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April Pattern Disco -2016


Damage In Tolland

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Welcome back mr block. Where have you been for the past few months?

If everything comes together, it will be a very special period for Boston and many parts of New England.

 

If the GFS MOS is reasonably accurate, Boston would have a total of 5 days with low temperatures falling below 30°. That would be the most such days since April 1982 when there were 6. Boston would also have 3 days with low temperatures below 25°, which would be the most since 1943 when there were also 3. The MOS may be somewhat understating this weekend's cold shot, so the number could conceivably be 4. 1881 saw 5 such days.

 

Today should see Boston pick up its second measurable snowfall of April. Since 1950, only April 1967, 1975, and 1996 had two measurable snowfalls in Boston. 1907 had four: 4/1-2 1.0"; 4/8 1.5"; 4/11 0.1"; and, 4/13 0.5"

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If everything comes together, it will be a very special period for Boston and many parts of New England.

 

If the GFS MOS is reasonably accurate, Boston would have a total of 5 days with low temperatures falling below 30°. That would be the most such days since April 1982 when there were 6. Boston would also have 3 days with low temperatures below 25°, which would be the most since 1943 when there were also 3. The MOS may be somewhat understating this weekend's cold shot, so the number could conceivably be 4. 1881 saw 5 such days.

 

Today should see Boston pick up its second measurable snowfall of April. Since 1950, only April 1967, 1975, and 1996 had two measurable snowfalls in Boston. 1907 had four: 4/1-2 1.0"; 4/8 1.5"; 4/11 0.1"; and, 4/13 0.5"

 

if everything comes to together, the system at the end of the week is the biggest April event in history - ...don't think it will, tho.  But the 06z GFS drops a helluva -SD mid and U/A quasi closed feature right through New England ending 132 hours off the 00z initialization, ...erstwhile, there have been plenty of runs that have signaled some sort of coastal just prior to that. 

 

the only difference separating it from something hugely more cryospherically dystopian would be that the N-stream quasi closed feature has yet to "capture" said coastal.  

 

haven't seen a single model run do it, but ...they have been teasing with wanting to for days of cycles.  It was really a whole scenario flagged way last week; not to toot horns by I brought it up on a couple/few occasions as a time when the flow over all tries to ease off the gradient throttle, and that allows for a brief period for positive interference as opposed to...

 

the plague of 2015-2016's winter.  in some lesser than scientific poetic sentiment, how fitting would the final curtain call on this crippled limper be if somehow it won the race.   i hope not ...

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Napril FTW

ao.sprd2.gif

nao.sprd2.gif

 

it's not that simple:

 

1) a -ao is not a slam dunk for cold on this side of hemisphere; certainly not in spring/summer.  the established conveyors for cold transport around the entire hemisphere means more for "how" a -ao correlates to our mid latitude temperatures.  having said that ... yes, a -ao would tend to correlate more so than not (positive coefficient), but it is possible to have -ao's with above normal temperatures

 

2) the loss of the -epo we had 10 days leading, and the lax appearance of any new ones in guidance et al, is a break-down of the primary cold load for our side of hemisphere.  that may in fact signal that any -ao will not correlated as well, this/that time.

 

3) in april, the r-wave counts around the hemisphere tend to increase as the gradient begins to seasonally slacken because we are being absolutely blow torched by the sun now that we are a solid 10 days and counting on the polarward side of the equinox. that is a modulation source that is substantially more powerful than a single index suggestion.  we can already observe the gefs members suddenly losing pattern coherence as of late, peering beyond this particularly week.  as the rossby wave number increase, the standard correlations break down - they have to... different wave numbers mean different transport of mass in the atmosphere, so the standard cold season statistical packages breaks-down... that is why cdc doesn't even calculate the pna's correlation - for example - during the warm season months. 

 

conclusion: if this were the latter half of N and DJF into the first half of M, I'd say a -ao is great as a base-line for cold delivery, specifically if and when the standard north american transport/conveyors are being established in a timely fashion.  not saying this -ao that is modeled at cpc won't correlate, but that i wouldn't just eye-pop over that as meaning it's going snow through the end of the month.  

 

edit: the NAO is falling, so that mapped on top of a -AO could spell trouble for warm enthusiasts - 

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it's not that simple:

 

1) a -ao is not a slam dunk for cold on this side of hemisphere; certainly not in spring/summer.  the established conveyors for cold transport around the entire hemisphere means more for "how" a -ao correlates to our mid latitude temperatures.  having said that ... yes, a -ao would tend to correlate more so than not (positive coefficient), but it is possible to have -ao's with above normal temperatures

 

2) the loss of the -epo we had 10 days leading, and the lax appearance of any new ones in guidance et al, is a break-down of the primary cold load for our side of hemisphere.  that may in fact signal that any -ao will not correlated as well, this/that time.

 

3) in april, the r-wave counts around the hemisphere tend to increase as the gradient begins to seasonally slacken because we are being absolutely blow torched by the sun now that we are a solid 10 days and counting on the polarward side of the equinox. that is a modulation source that is substantially more powerful than a single index suggestion.  we can already observe the gefs members suddenly losing pattern coherence as of late, peering beyond this particularly week.  as the rossby wave number increase, the standard correlations break down - they have to... different wave numbers mean different transport of mass in the atmosphere, so a the cold season model breaks-down... that is why cdc doesn't even calculate the pna's correlation - for example - during the warm season months. 

 

conclusion: if this were the latter half of N and DJF into the first half of M, I'd say a -ao is great as a base-line for cold delivery, specifically if and when the standard north american transport/conveyors are being established in a timely fashion.  not saying this -ao that is modeled at cpc won't correlate, but that i wouldn't just eye-pop over that as meaning it's going snow through the end of the month. 

Well the models are signaling a big trough in the east this upcoming weekend thanks to a -NAO and -AO. Hopefully we get a storm to come through. It does look like it warms up as we end deeper into April.

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it's not that simple:

 

1) a -ao is not a slam dunk for cold on this side of hemisphere; certainly not in spring/summer.  the established conveyors for cold transport around the entire hemisphere means more for "how" a -ao correlates to our mid latitude temperatures.  having said that ... yes, a -ao would tend to correlate more so than not (positive coefficient), but it is possible to have -ao's with above normal temperatures

 

2) the loss of the -epo we had 10 days leading, and the lax appearance of any new ones in guidance et al, is a break-down of the primary cold load for our side of hemisphere.  that may in fact signal that any -ao will not correlated as well, this/that time.

 

3) in april, the r-wave counts around the hemisphere tend to increase as the gradient begins to seasonally slacken because we are being absolutely blow torched by the sun now that we are a solid 10 days and counting on the polarward side of the equinox. that is a modulation source that is substantially more powerful than a single index suggestion.  we can already observe the gefs members suddenly losing pattern coherence as of late, peering beyond this particularly week.  as the rossby wave number increase, the standard correlations break down - they have to... different wave numbers mean different transport of mass in the atmosphere, so the standard cold season statistical packages breaks-down... that is why cdc doesn't even calculate the pna's correlation - for example - during the warm season months. 

 

conclusion: if this were the latter half of N and DJF into the first half of M, I'd say a -ao is great as a base-line for cold delivery, specifically if and when the standard north american transport/conveyors are being established in a timely fashion.  not saying this -ao that is modeled at cpc won't correlate, but that i wouldn't just eye-pop over that as meaning it's going snow through the end of the month.  

 

edit: the NAO is falling, so that mapped on top of a -AO could spell trouble for warm enthusiasts - 

Too bad we couldn't get this during the winter, but we all knew this was coming.....so many of us said right when baseball season started, and that was right on. :lol:

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GYX not enthused about late week/weekend.  snow and rain Wed night, rain thrusday and then showery weather but colder over the weekend.   Are we talking about a big storm in this time period?  WPC maps don't look impressive at all.

 

it's not 0 percent chance ... 

 

this time of year, you almost have to bide time and wait for ingredients to sample at short terms ...because, one thing we CAN count on is the normalization of baroclinic gradients endemic to this time of year.  it's the sun sun sun sun... 

 

again, you can see that in the extended gefs members - the flow contstruct in every member goes from a clear and coherent +PNAP to a nebular cluster f during this particularly next 10 days - that's seasonal stress in the physics of the models.

 

all that can be compensated and a storm delivered, in lieu of timing local-er scaled anomalies that temporarily enhance gradients at the right timing...

 

otherwise, troughs like that one at week's end become wasted mid level potential gliding over top a rotted lower troposphere. 

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Well the models are signaling a big trough in the east this upcoming weekend thanks to a -NAO and -AO. Hopefully we get a storm to come through. It does look like it warms up as we end deeper into April.

 

troughs over the east at mid latitudes correlate better with nao alone, and in fact, correlated stronger with PNA/PNAP modalities coming from the west.  

 

making a blanket statement that troughing at week's end is 'thanks' to those particular polarward indices is not so - 

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troughs over the east at mid latitudes correlate better with nao alone, and in fact, correlated stronger with PNA/PNAP modalities coming from the west.  

 

making a blanket statement that troughing at week's end is 'thanks' to those particular polarward indices is not so -

Tip, so next weekend or so we can basically see the same as what we are seeing today? Am I correct?
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Tip, so next weekend or so we can basically see the same as what we are seeing today? Am I correct?

 

different sort of set up ...pretty much entirely... 

 

today is known as a "alberta clipper" system; shallow latitude waves that as the name would suggest ...seem to originate from that province of Canada (but in reality the wave genesis and origin is much further up stream/elsewhere).  they can be potent ...weak, in between ...etc, but they don't tend to encompass/influence the weather beyond 5 to 10 deg of latitude width - tending to traverse over NJ to Maine as their continental exit points.  sometimes a particularly potent one can come down and time well with the following, which can feed back and give rise to bigger impacts.

 

contrasting, the system at the end of the week is an attempt at a full-latitude trough amplification.  the best way to think of this difference between today and then, is today's impulse runs down a pattern already in place; where at the end of the week, that trough carves out as a new feature.  

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different sort of set up ...pretty much entirely... 

 

today is known as a "alberta clipper" system; shallow latitude waves that as the name would suggest ...seem to originate from that province of Canada (but in reality the wave genesis and origin is much further up stream/elsewhere).  they can be potent ...weak, in between ...etc, but they don't tend to encompass/influence the weather beyond 5 to 10 deg of latitude width - tending to traverse over NJ to Maine as their continental exit points.  sometimes a particularly potent one can come down and time well with the following, which can feed back and give rise to bigger impacts.

 

contrasting, the system at the end of the week is an attempt at a full-latitude trough amplification.  the best way to think of this difference between today and then, is today's impulse runs down a pattern already in place; where at the end of the week, that trough carves out as a new feature.  

Thank you for explaining, however, others, on another other thread show GFS a good snow? I am learning little by little how models are ways out!

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if everything comes to together, the system at the end of the week is the biggest April event in history - ...don't think it will, tho.  But the 06z GFS drops a helluva -SD mid and U/A quasi closed feature right through New England ending 132 hours off the 00z initialization, ...erstwhile, there have been plenty of runs that have signaled some sort of coastal just prior to that. 

 

the only difference separating it from something hugely more cryospherically dystopian would be that the N-stream quasi closed feature has yet to "capture" said coastal.  

 

haven't seen a single model run do it, but ...they have been teasing with wanting to for days of cycles.  It was really a whole scenario flagged way last week; not to toot horns by I brought it up on a couple/few occasions as a time when the flow over all tries to ease off the gradient throttle, and that allows for a brief period for positive interference as opposed to...

 

the plague of 2015-2016's winter.  in some lesser than scientific poetic sentiment, how fitting would the final curtain call on this crippled limper be if somehow it won the race.   i hope not ...

It will be interesting to see if New England can get some more snow this weekend. Certainly, the trough looks exceptionally deep and there should be a very cold air mass, but the models haven't been very consistent that far out.

 

At least, parts of the area have done quite well today.

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It will be interesting to see if New England can get some more snow this weekend. Certainly, the trough looks exceptionally deep and there should be a very cold air mass, but the models haven't been very consistent that far out.

 

At least, parts of the area have done quite well today.

 

 

the problem with that whole evolution is quite consistent with the plight of this past winter.  We've seen troughs amplify time and time again, absolutely loaded with gradient and festooned with impulses; the problem has been (as not surprising, is currently modeled to be) that it's been excises in muting/damping discord

 

EVERY SINGLE TIME.

 

can't emphasize destructive wave interference ...more importantly, that specific role in keep our eastern N/A winter tame this season.  

 

this thing at the end of the week is just doing the same damn thing ... and wasting epic potential.   NCEP's Kocin (our buddy :) ) ...seems to be picking that idea, and based on said persistence ... it's probably the course of least regret.  Unless something (that would seemingly need to be a miracle) happens to make this a CONSTRUCTIVE wave interference scenario:

 

"...A COMPLEX DEEPENING TROUGH WILL AFFECT THE EASTERN UNITED STATES THROUGH THE ENTIRE MEDIUM RANGE PERIOD/DAYS 3 - 7/THURSDAY THROUGH MONDAY...WITH MULTIPLE SHORTWAVES INFLUENCING THE WEATHER PATTERN RATHER THAN ONE DOMINATING AN INTENSIFYING PHASED SYSTEM AS SOME

EARLIER SOLUTIONS SUGGESTED."  heh. ... not a shocker!

 

unfortunately...we lose either way.   we don't get to offset typical loathsome April misery with something entertaining, but by missing that, we get misery and a side of misery. 

 

enjoy your schit sandwich folks - 

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same is same ... that system at the end of this week is still fraught with destructive interference in most guidance/ensembles i've seen, and that is also keeping with every single L/W event we've seen unfold now spanning months.  

 

there's been something odd going on with the n-stream.  it's just been in discord both with the s-stream, but also with wave embedded in the n-stream its self.  neither can can find a single ball or concentrated energetic restoring.  interesting.

 

who knows why, but this trough at weeks end ...while certainly was a candidate for the last hurrah, appears destined for the same old repetitive bag of impressive nothing. 

 

can't say i'm personally disappointed at this point. i like summer, and summer weather... not that anyone asked, but i'm looking forward to the warmer/relaxed appeal over all set to come in next week in most guidance.  this year failed in my book.  time to stop languishing in it, or have it bucking for a save check with insults like yesterday (haha) when it can't change the ending opinion in my mind.  

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I will say despite the mess of s/w's this season...we had two well timed systems over the last frew days. Talk about utilizing the cold we had. Speaking SNE only.

 

true, but there's a difference there?  

 

the one yesterday - being the best example of this - was not associated with large wave migration, whereby the governing structure had/has to manage embedded stream dynamics. 

 

it was single pulsed wave in one stream, in an in situ L/W that was temporarily fixed in position.  it may lend ... if not be why, that one in particular was so well behaved in the majority of guidance going back over a week in some cases. 

 

but these large scale waves with embedded closely packed S/W zipping through them - those waves have just been out of harmonic wave numbers this entire season. 

 

"my" personal hypothesis on that has to do with the North Pacific entering a multi-decadal AA phase tendency over the top of a broiling ENSO signal... I.e., waaay too much potential and the system was both in models and reality, simply overwhelmed - 

 

hint hint: sans El Nino, boom.  i don't think last year and the year before in the midwest were accidents of chance, and probably can be keyed into that AA thing out west.  that sucker should want to build cold season, NE Pac -EPO walls more so than not through ...perhaps 2025   ;)

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hint hint: sans El Nino, boom.  i don't think last year and the year before in the midwest were accidents of chance, and probably can be keyed into that AA thing out west.  that sucker should want to build cold season, NE Pac -EPO walls more so than not through ...perhaps 2025   ;)

 

Coinciding with what is expected to be a "min mins" solar cycle.

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