March 6-8th Ocean Storm Discussion Part IV

[CoastalWx]

The RGEM had a little weenie area of enhanced snow here on several of it's runs..It was the only meso model to pick up on it. I wonder if being just to the west of that dryslot had anything to do with enhacing the amounts in NE CT? 

 

Also..east flow does well here..I always laugh when folks think it downslopes on an east wind..On a NE wind it can a little bit..but an east wind when you have a 1000 mile NE fetch for days and days is going to wring out the moisture as it banks up against the hills

 

You didn't have east winds though. Your winds were NE at the surface.

[Ice Warrior commander]

New to this forum, but am really enjoying the discussion that goes on here. Wish I knew a bit more to engage in the conversation but enjoying reading what the wise ones say.

Welcome to the board.

[Damage In Tolland]

You didn't have east winds though. Your winds were NE at the surface.

i meant at upper levels . What do you think the reason was?

[CoastalWx]

i meant at upper levels . What do you think the reason was?

 

Mesoscale banding. When you have mesoscale banding that occurs from processes in the mid levels..downsloping won't be an issue. That's how many cities out west and in Alaska end up getting decent snows when surrounded by 10,000' peaks. I attribute it mostly to that phenomenon. I remember looking at radar seeing how sharp the line was when you went from nothing to moderate snow. That's a classic sign of air rising and probably some sort of frontogenesis or something. I mean being at 1000ft helps obviously, but I don't think upslope was a big component to your snow...atleast IMHO.

[Damage In Tolland]

Mesoscale banding. When you have mesoscale banding that occurs from processes in the mid levels..downsloping won't be an issue. That's how many cities out west and in Alaska end up getting decent snows when surrounded by 10,000' peaks. I attribute it mostly to that phenomenon. I remember looking at radar seeing how sharp the line was when you went from nothing to moderate snow. That's a classic sign of air rising and probably some sort of frontogenesis or something. I mean being at 1000ft helps obviously, but I don't think upslope was a big component to your snow...atleast IMHO.

No I agree it wasn't the main component but I do think it did play a role in it. I can't help but feel the dryslot to the east contributed to it somehow or vice versa?

[Ginx snewx]

There is no doubt the dryslot contributed Kev. I reported many times that night how my winds would suddenly howl the radar to my west explode then my winds would go dead calm. Turbulence to the max.

[CoastalWx]

No I agree it wasn't the main component but I do think it did play a role in it. I can't help but feel the dryslot to the east contributed to it somehow or vice versa?

 

Well there was clearly this up-down-up wave of motion from east to west across SE MA, RI, and CT. I've seen RI be in a sucker hole from lots of convergence and rising air over SE MA, but never like that and never so stationary. I think your snow in CT was fascilitated by the other s/w moving in. You had this packing of isotherms and deformation which aided in snow banding over your area and especially down by BDR. That's why BDR had the snow they did.

[Damage In Tolland]

Well there was clearly this up-down-up wave of motion from east to west across SE MA, RI, and CT. I've seen RI be in a sucker hole from lots of convergence and rising air over SE MA, but never like that and never so stationary. I think your snow in CT was fascilitated by the other s/w moving in. You had this packing of isotherms and deformation which aided in snow banding over your area and especially down by BDR. That's why BDR had the snow they did.

But that area down there was pegged with norlun for a few days. All the way up to the HV. Their snow was kind of fluff snow whereas ours was Atlantic driven high water content stuff whic tells me it was more ocean driven from here to ORH

[CoastalWx]

But that area down there was pegged with norlun for a few days. All the way up to the HV. Their snow was kind of fluff snow whereas ours was Atlantic driven high water content stuff whic tells me it was more ocean driven from here to ORH

 

Yeah their snow was all due to the other s/w. I think your snow was also enhanced by that. There were times where radar just showed echoes somewhat stationary there and not always being advected in from the northeast. It wasn't the main reason, but I do think it helped with sustaining banding there. Your snow was the result of a few things..all mesoscale so tough to pin down. I don't think the dryslot itself enhanced snow like a typical dryslot. A typical dryslot enhanced snow right along the edge because it's advecting in instability into that band and it naturally a pocket of unstable air in a mature cyclone. That dryslot was pure subsidence and probably sinking rather rapidly. If you want to get specific, I suppose you could argue that the rapid decent of air can be counterbalanced by rapidly rising air to the west. That's possible too, because in the atmosphere..what goes up, must come down and vice-versa.

[Ginx snewx]

Roller coaster analogy

[Damage In Tolland]

Yeah their snow was all due to the other s/w. I think your snow was also enhanced by that. There were times where radar just showed echoes somewhat stationary there and not always being advected in from the northeast. It wasn't the main reason, but I do think it helped with sustaining banding there. Your snow was the result of a few things..all mesoscale so tough to pin down. I don't think the dryslot itself enhanced snow like a typical dryslot. A typical dryslot enhanced snow right along the edge because it's advecting in instability into that band and it naturally a pocket of unstable air in a mature cyclone. That dryslot was pure subsidence and probably sinking rather rapidly. If you want to get specific, I suppose you could argue that the rapid decent of air can be counterbalanced by rapidly rising air to the west. That's possible too, because in the atmosphere..what goes up, must come down and vice-versa.

Could that have possibly been forecast ahead of time?

[CoastalWx]

Could that have possibly been forecast ahead of time?

 

The dryslot and your enhanced band? Well some models pegged that dryslot so clearly they saw some sort of subsidence there. As far as the enhanced band goes..I don't think you could have seen that. The one thing that looked possible was that night 10" band near Joe...you could see signs that they would do well there. I don't really think you could have forecasted 20"+ for your area.

 

I do remember looking at H7 and there was a nice ring of VVs curving back into NE CT. There also was an area of downward motion shown near BOS and just SW at times on the GFS. Clearly that was wrong with the location..but perhaps even the globals saw something.

[codfishsnowman]

in regards to all this measuring stuff:

 

it just amazes me how it varies from storm to storm and one person's perception. I have asked so many different people so many times did they clear a board or was that a depth measurement when arriving at a total and ALMOST NO ONE ever answers.

 

there was a poster who lives in tolland who said he didnt measure more than 30 inches otg with the blizzard and ct blizz reported 35 inches. well if there was a depth of 30 inches than i would think a total of 33 or 34 inches would certainly be acceptable bc there was compacting in that event and there was damage to the snow due to the strong winds which affected accums so to me 35 inches is pretty reasonable although there seemed to be some noise regarding that total. at the same time those folks down in the ct snowbelt who had nearly three feet of snow on the ground at the end of the event easily couldve had 40 inches according to nws guidelines..perhaps a bit more but there was all kinds of noise over that 40 inch total in hamden..well exactly how was that total measured??

 

i really do not want to think that ANYONE would falsely inflate snow totals imby to have a "mine is bigger than yours" attitude. please tell me no one would stoop to that level.

 

furthermore the pns statements should say if the measurements were depth or every six hours bc we all know there are lots of depth measurements mixed in on those pns. i know i read here at some point a long time ago that adding 10 pct for longer duration events was generally acceptable. in some long duration events with more variables perhaps it is as high as 15 pct.

 

for this storm if the measurement at blue hills was almost thirty inches then what was the maximum depth at one point and why cannot any one answer that esp if weather record keeping is so important. in the end are we really measuring any better than years ago? the other end of this spectrum is the obvously over inflated totals that some major airports are guilty of in the past such as bdl and bwi and i am a tad suspicous of those philly totals back in 09-10.

[CoastalWx]

I was trying to look at H5 and H3 yesterday...at times there looked to be weak shortwave ridging in ern CT, but man it was tough to really see how that would create a nasty dryslot. I think the combo of speed convergence in this area , lift over ern ma, as well as lift to the west caused that pocket of subsidence there. Speed convergence aloft means that air piles up and has nowhere to go but down. Because the whole system was being captured and stalled...that may have resulted in the stationary look. Just my guess...you really need to disect models with cross sections to show these things and maybe Ekster can shed some light with those when he has some time.

[Damage In Tolland]

What?

[CoastalWx]

What?

 

Killroy was here?

 

[OceanStWx]

in regards to all this measuring stuff:

 

it just amazes me how it varies from storm to storm and one person's perception. I have asked so many different people so many times did they clear a board or was that a depth measurement when arriving at a total and ALMOST NO ONE ever answers.

 

there was a poster who lives in tolland who said he didnt measure more than 30 inches otg with the blizzard and ct blizz reported 35 inches. well if there was a depth of 30 inches than i would think a total of 33 or 34 inches would certainly be acceptable bc there was compacting in that event and there was damage to the snow due to the strong winds which affected accums so to me 35 inches is pretty reasonable although there seemed to be some noise regarding that total. at the same time those folks down in the ct snowbelt who had nearly three feet of snow on the ground at the end of the event easily couldve had 40 inches according to nws guidelines..perhaps a bit more but there was all kinds of noise over that 40 inch total in hamden..well exactly how was that total measured??

 

i really do not want to think that ANYONE would falsely inflate snow totals imby to have a "mine is bigger than yours" attitude. please tell me no one would stoop to that level.

 

furthermore the pns statements should say if the measurements were depth or every six hours bc we all know there are lots of depth measurements mixed in on those pns. i know i read here at some point a long time ago that adding 10 pct for longer duration events was generally acceptable. in some long duration events with more variables perhaps it is as high as 15 pct.

 

for this storm if the measurement at blue hills was almost thirty inches then what was the maximum depth at one point and why cannot any one answer that esp if weather record keeping is so important. in the end are we really measuring any better than years ago? the other end of this spectrum is the obvously over inflated totals that some major airports are guilty of in the past such as bdl and bwi and i am a tad suspicous of those philly totals back in 09-10.

 

In reality the guidelines for official measurements are just that they are no more frequent that every 6 hours. If we're paying observers or have volunteers for a climate site we would like them to be every 6 hours and preferably on the synoptic times, but sometimes that's not always possible. A snow total taken after the snow has stopped is just as official as a snow total that was measured and cleared every 6 hours. Obviously, for your own personal records it's probably best to stick to one measurement routine, so comparing storms will be more accurate.

[Arnold214]

I was trying to look at H5 and H3 yesterday...at times there looked to be weak shortwave ridging in ern CT, but man it was tough to really see how that would create a nasty dryslot. I think the combo of speed convergence in this area , lift over ern ma, as well as lift to the west caused that pocket of subsidence there. Speed convergence aloft means that air piles up and has nowhere to go but down. Because the whole system was being captured and stalled...that may have resulted in the stationary look. Just my guess...you really need to disect models with cross sections to show these things and maybe Ekster can shed some light with those when he has some time.

I am creating some RAP isent plan loops and cross section loops. Pretty telling.

[CoastalWx]

I am creating some RAP isent plan loops and cross section loops. Pretty telling.

 

Nice, looking forward to it.

[H2Otown_WX]

I was trying to look at H5 and H3 yesterday...at times there looked to be weak shortwave ridging in ern CT, but man it was tough to really see how that would create a nasty dryslot. I think the combo of speed convergence in this area , lift over ern ma, as well as lift to the west caused that pocket of subsidence there. Speed convergence aloft means that air piles up and has nowhere to go but down. Because the whole system was being captured and stalled...that may have resulted in the stationary look. Just my guess...you really need to disect models with cross sections to show these things and maybe Ekster can shed some light with those when he has some time.

Wasn't there a good deal of speed convergence at H7 too Scott?

[powderfreak]

Well there was clearly this up-down-up wave of motion from east to west across SE MA, RI, and CT. I've seen RI be in a sucker hole from lots of convergence and rising air over SE MA, but never like that and never so stationary. I think your snow in CT was fascilitated by the other s/w moving in. You had this packing of isotherms and deformation which aided in snow banding over your area and especially down by BDR. That's why BDR had the snow they did.

 

There was a pretty crazy wave motion to the lift... it almost looked like a mountain wave event minus the mountains, lol.  The massive lift and convergence as all that moisture piled into SE MA must have started the up-and-down turbulence from the strong easterly winds aloft and the downward motion just happened to be over RI and extreme eastern CT...then the wave started building again over Blizz's area with intense lift.  

 

I think that wave motion that became so stationary certainly helped Blizz and that area of CT as they ended up under a pretty stationary region of rising air.  There was certainly meso-scale frontogenesis in play, but I bet whatever up-and-down wave motion in the atmosphere that developed from that incredible lift and east winds in SE MA, was what sort of really bumped the totals way up over model guidance in that local area of CT.  

[powderfreak]

The MQE number is probably legit IMHO. The lower elevations had 3-4" Thursday morning and then accumulated a little more during the day while remaining in the lower 30s while MQE stayed near 32 for a while before creeping up briefly to 34 and then below 32 mid aftn. The lower spots has 24-25" at say 200' an elevation. I could buy the 29.8..especially given the QPF they received and perhaps slight upslope.

 

Yeah I thought it sounded right before Its Always Sunny said the highest depth the observer measured at first was 22 inches?  If what he said is correct, its a little dubious to take melted precipitation and just apply a 9:1 ratio and call it "official" because they weren't satisfied with just measuring the snow depth at the end of the storm. 

 

I guess it is more scientific than the weenie method of just guessing "I have 18 inches on the ground so I must've gotten two feet total", but I guess I was just shocked that a spot like MQE (that seems to be an important climate spot) would go with a storm total that no one actually measured, if what Always Sunny said is correct.

[Ginx snewx]

Saw Ecks post before it was deleted, good stuff. Matches what I observed and thought. Roller coaster drying held. Cul like.

[CoastalWx]

Wasn't there a good deal of speed convergence at H7 too Scott?

 

I mean there wasn't a huge area where it went from 70kts to 0 or anything...but I think there was some issues there. 

 

We'll see what the cross sections and isentropic analysis says. Since air parcels will follow the path of same density surface..isentropic analysis is a good way to follow the path of air parcels as they move (in this case) from east to west.

[Arnold214]

Here is a cross section of the March 7th 22z RAP at 10z on the 8th. The cross section line for reference is in the top right corner of the loop...following the 280k wind from northeast to southwest. Therefore, the right hand side of the cross section is a point somewhere east of Cape Ann, MA, with the leftmost side being a point just south of Eastern Long Island, NY. The center of the cross section is right around the area of interest in Rhode Island. The image is net adiabatic omega with the cold colors being downward motion, and the warm colors representing upward. Adiabatic omega is also contoured in green with negative values representing downward motion here. The theta surfaces are blue. The result is a very persistent and pronounced area of downward vertical motion over or near RI in the lowest 1.5 km or so owing mainly to downglide (I looked at the terms separately) likely responsible for the drying out of echoes over RI during much of the storm.

 

I tried uploading an animated gif loop of this cross section but the bleepin board won't let me do it even though it is below the size limit. either way, most of the frames in the loop look just about like this one with a lot of downward motion over/near ri.

[CoastalWx]

That's interesting Mike. Although, at first glance..I guess I would not expect such a violent dryslot..but that subtle tick downward of those isentropes does explain some of the issues going on. ALso, the tighly packed isentropes certainly are not what you want for rising motion and conditional instability.

[Arnold214]

Here is a plan view of adiabatic omega, pressure, and wind on the 280k surface...also at 10z on the 8th.

 

now if I could just get these loops to upload.

[Arnold214]

That's interesting Mike. Although, at first glance..I guess I would not expect such a violent dryslot..but that subtle tick downward of those isentropes does explain some of the issues going on. ALso, the tighly packed isentropes certainly are not what you want for rising motion and conditional instability.

It was still snowing...just not much. Like Colle and Yuter, 2006 showed, as well as Passarelli and Beohme 1983 showed...that even small 30m to 100m hills can produce similar dvm values to what we have here to really dry things out significantly...ie...it doesn't take much as long as the relatively weak dvm is persistent and fairly deep. Terrain probably wasn't the issue on the morning of the 8th, but similar values were seen in the isentropic plots.

[eekuasepinniW]

now if I could just get these loops to upload.

This bug started after the last board software update. 

 

There is another upgrade out now which supposedly fixes this bug, but god knows what else it will break instead.

[CoastalWx]

It was still snowing...just not much. Like Colle and Yuter, 2006 showed, as well as Passarelli and Beohme 1983 showed...that even small 30m to 100m hills can produce similar dvm values to what we have here to really dry things out significantly...ie...it doesn't take much as long as the relatively weak dvm is persistent and fairly deep. Terrain probably wasn't the issue on the morning of the 8th, but similar values were seen in the isentropic plots.

 

Yeah if you have an environment that is already prone to DVM..then the flow off the hills is the nail on the coffin. I'm just totally shocked it stayed so persistent. Maybe you have, but I have never seen anything like that. Just incredible.I gotta imagine the bottleneck in the atmosphere may have helped in the persistence of this.