the coast from NH / ME around mid-day .. could this process be established sooner? Link to comment Share on other sites More sharing options...
ORH_wxman Posted February 5, 2019 Author Share Posted February 5, 2019 1 minute ago, Typhoon Tip said: Yeah .. still the NAM beyond 30 hours.. But, the FRH grid crude method/triangulation would pretty much squarely mean warning ice probably along the axis of roughly ASH to ORH ... and actually, in an usual circumstance related to very good timing of this event with the "freshness" idiosyncrasy of the leading polar air..the eastern side of the axis might even accrete inside the I-95 regions by some distance. Interesting... The present ice storm warning graphic at NWS/Gov situated west of ORD would be required here. We'll see what like ALL or any other guidance suggests here shortly... RGEM is coming in colder now too...and its really ugly actually for N CT into MA....S NH is more of a sleet column. It has like an inch of QPF as ZR for a good chunk of MA. That QPF map is all ice for interior MA and mostly ice for N CT. But yeah, caveats noted...both for NAM and RGEM....36-48 hours is still kind of on the edge of their reliability. But one thing I do like is they are both pretty cold....and it matches what we've been saying intuitively. We expect the models to be behind the curve if anything on the lower level cold drain. Link to comment Share on other sites More sharing options...
CoastalWx Posted February 5, 2019 Share Posted February 5, 2019 This looks like it will transition to maybe more of an elevated event in ORH county and perhaps lower near ground level in SNH on Thursday. Looks pretty significant perhaps in those areas. We may flip to a more ENE wind in NE MA which could stop the drainage there, but trajectory still could be go for elevated areas and SNH. Thursday will feature the warm layer very close by off the ground and perhaps some loss of source region cold and from latent heat release. THe cold tuck will only be viable if SNH source region isn’t rotted near 32. My guess is maybe a pool of upper 20s can be tapped? Maybe those areas that go to a 32.00000001 rain could re-ice again? Link to comment Share on other sites More sharing options...
ORH_wxman Posted February 5, 2019 Author Share Posted February 5, 2019 9 minutes ago, ma blizzard said: I think CAD could really hold strong through Thursday night .. question is whether temps are sub-freezing or holding in the mid 30s by then. Seems like the low passing underneath Thursday will set-up a solid drain down the coast from NH / ME around mid-day .. could this process be established sooner? Yeah the process usually happens faster than models show...it's because we typically get a "tug" on the isobars as the low starts to approach from the southwest and it helps increase the ageostrophic vector....on top of that, we have the terrain with the Monads and ORH hills to the west....so once the "tug" happens, we start to develop a barrier jet and its like a self-feedback loop....it accelerates the cold drain southwestward. We saw this in the Jan 20th event...the model guidance didn't want to really cold tuck until about 12-15z, but we saw it happening by late evening the night before. Link to comment Share on other sites More sharing options...
ORH_wxman Posted February 5, 2019 Author Share Posted February 5, 2019 3 minutes ago, CoastalWx said: This looks like it will transition to maybe more of an elevated event in ORH county and perhaps lower near ground level in SNH on Thursday. Looks pretty significant perhaps in those areas. We may flip to a more ENE wind in NE MA which could stop the drainage there, but trajectory still could be go for elevated areas and SNH. Thursday will feature the warm layer very close by off the ground and perhaps some loss of source region cold and from latent heat release. THe cold tuck will only be viable if SNH source region isn’t rotted near 32. My guess is maybe a pool of upper 20s can be tapped? Maybe those areas that go to a 32.00000001 rain could re-ice again? Max cold layer is about 950mb for much of pre-dawn Thursday and into 12z Thursday....so I think the event will definitely start going more elevated by Thursday morning....which often happens anyway. But by then the damage may be done....could already have over a half inch of QPF as ice even in the lower elevations of 128-495 belt. The wildcard is definitely how quickly we get a barrier jet going and how cold the temps are that it is tapping into...if we're advecting 26-27F southwest past Ray's fanny, then that is trouble right into Thursday and maybe even Thursday night....but if it's like 31-32F, then I think it will have a hard time not rotting out to 33-34F by lunchtime Thursday. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted February 5, 2019 Share Posted February 5, 2019 43 minutes ago, Typhoon Tip said: Mixed emotions ... I've opined plenty in the past, buut, I think icing is a fascinating phenomenon... both for science and wonder, but the aesthetic specter of a trillion prisms shimmering under azure skies when the sun recommences ... defies physical description. But, that whole splendor disappears for me real, real fast when I'm standing there in a chilly living room and just about every single act in real-time we are programmed in our western civility requires electricity that I know longer have access to - including so much as a slice of toast or heating the f'n home... - the novelty of all that can go f its self. I dunno ... dystopian awe, or incalculable inconvenience ... interesting balancing act. I think at the end of the day, ..given to my age and sense of responsibility to life and home and "adulting" (... as Millenials both invented and loathe) ... I probably edge on the side of go f its self. If it stops at precisely .24" accretion, we can really have both the splendor and have the toast. It is beautiful, but I've seen the bad effects of big ice storms and minor glazes. 2008 brought destruction of high magnitude. An ice event in 2016 (or 2017... I should know) claimed the life of a friend's daughter and severely injured their son, who was our son's friend. The beauty is there, but I'm all set with it personally. Splendor and toast are good things though Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 31 minutes ago, ORH_wxman said: Yeah the process usually happens faster than models show...it's because we typically get a "tug" on the isobars as the low starts to approach from the southwest and it helps increase the ageostrophic vector....on top of that, we have the terrain with the Monads and ORH hills to the west....so once the "tug" happens, we start to develop a barrier jet and its like a self-feedback loop....it accelerates the cold drain southwestward. We saw this in the Jan 20th event...the model guidance didn't want to really cold tuck until about 12-15z, but we saw it happening by late evening the night before. This counter vector at low levels is always in place, too ... It's what corrupts a warm frontal forecast in April, ... At all times, there is a llv offset that has to be overcome to get a warm air to displace E of those elevations you describe. It's almost like the jet you describe will always form period; not succeeding to do so has more to do with those compensating vectors already overcoming.. Think of it this way... this region east of that elevation tract is really an air-foil behind a wing's edge...where the flow turns around.. The only way that's overcome is if the whole mass field turns around and bodily/gradient points seaward, such that the flow in that "tuck" alley is also bodily moving away. That does happen from time to time ..yes ..even in the dreaded April. Having a 1036 mb high N of Maine? that is precisely the opposite of the moving away model. Yeah, this was slam dunk for correcting colder "IF" these models overall features are correct. I agree with Scott...the standard 6 or even 12 hours additional tack on the rise rate of the temperatures in that interior region is also necessary. Link to comment Share on other sites More sharing options...
dendrite Posted February 5, 2019 Share Posted February 5, 2019 Hopefully it's ZR and not IP. ZR melts and goes away way faster. 1 Link to comment Share on other sites More sharing options...
CoastalWx Posted February 5, 2019 Share Posted February 5, 2019 23 minutes ago, ORH_wxman said: Max cold layer is about 950mb for much of pre-dawn Thursday and into 12z Thursday....so I think the event will definitely start going more elevated by Thursday morning....which often happens anyway. But by then the damage may be done....could already have over a half inch of QPF as ice even in the lower elevations of 128-495 belt. The wildcard is definitely how quickly we get a barrier jet going and how cold the temps are that it is tapping into...if we're advecting 26-27F southwest past Ray's fanny, then that is trouble right into Thursday and maybe even Thursday night....but if it's like 31-32F, then I think it will have a hard time not rotting out to 33-34F by lunchtime Thursday. Yeah I think ice to Logan for a time too...at least some IP anyways. And then how much QPF will fall? GFS is definitely much lighter while NAM has some areas near 1" QPF in SNH and another bullseye near and south of pike. Link to comment Share on other sites More sharing options...
Damage In Tolland Posted February 5, 2019 Share Posted February 5, 2019 36 minutes ago, ORH_wxman said: RGEM is coming in colder now too...and its really ugly actually for N CT into MA....S NH is more of a sleet column. It has like an inch of QPF as ZR for a good chunk of MA. That QPF map is all ice for interior MA and mostly ice for N CT. But yeah, caveats noted...both for NAM and RGEM....36-48 hours is still kind of on the edge of their reliability. But one thing I do like is they are both pretty cold....and it matches what we've been saying intuitively. We expect the models to be behind the curve if anything on the lower level cold drain. Oh yes yes please Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 The RGEM QPF dosing is noted.. I have seen the NAM pop into awareness on these system passing inside the 60 hour range with an initial stab at huge QPF numbers in the past. Then, we see it whittle back ...perhaps taking four cycles to do it - needs to be inside of 24 hour lead before I take the QPF too seriously. But the RGEM bias spectrum I'm less certain about that tool... It seems to do well with general low position and CCB genesis scenarios that I have noticed, but this is not one of those synoptic sort of evolutions so I really don't know - Link to comment Share on other sites More sharing options...
ORH_wxman Posted February 5, 2019 Author Share Posted February 5, 2019 1 minute ago, Typhoon Tip said: The RGEM QPF dosing is noted.. I have seen the NAM pop into awareness on these system passing inside the 60 hour range with an initial stab at huge QPF numbers in the past. Then, we see it whittle back ...perhaps taking four cycles to do it - needs to be inside of 24 hour lead before I take the QPF too seriously. But the RGEM bias spectrum I'm less certain about that tool... It seems to do well with general low position and CCB genesis scenarios that I have noticed, but this is not one of those synoptic sort of evolutions so I really don't know - I've noticed the canadian models tend to be a little too juicy...but that doesn't mean they are always wrong. Here's the ptype algorithm total for the RGEM...even if these are a little high, that's pretty threatening. Total precip that falls as ZR: Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 5 minutes ago, ORH_wxman said: I've noticed the canadian models tend to be a little too juicy...but that doesn't mean they are always wrong. Here's the ptype algorithm total for the RGEM...even if these are a little high, that's pretty threatening. Total precip that falls as ZR: 25 and change mm = an inch ...so... that squarely ranges from warning ice I-95 to grid failures N. Worc. Ha ha... they should do that... having warning types that more physically appealing to the bus stop crowd. Like, "Grid failure Ice warning" ... Or, "Grid failure ice watch..." ...and, "Prism ice alert" when it's less threatening and more accessible to just being pretty ... heh Then, the most devastating criteria of all ... "Pancaked Tolland" Link to comment Share on other sites More sharing options...
Modfan Posted February 5, 2019 Share Posted February 5, 2019 1 minute ago, Typhoon Tip said: 25 and change mm = an inch ...so... that squarely ranges from warning ice I-95 to grid failures N. Worc. That looks nasty from NW RI,NE CT right through Central Mass Link to comment Share on other sites More sharing options...
dendrite Posted February 5, 2019 Share Posted February 5, 2019 Man it's really borderline IP vs ZR here on the NAM. That's a decent 50mb deep layer of +3C to +4C aloft with -5C to -6C at H95. I'm not sure there's enough time to really refreeze those droplets before they hit the ground. If it isn't ZR that could be some really efficient accretion. Link to comment Share on other sites More sharing options...
Typhoon Tip Posted February 5, 2019 Share Posted February 5, 2019 5 minutes ago, dendrite said: Man it's really borderline IP vs ZR here on the NAM. That's a decent 50mb deep layer of +3C to +4C aloft with -5C to -6C at H95. I'm not sure there's enough time to really refreeze those droplets before they hit the ground. If it isn't ZR that could be some really efficient accretion. mm... and if the cold loads more robustly in the lowest levels, it'll start having to correct deeper too ... so that warm layer may be adjusted higher and thus cooler, if that adds any more wanted pang to the headache - no ...not saying snow to anyone else reading this... it's would mean more sleet versus straight up ZR in this context... Link to comment Share on other sites More sharing options...
Damage In Tolland Posted February 5, 2019 Share Posted February 5, 2019 13 minutes ago, dendrite said: Man it's really borderline IP vs ZR here on the NAM. That's a decent 50mb deep layer of +3C to +4C aloft with -5C to -6C at H95. I'm not sure there's enough time to really refreeze those droplets before they hit the ground. If it isn't ZR that could be some really efficient accretion. Hope you get a couple inches of sleet that won’t melt until Napril and maybe ice issues with coops 1 Link to comment Share on other sites More sharing options...
dendrite Posted February 5, 2019 Share Posted February 5, 2019 3 minutes ago, Typhoon Tip said: mm... and if the cold loads more robustly in the lowest levels, it'll start having to correct deeper too ... so that warm layer may be adjusted higher and thus cooler, if that adds any more wanted pang to the headache - no ...not saying snow to anyone else reading this... it's would mean more sleet versus straight up ZR in this context... And if not we end up with more ZR further north and more latent heating for the SNE source region...so we'll see how this trends. Normally in borderline IP/ZR situations I tend to lean on the frozen instead of the freezing side. Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted February 5, 2019 Share Posted February 5, 2019 Any rule of thumb that people sometimes use for ice accretion vs qpf? For example, does 1.0" of qpf roughly translate to 0.25" accretion? I know it's not that simple, but I was wondering... Link to comment Share on other sites More sharing options...
dendrite Posted February 5, 2019 Share Posted February 5, 2019 3 minutes ago, Damage In Tolland said: Hope you get a couple inches of sleet that won’t melt until Napril and maybe ice issues with coops The roof is clear thanks to the past 2 days. An inch of w.e. is nbd. Hope you get your icestorm shawty. 1 Link to comment Share on other sites More sharing options...
STILL N OF PIKE Posted February 5, 2019 Share Posted February 5, 2019 3 minutes ago, HoarfrostHubb said: Any rule of thumb that people sometimes use for ice accretion vs qpf? For example, does 1.0" of qpf roughly translate to 0.25" accretion? I know it's not that simple, but I was wondering... Depends on rate of precipitation . Believe steady rain has at least 50% or so accretion maybe 60%. Heavy pounding rain no maybe 25% Smart folks refute this Link to comment Share on other sites More sharing options...
dryslot Posted February 5, 2019 Share Posted February 5, 2019 34 minutes ago, dendrite said: Hopefully it's ZR and not IP. ZR melts and goes away way faster. What a Link to comment Share on other sites More sharing options...
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