53 replies to this topic

[wxwatcher91]

--- REVIEW ---

The past two boreal winters have featured some extreme conditions around the world. In 2009-2010, the strongest west-based El Nino on record developed in the central equatorial Pacific, forced by three significant westerly wind bursts combined with persistent trade winds over the east Pacific. In concert with a strong easterly QBO, a record breaking low index NAM developed. This pattern contributed to multiple historic snow storms for the eastern U.S. The summer of 2010 followed with a massive transformation of the general circulation. Intensifying trade winds spread cooler waters westward, and a moderate La Nina was rapidly developing. Consequently, tropical forcing made a complete 180. In addition, the QBO westerly shear zone was rapidly descending. Combined with depleted ozone from the strong El Nino, the SAM was persistently in a high index state through the austral winter. Despite the preset conditions of a moderate La Nina and westerly QBO, the winter of 2010-11 once again featured a predominantly low index NAM. And once again, major snow storms pounded the northeast U.S. in December and January.

Since January, the La Nina has weakened, in fact at a very fast rate through April and May. Current conditions in the equatorial Pacific may be considered as neutral, though the general circulation still displays characteristics of La Nina. For example, twin upper level cyclones have been persistent over the eastern Pacific. In addition, a solidly negative PDO remains in place with above normal SSTs over the north Pacific and cold SSTs along the North America west coast. The result has been dominating ridging over the North Pacific, a downstream trough over the western U.S., and ridging over the central Plains and Midwest. One big effect of this pattern is the historic heat wave that has impacted the eastern two thirds of the nation this summer. Another persistent feature in the last couple months has been above normal heights over the Arctic. At the same time, heights have been predominantly above normal across the midlatitudes as well, with ridging over the Pacific, Atlantic, northern Europe, and central Russia. So calculations of the AO may return a weak signal, but the NAM is still in a low-index state.

In the stratosphere, westerly anomalies around 30 to 70mb continue to slowly diminish, while the easterly shear zone descends. As a result, 30mb temperatures have cooled over the equator and have warmed significantly over the subtropics. Temperatures throughout the stratosphere will continue to cool over the equator, and warm off-equator, as the easterlies descend and become more dominant. The QBO in July was close to zero, and it will continue to decrease through the fall and winter.

The combination of a moderate La Nina and warm equatorial stratosphere last winter resulted in suppressed convection near the dateline, and primary tropical forcing over Indonesia. By April, the MJO was becoming active again, though was still suppressed in the central and eastern Pacific. Recently, the low-frequency forcing regime has become less dominant, and convection has migrated eastward over the last few months. The cooling equatorial stratosphere will continue to promote stronger tropical forcing, further east. At the same time, this will dampen off-equator convection, perhaps also prematurely ending the Northern Hemisphere hurricane season.

Anomalous westerly winds associated with convection in the west Pacific occasionally migrate toward the dateline in association with the MJO, however anomalous trade winds are still in control of the central Pacific for the most part. This results in convergence averaged near 160E ... where weak low frequency forcing currently resides. While the La Nina weakened considerably over the spring and early summer, it will likely rebuild this fall. Subsurface anomalies have cooled notably over the last month, and the persistent Nina general circulation suggests that the we will not make it over the proverbial hump. Forecast models all support the redevelopment of at least a weak La Nina this winter. However, the increasing equatorial convection associated with the descending negative QBO makes me cautious to go with anything more than a weak Nina. At the same time, QBO-related SLP anomalies can encourage mountain torque events over the Andes that yields stronger trades over the eastern Pacific, pumping colder waters north and west. The main effect of this will be try to focus cold anomalies east (i.e. an east-based La Nina). In this preset, MJO related forcing may propagate into the central Pacific, while convection is predominantly suppressed over the eastern Pacific and South America. This weakens the South America hadley circulation, which would encourage a negative NAO regime over the North Atlantic.

One last consideration for the preset is snow and ice cover, which is near all-time minimums right now. However, meaningful statistical correlation to the NAM and winter midlatitude temp anomalies is usually limited to October during snow and ice recovery. Intra-annual cycle (period ~195 days) in the NAM would suggest a high index state for the fall, which would promote a fast recovery. Also of note, the intra-annual cycle will be in a low index state for the winter...

Now to apply intra-seasonal variation on top of the preset...


--- DECEMBER ---

The start of the month looks generally warm and dry for much of the nation, outside the Northwest where disturbances will amplify downstream of Pacific ridging. Stormier weather will be introduced into the eastern half of the nation for the second half of the month, with colder air reaching the Plains.

Mean vortex anomalies will be found over Siberia, western Canada (strong), and eastern Europe. Ridging will dominate the north Pacific up through the Aleutians, with weaker ridging over the northeast Atlantic toward Europe, and above normal heights across the southern U.S. Disturbances will track under the west Canada trough, and get whisked quickly across the central Plains along the gradient between the Canadian vortex and southern heights. East based NAO block will fail for the most part to suppress heights on the east coast against ridging over the southeast, while disturbances amplify downstream of southern plains ridging. Meanwhile, heights are pumped up toward Newfoundland. The amplification may offer the possibility of a late blooming Miller B clipping eastern New England.

The middle of the month will follow typical evolution of frictional torque, with a major trough ejecting south from the vortex over Canada. This will scour out southern Plains ridging, leading to a significant storm tracking into the Ohio Valley and Northeast around Dec 15-20. Amplification of the wave pattern into eastern Canada will help retrograde the east-based NAO block into Greenland. Following this event, ridging is established in the southeast U.S., and over the northeast Pacific in a developing Rex block. Vortex anomaly stretches across central Canada and down the Rockies. Baroclinic zone is now well established from the central Plains into the Tennessee Valley. Disturbance ejecting out of the southwest will follow zone toward the Mid Atlantic, with redeveloping storm affecting the Northeast in the final week.


--- JANUARY ---

The first half of the month will feature a major arctic outbreak across the eastern two thirds of the nation, accompanied by a number of snow and ice threats. A thaw is likely for the second half of the month across much of the nation, while still maintaining stormy conditions in the northern tier.


Developing highly amplified quasi-stationary pattern across the North Pacific and Canada, crossing the Rockie Mountains, supports upward planetary wave propogation, and given preset of the stratosphere, a major stratospheric warming is possible to end the month of December. Following typical time scale, the NAM should respond by the end of the first week. Combined with favorable forcing in the Pacific as high amplitude MJO progresses eastward, this will trigger a rapid displacement of the Canada vortex south into the already established long wave trough in the Plains. This fits the recipe for a major Miller A storm for the eastern half of the nation around Jan 4-9.

Clipper track and Miller A track will be predominant following this event, keeping much of the nation, outside the Gulf and east coast, on the dry side. Given the expected forcing on top of the preset, should see strong blocking that will support storm tracks through the Mid Atlantic and off the New England coast through week 2.

As MJO forcing diminishes east of the dateline, a resurgence of the southeast ridge will shift the storm track north, and introduce ice threat for Mid Atlantic region. Cyclonic wave breaking northeast of the ridge into eastern Canada and the Davis Straight will break down the NAO block / shift it east, though the NAM remains slightly negative. Renewed Indian Ocean convection by week 2 will trigger east Asia mountain torque that sets the stage by the end of the month for westerlies gaining latitude and rising heights. This is generally a warmer signal for much of the nation, though transient troughs will keep the Northwest cool and stormy and this may translate into the Plains and Ohio Valley as disturbances amplify downstream of the East Pacific ridge. Vortex still over east Canada fighting against southeast ridging will increase gradients, presenting possible overrunning scenarios for the end of the month.


--- FEBRUARY ---

First half starts out on the warm side, with cool and wet weather confined to the Northwest. Colder and stormier weather returns in the center of the nation, with southwest flow into the east, offering snow and ice threats in the northeast for the second half.

February looks to be dictated primarily by a La Nina regime with low AAM through all levels of the atmosphere, and primary forcing focused near Indonesia and the west Pacific. Anomalously high latitude westerlies to start the month will keep the nation on the warm side initially, apart from the Pacific Northwest. Another friction torque event by end of the first week sends Canadian airmass south into the Plains. Negative AAM tendency propagating poleward will help intensify ridging from the North Pacific into Alaska, continuing to drain colder air south. Moderate ridging develops over the southeast, with typical cycle of troughs diving into the western Plains and breaking in the Ohio Valley. Considering preset conditions, presents more overrunning opportunities in New England for the second half of the month. Another stratospheric warming is possible at the end of the month, but most effects will be during March, which may for the first time in several years be a wintry month.

[Nikolai]

Our outlooks are pretty much identical.

[kab2791]

Wow, awesome job. Great analysis of a very complex forecast. I learned a great deal from that, thanks.

[nzucker]

The cold January seems to be a common feature of most preliminary winter forecasts this season. I know people have been looking at analogs with a frigid January like 08-09, 62-63, and 56-57. It seems that most second year La Niñas do have a colder than normal January; even January 2000 was relatively chilly compared to a blowtorch winter. Here are some of the temperature maps for January of years that could serve as analogs for Winter 11-12...

January 1957:



January 1963:



January 1968:
 jan68temps.png   130.11K   1 downloads


January 1972:
 jan72temps.png   114.53K   1 downloads


January 1975:
 jan1975temps.png   123.59K   1 downloads


January 1985:
 jan85temps.png   133.16K   1 downloads


January 2001:
 jan01temps.png   107.61K   1 downloads


January 2009:
 jan09temps.png   114.84K   2 downloads


Composite:
 jancompositetemps.png   127.78K   0 downloads


Just an overwhelming signal there for a colder than normal January this coming winter.

[BeastFromtheEast]

wxwatcher91, on 5 August 2011 - 08:17 PM, said:

Great outlook ! A lot of good info!

[Snow88]

Very nice outlook.Good luck with your call.

[Riptide]

Based on your outlook, I can't wait for January! Solid reasoning, thanks for the insight.

[wxwatcher91]

Thanks everyone! Yes, a frigid January does have a good amount of support. If I were to choose analogs for January, I'd say 1963, 1994, and 2009. I include 1994 for it's strong resemblance to the stratospheric preset, and anticipated evolution.

[tornadotony]

As much as I hate to say it (given how brutal the winter of '08-'09 was here) I think you did a fantastic job with this. I'm not a big climo guy (most of my climo knowledge ties to severe wx) but your forecast seems to make sense just based off of winters that follow previous winters that were high mdt-strong Niña.

[goobagooba]

Major props for putting such a detailed and well reasoned forecast this early. Kudos and good luck.

[Stebo48858]

Excellent outlook, what's your thoughts on precipitation for the winter and the mean storm tracks that you think will develop this winter?

[wxwatcher91]

Thanks all!

Tony -- your severe weather knowledge arsenal is one to be envied!

Stebo48858, on 5 August 2011 - 11:40 PM, said:

Excellent outlook, what's your thoughts on precipitation for the winter and the mean storm tracks that you think will develop this winter?

Here's kind of a rough sketch of precip and storm tracks for the winter. Not much different from 2nd year Nina climo, except I think we may have to deal with a storm of more Pacific origins in early December. Also, a couple notable Miller A threats in January.

For anyone who's interested, I averaged the temp maps for a DJF anomaly.

 Slide4.PNG   54.99K   8 downloads


 Slide5.PNG   51.25K   4 downloads

[Stebo48858]

wxwatcher91, on 6 August 2011 - 01:08 AM, said:

Thanks all!

Tony -- your severe weather knowledge arsenal is one to be envied!


Here's kind of a rough sketch of precip and storm tracks for the winter. Not much different from 2nd year Nina climo, except I think we may have to deal with a storm of more Pacific origins in early December. Also, a couple notable Miller A threats in January.

For anyone who's interested, I averaged the temp maps for a DJF anomaly.

Slide4.PNG


Slide5.PNG

Nice, thanks for the additions too.

[Harry]

wxwatcher91, on 5 August 2011 - 08:17 PM, said:

--- REVIEW ---

The past two boreal winters have featured some extreme conditions around the world. In 2009-2010, the strongest west-based El Nino on record developed in the central equatorial Pacific, forced by three significant westerly wind bursts combined with persistent trade winds over the east Pacific. In concert with a strong easterly QBO, a record breaking low index NAM developed. This pattern contributed to multiple historic snow storms for the eastern U.S. The summer of 2010 followed with a massive transformation of the general circulation. Intensifying trade winds spread cooler waters westward, and a moderate La Nina was rapidly developing. Consequently, tropical forcing made a complete 180. In addition, the QBO westerly shear zone was rapidly descending. Combined with depleted ozone from the strong El Nino, the SAM was persistently in a high index state through the austral winter. Despite the preset conditions of a moderate La Nina and westerly QBO, the winter of 2010-11 once again featured a predominantly low index NAM. And once again, major snow storms pounded the northeast U.S. in December and January.

Since January, the La Nina has weakened, in fact at a very fast rate through April and May. Current conditions in the equatorial Pacific may be considered as neutral, though the general circulation still displays characteristics of La Nina. For example, twin upper level cyclones have been persistent over the eastern Pacific. In addition, a solidly negative PDO remains in place with above normal SSTs over the north Pacific and cold SSTs along the North America west coast. The result has been dominating ridging over the North Pacific, a downstream trough over the western U.S., and ridging over the central Plains and Midwest. One big effect of this pattern is the historic heat wave that has impacted the eastern two thirds of the nation this summer. Another persistent feature in the last couple months has been above normal heights over the Arctic. At the same time, heights have been predominantly above normal across the midlatitudes as well, with ridging over the Pacific, Atlantic, northern Europe, and central Russia. So calculations of the AO may return a weak signal, but the NAM is still in a low-index state.

In the stratosphere, westerly anomalies around 30 to 70mb continue to slowly diminish, while the easterly shear zone descends. As a result, 30mb temperatures have cooled over the equator and have warmed significantly over the subtropics. Temperatures throughout the stratosphere will continue to cool over the equator, and warm off-equator, as the easterlies descend and become more dominant. The QBO in July was close to zero, and it will continue to decrease through the fall and winter.

The combination of a moderate La Nina and warm equatorial stratosphere last winter resulted in suppressed convection near the dateline, and primary tropical forcing over Indonesia. By April, the MJO was becoming active again, though was still suppressed in the central and eastern Pacific. Recently, the low-frequency forcing regime has become less dominant, and convection has migrated eastward over the last few months. The cooling equatorial stratosphere will continue to promote stronger tropical forcing, further east. At the same time, this will dampen off-equator convection, perhaps also prematurely ending the Northern Hemisphere hurricane season.

Anomalous westerly winds associated with convection in the west Pacific occasionally migrate toward the dateline in association with the MJO, however anomalous trade winds are still in control of the central Pacific for the most part. This results in convergence averaged near 160E ... where weak low frequency forcing currently resides. While the La Nina weakened considerably over the spring and early summer, it will likely rebuild this fall. Subsurface anomalies have cooled notably over the last month, and the persistent Nina general circulation suggests that the we will not make it over the proverbial hump. Forecast models all support the redevelopment of at least a weak La Nina this winter. However, the increasing equatorial convection associated with the descending negative QBO makes me cautious to go with anything more than a weak Nina. At the same time, QBO-related SLP anomalies can encourage mountain torque events over the Andes that yields stronger trades over the eastern Pacific, pumping colder waters north and west. The main effect of this will be try to focus cold anomalies east (i.e. an east-based La Nina). In this preset, MJO related forcing may propagate into the central Pacific, while convection is predominantly suppressed over the eastern Pacific and South America. This weakens the South America hadley circulation, which would encourage a negative NAO regime over the North Atlantic.

One last consideration for the preset is snow and ice cover, which is near all-time minimums right now. However, meaningful statistical correlation to the NAM and winter midlatitude temp anomalies is usually limited to October during snow and ice recovery. Intra-annual cycle (period ~195 days) in the NAM would suggest a high index state for the fall, which would promote a fast recovery. Also of note, the intra-annual cycle will be in a low index state for the winter...

Now to apply intra-seasonal variation on top of the preset...


--- DECEMBER ---

The start of the month looks generally warm and dry for much of the nation, outside the Northwest where disturbances will amplify downstream of Pacific ridging. Stormier weather will be introduced into the eastern half of the nation for the second half of the month, with colder air reaching the Plains.

Slide1.PNG


Mean vortex anomalies will be found over Siberia, western Canada (strong), and eastern Europe. Ridging will dominate the north Pacific up through the Aleutians, with weaker ridging over the northeast Atlantic toward Europe, and above normal heights across the southern U.S. Disturbances will track under the west Canada trough, and get whisked quickly across the central Plains along the gradient between the Canadian vortex and southern heights. East based NAO block will fail for the most part to suppress heights on the east coast against ridging over the southeast, while disturbances amplify downstream of southern plains ridging. Meanwhile, heights are pumped up toward Newfoundland. The amplification may offer the possibility of a late blooming Miller B clipping eastern New England.

The middle of the month will follow typical evolution of frictional torque, with a major trough ejecting south from the vortex over Canada. This will scour out southern Plains ridging, leading to a significant storm tracking into the Ohio Valley and Northeast around Dec 15-20. Amplification of the wave pattern into eastern Canada will help retrograde the east-based NAO block into Greenland. Following this event, ridging is established in the southeast U.S., and over the northeast Pacific in a developing Rex block. Vortex anomaly stretches across central Canada and down the Rockies. Baroclinic zone is now well established from the central Plains into the Tennessee Valley. Disturbance ejecting out of the southwest will follow zone toward the Mid Atlantic, with redeveloping storm affecting the Northeast in the final week.


--- January ---

The first half of the month will feature a major arctic outbreak across the eastern two thirds of the nation, accompanied by a number of snow and ice threats. A thaw is likely for the second half of the month across much of the nation, while still maintaining stormy conditions in the northern tier.

Slide2.PNG


Developing highly amplified quasi-stationary pattern across the North Pacific and Canada, crossing the Rockie Mountains, supports upward planetary wave propogation, and given preset of the stratosphere, a major stratospheric warming is possible to end the month of December. Following typical time scale, the NAM should respond by the end of the first week. Combined with favorable forcing in the Pacific as high amplitude MJO progresses eastward, this will trigger a rapid displacement of the Canada vortex south into the already established long wave trough in the Plains. This fits the recipe for a major Miller A storm for the eastern half of the nation around Jan 4-9.

Clipper track and Miller A track will be predominant following this event, keeping much of the nation, outside the Gulf and east coast, on the dry side. Given the expected forcing on top of the preset, should see strong blocking that will support storm tracks through the Mid Atlantic and off the New England coast through week 2.

As MJO forcing diminishes east of the dateline, a resurgence of the southeast ridge will shift the storm track north, and introduce ice threat for Mid Atlantic region. Cyclonic wave breaking northeast of the ridge into eastern Canada and the Davis Straight will break down the NAO block / shift it east, though the NAM remains slightly negative. Renewed Indian Ocean convection by week 2 will trigger east Asia mountain torque that sets the stage by the end of the month for westerlies gaining latitude and rising heights. This is generally a warmer signal for much of the nation, though transient troughs will keep the Northwest cool and stormy and this may translate into the Plains and Ohio Valley as disturbances amplify downstream of the East Pacific ridge. Vortex still over east Canada fighting against southeast ridging will increase gradients, presenting possible overrunning scenarios for the end of the month.


--- FEBRUARY ---

First half starts out on the warm side, with cool and wet weather confined to the Northwest. Colder and stormier weather returns in the center of the nation, with southwest flow into the east, offering snow and ice threats in the northeast for the second half.

Slide3.PNG


February looks to be dictated primarily by a La Nina regime with low AAM through all levels of the atmosphere, and primary forcing focused near Indonesia and the west Pacific. Anomalously high latitude westerlies to start the month will keep the nation on the warm side initially, apart from the Pacific Northwest. Another friction torque event by end of the first week sends Canadian airmass south into the Plains. Negative AAM tendency propagating poleward will help intensify ridging from the North Pacific into Alaska, continuing to drain colder air south. Moderate ridging develops over the southeast, with typical cycle of troughs diving into the western Plains and breaking in the Ohio Valley. Considering preset conditions, presents more overrunning opportunities in New England for the second half of the month. Another stratospheric warming is possible at the end of the month, but most effects will be during March, which may for the first time in several years be a wintry month.

WOAH.. This is a pretty cold outlook. brrrr

Nice write up..

[VirginiaHippie]

It's a nice outlook. I respectfully disagree with the idea of a well established SE Ridge however as a -QBO along with the possibility of a -NAO again doesn't support that all that well. I dont see a very La Nina-esque pattern until late Winter, so we do agree there in a sense. Also, the analogues that others and myself have been looking at produce a cold signal for december.

I do agree with the above normal precipitation for the Mid-Atl and NE. I guess im trying to say I feel it wont be quite that "dud"-y outside of the NE, MW, and PNW.


But good job anyway!

[New England Storm]

Good luck on your call, cant wait for January, a semi mild febuary is also nice. Thanks for the nice write-up. You put your forcast in way so that even a non met such as myself can understand.

[snowNH]

No knock to you. Great outlook. But I don't think the storm tracks should have been added in there. That's almost like Farmer's Almanac stuff. Thats more of a hard line prediction instead of an outlook. Just my opinion. Like I said, Great, detailed outlook.

[JoMo]

snowNH, on 6 August 2011 - 10:47 AM, said:

No knock to you. Great outlook. But I don't think the storm tracks should have been added in there. That's almost like Farmer's Almanac stuff. Thats more of a hard line prediction instead of an outlook. Just my opinion. Like I said, Great, detailed outlook.

There are predominate tracks that occur during ENSO episodes.

[snowNH]

JoMo, on 6 August 2011 - 11:19 AM, said:

There are predominate tracks that occur during ENSO episodes.

Not about that, like when wxwatcher says "A storm will be likely between the Jan 4-9 time frame"

I'm just nitpicking cause this weather period is SOOOO boring.

From what wxwatcher wrote though, it looks to be a great, heavy winter for NE!

[MariettaWx]

nice writeup.... southeast Ridge I really hope you are wrong about that.

[Nikolai]

VirginiaHippie, on 6 August 2011 - 08:18 AM, said:

It's a nice outlook. I respectfully disagree with the idea of a well established SE Ridge however as a -QBO along with the possibility of a -NAO again doesn't support that all that well. I dont see a very La Nina-esque pattern until late Winter, so we do agree there in a sense. Also, the analogues that others and myself have been looking at produce a cold signal for december.

I do agree with the above normal precipitation for the Mid-Atl and NE. I guess im trying to say I feel it wont be quite that "dud"-y outside of the NE, MW, and PNW.


But good job anyway!

Strongly disagree. There is likely going to be a very tight gradient this winter, similar to past winters that are close analogs (and typical of weak Nina/-neutral ENSO). I think DC may pull out one decent month (and DC will still see the cold), but it's not going to be pretty for people south of the M/D line, especially as you head south of DC.

[Isotherm]

snowNH, on 6 August 2011 - 11:30 AM, said:

Not about that, like when wxwatcher says "A storm will be likely between the Jan 4-9 time frame"

I'm just nitpicking cause this weather period is SOOOO boring.

From what wxwatcher wrote though, it looks to be a great, heavy winter for NE!

Yeah I felt like I was reading an HM long range outlook, as he usually tries to pin down date ranges far in advance as well, not to mention the word "will" was used a lot, signifying high confidence. That's not a bad thing, I'm all for pushing the boundaries and being gutsy with forecasting. Playing it safe prevents us from learning and recognizing our mistakes, so we can improve in the future.

With that being said, there's not much I can argue with at this point given I haven't researched yet and its still early in the game. So good job providing such detailed reasoning at this stage, I enjoyed reading.

[wxwatcher91]

I'm not saying the SE ridge is going to be a persistent feature the whole winter. That's the trouble with monthly temp maps, reflecting the average of multiple patterns. Especially during the first half of January, the arctic outbreak will make an impact down to the Gulf Coast. But warmth later in the month averages that out. There is a threat for multiple rounds of snow and ice in the Mid Atlantic, or even interior Southeast during this period.

[wxwatcher91]

Isotherm, on 6 August 2011 - 12:55 PM, said:

Yeah I felt like I was reading an HM long range outlook, as he usually tries to pin down date ranges far in advance as well, not to mention the word "will" was used a lot, signifying high confidence. That's not a bad thing, I'm all for pushing the boundaries and being gutsy with forecasting. Playing it safe prevents us from learning and recognizing our mistakes, so we can improve in the future.

With that being said, there's not much I can argue with at this point given I haven't researched yet and its still early in the game. So good job providing such detailed reasoning at this stage, I enjoyed reading.

I'm just trying out some new things. By talking about absolutes and specifics, it's easier for me to hold myself accountable for my forecast and learn more effectively ... and it's entertaining for everyone else when I either nail it or fail miserably

Your outlook is one I always look forward to!

[Typhoon Tip]

VirginiaHippie, on 6 August 2011 - 08:18 AM, said:

It's a nice outlook. I respectfully disagree with the idea of a well established SE Ridge however as a -QBO along with the possibility of a -NAO again doesn't support that all that well. I dont see a very La Nina-esque pattern until late Winter, so we do agree there in a sense. Also, the analogues that others and myself have been looking at produce a cold signal for december.

I do agree with the above normal precipitation for the Mid-Atl and NE. I guess im trying to say I feel it wont be quite that "dud"-y outside of the NE, MW, and PNW.


But good job anyway!

This is not in opposition or support for the forecast presently but your -NAO and SE ridge assumption is a bit of a miss-conception.

-NAO can in tandem exist with positive height anomalies from TX-GA-Bermuda; the result is an anomalously fast balance geopotential wind velocity, and is a circumstance that takes place quite frequently. In fact, sometimes the suppressed ridge becomes so extreme that ambient wind fields can exceed 75kts. S/W's in these flow regimes often disappear and get minored out.

[VirginiaHippie]

Typhoon Tip, on 6 August 2011 - 04:13 PM, said:

This is not in opposition or support for the forecast presently but your -NAO and SE ridge assumption is a bit of a miss-conception.

-NAO can in tandem exist with positive height anomalies from TX-GA-Bermuda; the result is an anomalously fast balance geopotential wind velocity, and is a circumstance that takes place quite frequently. In fact, sometimes the suppressed ridge becomes so extreme that ambient wind fields can exceed 75kts. S/W's in these flow regimes often disappear and get minored out.

Well, I live in Virginia so if theres ridging in Georgia then I feel sorry for them. I didnt say that I feel it would be as cold and/or snowy as the past two winters throughout the south and east. But I strongly disagree with Nikolai's pessimistic view of a flatout dud winter south of DC. I don't see it. The consensus in these prelims Ive seen doesnt see it. I dont know what analogues othes have looked at say, but the ones im looking at dont support it. And the atmosphere, sun, and ENSO don't seem to be going the warm and dry route IMHO. It may be warmer at times, but speaking solely for my home state, from what ive been noticing so far...a colder winter seems likely (for at least VA north).


Snow is totally questionable at this time and one storm can wreck a forecast anyway so I wont bother discussing that.

[Typhoon Tip]

VirginiaHippie, on 6 August 2011 - 04:40 PM, said:

Well, I live in Virginia so if theres ridging in Georgia then I feel sorry for them. I didnt say that I feel it would be as cold and/or snowy as the past two winters throughout the south and east. But I strongly disagree with Nikolai's pessimistic view of a flatout dud winter south of DC. I don't see it. The consensus in these prelims Ive seen doesnt see it. I dont know what analogues othes have looked at say, but the ones im looking at dont support it. And the atmosphere, sun, and ENSO don't seem to be going the warm and dry route IMHO. It may be warmer at times, but speaking solely for my home state, from what ive been noticing so far...a colder winter seems likely (for at least VA north).


Snow is totally questionable at this time and one storm can wreck a forecast anyway so I wont bother discussing that.

It's all good - you had said the -NAO didn't fit with a SE ridge and I'm just here to say that is not really true.

[40/70 Benchmark]

Reminds me of last winter....giant pants tent through Jan, then it wanes.
Great job and good luck.

[wxwatcher91]

40/70 Benchmark, on 7 August 2011 - 11:16 AM, said:

Reminds me of last winter....giant pants tent through Jan, then it wanes.
Great job and good luck.

Thanks Ray! I'd take last winter in a heartbeat. This one might be better.

[Isotherm]

wxwatcher91, on 6 August 2011 - 01:15 PM, said:

I'm just trying out some new things. By talking about absolutes and specifics, it's easier for me to hold myself accountable for my forecast and learn more effectively ... and it's entertaining for everyone else when I either nail it or fail miserably

Your outlook is one I always look forward to!

Thanks! I think you did a great job putting everything together, and are certainly holding yourself accountable with those detailed departure maps. I also think the throwing out dates for storms is something fun to do, even if it has a low chance of verifying, it's a good learning experience. With that said I don't know if I'll be adding that to my outlook this year.

[JBG]

wxwatcher91, on 5 August 2011 - 11:01 PM, said:

Thanks everyone! Yes, a frigid January does have a good amount of support. If I were to choose analogs for January, I'd say 1963, 1994, and 2009. I include 1994 for it's strong resemblance to the stratospheric preset, and anticipated evolution.

I hope you're right but the NAO is a lot more negative these years than 1994. Also we're in PDO cold phase.

[A-L-E-X]

Nikolai, on 6 August 2011 - 12:42 PM, said:

Strongly disagree. There is likely going to be a very tight gradient this winter, similar to past winters that are close analogs (and typical of weak Nina/-neutral ENSO). I think DC may pull out one decent month (and DC will still see the cold), but it's not going to be pretty for people south of the M/D line, especially as you head south of DC.

Weak la nina is our second snowiest ENSO signal, however, there may be other signals at play this winter (like QBO) that will play a more prominent role than ENSO.

[A-L-E-X]

Isotherm, on 7 August 2011 - 04:35 PM, said:

Thanks! I think you did a great job putting everything together, and are certainly holding yourself accountable with those detailed departure maps. I also think the throwing out dates for storms is something fun to do, even if it has a low chance of verifying, it's a good learning experience. With that said I don't know if I'll be adding that to my outlook this year.

I know we've been talking about this in our subforum-- but second and third year la ninas tend to be colder than first year ones. Of course, it can easily be colder and snow less-- at least two of our three big snowstorms last winter involved extremely delicate set ups that were thread the needle type scenarios.

[River Card]

Nice writeup and thanks for taking time to post this. Wow -6 to - 10 below norm for Jan? Now that is one part of the equation I hope you miss on. Great work though and much thanks.

[BethesdaWX]

I an curious what methods you used in pinning down exact time-periods of focus with a seemingly high level of confidence?

Also wondering with the general analog selection if using active sun activity years is perhaps a bad move? Active solar periods seem to have some sort of impact on the upper atmosphere near the polar regions, too complicated/many abbreviations to type on my iPhone right now though!