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May weather discussion

Mr Torchey

By Mr Torchey,
in New England

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Typhoon Tip

Typhoon Tip

Posted
Posted

looks like we are just about out of the worst of this stretch of grey skies/cool temps. slightly better % of the region sees some breaks of sun today, more tomorrow, then sunday most of us are cleared out finally.

disappointing the rain shield split around a lot of the region. but still a good signal for more rain next week so all is not lost on that front.

It may take longer than today... We'll see. The wind fields are light and we really need that to ventilate this garbage out of the "bowl" - so to speak, but it's the region between the elevations, west, and the cold wall of the oceanic boundary layer, east.

The other method is straight up diabatic heating to cause some vertical mixing. We are retarded for that though, because upon looking over hi res sat imagery, there's substantial mid and upper level cloud debris wafting over top, shading the sun from doing a better job heating the llvs, thus getting that process of overturning underway (heh, "overturning underway" :wacko2: ) Otherwise, ...this would probably be the way it would do it for today.

Boy, we really just uber saturated this boundary layer, and doing into a very dense air mass initially. I recall the runs from 3 days back; particularly in the NAM and GFS, they kept minorly deepening low pressure S of LI from an initial pressure pattern where the isobars were aligned do N/S through the area - i.e. not greater pressure N, which is the preferred state for that sort of cyclonic forcing. It was minor deepening, but just enough to keep the wind backed. I couldn't figure out why they were doing that so stubbornly, run after run, and then it dawned on me. The thermodynamics: this air mass was very very cold leading into this gray regime. Dew points the day before were 13F from ALB to BOS to CAR ...all over. It rained into that and the next thing we know it was 42-46F at 100% RH the next morning. ...like, everywhere east of the Berks and N of the S Coast, and the sounding was cold and saturated through 850mb, with light winds. That whole evolution was figuratively, "powdered damming, just add water" :)

That air mass became just immovable. Particularly at this time of year, when you have 3,000' elevations west, and a cold land/sea interface along the S and E coasts for NE. It really does act somewhat like a San Fernando valley trapped smog scenario when this happens, only our plight isn't photo-synthetic ozone aerosols, but strata-fog saturated goop.

I can't stress this phenomenon as a very real one up in this part of the country, enough. When I see this sort of thing modeled in April through early June, I typically throw my hands and stop looking at weather models and stuff for a minimum of 5 days. The atmosphere is destined to abandon the low levels leaving us stranded in this mist down here. That's ...pretty much on target here if off by a tick. Who knows. But per the course you can see the air mass aloft moving swiftly over top this low level stuck air mass, and it is as though the atmosphere above 850 and below are completely disconnected.

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Tropopause_Fold

Tropopause_Fold

Posted
Posted

It may take longer than today... We'll see. The wind fields are light and we really need that to ventilate this garbage out of the "bowl" - so to speak, but it's the region between the elevations, west, and the cold wall of the oceanic boundary layer, east.

oh yeah it'll definitely take longer than today - i hope that's not how that was interpreted. :lol:

what i was implying was i think we'll see more holes / breaks in the OVC develop over the course of today, much more so tomorrow...then we are flushed clean finally by the second half of the weekend.

today should be one of those days where a lucky few end up with a decent midday/afternoon as a whole but the majority are kind of f-ed still - especially C and E areas.

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Typhoon Tip

Typhoon Tip

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Posted

oh yeah it'll definitely take longer than today - i hope that's not how that was interpreted. :lol:

what i was implying was i think we'll see more holes / breaks in the OVC develop over the course of today, much more so tomorrow...then we are flushed clean finally by the second half of the weekend.

today should be one of those days where a lucky few end up with a decent midday/afternoon as a whole but the majority are kind of f-ed still - especially C and E areas.

Yes there are probably some sky-lights over the western and SW zones as the hi res imagery would suggest - not likely to erode east unless these plaguing mid and upper level debris clouds move off, or the gradient kicks up or both.

WNW motion aloft dictates thunderstorm motion.. This is one of those deals where the atmosphere has set up a perfect torment for those interested in that entertainment source (for SNE) I could easily visualize a cluster or two of explosive convection erupting NW of ALB, then diving to the right of the environmental flow seemingly, perfectly to appear like elevated stuff will pass over, only end up nicking western CT - bringing anvil drabble to refog up the f lot of us ...

eh, not impressed and not getting duped by this pos set up. No optimism from me based on experience and knowledge with this sort of back in butt plug air mass, with WNW flow that is disconnected over top.

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HoarfrostHubb

HoarfrostHubb

Posted
Posted

eh, not impressed and not getting duped by this pos set up. No optimism from me based on experience and knowledge with this sort of back in butt plug air mass, with WNW flow that is disconnected over top.

Lovely imagry

We seem to get this pretty often as you said. Models be damned. We are cursed by geography.

Helps us a lot in winter storms though

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Typhoon Tip

Typhoon Tip

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Lovely imagry

We seem to get this pretty often as you said. Models be damned. We are cursed by geography.

Helps us a lot in winter storms though

It's a give and take... Many winter storm "positive busts", as they are deemed, often occur around this part of the country because of this very same phenomenon; one that is often poorly handled by modeling. It's a resolution issue, and that things tend to get fuzzy in the lowest 200mbs. If you have a marginal atmosphere above 800mb, and a poorly handled cold layer in the 800 -1000mb thickness, you have a fair chance of staying white longer than forecast.

Somewhat of an example of this was the big snow bomb of December 23, 1997. The day before the (at the time) ETA model FOUS grid had 03, 02, 98 over BOS with .6 or .7 liquid, and so the forecast was cat's paws and rain for the cost, with a rotted 2-3" for the ORH Hills.

Heh. Yeah.

The thing is, at the time the synoptic layout had an entirely different appeal. There was a 1032mb-like polar high parked about 100 naut miles NNW of CAR, ME, with a clearly depicted nose damming pointed directly AT the vort max - which is to say, the v-max was riding directly over that ridge axis. That was sure to excite a truck-load of UVM, and I think the FOUS grid (I could be wrong) did have an interval over 20 microbars - which is getting quite high. It was that 02 and 98, though, that was problematic. That translated to +2C and -2C at 900 and 800 mb respectively. So the rough was 0C at 850mb, in other words marginal snow skies existing over the top of poorly handled llv boundary layer conditions incarnate.

The real tipper was that synoptic appeal as mentioned. Because of the ridge axis being present and resistant, the overnight hours immediately preceding had clear bone chilling radiator conditions. Thus entered, poorly handled low levels. That literally generated low 20s type cold, with DPs that were happenstance in the teens. So what did we have? We had a day dawning with a rather abruptly dense cirrus hat capping over a boundary layer that was handled with neolithic incompetence, and a 40 vmax about to ride straight up and over a damming pressure pattern that was made to be so cold.

I was living in Acton Mass at the time, which is middle lat/lon Middlesex Country in Mass. At about 9 or 9:30, teeny aggregates of dendrites broke out in a straight down fashion. I had a routine dental exam scheduled for 11am; I recall it being about 10:45 in route, and already, 4" of powder at 24F had occurred, and the roads were deteriorating fast, visibility crashing. In the hour immediately before hand, a buddy of mine call from his place of work to inform me that a 55dbz wall of radar bliss was about to swath over the interior. At first we thought it was the inevitable bright band before pancake shoots would go over to balls of sleet. But nope... pure snow. The teeny aggregates only grew slightly in clustered size, and while I was in the dental chair the visibility outside dropped ... oh, I'd say to about 100 feet or less.

Nil on the exaggeration there. It stayed that way for 2 hours, in which time a solid foot fell. It was up until that time the heaviest short duration accumulation of snow I had ever experienced. The dentist office was about 2 blocks from my house; luckily I walked it, because there was no traffic moving anywhere. All at once, on one of the heaviest anticipated shopping days of that year, the 23rd of December being a Saturday, society halted!

with the 4" that fell before that foot, and the 2" that lingered in the after glow of that tar and feathering... we totalled 16-18" at my place. Other townships did a good bit better, too. Townsend Mass, I believe, took the prize with 24". Again, all of this happened essentially in 6 hours, with more than half occurring in the middle 2 for most locales.

Come to think about it; even if the thermal fields were handled better, that event doubled up the magnitude of the positive bust in that the QPF was modeled about 1/3 what actually took place. I believe BOS still managed a 4-6" of snow out of that - so the bust was unilateral. Interestingly, there was no thunder that I recall.

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HoarfrostHubb

HoarfrostHubb

Posted
Posted

It's a give and take... Many winter storm "positive busts", as they are deemed, often occur around this part of the country because of this very same phenomenon; one that is often poorly handled by modeling. It's a resolution issue, and that things tend to get fuzzy in the lowest 200mbs. If you have a marginal atmosphere above 800mb, and a poorly handled cold layer in the 800 -1000mb thickness, you have a fair chance of staying white longer than forecast.

Somewhat of an example of this was the big snow bomb of December 23, 1997. The day before the (at the time) ETA model FOUS grid had 03, 02, 98 over BOS with .6 or .7 liquid, and so the forecast was cat's paws and rain for the cost, with a rotted 2-3" for the ORH Hills.

Heh. Yeah.

The thing is, at the time the synoptic layout had an entirely different appeal. There was a 1032mb-like polar high parked about 100 naut miles NNW of CAR, ME, with a clearly depicted nose damming pointed directly AT the vort max - which is to say, the v-max was riding directly over that ridge axis. That was sure to excite a truck-load of UVM, and I think the FOUS grid (I could be wrong) did have an interval over 20 microbars - which is getting quite high. It was that 02 and 98, though, that was problematic. That translated to +2C and -2C at 900 and 800 mb respectively. So the rough was 0C at 850mb, in other words marginal snow skies existing over the top of poorly handled llv boundary layer conditions incarnate.

The real tipper was that synoptic appeal as mentioned. Because of the ridge axis being present and resistant, the overnight hours immediately preceding had clear bone chilling radiator conditions. Thus entered, poorly handled low levels. That literally generated low 20s type cold, with DPs that were happenstance in the teens. So what did we have? We had a day dawning with a rather abruptly dense cirrus hat capping over a boundary layer that was handled with neolithic incompetence, and a 40 vmax about to ride straight up and over a damming pressure pattern that was made to be so cold.

I was living in Acton Mass at the time, which is middle lat/lon Middlesex Country in Mass. At about 9 or 9:30, teeny aggregates of dendrites broke out in a straight down fashion. I had a routine dental exam scheduled for 11am; I recall it being about 10:45 in route, and already, 4" of powder at 24F had occurred, and the roads were deteriorating fast, visibility crashing. In the hour immediately before hand, a buddy of mine call from his place of work to inform me that a 55dbz wall of radar bliss was about to swath over the interior. At first we thought it was the inevitable bright band before pancake shoots would go over to balls of sleet. But nope... pure snow. The teeny aggregates only grew slightly in clustered size, and while I was in the dental chair the visibility outside dropped ... oh, I'd say to about 100 feet or less.

Nil on the exaggeration there. It stayed that way for 2 hours, in which time a solid foot fell. It was up until that time the heaviest short duration accumulation of snow I had ever experienced. The dentist office was about 2 blocks from my house; luckily I walked it, because there was no traffic moving anywhere. All at once, on one of the heaviest anticipated shopping days of that year, the 23rd of December being a Saturday, society halted!

with the 4" that fell before that foot, and the 2" that lingered in the after glow of that tar and feathering... we totalled 16-18" at my place. Other townships did a good bit better, too. Townsend Mass, I believe, took the prize with 24". Again, all of this happened essentially in 6 hours, with more than half occurring in the middle 2 for most locales.

Come to think about it; even if the thermal fields were handled better, that event doubled up the magnitude of the positive bust in that the QPF was modeled about 1/3 what actually took place. I believe BOS still managed a 4-6" of snow out of that - so the bust was unilateral. Interestingly, there was no thunder that I recall.

Some of you folks have amazing recall. Excellent descriptors as well...

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CoastalWx

CoastalWx

Posted
Posted

Well good news is that the storm next week looks a little more progressive now. Srly flow ahead of it sure warm temps and dews up a bit. After that, the trough may be far enough west to allow some warm temps in here, but every now and then, I see a kink in the pressure fields to our south which may signify fronts stalling and more onshore flow. Details TBD, but that's how it looks. Not terrible, but not high and dry either.

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