• Hello, please take a minute to check out our awesome content, contributed by the wonderful members of our community. We hope you'll add your own thoughts and opinions by making a free account!

Pattern December, Make analogs relevant again

Webberweather53 said:
Nope, exactly the opposite. As I discussed on this forum a month or two ago, while the release of sulfuric aerosols into the stratosphere actually cools the troposphere, at and above the level where these aerosols are temporarily deposited in the stratosphere, it warms as incoming solar radiation and terrestrial radiation emitted from earth's surface are absorbed. If the volcanic eruption occurs in the tropics, this also means the tropical stratosphere warms in response and warms more significantly than the polar regions. The warming of the tropical stratosphere relative to the polar stratosphere steepens the meridional temperature gradient between the poles and the tropics which strengthens the mid latitude westerlies (due to thermal wind relation), the stronger westerlies imply the polar vortex (and thus northern annular mode) is more intense, and these anomalies propagate down into the troposphere over the course of the winter, enticing the tropospheric AO/NAO to become strongly positive, which significantly increases the probability for a warmer winter here in the east-central US. The impact of tropical volcanic eruptions on the polar vortex can linger for several years as stratospheric aerosols released by the eruption also liberate chlorine ions which destroy ozone in the tropical stratosphere. As this ozone is transported poleward via the Brewer-Dobson Circulation over the years that follow, less ozone reaches the polar stratosphere, which forces a net cooling of the polar stratosphere, which again steepens the meridional temperature gradient and thus increases the strength of the mid latitude westerly jet stream and attendant polar vortex in the longer term, indicative of a +AO/NAO.

From Robock (2000)...
http://climate.envsci.rutgers.edu/pdf/ROG2000.pdf
"The radiative and chemical effects of this aerosol cloud produce responses in the climate system. By scattering some solar radiation back to space, the aerosols cool the surface, but by absorbing both solar and terrestrial radiation, the aerosol layer heats the stratosphere. For a tropical eruption this heating is larger in the tropics than in the high latitudes, producing an enhanced pole-to-equator temperature gradient, especially in winter. In the Northern Hemisphere winter this enhanced gradient produces a stronger polar vortex, and this stronger jet stream produces a characteristic stationary wave pattern of tropospheric circulation, resulting in winter warming of Northern Hemisphere continents. This indirect advective effect on temperature is stronger than the radiative cooling effect that dominates at lower latitudes and in the summer."
Click to expand...
this has got to be the most intersting post i have ever read on this forum... thanks webber... great post... learned somthing today... hopefully this can increase some severe weather chances this winter some... plus this bing a la nina also... me being a big severe weather fan and chaser.... thanks again... i have my eye on this
 
I heard that the last eruption was in 1964. Did that have a negative impact on our winter? I thought the 60's were gangbusters. Maybe the day of the year that it erupted was different.
 
Really do wonder if this coming month ends up being a better version of what November was. Warm early stretch, otherwise cold. Maybe not as cold as what fantasy land is suggesting though, unfortunately. ;\

Only bad thing about this November was there was no precip.
 
GeorgiaGirl said:
Really do wonder if this coming month ends up being a better version of what November was. Warm early stretch, otherwise cold. Maybe not as cold as what fantasy land is suggesting though, unfortunately. ;\

Only bad thing about this November was there was no precip.
Click to expand...
The lack of precip is my main concern. Hoping we can turn that around once the pattern gets colder.
 
GaStorm said:
The lack of precip is my main concern. Hoping we can turn that around once the pattern gets colder.
Click to expand...
the way almost over half time... colder air equals drier air... our cards are stacked to begin with... la nina winteres usually produce drier patterns in long run... im with you... hope for a change
 
tennessee storm said:
the way almost over half time... colder air equals drier air... our cards are stacked to begin with... la nina winteres usually produce drier patterns in long run... im with you... hope for a change
Click to expand...
The 2011 winter was drier than normal from what I remember and we did quite well even with a moderate nina. We are way overdue for a big storm for sure.
 
tennessee storm said:
no dreams on that run.... all i saw was cold chasing moisture for the upper south... dilly dilly
Click to expand...
Yes that run was great. So much potential there to get a storm, will it happen who knows? One things for sure, the cold is coming and there has been some wintry mischief on the gfs, more than a cold chasing moisture. As much as i love snow and ice, i can dig some severe weather to:)
 
packfan98 said:
I heard that the last eruption was in 1964. Did that have a negative impact on our winter? I thought the 60's were gangbusters. Maybe the day of the year that it erupted was different.
Click to expand...

The winters immediately following the eruption were still stellar due in large part to other external forcings ((+AMO >>> -NAO), cooler background climate, ongoing moderate CP El Nino coupled with solar minimum destructively interfering w/ the volcanic eruption in attempting to force a stronger BDC etc.) but the impact the eruption had on the Northern Annular Mode remained consistent w/ observations and GCM studies w/ a stronger than normal polar vortex (+AO) being observed in 1963-64.
TuKO8ZzlQ3.png

However, as usual, there's no linear or clear-cut, direct relationship and other variables need due consideration when assessing the sensible impact from a major tropical volcanic eruption, but if you isolate its forcing from the array of variables and forcings that impact our winter, the net effect of a volcanic eruption is to force a +AO and thus skew the chances towards above normal temperatures here.
Obviously we know (especially after 2013-14 & 2014-15) that even w/ a +AO this doesnt automatically mean the winter is a dud/bust or will be warm (of course it does change the character of the winter storms that are observed here w/ +AO coupled w/ NP blocking favoring Miller B/CAD events), however when you analyze the overall collective body of winters w/ a stronger than normal polar vortex, as is often observed following major tropical volcanic eruptions, the signals tend towards above normal temps here in the southeastern US.
 
packfan98 said:
I heard that the last eruption was in 1964. Did that have a negative impact on our winter? I thought the 60's were gangbusters. Maybe the day of the year that it erupted was different.
Click to expand...

In support of Webb: Regarding the June of 1991 huge eruption of Pinatubo, the following winter's AO was the most positive of the 24 El Niño winters since 1950. Coincidence? Furthermore, the subsequent winter's (1992-3) AO was the 2nd highest and Jan of 1993 was the highest for ANY month since 1950. Another coincidence? Would these have occurred had there been no eruption? Who can say? From a purely statistical point of view, I'd want to see many other examples but we don't have them since the number of eruptions since 1950 capable of significantly affecting the AO is very low. But at least these 2 winters' AO appear to support what Webb is saying.
 
Last edited:
Webberweather53 said:
The winters immediately following the eruption were still stellar due in large part to other external forcings ((+AMO >>> -NAO), cooler background climate, ongoing moderate CP El Nino coupled with solar minimum destructively interfering w/ the volcanic eruption in attempting to force a stronger BDC etc.) but the impact the eruption had on the Northern Annular Mode remained consistent w/ observations and GCM studies w/ a stronger than normal polar vortex (+AO) being observed in 1963-64.
View attachment 1592

However, as usual, there's no linear or clear-cut, direct relationship and other variables need due consideration when assessing the sensible impact from a major tropical volcanic eruption, but if you isolate its forcing from the array of variables and forcings that impact our winter, the net effect of a volcanic eruption is to force a +AO and thus skew the chances towards above normal temperatures here.
Obviously we know (especially after 2013-14 & 2014-15) that even w/ a +AO this doesnt automatically mean the winter is a dud/bust or will be warm (of course it does change the character of the winter storms that are observed here w/ +AO coupled w/ NP blocking favoring Miller B/CAD events), however when you analyze the overall collective body of winters w/ a stronger than normal polar vortex, as is often observed following major tropical volcanic eruptions, the signals tend towards above normal temps here in the southeastern US.
Click to expand...

Where the major volcanic eruption occurs (& hence where the aerosols are deposited) definitely matters as we saw after the major volcanic eruption in Iceland in 2010 (which likely aided in maintaining the rather unexpected and persistent blocking in 2010-11), if it occurs in the high latitudes, this changes everything and the radiative imbalance caused by the aerosols can actually benefit us but the relationships wrt our sensible weather following major arctic/high latitude volcanic eruption are less clear cut and even more convoluted than tropical volcanic eruptions...
 
Webber do you know if there is a window where if it becomes major it will not have a negative effect on our winter? Maybe by the time it does effect the AO it won't matter.
 
GaWx said:
In support of Webb: Regarding the June of 1991 huge eruption of Pinatubo, the following winter's AO was the most positive of the 24 El Niño winters since 1950. Coincidence? Furthermore, the subsequent winter's (1992-3) AO was the 2nd highest and Jan of 1993 was the highest for ANY month since 1950. Another coincidence? Would these have occurred had there been no eruption? Who can say? From a purely statistical point of view, I'd want to see many other examples but we don't have them since the number of eruptions since 1950 capable of significantly affecting the AO is very low.
Click to expand...

Probable-likely not a coincidence... It's arguable that we may have observed a +AO in the winters that followed anyway because the multidecadal bgd signaling was very unfavorable for a -AO in the early-mid 1990s, but there's little-no doubt that the Pinatubo eruption gave a massive boost to the very strong +AO regime that was observed in this time period. As aforementioned, not every winter was a bust/dud even with a strong +AO, but the comprehensive character of the winter storms that affected NC from 1990-95 definitely seemed to change with (aside from the March 1993 superstorm) a plethora of CAD/ice events relative to Miller As, as one would expect from the relationships between a +AO/+NAO - North Pacific blocking (-EPO/-WPO) couplet and the synoptic scale pattern that accompanies it over North America. (North Pacific block seeds troughs over south-central Canada and the northern tier w/ arctic and siberian air, big cold highs follow in their wake, and the NP blocking aids in forcing a ridge over or off the SE US coast which induces broad/moist southwesterly flow that overruns the cold domes that settle over the SE US in association w/ these cold highs leading to CAD.)
Significant ice storms were observed on December 27-28 1992, December 28-29 1993, February 10-11 1994, & February 1995. I recently analyzed the December 1993 event and the map is shown below

December 28-29 1993 NC Snowmap.png
 
GaStorm said:
Webber do you know if there is a window where if it becomes major it will not have a negative effect on our winter? Maybe by the time it does effect the AO it won't matter.
Click to expand...

The time table for sulfate aerosols to completely encircle the equator after a major tropical volcanic eruption occurs on the order of a few weeks (2-4 or so) & thus if this were to undergo a major eruption within the next week or so, the impacts on the AO would commence within in relative short order, potentially having a role in strengthening the mid-late winter (January-March) polar vortex.
 
I really like the look of things headed into December. Keep that -AO and -NAO going.
 
tennessee storm said:
the way almost over half time... colder air equals drier air... our cards are stacked to begin with... la nina winteres usually produce drier patterns in long run... im with you... hope for a change
Click to expand...
Lol can't have wintry weather without cold. Give me cold air first and I'll take my chances. I'm not worried at all about precipitation.
GaWx said:
To maximize this chance per what Webb is saying, the volcano needs to avoid a major eruption for at least several weeks.
Click to expand...
Hahah leave it to a damn volcano to screw up our winter lol.
 
GaWx said:
To maximize this chance per what Webb is saying, the volcano needs to avoid a major eruption for at least several weeks.
Click to expand...
We probably won't really see the impacts in the upcoming period to a large extent and probably not until we near or get into January or so. The impacts from sulfate aerosols are cumulative and there's a lagged response from the tropospheric vortex after alterations occur in the stratosphere, & even the aerosols that are being released now won't encircle the global tropics and until the 3rd week of December or so and their concentrations aren't too high, at least not yet anyways. I would not worry about it too much for the moment, it's something we may potentially have to contend with in several weeks time if the eruption continues and grows more violent..
 
Storm5 said:
Lol can't have wintry weather without cold. Give me cold air first and I'll take my chances. I'm not worried at all about precipitation.
Click to expand...

I agree because there actually hasn't been much of a correlation at all over the many years of records between precip amounts and wintry precip in most of the SE US since the vast majority of SE precip amountwise is practically always nonwintry even during wintry winters. Even 1935-6's prolific wintry precip total amounts were MUCH lower than nonwintry in much of, if not all of the SE US. Many of the coldest winters that produced high wintry precip were still dry since a winter with many cold plunges is often dry in the SE US. Otoh, the correlation to cold is much higher though a good number of near normal winters and even some mild winters had high wintry precip due often to just one storm.
 
Last edited:
You must log in or register to reply here.
Back
Top