Winter 2022-2023 Promises Plenty of Mid Season Mayhem

[40/70 Benchmark]

9 hours ago, WEATHER53 said:

How much for DC?

I'm a bit lower than you are....5-15".

[WEATHER53]

2 hours ago, 40/70 Benchmark said:

I'm a bit lower than you are....5-15".

Thank you and you had to put At Least 20 hours into your write up?!!

[40/70 Benchmark]

5 minutes ago, WEATHER53 said:

Thank you and you had to put At Least 20 hours into your write up?!!

Literal writing, probably about...but the thought process and parsing through copious data made it considerably longer. I am obsessive about how I connect ideas and integrate information in order to convey it in precisely the manner that I intend...presentation with graphics and what not is important.

[WEATHER53]

1 hour ago, 40/70 Benchmark said:

Literal writing, probably about...but the thought process and parsing through copious data made it considerably longer. I am obsessive about how I connect ideas and integrate information in order to convey it in precisely the manner that I intend...presentation with graphics and what not is important.

That’s great work

Hi to my NE buds all!

 

[40/70 Benchmark]

Winter 2022-2023 Looks to Begin on Schedule & Have Staying Power

 December to Turn More Wintery

It was was asserted in the 9th annual Eastern Mass Weather Winter Outlook, released on November 10th, that the month of December would begin relatively mild before gradually turning colder and eventually more snowy. And this appears very much on track to come to fruition for a variety of different reasons. Not the least of which is consistent agreement amongst out most skilled ensemble guidance.

 

Ensemble Consensus Bolsters Forecast Confidence

Obviously consistent agreement of our most reliable guidance is one of the more coveted aspects of forecaster confidence, and we surely have this.

 

Note the the agreement between two of the more skilled models on the evolution of the pattern change, as two discrete disturbances act to transfer energy poleward.

The first one occurring on Wednesday to close out the month of November, which supplies tomorrow's mild and gusty rain showers:

 

ECMWF Ensemble Mean:

 

 

GFS Ensemble Mean:

 

And the next one will be a rain maker on Sunday:

 

ECMWF Ensemble Mean:

 

 

GFS Ensemble Mean:

 

The similarity to the December forecast composite is rather striking at this point:

 

However, by this point, we are beginning to see the NAO block materialize perhaps even a bit more rapidly than implied by the seasonal outlook. This entails perhaps a slightly colder look relatively to the forecast composite:

 

 

 But it remains to be seen how extensive any respite is during the holiday period.

 

By the time we approach mid December, the block matures and there is a much colder regime in place across the eastern US and even down into the mid Atlantic.

 

ECMWF Ensemble Mean:

 

GFS Ensemble Mean:

 

 

As the block continues to mature and attenuate towards mid month, a potential relaxation of the predominate RNA state due to a shift in tropical forcing may provide the region with the opportunity for its first major winter storm. It is also this reconfiguration of tropical forcing that is lending additional support to the model consensus with respect to the impending NAO block.

 

Tropical Forcing Supportive of Model Consensus

Currently the MJO is crossing from phase 7 into phase 8:

 

ECMWF:

 

GFS:

 

The consensus forecast, as illustrated above, is for it to waken into obscurity though the early portion of the month of December.

This makes sense, since phase 7 of the MJO during a la nina favors somewhat of a southeast ridge feature, similar to the initial early December pattern and aforementioned monthly forecast composite:

 

 

 

 

And how phase 8 during a la nina in the month of December resembles the new pattern that is so highly agreed upon by the ensemble consensus.

 

 

 

The shift in forcing towards the dateline is evident on the Homvoller diagram, pictured below.

 

This displacement towards the central Pacific is consistent with the east-based la nina data set.

 

 

 

 This aligns with the current trends for la nina to both begin to decay and shift further to the east, with the eastern flank of region 1.2 a very impressive -1.7 departures as of 11/23.

 

02NOV2022 19.6-1.8 24.0-1.1 25.7-1.1 27.6-1.0

09NOV2022 20.1-1.4 24.2-0.9 25.8-1.0 27.8-0.9 16NOV2022 20.5-1.3 24.2-0.9 25.9-0.8 27.7-0.9 23NOV2022 20.3-1.7 24.3-0.8 25.9-0.8 27.7-0.9

 

 

 

Note the contrast to the west based la nina data set, which focuses ascent over Indonesia and descent over the dateline region:

 

 

 

 

This is crucial because once the MJO waves decays, the base state forcing will reside over the central Pacific, which should render blocking over the polar domain remarkably resilient following any reloading periods. This may also act to induce periods of more poleward ridging over the western US, or at least a relaxation of the prevalent RNA, which would couple with the polar blocking to increase the magnitude of storm chances and extend said chances further to the south to include the mid Atlantic. 

This potential relaxation of the RNA is hinted at among the European teleconnector projection, which also implies a period of increased storm potential after approximately December 10th, due to mass flux with the Pacific domain.

 

The arctic domain, while less emphatic regarding major storm potential, does strongly imply the arrival of the sustained colder period.

Confidence of an eventual recovery following any relaxation of said high latitude blocking during the month of December and into January is also supported by an overall warmer than average polar stratosphere:

 

 

And the strong tendency for sustained blocking during the first half of the winter seasons following substantial southern stratospheric warmings, as observed this year.

 

 

Buckle up because mother nature is feeling festive-

[40/70 Benchmark]

Active Mid-December Pattern Poised to Take Shape

Book-End Threats to Begin & End the Work Week

As we begin to approach the all important holiday period, the more active pattern post December 10th appears poised to begin as advertised late in the month of November. 

The first of two winter storm threats is slated for Monday. In the annotation below derived from the 00z Wednesday ECMWF ensemble mean valid late Thursday night and early Friday morning, it is apparent that the shortwave is careening to the east and towards a compressed flow between the fledgling NAO block to the north, and mature southeast ridge to the south that is in response to the deep west coast trough.

 

 

In fact, that southeast ridge is so pervasive early on that it initially causes the fledgling NAO block to conjoin with it, which both acts to negate the influence of the negative NAO and cause a very compressed flow. This compressed flow acts as a source of deconstructive interference for the shortwave that is very reminiscent of this past December 2021.

Towards the end of the week, the shortwave continues to struggle in the compressed flow and attenuates to an open wave over the Ohio valley by late Friday night and early Saturday AM.

Note the absence of a notable gap or area of lower heights between the south east ridge and NAO block.

 

However, by Monday AM, the southeast ridge begins to relax as the west coast trough matures, which creates separation and falling heights in between the two ridge nodes in a more traditional configuration. This in conjunction with the strengthening NAO block that is becoming better positioned to exert enough an influence to reduce the compression to the flow allows the storm to quickly begin to re-amplify and close off as it exits the coast.

 

The trend began to emerge yesterday, as the NAO block began to distinguish itself from the southeast ridge and exert more of an influence, faster, which allowed for quicker re-amplification of the exiting wave.

 

 

Just how quick this system is able to amplify and produce the first significant winter storm of the seasons for the region is dependent on two factors:

-Just how close is the major storm over New Foundland. It is is too close, the coastal storm will not b able to amplify as far to the north, and may skirt southern areas of the region.

-How strong is the NAO block and where is the ridge axis in the plains located. A weaker NAO block allows the ridge axis to progress further to the east, which will force the redevelopment of the storm later/ downstream and further off of the coast. However, a stronger NAO block will tend to slow the flow down, which causes the plain ridge axis to be further west, and accordingly, the downstream coastal also amplifies further to the west/closer to the coast. 

 

The Newfoundland low dictates to a large extend how far north the system does or does not get and the NAO block determines whether or not the flow is too fast to allow the system to amplify close enough to the coast for the northern extend to matter.

 

OPTION 1: One possibility is on the benign end of the continuum of possible outcomes. If the Maritimes low near New Foundland on Monday ends up slightly closer to the region (further south) and the NAO block weaker, then the developing coastal will be develop later (further east and off of the coast) and not allowed to amplify (squahsed to the south).

This represents wither no storm of a very minor impact.

 

OPTION 2: However, if the Newfoundland low is slightly further to the north and the NAO ridge stronger, than the storm develops faster and amplifies more to the north. This would represent the first major winter storm of the season.

 

 

It a blocked pattern like the one that is developing, it is likely that whatever happens next Monday will impact what happens further upstream, on Friday.

 

Double Jeopardy

There is the potential for the development of another major coastal storm (get used to this) on or around Friday, December 16th, which, is signaled well via teleconnector convergence.

 

 

Thus the degree to which the Monday system can amplify and just how quickly it can do so will have a large impact on how much resistance it can provide to the Friday system taking an inland track.

OPTION 1: A more intense and slower to exit first storm acts as a "50/50 low" to work in tandem with the resistance provided by the NAO block to induce a more rapid and proficient transfer of energy from the primary tracking through the Great Lakes, to the secondary coastal development. This results in (another) major winter storm with a potpourri of mixed precipitation that would produce major travel headaches to end the work week. These type of systems are referred to as SouthWestFlowEvents (SWFE) due to the prominent southwesterly flow aloft that results from warm air advect in he mid levels of the atmosphere due to the dying primary low.

 

OPTION 2: The first storm is less and intense and faster to move out, which while this is still likely to force the ultimate development of a "triple point low" at the surface near the coast (limits low level warmth), most of the precipitations falls as rainfall after perhaps a very brief bout of wintry precipitation near the onset. Travel impact is limited.

 

 

Clearly given the state of the Pacific pattern, the key to an early and aggressive onset to winter here in the eastern US is heavily dependent on just how pervasive a force the NAO block can become and thus how proficiently it can offer up resistance in the flow.

While the result is likely to fall somewhere in the middle of the continuum of potential outcomes, the trend is to increase the risk for a more noteworthy initial onslaught of winter 2022-2023 next week.

Stay tuned for a potential Friday issuance of First Call with respect to Monday-

[40/70 Benchmark]

First Major Winter Storm Potential Friday with Minor "Primer" Event Monday

Monday Primer Impact Mainly West

The synopsis from Wednesday regarding this storm threat remains largely the same.

 

The shortwave is currently careening to the east and towards a compressed flow between the fledgling NAO block to the north, and mature southeast ridge to the south that is in response to the deep west coast trough.

 

 

In fact, that southeast ridge has been so pervasive this week that it has been causing the fledgling NAO block to conjoin with it, which both acts to negate the influence of the negative NAO and cause a very compressed flow. This compressed flow acts as a source of deconstructive interference for the shortwave that is very reminiscent of this past December 2021.

At present, the shortwave is continuing to struggle in the compressed flow and will attentuate to an open wave over the Ohio valley by late tonight and early Saturday AM.

Note the absence of a notable gap or area of lower heights between the south east ridge and NAO block.

 

However, by Monday AM, the southeast ridge begins to relax as the west coast trough matures, which creates separation and falling heights in between the two ridge nodes in a more traditional configuration. This in conjunction with the strengthening NAO block that is becoming better positioned to exert enough of an influence to reduce the compression to the flow , which allows the storm to quickly begin to re-amplify and close off as it exits the coast.

 

However, note that the system does not close off in the mid levels quite as fast on latest guidance. This is due to the powerful Maritimes low acting as an inhibiting force by not allowing it to amplify as much and compressing precipitation to the southeast as it enters the region:

 

 

 

This is important because it was explained on Wednesday that the proximity of this low was one of two factors that would determine just how quickly this system would be able to amplify.

The other being the strength of the NAO block and where is the ridge axis in the plains located. A weaker NAO block allows the ridge axis to progress further to the east, which will force the redevelopment of the storm later/ downstream and further off of the coast. However, a stronger NAO block will tend to slow the flow down, which causes the plain ridge axis to be further west, and accordingly, the downstream coastal also amplifies further to the west/closer to the coast. 

 

The Newfoundland low dictates to a large extent how far north the system does or does not get and the NAO block determines whether or not the flow is too fast to allow the system to amplify close enough to the coast for the northern extend to matter. This continuum of possibilities was categorized into two distinct group.

 

Option #1 Means Limited Impact

Here are the two options as presented on Wednesday:

 

OPTION 1: One possibility is on the benign end of the continuum of possible outcomes. If the Maritimes low near New Foundland on Monday ends up slightly closer to the region (further south) and the NAO block weaker, then the developing coastal will be develop later (further east and off of the coast) and not allowed to amplify (squahsed to the south).

This represents wither no storm of a very minor impact.

 

OPTION 2: However, if the Newfoundland low is slightly further to the north and the NAO ridge stronger, than the storm develops faster and amplifies more to the north. This would represent the first major winter storm of the season.

 

 

It is now clear the the pattern is evolving much more similarly to option 1 with respect both the position of the Maritimes low and the ridge axis in the plains, which means a minor system is on the horizon early next week.

 

Be that as it may, there remains potential for the first measurable snowfall of the season for a relatively large portion of the region on Sunday night into early

Monday.

 

 

 

 

MONDAY FIRST CALL:

 

A Final update on Sunday regarding Monday, especially since this evolution may have an impact on what transpires on Friday.

 

Option #1 Means Limit

 

There is the potential for the development of another major coastal storm (get used to this) on or around Friday, December 16th, which, is signaled well via teleconnector convergence.

 

 

Thus the degree to which the Monday system can amplify and just how quickly it can do so may play a role in how much resistance it can provide to the Friday system taking an inland track.

OPTION 1: A more intense and slower to exit first storm acts as a "50/50 low" to work in tandem with the resistance provided by the NAO block to induce a more rapid and proficient transfer of energy from the primary tracking through the Great Lakes, to the secondary coastal development. This results in (another) major winter storm with a potpourri of mixed precipitation that would produce major travel headaches to end the work week. These type of systems are referred to as SouthWestFlowEvents (SWFE) due to the prominent southwesterly flow aloft that results from warm air advect in he mid levels of the atmosphere due to the dying primary low.

 

OPTION 2: The first storm is less and intense and faster to move out, which while this is still likely to force the ultimate development of a "triple point low" at the surface near the coast (limits low level warmth), most of the precipitations falls as rainfall after perhaps a very brief bout of wintry precipitation near the onset. Travel impact is limited.

 

W

 

While it is now clear that option 2 is going to materialize, which favors a warmer outcome in the absence of a more pervasive 50/50 low, a major winter storm remains a distinct possibility due to guidance continuing to adjust to the strength of the negative NAO block.

 

 

As of now, transfer to the coast somewhat later if the most likely scenario, which would result in a wintry mix of precipitation across the region with the heaviest snow amounts likely across the interior.

 

 

 

 

 

 

First Call with respect to Friday likely  on Tuesday.

[40/70 Benchmark]

Sunday-Monday Snows: Final Call

Focus West

The Situation:

The forecast rationale from First Call on Friday remains largely unchanged, as the approaching system will be forced to track around a large low pressure that will stationed in the Canadian Maritimes, which will cause its eastward progression to halt and veer to the southeast as it enters Westrern New England.

 

This means that most of the accumulating snowfall will be confined to western New England.

 

Expected Storm Evolution:

Light snowfall should break out across the Berkshires around or shortly after midday today.

 

1pm Sunday:

And continue to spread east throughout the afternoon.

 

4pm Sunday:

The system will begin to feel the influence of the system over the Maritimes as it enters central potions of the region during the evening, and precipitation will begin to track more to the southeastward.

 

7pm Sunday:

This will greatly limit measurable snowfall east of about the Worcester hills, aside from some potential areas of ocean enhanced snow on the south shore.

 

1am Monday:

 

 

Snowfall should be winding down prior to the morning commute on Monday, so while it would be wise to leave some extra time, delays should be minor.

 

7am Monday:

 

Sunday-Monday FINAL CALL: 

 

 

Sunday-Monday FIRST CALL: Issued Friday 12/9 @ 12pm

 

Then during this coming week all eyes will shift to a large storm that looks to potentially bring mixed bag of precipitation to the region.

[40/70 Benchmark]

Season's First Significant Snowfall Forecast Fairly Well

Max Snowfall Under Forecast

The first significant snowfall of the 2022-2023 winter season, for at least the western half of the forecast area, is now behind us and it is time to offer a critique of the Eastern Mass Weather forecasting effort.

It is apparent from the comparison below between the Eastern Mass Weather Final Call and actual snowfall totals that the forecast for the majority of the region was very accurate.

 

 

 

 

However, what is also apparent is that there was in fact one glaring weakness with respect to the forecast map. And that is that the area of maximum snowfall over western Mass and NW Connecticut was positioned slightly too far to the north, but more importantly was too light. A forecast range of 5-9" would have been more representative for this area than the 3-6" forecast range. There is a reason why Eastern Mass Weather did not go quite so heavy with respect to totals in this region.

Trust the Soundings

There was model support for a period of significant snowfall that would accumulate very proficiently throughout much of western New England.

 

 

The annotation above is a forecast sounding from the NAM model for Bradley International Airport, which is located in Winsdor Locks,  Connecticut. What is very apparent is the well defined "crosshair" signature on the sounding for last night. A cross hair signature refers to when there is ample lift and moisture co located perfectly within the center of the snow growth zone, which is the area between -12 and -18 degrees Celcius that is ideal for the genesis of snow flakes. Immaculately developed dendrite accumulate much more efficiently than poorly developed once, which significantly impacts accumulations. This is why the forecast of 3-6" within that max zone was slightly heaver than some of the model guidance, which forecast no amounts of 6" or greater. However, not all guidance had a signal this emphatic, so the forecast remained relatively conservative. In hindsight this was clearly a mistake, especially since the location of the sounding,  Winsdor Locks was not even in the area of heaviest forecast amounts. Thus the forecast soundings over the Berkshires were at least as impressive and likely featured an even more pronounced cross hair signature. It is with this in mind that the forecast obviously

 should have been more aggressive in this area.

 

FINAL GRADE B-

[40/70 Benchmark]

Major-Long Duration Winter Storm Likely for the Deep Interior Friday-Saturday

Elevations favored

The first major winter storm of the season look to arrive early on Friday, and as advertised in last week's initial threat assessment, it looks to be a mixed bag that promises to present many precipitation type issues across the region

The Synoptic Situation:

Deep low pressure will be begin to encounter the negative NAO block currently in place, as it moves northeast through the plains on Wednesday.

 

 

 

Ordinarily, a storm system on the trajectory in the plains would mean a mild rainstorm for most of New England, however, it will ultimately succumb to resistance from the block and redevelop to the east. This is what will allow a portion of the area to still experience a significant snowfall.

 

 

But notice that while the block ultimately does win the battle, it is not before the powerful primary closed low in the in midwest has forced the block to cede just enough ground the system to make it all the way north into the Great Lakes. This is why it is important to remember that it is the synoptic scale nuances that dictate the details of a storm, not necessarily the mode of large scale index, as evidenced by the fact that the NAO remains quite negative despite the small cessation of ground that proves crucial to the forecast.

 

Anticipated Storm Evolution:

Precipitation should begin as snow anywhere roughly outside of I495 and off of the south coast after midnight early Friday morning.

 

 

However, the aforementioned stronger and more resilient primary low results in a stronger southwest flow aloft for a longer duration of time that ultimately scours out the antecedent cold more efficiently, and allows the secondary to track closer to the coast, which creates an easterly fetch into the lower levels of the atmosphere. 

 

 

 

Given the fact that sea surface temperatures this early in the season are near 50 degrees, this renders it impossible for any initial snowfall to last very long on the coastal plain of southern New England. Thus the precipitation will rapidly transition to sleet and then rain anywhere east of the Worcester hills early Friday morning, so that by midday Friday, only the hills of Worcester county, northwestern Connecticut and the Berkshires are snowing heavily. While it may continue to snow at some valley locations of western mass during Friday afternoon, it will likely struggle to accumulate as efficiently as locales at higher elevations above approximately 700', where power outages will be possible across the Berkshires, northern Worcester hills and Monadnocks of southern New Hampshire.

 

 

Rain may begin to change back to snowfall on early Saturday morning from west to east, as the secondary low pressure areas passes the region.

 

 

And the midlevel low begins to redevelop off of the coast.

 

 

Had the block not eroded as much and allowed the primary to penetrate as high up in latitude as it did, this mid level redevelopment could have limited the change to rain, but it still may aid in a period of snow showers on Saturday afternoon all of the way to the coast before precipitation tapers off entirely.

 

 

First Call:

 

Initial Threat Assessment Issued on Friday, December 9 at 12pm:

 

 

 

Final call will be issued on Thursday-

[Jebman]

On 11/10/2022 at 8:50 PM, 40/70 Benchmark said:

https://easternmassweather.blogspot.com/2022/11/winter-2022-2023-promises-plenty-of-mid.html

Wow. That is one YUGE article, kind of like an Opus about the weather this winter. This place is an exciting university where I learn so much it is unbelievable!

[Jebman]

40/70 Benchmark, You really need to go to meteorological school and become a degreed meteorologist!  You have serious talent, you are a meteorological Einstein 2.0. You need to put these Brobdingnagian weather skills to work and make some money from them! Maybe as a kind of consultant. You are right up there with HM and Typhoon Tip. No. fracking. kidding.

[40/70 Benchmark]

3 hours ago, Jebman said:

40/70 Benchmark, You really need to go to meteorological school and become a degreed meteorologist!  You have serious talent, you are a meteorological Einstein 2.0. You need to put these Brobdingnagian weather skills to work and make some money from them! Maybe as a kind of consultant. You are right up there with HM and Typhoon Tip. No. fracking. kidding.

I really appreciate the kind words, as it is that, in addition to the whole winter experience makes all of the time worth it.

I def. do not have the understanding of the background physics that drive the atmosphere like they, along with other degreed mets do, but I have tried to compensate for that with really rigorous research to get a feel for climo and general understanding of synoptics.

[Jebman]

11 hours ago, 40/70 Benchmark said:

I really appreciate the kind words, as it is that, in addition to the whole winter experience makes all of the time worth it.

I def. do not have the understanding of the background physics that drive the atmosphere like they, along with other degreed mets do, but I have tried to compensate for that with really rigorous research to get a feel for climo and general understanding of synoptics.

You do a very thorough job. That, is an outright Brobdingnagian dissertation. Its gonna take some time to go through it and fully appreciate it.

I hope you, and your entire region, gets far more snow this winter, than Jay Peak Resort gets in a good winter for them! I hope you and everyone else up there in the Northeast, enjoys it to the full and stays safe as well. Happy Holidays too!

[40/70 Benchmark]

2 minutes ago, Jebman said:

You do a very thorough job. That, is a massive dissertation. Its gonna take some time to go through it and fully appreciate it.

I hope you, and your entire region, gets far more snow this winter, than Jay Peak Resort gets in a good winter for them! I hope you and everyone else up there in the Northeast, enjoys it to the full and stays safe as well. Happy Holidays too!

I'll take a Jebwalk for ya haha

[40/70 Benchmark]

Major-Long Duration Winter Storm Likely for Deep Interior Elevations Friday-Saturday

Power Outages Likely Berkshires and Possibly Northern Worcester Hills

The first major winter storm of the season will be arriving late tonight and early tomorrow morning. The forecast remains largely unchanged from First Call issued on Tuesday, and even the same general synoptic conceptualization expressed in last Friday's Initial Assessment remains relatively consistent.

The Synoptic Situation:

Yesterday, deep low pressure began to interact with the negative NAO block that currently in place across southeastern Canada, which has slowed its northeast progression through the plains.

 

Ordinarily, a storm system on the trajectory in the plains would mean a mild rainstorm for most of New England, however, it is beginning succumb to resistance from the block, which will eventually cause it to redevelop closer to the east late Friday night and early Saturday morning. This is what will allow a portion of the area to still experience a significant snowfall.

 

Had the block not ceded any ground, then this transfer would have occurred earlier and more aggressively, which would mean that the secondary coastal low would take over faster and more aggressively, while also tracking further off shore. This would have resulted in a major snow storm for most of the area. But since the primary low is remaining dominant for a longer duration of time, the secondary low is developing later and tracking along  the coast, which results in the majority of the forecast area experiencing primarily rain.

This is why it is important to remember that it is the synoptic scale nuances that dictate the details of a storm, not necessarily the mode of large scale index, as evidenced by the fact that the NAO remains quite negative despite the small cessation of ground that proves crucial to the forecast.

 

Anticipated Storm Evolution:

Precipitation should begin as snow anywhere roughly outside of I495 and off of the south coast by around midnight early Friday morning, and perhaps by around 10pm late Thursday evening across western New England.

 

 

However, the aforementioned stronger and more resilient primary low results in a stronger southwest flow aloft for a longer duration of time that ultimately scours out the antecedent cold more efficiently, and allows the secondary to track closer to the coast, which creates an easterly fetch into the lower levels of the atmosphere. 

 

 

 

Given the fact that sea surface temperatures this early in the season are near 50 degrees, this renders it impossible for any initial snowfall to last very long on the coastal plain of southern New England. Thus the precipitation will rapidly transition to sleet and then rain anywhere east of the Worcester hills early Friday morning, However, this same easterly feature that results in rainfall further to the east will actually enhance snowfall over the Monadnocks and especially the east-faced slopes of the Berkshires. which means that very heavy snowfall is likely to continue through these areas all day on Friday and even perhaps into early Saturday morning. While it may continue to snow at some valley locations of western mass during Friday afternoon, it will likely struggle to accumulate as efficiently as locales at higher elevations above approximately 700', where power outages will be likely across the Berkshires, northern Worcester hills and Monadnocks of southern New Hampshire.

 

 

 

Rain may begin to change back to snowfall on early Saturday morning from west to east, as the secondary low pressure areas passes the region.

 

 

And the midlevel low begins to redevelop along the coast.

 

 

Had the block not eroded as much and allowed the primary to penetrate as high up in latitude as it did, this mid level redevelopment could have limited the change to rain, but it still may aid in a period of snow showers on Saturday afternoon all of the way to the coast before precipitation tapers off entirely.

 

 

Final Call:

 

First Call:

Issued Tuesday December 13 at12pm.

 

Initial Threat Assessment Issued on Friday, December 9 at 12pm:

 

[40/70 Benchmark]

Severe Winter Storm Likely Around of Just Prior to Christmas Eve

Track to be Determined But Confidence High Relative to Long Lead Time

Ideally, in order to maximize potential for major east coast cyclogenesis, what is more important than simply having negative modes of the EPO, NAO, AO and positive PNA is having increased modularity. In other words, the idea that the teleconnections are changing is even more important than what particular mode that they are because the key is to have mass fields in flux, which is precisely what is emphatically being advertised for the period leading up to the Christmas holiday. Thus the advertised mid season mayhem maybe set to begin as we near the final week of 2022.

 

Teleconnector Convergence

 

Teleconnection is a term employed in the weather bussiness to denote a casual connection or correlation between meteorological or other environnmental phenomena that occur over an expansive geographical area. Eastern Mass Weather often refers to these phenomena as part of the intricate cycle of land, sea and air that the earth uses as a means by which to incessantly strive to maintain an elusive state of equilibrium that will never be established. It is the mission of the earth in its truest essence to harness the surplus of solar heat focused near the equator, and in so doing utilize the vast array of oscillations and telcconnections as a vehicle for the redistribution of said heat poleward. Please refer here and here a more detailed and exhaustive tutorial on the various oscillations and the role that they play on a global scale, however, they will be explored through a medium range forecasting lens for the purpose of this writing.

 

"Archambault Events"

Research conducted by Heather Archambault et al. (2007) concluded that there exists a statistically significant correlation between large precipitation events in the northeastern US during the cool season, which encompasses the period November through April, and exaggerated positive and negative modes of the PNA and NAO, respectively. More specifically, heavy bouts of winter time precipitation occur more frequently when the PNA is +2 SDs of higher, and the NAO +2 SDs or lower. This is due to the fact that upper air systems, or shortwaves, careening down the east side of a stout PNA ridge are able to dig deeper at the base of the trough since they are beginning at a higher latitude. We would advise being mindful of our garden hose analogy here, and the fact that for every action in the atmosphere, there is an equal, and opposite, more stochastic reaction. The higher the ridge, the deeper the trough. 

 

Stronger Western Ridge Equates to Deeper Easter Trough/More Significant Storm

 

This is a high stakes scenario because since PNA is expected to be on the rise and cross into the positive mode during the lead up to Christmas, higher heights out west will tend to promote more phasing  and the more proficient delivery of cold downstream on the east coast.

 

 

This why we are seeing a powerful, phased system on much of the guidance. It is also likely to be a slow-moving storm because it will tend to slow as it rounds the base of the trough, and its continued eastward progression would then be met with resistance from the higher north atlantic heights inherent of the negative mode of the NAO, which also means that the cold air can not exit prior to the arrival of the system as it will this Friday.

 

Blocking North Atlantic High Slows Exit of Storm

Note the agreement on this general scenario amongst the various ensemble suites for the evening leading into Christmas Eve:

 

European Ensemble Mean:

 

 

GFS Ensemble Mean:

Canadien Ensemble Mean:

 

 

It is the aforementioned Archambault research that "precipitated" the promulgation of the term "Archambault event" throughout meteorological circles to describe a large precipitation event during highly anomalous +PNA/-NAO regimes. In this particular context that the mode of the oscillation is paramount for identifying intervals of heightened storm risk. However, the previously cited importance of modularity and mass flux in the development of major storm development has prompted Eastern Mass Weather to expound upon this research in an effort to identify said modularity as having perhaps an even more  of a profound proclivity to foster an environment ripe for the development of major east coast winter storms.

 

Dynamic vs Static Mass Fields 

The fact that heights are elevating across the western US as we transition from an RNA to PNA regime, coupled with the maturation and subsequent slow attenuation of the high latitude blocking node across the polar domain represents a great deal of motion among mass fields

 

 

This refers to the fact that because oscillations such as the PNA, NAO, and AO being in a state of flux, air masses will be colliding as one cedes ground to the other. This is what Eastern Mass Weather refers to as a "dynamic" atmospheric regime, in which, some, not necessarily all, of the oscillations are in a heightened state of modularity. This simply means that they are either growing more positive or more negative. It is these phase change events that are cultivated within an environment rife with baroclincity and abundant avenues for moisture transport via the release of heat and/or isentropic lift. It is this heightened state of modularity that is more crucial to the genesis of heavy precipitation events than is the need for a given oscillation to be firmly fixed in an anonymously high or low mode. Dynamic teleconnector convergence is more crucial to the development of major east coast winter storms than is static teleconnector convergence, and this is precisely what is currently modeled for the major North American teleconnections approximately one week from today. The evolution of the PNA ridge in guidance over the next several days will be crucial, as faster ascent and building to the west will likely mean a more proficient phasing of the downstream eastern energy...ie the PV love over southeastern Canada with the developing coastal low.

Stay tuned over the course of the next week due to potential travel ramifications for the upcoming holiday week. While First Call will not be issued until around Tuesday, it is safe to say that certainly all air travel, and preferably ground travel, be rushed to completion by Thursday, December 22, or else arrival at the final destination is very likely to occur before Christmas.

 

[40/70 Benchmark]

Major, Long Duration Winter Storm Friday-Saturday Generally Forecast Well 

The forecast for the major winter storm at the conclusion of this past week and into the weekend was well forecast overall

Below are reported snowfall totals from across the region.

This was a very difficult forecast because the airmass was very marginal, and this it was highly elevation dependent, which is a point that was conveyed in the forecast. Note that while the forecast across northwestern half of the forecast verified very well, the southeastern edge of the snowfall, across the southern Worcester hills and the hills of north eastern Connecticut was overdone.

 

 

The reason being that the airmass was just so marginal that iy was very difficult to discern what exactly would transpire. Not only does climatology dictate that more often than not the higher terrain of this area will see appreciable snowfall, but much of the forecast did, as well. However, clearly did not end up being the case in this area, as the 3-6" forecast verified as 1-3". Another area of difficulty was the lowest portion of the Connecticut river valley in Massachusetts, in was some areas such as Greenfield were forecast to receive 3-6" of snowfall and actually received under an inch. The rest of the forecast verified well, with areas such as Wilmington, VT, on the east slopes of the Green mountain range, accumulating over 2' of snowfall, as was expected in isolated area. Several locales in the higher terrain of the northern Berkshires received upwards of one foot and a half of snowfall.

 

Final Grade: B+

[40/70 Benchmark]

Mild & Rainy Friday Before Slight Storm Threat Just after Christmas

 

No White Christmas for Most of Southern New England But Travel Delays Still Expected

It has become clear over the past several days that the worst nightmare for travelers across the northeast will not be realized, as the severe winter storm that has been expected to develop for quite come time now looks to track too far to the west for significant snowfall across the region. This is due to the fact that not only is the PNA ridge displaced to the west, just off the west coast as opposed to over the Rocky mountains, but the polar vortex became stationed over western Canada, as opposed to becoming lodged just underneath the block closer to James Bay in Canada. 

 

 

This allows the storm system to dig far enough to the west that it initially gains enough latitude to drive enough warm air into the region to ensure a mainly rain event, before becoming lodged underneath the block. However, while this does mean that the east coast will not be dealing with a blizzard in the days leading up to Christmas, there will still be very adverse weather conditions across many portions of the country. Thus the most prudent course of action would still be to preferably fly out today and no later tomorrow in order to avoid potential delays.

 

Looking Ahead

As we peer beyond Christmas and into the holiday week, there is a slight chance for a winter storm along about Tuesday, however,  a phase of the two parcels of energy remains exceedingly unlikely given the more progressive nature of the flow in the wake of the major pre-Christmas storm system.

 

The European suite was the most ominous with a near miss:

 

 

The Canadian ensemble less emphatic:

 

 

And the GFS remains very benign with the two streams very far apart in a very progressive flow:

 

[40/70 Benchmark]

December Largely Evolves as Forecast with Active January on Tap

Changes afoot in the Pacific Herald Explosive January Potential

December 2022 Review

December Analogs: 1970, 1971, 1973, 1975, 1984,1992, 1996, 2005, 2007, 2008, 2013, 2016 

Before delving into 2023, it is only appropriate to recap the final forecasting effort of 2022 given that the ball has yet to drop in Times Square. 

The season was forecast remarkably well with the notable exception being that the blocking within the polar domain was more prominent than anticipated, as the most anomalous episode was postulated to instead take place in January.

 

 

 

However, as illustrated in the above annotation, clearly the massive episode of blocking materialized during the month of December. While this did not effect the forecast much for the primary area of focus, here in southern New England, it did mean a slightly cooler outcome relative to the expectation across the mid atlantic and southeast, with slightly warmer outcome than forecast across northern New England.

 

December Temp Anomaly Forecast vs 1991-2020:

Actual December Temp Anomalies Through 12/27:

The stronger than anticipated high latitude blocking during the month of December is represented very clearly in the H5 anomaly plot:

 

vs the composite December forecast and the more modest degree of high latitude blocking, which allowed for some southeast ridging and thus a slightly milder outcome in that region:

 

What is also apparent in the composites above is that the Pacific largely behaved as anticipated with a predominately negative phase of the PNA, which favored cold loading to the west.

 

Thus it is not too surprising that precipitation on the west coast was more prolific than the sensible weather composite had indicated for the month of December:

 

Actual: 

Forecast Composite:

 

 

 

This is very reminiscent of the -PNA style extra tropical Pacific pattern, which features 3/5 primary ENSO analog seasons in 1955-1956, 1970-1971 and 2010-2011, respectively.

 

 

 

 

Be that as it may, while the national forecast was not perfect, the forecast narrative for the month of December favoring the deep interior and elevations, as well as northern New England for snowfall was generally correct.

 

"The month will gradually turn colder as the high latitudes become more disturbed, and while the mid Atlantic may find snowfall scarce, New England should not...especially north and interior. However, coastal areas/lower terrain may have frequent precip type issues during coastal storms due warm SSTs. Some elevation events are certainly possible. There will also be southwest flow events/warm air advection events, which will be more fruitful for the coast in terms of snow. A white Christmas is likely across the interior and northern New England, and possible along coastal southern New England. It is very unlikely for at least the lower terrain of the mid Atlantic". 

Note that some changes are apparent with respect to the PNA over the course of the last week to ten days of December that may serve as an important harbinger of things to come as we enter the new year.

 

Active January Pattern & Potential Deviation from La Nina Regime to Ensue Following Warm Start

Although much of what was postulated regarding the month of January in the release of the Eastern Mass Weather Winter Outlook back in November still remains valid, there are some adjustments to be made in the closer range.

 

Here is the January portion of the forecast from November as a refresher:

 

"January Analogs:1971, 1976, 1985, 1986,1996 2011, 2014, 2021, 2022

January is like to be consistent with climatology in that it will be the most consistently fierce month in that there is likely to be "storms and rumor of storms", to quote an old and wise weather weenie. It was mentioned that opportunities for a coupling of EPO/PNA style blocking with NAO blocking would be scarce this season, but if it is to occur, it will be this month, as evidenced by the January 2023 forecast H5 composite:

The recovery of  the PNA from the RNA month of December is also evident in the ECMWF forecast:

 

Note the opportunity for cross polar flow and what will at times be frigid conditions. This will also be a month of great flux, which will likely couple with well above average N hemispheric SSTs and a surplus of water vapor owed to the submarine eruption of Hunga Tonga last January help to facilitate a large scale and perhaps generation storm opportunity. This event will be the signature storm of the season, and will have the potential to cripple travel over a widespread area for a time in a window between approximately January 6th-20th

This is the month that the mid Atlantic likely receives the bulk of its seasonal snowfall. January will be the inverse of December in that it will be biased more wintery earlier, but blocking should relinquish its grip and it should modify with flooding threats possible during a major thaw.

 

January 2023 Forecast Temp Anomalies:

 

1951-2010:

 

1991-2020:

 

 

January 2023 Forecast Precip Anomalies:
 

1951-2010:

 

1991-2020:

 

It would not be a surprise if precipitation was underestimated especially during the month of January in the analog composites, but also even during the season in general given the unique circumstances surrounding Hunga Tonga".

January Polar domain

The primary deviation from initial iteration of the forecast back in November is that the anticipated thaw period is occurring during the first week of the month, as opposed to later in the month. This is due to December's midwestern blizzard phasing so far to the west given the PV lobe being trapped in western Canada, that it acted to bombard said block and hasten its demise, which has expedited the warm up. 

 

 

 

This is why coastal southern New England observed less snow during the month of December than implied in the outlook during and why the NAO trended positive later in the month, as opposed to lasting into early January as forecast. Not only does this most the thaw from the latter half of January to the first week of the new year, but it also renders an extreme amount of high latitude blocking during the month relatively unlikely, given that it would be quite anomalous for another round of blocking to first the first in such a rapid succession. However, it DOES NOT mean that the high latitudes will be hostile to sustained wintery weather across the area during the month of December because that is not at all appear to be the case. In fact, there are still some signs that high latitudes will be somewhat disturbed, as evidenced by guidance suggesting the Arctic Oscillation will trend strongly negative again:

 

 

 

 

And the NAO perhaps modestly negative, but not at all exceedingly positive beyond New Year's week.

 

 

There corroborates growing evidence that the polar vortex will continue to sustain some assaults and become somewhat elongated toward this side of the globe.

 

 

This will not only sure at least seasonable cold after a very mild first week, but heighten the risk for lobes of the polar vortex to phase with Pacific shortwaves. This is especially given the occurrence of west coast ridging, and since here is reason to believe that there will be just that over the course of  the month of January, there exists explosive east coast storm potential during this time frame.

Guest Appearance by El Nino Looks Ominous in January

It has always appeared as though the Pacific domain would undergo fairly dramatic changes from December to January, as perhaps a harbinger of the ENSO related passing of the guard to ensue over the course of the coming year. And while perhaps the ominous check from the polar domain may have been cashed a bit earlier than anticipated, but Pacific appears prime to deliver based upon latest tropical guidance. The are signs from both the European and GFS camp that the MJO looks to make another attempt at advancing into phase 8 as we approach mid January.

 

 

 

And while previous attempts have failed due to the deconstructive interference pose by cool ENSO's proclivity to relegate tropical forcing to the marine continent, there are drastic, albeit not unanticipated changes taking place.

 

Here is the forecast for the progression of tropical forcing over the course of the first half of January, courtesy of Mike Ventrice:

 

Note the steady progression of the the tropical forcing, denotes by negative vertical velocities steadily progressing towards the dateline. 

This is the polar opposite of modoki la nina favored tropical forcing, which is the milder type of la nina regime that that favors forcing in the maritime continent and mild conditions on the east coast.

 

Note the increased similarity relative to the east-based la nina composite, which favors more poleward Aleutian ridging.

 

But perhaps most importantly is the closest match with respect to tropical forcing, which is that of the prototypical modoki el nino season of 2009-2010, granted with a less pronounced sub tropical jet. 

 

This pattern offers the most explosive east coast storm potential due to amplified west coast ridging. 

There are three caveats:

 

1) Despite residual surplus water vapor from Hunga Tonga, this is still a la nina season, granted with a steadily decreasing intensity and coupling to the atmosphere. Thus with somewhat less of a STJ presence than observed with an actual modoki el nino pattern, cyclogenesis will likely be more prone to Miller B bias relative that seasonal composite.

 

2) The previously referenced VP plot is MJO filtered, thus is assumes some level of successful MJO propagation as a baseline. However, event the unfiltered guidance is implying some level of dateline propagation of forcing.

 

 

3) What is relatively high confidence is periods of rather strong PNA style ridging during the month of January.

 

However, said ridging may not be as prevalent in the vicinity of Alaska, which is why seasonal cold is more likely this month and any true arctic invasions may be relatively fleeting and/or offset by the mild onset of the month.

This is evidenced by an East Pacific Oscillation that may be fairly neutral in the mean.

 

 

Current long range guidance reflects the evolution of the changes in the Pacific quite well.

 

From week one:

 

Through mid month:

 

[40/70 Benchmark]

Mid Month Winter Mayhem Potential Looms 

Multiple Winter Storm Threats on Horizon

It was discussed last week how changes in the tropical Pacific would lead to a reprieve from the la nina like regime and lead to a much more active winter pattern across the area. Current long range guidance continues to carry a rather emphatic three-pronged signal that is centered on mid month.

The first system for next Monday looks to pass out to sea, as it does no look to have enough room to amplify in time given the lack of ridging over the western US and the significant confluence in place over se Canada behind this week's rainfall.

 

European Ensemble Mean:

GFS Ensemble Mean:

 

 

The second system looks to make its closest pass Friday, January 13. And while it does pose more of a threat than the first system given some slight ridging in the vicinity of the Rocky mountains:

 

European Ensemble Mean:

 

 

Said ridging  is very modest and still may not be quite strong enough to allow the system to amplify enough for a major strike of the area, especially with no apparent downstream low southeast of the Canadian Maritimes to slow downt he flow (50/50 low).

 

GFS Ensemble Mean:

 

 

But its the third threat that has been consistently modeled on guidance to threaten the region on or around Saturday, January 14th  that poses the largest threat given a more significant PNA ridge out to the west to allow for more amplification.

 

European Ensemble Mean:

 

GFS Ensemble Mean:

 

 

Stay tuned to forecasts over the course of the next week.

[40/70 Benchmark]

Active Pacific Jet Finally Poised to Subside Later in January

More Wintery Pattern Delayed But Not Denied

Thus far the month of January has not evolved as anticipated. Although the RNA that was so prevalent throughout the month of December has in fact abated as forecast due to more el nino like tropical forcing,  it has been very mild with a notable dearth of snowfall across much of the northeast, regardless.

 

 

This has been primarily due to a stronger than anticipated Pacific jet stream, which has eradicated the cold air supply across much of the continent.

 

While this was expected to be a recurrent theme over the course of winter 2022-2023, it was not at all expected to be so prominent throughout the month of January and has led to a very mild first half of the month.

 

However, there are signs that the active Pacific jet will relax over the course of the final third of the month.

 

Mid Month Pattern Changes to Ensue

There is a growing consensus among ling range ensemble guidance that the very active Pacific jet will finally begin to relax and allow the supply of cold air to be replenished, as a ridge develops in the vicinity of the west coast and aids in the delivery of said cold to the eastern US.

 

 

 

The relaxation of the mild Pacific jet is also apparent in the ensemble forecast of the EPO index, with a notable descent evident in both the European:

 

And GFS ensemble suites:

 

This period also denotes the onset of the window of opportunity for significant winter storms across the region, which at least initially, look to be primarily Pacific driven.

 

Neutral Signal from Tropics and Polar Domain

While a there is likely to be a reoccurrence of the early season episode of high latitude blocking, at least to some degree, later this season, it is unlikely to occur during the month of January. Tropical forcing appears to remain relatively weak, as noted with respect to the low amplitude MJO wave passing out of phase 8 and through phases 1 and 2:

 

And continued decay of the wave of el nino like regime that has been situated closer to the dateline during the majority of first half of the month of January.

 

What his likely entails is a continuation of the current + PNA regime, as evidenced by the aforementioned west coast ridging apparent on long range guidance, with a possible stagnation towards the end of January, and essentially an inconsequential signal from the high latitudes.

 

 

Given the lack of major high latitude blocking in conjunction with a progression towards modest MJO phase 2 wave progression, an inland track of low pressure areas, in addition to inherent coastal precipitation type issues, continues to be a risk factor moving forward.
However, even in the absence of any major high latitude blocking at least through the duration of January, there does appear to be a tendency for the polar vortex to become more elongated towards the western Hemisphere. This may act to redistribute more of the global supply of cold back closer to home as January continues to age.

 

[Torch Tiger]

all that time spent and writing for 3 lousy inches

[40/70 Benchmark]

18 hours ago, Torch Tiger said:

all that time spent and writing for 3 lousy inches

I know.....this is why I am so frustrated, but those are the risks. The payoff is worth it when things pan out.

[CoastalWx]

If someone is passionate about it, I don't see an opportunity as "wasted." 

[40/70 Benchmark]

1 hour ago, CoastalWx said:

If someone is passionate about it, I don't see an opportunity as "wasted." 

Yea, I mean...its my passion for major snowfall that drives the effort, and while its disappointing when potential isn't realized, it doesn't negate the effort. I have still learned a great deal.

[Torch Tiger]

6 hours ago, 40/70 Benchmark said:

I know.....this is why I am so frustrated, but those are the risks. The payoff is worth it when things pan out.

Yeah I was just trolling a bit, very sardonic.  December was unlucky and January (so far) has been pretty ugly.  We'll see what happens.

[Baroclinic Zone]

Ray, I know you beat yourself up over busted outlooks and forecasts.  I love your passion, commitment, and dedication to putting these together.  It takes a lot of time and effort.  Keep at it and continue to learn/grow.  

[40/70 Benchmark]

3 hours ago, Baroclinic Zone said:

Ray, I know you beat yourself up over busted outlooks and forecasts.  I love your passion, commitment, and dedication to putting these together.  It takes a lot of time and effort.  Keep at it and continue to learn/grow.  

I mean, I want to succeed....don't get me wrong. But I think it seems like I take this harder than I really do because I reference everything so much, etc. I know people joke about how I refer to the outlook a million times all winter, but the way I look at it is why bother to do all of that work if you aren't going reference it and grade it, etc.

[512high]

20 minutes ago, 40/70 Benchmark said:

I mean, I want to succeed....don't get me wrong. But I think it seems like I take this harder than I really do because I reference everything so much, etc. I know people joke about how I refer to the outlook a million times all winter, but the way I look at it is why bother to do all of that work if you aren't going reference it and grade it, etc.

Don’t ever stop being “you” , I can tell your not a quitter, you enjoy doing the outlooks, continue….. I enjoy them as many others do as well.