HECS Checklist.....What to Look for to Avoid

[40/70 Benchmark]

I'm going to start this thread with some rudimentary principles that I have gathered and I'd appreciate it if the mets (namely Will, Scott, Tip and Phil) would expound upon this and add others.

It has become painfully obvious that it takes more than a deep, relatively slow moving low passing east of SNE to produce historically prolific amounts and what took place this Sunday night really drove that point up many of our fannies. There was a small stretch near I 95 (granted the most densely populated stretch) that reached low-end HECS amounts due to enhanced lift via the coastal front, but for the rest of sne, it was a run-of-the-mill event.....impressive, but nothing historic; why!!! We had a 961 mb low track just under ACK....WTF!! From what I have gleaned, there were 3 major reasons why:

1) Though the entire system did get shunted ene and avoided torching much of the area, the fact of the matter is that this beast initially cut just too close to the coast, namely the mid level centers; what this did was render our share of the storm nothing more than cellular inflow to support the orgy that took place over N NJ and NYC, after our initial front end dump. I view this as akin to heading to a fun party with your best friend and chatting away with this smoke-show of a chick, only to end the night by driving them over to his house and droping them off..... :arrowhead: .

Lesson learned...be weary of foreasting much over a foot of snow when the mid level centers tuck so close to the coast.

2) In the vast majority of our most prolific events, there existed a fairly robust high in the vicinity of N ME or a bit N, but in this instance we had merely a relatively modest arm of a +pp extending from the midwest. What this did was deprive us of a one of the primary means of producing heavy, heavy snow, isentropic lift....IOW, there wasn't much resistance to this monster low trucking in the vicinity of NE...BAD NEWS. Any wx enthusiast knows that the foundation of most exciting wx is advection, or "clashing"....you want forces meeting to have all he11 break loose. What would have helped is to have an arctic dome of high pressure situated just to the N of ME to counter the monster lp center coming up from the south and we lacked in this department, thus unless you were fortunate enough to see enhanced lift from the cf....you were going to see a nice snowstorm, but nothing to write books about. One way to get around the isentropic lift deficiency without the aid of the cf is probably the most prolific, hallowed producer of them all, but much like romantic endeavors, TIMING IS EVERYTHING.

3) When I referenced the mid levels lows in the 1st passage, I was speaking namely of H85 and H7, but passage #3 is an addendum to that on that it addresses H5. The timing of when H5 deepens the most rapidly and closes off is one of the most crucial elements to getting 2-3' of snow because those to the NW of this point are best suited to bare the fruit of the most intense CSI banding.....which is by far the most prominent "smoking gun" for exotically anomalous heavy snowfall. In the case of this last event, it did so about 100 miles sw of the optimal location\time for us, thus NYC, N NJ and to a bit lesser extent, E NYS and portions of nne saw the truly prolic snows that we so long for.

Hopefully we can refer back to these guidlines in the future, as opposed to drooling at qpf charts and setting the stage for the next wave of suicides.

All three of these conditions do not need to be met, but in the future we should know better than to expect much more than 1' of snow if NONE of them are met, regardless of how strong or where the little "L" on the GFS is positioned.

IMH and uneducated opinion, condition #3 is most important and the one that I would choose over all others.

Hopefully others can chime in and not only correct any mistakes because there may defintely be some, but add more to avoid the sh** show that some of those obs threads devolved into.

Charts from past events welcomed to better illustrate these points.

[HoarfrostHubb]

Thank you, Ray, for the detailed writeup.

I also got some good info from Wiz and I think Scott about the banding

[ORH_wxman]

I think you were able to gather most of the main reasons well. There's always going to be some stuff we don't entirely understand too...I've seen the precip field look better than it did Sunday night even with very similar tracks...but that is likely just a nuance of the storm that cannot be accurately predicted. But you definitely want to see the best ML frontogenesis with -EPV (from the closing off and rapidly deepening upper level low) over you for a prolonged period.

The models forecasted it well initially being over NNJ and SE NY...but they definitely tries to transfer it a bit NE and E as the storm deepened. In this event, it seemed as though that optimal area stayed to the SW longer than most guidance had it. So while the models did well with the general 2 jackpot idea, it was a bit too heavy in our region and not heavy enough to the SW...it didn't quite give the correct weight to each zone. The storm went nuts a little too far SW and took too long to transfer its best height falls northeastward....probably as a direct result of the extreme deepening that was going on to the SW...it closed it off and sort of acted as a positive feedback mechanism for stalling it or slowing it down there.

If the whole thing happens just a smidge later, then of course, we are talking about a top 5 storm of all time here.

[40/70 Benchmark]

I think you were able to gather most of the main reasons well. There's always going to be some stuff we don't entirely understand too...I've seen the precip field look better than it did Sunday night even with very similar tracks...but that is likely just a nuance of the storm that cannot be accurately predicted. But you definitely want to see the best ML frontogenesis with -EPV (from the closing off and rapidly deepening upper level low) over you for a prolonged period.

The models forecasted it well initially being over NNJ and SE NY...but they definitely tries to transfer it a bit NE and E as the storm deepened. In this event, it seemed as though that optimal area stayed to the SW longer than most guidance had it. So while the models did well with the general 2 jackpot idea, it was a bit too heavy in our region and not heavy enough to the SW...it didn't quite give the correct weight to each zone. The storm went nuts a little too far SW and took too long to transfer its best height falls northeastward....probably as a direct result of the extreme deepening that was going on to the SW...it closed it off and sort of acted as a positive feedback mechanism for stalling it or slowing it down there.

If the whole thing happens just a smidge later, then of course, we are talking about a top 5 storm of all time here.

Def.....it shouldn't have worked out that badly...I mean, as we have deomonstrated, it wasn't an ideal setup, but that was a fluke that it didn't perform better than it did (in this year; go figure).

It all goes back to the fact that there is more room to get screwed via variance when NONE of those 3 conditions are met......that would not have been allowed to happen, otherwise.

Anyway, I'm not fond of botching a forecast like I just did by calling for 15-25" imby, nor being dissapointed to that degree.

I'm a firm believer that anytime you are dissapointed in life, you have to thoroughly examine and reflect upon the situation to determine what you could have done, or what could have happened differently to achieve the desired outcome......if you do that and always convert adversity to a learning experience, than you will have been dissapointed far less and have achieved a great deal more success by the time you are old and grey.

[TalcottWx]

Ray,

A great write up. Maybe this well help us from learning from disasters of the past with future endeavors.

[cpickett79]

Ray,

A great write up. Maybe this well help us from learning from disasters of the past with future endeavors.

yes i second the write up part.

thou funny thing if the CF was 10 miles further inland ray would be dancing in the streets with 16-20"......

[40/70 Benchmark]

yes i second the write up part.

thou funny thing if the CF was 10 miles further inland ray would be dancing in the streets with 16-20"......

I know, but I would still be curious as to why the general area of precip shredded in the manner that it did.......I think there should have been a litte more than a general 8-14" outside of the cf enhancement in an event of that magnitude.

I was banking on the cf enhancement, but I knew by late afternoon that the ageostrophic flow was just too strong.

[cpickett79]

I know, but I would still be curious as to why the general area of precip shredded in the manner that it did.......I think there should have been a litte more than a general 8-14" outside of the cf enhancement in an event of that magnitude.

I was banking on the cf enhancement, but I knew by late afternoon that the ageostrophic flow was just too strong.

taunton certainly didn't mind. a 961 low and no big HP to the north and KTAN and EBOS stays all snow. wow

ray what caused that strong ageostrophic flow

i also remember a poster from the greater bos area report that after the intial temp run up that his temp had dropped back a couple degrees and you replied not too enthusiastically lol. it seemed like at that point you prob. gave up hope for 9'th inning (CF enhancement rally)

[40/70 Benchmark]

taunton certainly didn't mind. a 961 low and no big HP to the north and KTAN and EBOS stays all snow. wow

ray what caused that strong ageostrophic flow

Well, there was a respectable arm of hp to the N, extending from the MW......had that not been there, I probably would have gotten dumped on, but rained for a bit.

Would have been a net gain, though.....taint likely would have made it to near rt 495.

The low deepening so rapidly also accentuated the AG flow a bit, I think because it tightened the whole circulation and caused our wind direction to have a bit more n component than it may have otherwise had.

[40/70 Benchmark]

taunton certainly didn't mind. a 961 low and no big HP to the north and KTAN and EBOS stays all snow. wow

ray what caused that strong ageostrophic flow

i also remember a poster from the greater bos area report that after the intial temp run up that his temp had dropped back a couple degrees and you replied not too enthusiastically lol. it seemed like at that point you prob. gave up hope for 9'th inning (CF enhancement rally)

Exactly; I knew I was fooked then, though I had suspected so a bit beforehand.

[TalcottWx]

I know, but I would still be curious as to why the general area of precip shredded in the manner that it did.......I think there should have been a litte more than a general 8-14", outside of the cf enhancement in an event of that magnitude.

Well western areas did get the jackpot as forecasted, but eastern areas did not save the cf area. It seemed like the majority of the issue was related to the dryslot judging by the afd's at the time of the storm. The temperature gradient by the cf overcame that though supplying the lift in order to bury us down here.

So it seems like Wilmington would have been caught in a dry subsidence zone NW of the cf. I can't speak of what happened in the far interior. I'll blame it on the midlevels.

[40/70 Benchmark]

Well western areas did get the jackpot as forecasted, but eastern areas did not save the cf area. It seemed like the majority of the issue was related to the dryslot judging by the afd's at the time of the storm. The temperature gradient by the cf overcame that though supplying the lift in order to bury us down here.

So it seems like Wilmington would have been caught in a dry subsidence zone NW of the cf. I can't speak of what happened in the far interior. I'll blame it on the midlevels.

Right, but I don't really consider the Berkshires to be part of our area.....that is the Albany office.

They met condition 3, out there.

I think the subsidence from the cf enhancement did play a role, but it was likely negated by the times when I made it into the endhancement, so I still received 1'.

I agree RE the mid levels.

[Damage In Tolland]

What should have tipped all of us off immediately was the sleet/snowgrains that mixed in for about 1-2 hrs. No model showed anything remotley close to mixing like that. Most all of us including mets brushed it off and said not to worry..When in reality it was a warning sign that something wasn't right

[40/70 Benchmark]

What should have tipped all of us off immediately was the sleet/snowgrains that mixed in for about 1-2 hrs. No model showed anything remotley close to mixing like that. Most all of us including mets brushed it off and said not to worry..When in reality it was a the warning sign that something wasn't right

Yep....something was off in the mid levels.

[Damage In Tolland]

Yep....something was off in the mid levels.

It shocked all the mets..and we all ignored it

[TalcottWx]

What should have tipped all of us off immediately was the sleet/snowgrains that mixed in for about 1-2 hrs. No model showed anything remotley close to mixing like that. Most all of us including mets brushed it off and said not to worry..When in reality it was a warning sign that something wasn't right

From what I recall that was only a brief sneaky warm layer. It may have very well been a tip off that the upper levels were pretty fooked up at the time. Not sure how we can take a peek at that and prove or disprove.

One thing is for sure, it was not our usual storm.

[Damage In Tolland]

From what I recall that was only a brief sneaky warm layer. It may have very well been a tip off that the upper levels were pretty fooked up at the time. Not sure how we can take a peek at that and prove or disprove.

One thing is for sure, it was not our usual storm.

I think the thing was bombing so exposively that it threw some extremely warm air in the mid levels much farther north than anyone could have thought..and once that happened a HECS was out the door

[TalcottWx]

I think the thing was bombing so exposively that it threw some extremely warm air in the mid levels much farther north than anyone could have thought..and once that happened a HECS was out the door

Another key : Someone mentioned it went warm core as it passed to our south... with the low passing so close to us and with warmer air aloft then in a cold core system, that would have a dramatic effect on the system, no?

[powderfreak]

Exactly; I knew I was fooked then, though I had suspected so a bit beforehand.

I think relying on the coastal front to get big snows seems like a risky endeavor.

I haven't looked into a postmortem much, but how did the actual QPF fare? I'm assuming it was significantly lower than models progged?

Aside from the synoptics of the storm and what Ray already mentioned, here's one thing I noticed...

Ratios and Wind. I know some model runs leading up were showing ~2" of QPF (though in very small geographic areas) with more widespread amounts between 1.25-1.75. In my experience, it is VERY hard to get much above 10-12:1 ratios regardless of how good snow growth is in a windy storm. The wind causes collision in the air and shattering flake structure, along with wind-packing as the snow falls. It is never a good idea to bank on ratios in a windy storm. Personally, the biggest example of this to me is Valentines Day 2007 when BTV got 2" of liquid equivalent at temps between 0F and 5F with fantastic dendrites, but due to wind ended up with a standard 13:1 ratio. In a calm environment, that probably wouldn't been 45" of snow.

[Cold Miser]

Awesome discussion. Please keep this going, especially for the weather-science illiterate folks such as myself.

[40/70 Benchmark]

I think relying on the coastal front to get big snows seems like a risky endeavor.

I haven't looked into a postmortem much, but how did the actual QPF fare? I'm assuming it was significantly lower than models progged?

Aside from the synoptics of the storm and what Ray already mentioned, here's one thing I noticed...

Ratios and Wind. I know some model runs leading up were showing ~2" of QPF (though in very small geographic areas) with more widespread amounts between 1.25-1.75. In my experience, it is VERY hard to get much above 10-12:1 ratios regardless of how good snow growth is in a windy storm. The wind causes collision in the air and shattering flake structure, along with wind-packing as the snow falls. It is never a good idea to bank on ratios in a windy storm. Personally, the biggest example of this to me is Valentines Day 2007 when BTV got 2" of liquid equivalent at temps between 0F and 5F with fantastic dendrites, but due to wind ended up with a standard 13:1 ratio. In a calm environment, that probably wouldn't been 45" of snow.

Yea, I already said that I'll never do that again.

[ORH_wxman]

Right, but I don't really consider the Berkshires to be part of our area.....that is the Albany office.

They met condition 3, out there.

I think the subsidence from the cf enhancement did play a role, but it was likely negated by the times when I made it into the endhancement, so I still received 1'.

I agree RE the mid levels.

It actually ended up slightly further W into E NY and only extreme W MA.

But regardless, the better height falls took a bit too long to transfer northeastward. We should have gotten into some of that ML frontogenesis and deformation later on during the storm but just never really was able to. It was probably the biggest failure by the models...on a grand scheme it was a minor failure, but for IMBY totals it ended up mattering more. I probably would have ended up with 20"+ instead of 12" if it happened a bit more like models showed.

[40/70 Benchmark]

It actually ended up slightly further W into E NY and only extreme W MA.

But regardless, the better height falls took a bit too long to transfer northeastward. We should have gotten into some of that ML frontogenesis and deformation later on during the storm but just never really was able to. It was probably the biggest failure by the models...on a grand scheme it was a minor failure, but for IMBY totals it ended up mattering more. I probably would have ended up with 20"+ instead of 12" if it happened a bit more like models showed.

It usually does.

[H2Otown_WX]

I think you were able to gather most of the main reasons well. There's always going to be some stuff we don't entirely understand too...I've seen the precip field look better than it did Sunday night even with very similar tracks...but that is likely just a nuance of the storm that cannot be accurately predicted. But you definitely want to see the best ML frontogenesis with -EPV (from the closing off and rapidly deepening upper level low) over you for a prolonged period.

The models forecasted it well initially being over NNJ and SE NY...but they definitely tries to transfer it a bit NE and E as the storm deepened. In this event, it seemed as though that optimal area stayed to the SW longer than most guidance had it. So while the models did well with the general 2 jackpot idea, it was a bit too heavy in our region and not heavy enough to the SW...it didn't quite give the correct weight to each zone. The storm went nuts a little too far SW and took too long to transfer its best height falls northeastward....probably as a direct result of the extreme deepening that was going on to the SW...it closed it off and sort of acted as a positive feedback mechanism for stalling it or slowing it down there.

If the whole thing happens just a smidge later, then of course, we are talking about a top 5 storm of all time here.

Is there any specific reason why the precip. field was so narrow Will?

[ORH_wxman]

It usually does.

Well we see it happen frequently, but in extreme rapidly deepening systems its hard to forecast. In the Dec 9, 2005 system, we saw everything collapse rapidly toward the ML center and eastern MA ended up in that CCB from hell....it was forecasted to be a bit further west originally. Its not easy to forecast those types of evolutions. We knew there would likely be two jackpots...and one of them was going to be aided by CF enhancement...but we also counted on it getting a bit of a boost in the final 6 hours of the storm with some of the leftover deformation and ML frontogenesis transfering E and NE. It just didn't happen this storm, and there's probably a lot of reasons we can come up with in hindsight, but that were not very forecastable before the storm.

But I always say never expect 20" unless the evidence is overwhelming, and it really wasn't in this storm. We knew someone would probably get 20" but we just didn't know who and where around here...and areas outside that were going to be left with something short of a HECS...granted it was slightly less than we thought because of some of the reasons we already mentioned.

[powderfreak]

Right, but I don't really consider the Berkshires to be part of our area.....that is the Albany office.

They met condition 3, out there.

I think the subsidence from the cf enhancement did play a role, but it was likely negated by the times when I made it into the endhancement, so I still received 1'.

I agree RE the mid levels.

So is this thread specifically for BOX's CWA? Because if its a New England thread, then there were some impressive totals from the Berkshires/Taconics up through southern/central VT through NH and ME ski country. That poster in Franconia, NH had like 30" and most of the NH and ME ski areas made out like bandits.

The only area of New England that really didn't get hit with greater than 6" was far northern VT.

I just never know if people are strictly talking about within 60 miles of Taunton or are we actually talking about a HECS in New England? I know there are a lot of posters who include the entire region as a whole (BTV/GYX/BOX/ALB), and then there are other times that region wide threads only seem BOX CWA specific.

[powderfreak]

Yea, I already said that I'll never do that again.

Likewise, its also risky to rely on a 25 mile wide fronto band to reach high totals... which is really the only reason that area from NYC-POU-NY/MA/VT (intersection)-LEB-Whites-W.ME Mtns got crushed. Had that band not happened that NW edge would've only been a 3-6" event instead of 14-28"

[TalcottWx]

Likewise, its also risky to rely on a 25 mile wide fronto band to reach high totals... which is really the only reason that area from NYC-POU-NY/MA/VT (intersection)-LEB-Whites-W.ME Mtns got crushed. Had that band not happened that NW edge would've only been a 3-6" event instead of 14-28"

In a system as such the CF was pretty much confined to an area between plymouth and newton se to ne. We could have really saw heavy snow anywhere between there depending on how far the warm air pushed. Unfortunately I think Ray realized early on his was out of the game for the CF but did not expect everything else to **** the bed so violently. He got into the band at times, but could have easily seen 3-6" more additional if things weren't so ****ty outside of the CF.

[powderfreak]

I should probably re-phrase that other post... what I meant was this storm was a bust all-around... and are we talking about the what busted in BOX's CWA or can we include GYX's and BTV's? For some it was a bad bust, for others it was a good bust. Those folks on that NW fringe that weren't in the blizzard warning, probably saw equally bad, if not worse conditions than a lot of the blizzard warning area... that two or three county wide ribbon of 15-30" of wind-blown snow that spread along the entire NW edge of the storm probably witnessed conditions worse than some areas within the blizzard warnings (that's a bust, but in the good way for some folks if you like snow). I'm sure I-93 and I-89 in NH/VT was just brutal overnight with 2-3"/hr snows in 40-50mph winds... especially when they were only expecting 5-10" or 6-12" of snow, lol.

This will likely go down as one of the worst modeled storms in recent history, as Tippy said.

Any mets have a desire to do a case study?

[powderfreak]

In a system as such the CF was pretty much confined to an area between plymouth and newton se to ne. We could have really saw heavy snow anywhere between there depending on how far the warm air pushed. Unfortunately I think Ray realized early on his was out of the game for the CF but did not expect everything else to **** the bed so violently. He got into the band at times, but could have easily seen 3-6" more additional if things weren't so ****ty outside of the CF.

Yeah, I bet he would've seen a bit more, too... maybe even another .75"-1" per hour throughout the storm's duration.

Also, that band on the NW side was basically like Feb 2006 except instead of going through Hartford, it was 50 miles NW.

However, for folks outside of that band, Feb 2006 was rather forgettable, too.

What we need is a storm without a massive band because it seems when the atmosphere is so focused on dumping over one area, it is bound to screw a lot of other people. What ever happened to the storms with a widespread, heavy precipitation shield? Not a 20 mile wide destroyer stretching for 100s of miles amid a pedestrian light, to at times moderate snow shield?