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28 Dec 2016
Hey Everyone hope the holidays were grand. I have seen from other forums about opening up a Stratospheric discussion thread where anybody can post questions, have daily discussions on the development of the Polar Vortex (PV), and have an area that people can find decent information on where to find PV data and the basics.
So lets begin what exactly is described as the Stratosphere. The Stratosphere is a portion of the atmosphere directly beyond the Troposhperic, where we live, layer.
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The Stratosphere ranges from about 10 to 50km above the surface with pressure values in the range from 100 hPa at the lower levels to just under 1 hPa at the upper levels. They consider the middle portion of the stratosphere to be from ~10-30 hPa.
As we approach the Autumnal Equinox (September 20-22nd) each year in the northern hemisphere the PV begins its strengthening, as this region experiences less solar radiation that hits the ozone located in the Stratosphere allowing the PV to cool and strengthen. The PV will continue to strengthen as we head deeper into the season because of temperature differences between polar and mid latitude regions. The Stratospheric PV has a strong interdependence with the Tropospheric PV as one can effect the other. Strengthening of the Stratospheric PV will usually allow for a connection to allow the Tropospheric vortex to strengthen while the Tropospheric vortex can also influence the Stratospheric vortex strength, but this is not always true.
As we head down toward the surface the strength of the PV dictates what values we look at for the Arctic Oscillation (AO). A strong PV during the winter will set up a positive AO which will tend to retreat the polar jet stream and bottling up the cold in the Arctic regions. While a negative AO translates into a weaker Stratospheric PV and will tend to allow the cold air bottled up in the Arctic to be released into the mid latitude regions around the Northern Hemisphere (NH), now just because we have a negative AO does not necessarily mean every region will experience the same result this also applies to a positive AO.
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The stratospheric PV can be influenced by different factors such as QBO, state of ENSO, solar influence, ozone distribution and levels, and snow cover and extent.
The ozone layer is collocated in the middle portion of the Stratosphere and is warmed by the incoming UV radiation. The main circulation is the Brewer-Dobson Circulation (BDC) ozone is formed in the tropical stratosphere and transported to the polar stratosphere. This circulation changes from year to year and can be influenced from time to time by many different factors. The ozone content can dictate stratosphere polar temperatures with collecting of ozone allowing for warming to occur in the polar stratosphere.
Ozone Basics: https://en.wikipedia.org/wiki/Ozone_layer
Ozone Tracking: http://www.cpc.ncep.noaa.gov/products/stra...2to/index.shtml
The ENSO and the state that we see in the tropical Pacific region play a huge role in tropical regions but also the mid latitudes. During these events the effects on the Stratosphere change, when we experience El Nino (warming of Eastern Portion of the Pacific) the atmospheric upward propagating waves become more centered over the Pacific then the Indian Ocean and vice versa occurs.
Where these waves occur dictate the "attacks" on the PV as well as the weather that we experience from these changes.
Quasi-Biennial Oscillation (QBO):
The QBO is a wind pattern of alternating (easterly and westerly), descending winds that occur in the Tropical Stratosphere over a period of 26-32 months, with an average of around 28 months at about 30hPa is the main region to measure QBO but stretches over an area from 10-50hPa. The easterly (negative) phase is thought to contribute to a weakening of the stratospheric polar vortex, whilst a westerly (positive) phase is thought to increase the strength of the stratospheric vortex. These changes and how quickly or not these winds descend can have substantial implications in the NH winter PV.
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As mentioned before about the Ozone and the BDC, the QBO seems to play a role in distribution from the Tropical Stratosphere. The tropical upward momentum of ozone is stronger in the eQBO , whereas in the wQBO ozone transport is stronger into the lower mid latitudes, so less ozone will enter the upper tropical stratosphere to be transported to the polar stratosphere.
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When the QBO is in a west phase during solar maximum there are more warming events in the stratosphere, as there is also during an easterly phase QBO during solar minimum, so the strength of the BDC is also affected by this also known as the Holton Tan effect .
Sunspots and QBO
Solar Cycle also plays a role in conjunction with other factors as stated above here is the solar indices as we head into what looks to be a solar minimum.
So far we have gone over the ideas of QBO, ENSO, sunspots and Ozone on the startosphere and how they can influence the progression of the Stratosphere. We now turn to Sudden Stratospheric Warmings (SSW).
There is another name for these types of warmings called Major Midwinter Warming (MMW), does not necessarily mean this takes place in the middle of winter. SSWs can be caused by large-scale planetary tropospheric (Rossby) waves being deflected up into the stratosphere and towards the North Pole, often after a strong mountain torque event. This can lead to warmer then normal temperatures from the mid latitude to rise into the polar stratosphere and cause a drop in winds associated with the PV, and even allow a reversal of winds. To start these type of events we usually have to look into the Troposphere for activity that could spawn a change into the Stratosphere. We can look at tropical flare-ups in convection as a way to see a start of an atmospheric Rossby wave. The positioning and strength of the tropical activity is very important and can be seen from the Madden-Jullian Oscillation (MJO) and the surrounding ENSO state. As the rossby wave forms from such convection processes it can moved and deflected by various mountainous regions across the globe which can be monitored by changes in the Global Wind Oscillations (GWO).
When we do happen to get a Rossby wave to form from this process of tropical convection there is the possibility of this Rossby wave, after being deflected, to break. If the Stratosphere is more responsive to wave breaks then as time goes on we can see the development of a SSW or MMW. When a Rossby Wave break occurs in one place we see a wave 1 disturbance occur, usually involving a displacement of the PV. If we see two wave breaks, a wave 2 disturbance, we can see a squeeze on the PV occur and allow for a split.
Rossby Wave Break (RWB) Diagram:
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Currently the SSW is defined by a reversal of mean zonal mean winds from westerly to easterly at 60ºN and 10hPa, but this is being reviewed as to whether this definition will hold. If we do manage to see an SSW form this can lead to high latitude blocking (HLB) to occur, now this is not always the case but SSW's provide a better chance of this occurring where colder air is able to be transported to lower latitudes. The lag associated with an SSW to seeing tropospheric conditions seems to be around 6 weeks but there have been times where this is not quite the case.
One last thing is how snowcover could influence changes in the Stratosphere by ways of creating a SSW from such occurrence. Below we see what Dr. Cohen postulates for what could happen do to snowcover as many know this is not an exact science and the correlations are there but again I warn this does not always follow a linear path with so many other influences that can change this outcome.
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ECM/ Berlin Site
Instant Weather Maps
NASA Merra Site
NASA seasonal Evolution
* Various sites at the bottom of site
Current and previous seasons Temp and Wind
Please Please try to keep this thread on track with not posting single storm impacts unless it pertains to the evolution of the PV. Also if there is any information that anyone would like to add as far as websites, pictures, or any information feel free to add as needed. If you would like to help expand on this 1st post just shoot me a PM and I will add as see fit.
Have fun with discussion!
15 Jan 2016
With many of us getting precipitation should be interesting for some Euro has trended colder at the 12z run. Areas may get into some wet snows especially on the western side.
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16 Dec 2015
Well figured why not start one for this region. Just over a week out until the big holiday is here what kind of weather should you expect? We are still technically past hour 180 but the models are varying quite a bit.
I am not sure if can post the Euro from pro,if i can just let me know and ill change this.
So which do you believe? While the Euro has been pretty consistent, not always right, and the GFS known to have wild swings in the longer range. Well to get a somewhat clearer message we go to 500mb to understand why the models show as they do.
While i like the idea that we stay in a transient pattern with warm and small coolings to average. The big difference that seems to have created this large gap is how the energy to this system is handled. The GFS has been known to kinda zip things along quicker while the Euro likes to hold energy back and really dig systems.
As i stated above, the GFS really does not amplify the system in the plains but lets the energy dig out west pumping a ridge ahead and takes the energy from the plains east and develops it into Canada around Christmas developing what looks like an apps runner giving us a cool blast, no snow pack to the west moderated cold snap.
The Euro wants to send the energy in the plains flying ahead as a S/W along a boundary bring rain with it the day before Christmas eve. Instead it focuses on the energy that digs in the west and really digs a trough out for Christmas day pumping a ridge in the East and a developing storm in the plains.
While the models both have valid runs, its just that only one run, with the pattern we have been having there are expected to be wild swings since the models are very unsure of themselves in the next 2 weeks with maybe a resetting of the pattern or a complete change to the pattern. The biggest difference is the handling of the Pacific in the next week.
Post as you please on your thoughts.
23 Jun 2015
Well here we go again into the active pattern.
Both are for Thursday night into Friday. Might be quite the producer in some spots.
Synoptic System that follows is real impressivee on the GFS:
State College AFD
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
THE AIR CONDITIONERS GET A BREAK WED NIGHT AS LOWS FALL BACK INTO
THE 50S IN ALL BUT THE SOUTH CENTRAL MTNS AND LOWER SUSQ.
CLOUDS INCREASE ON THU AS A MID LEVEL SHORTWAVE BRINGS POTENTIAL
FOR SCT SHOWERS/TSTMS...ESP FOR SW HALF. TEMPS REMAIN CLOSE TO
NORMAL. DID EDGE TEMPS DOWN A LITTLE...AND UP POPS SOME.
DID NOT CHANGE MUCH FOR THE EXTENDED PERIOD. DID LOWER
TEMPERATURES A LITTLE.
OVERALL...AS WESTERN RIDGE BUILDS...LOOKING AT A SLIGHT COOL
DOWN ACROSS THE EAST. THE MAIN THING IS THIS IS A WET PATTERN.
ANYWAY...AFTER A BRIEF BREAK WITH THE SHOWERS ACROSS THE NORTH
ON FRIDAY...THE WEEKEND LOOKS WET.
PERHAPS A BRIEF BREAK FROM THE WET WEATHER BY NEXT TUE.
8 Jun 2015
Forgive me because I have not started a topic in quite some time so if needed please change around what needs to be changed. Im alos not sure if it is ok to post pro stuff on here but i posted one picture let me know if this ok as well.
But none the less we are about to get some heat coming our way. Above is from the 00z Euro showing a somewhat decent ridge trying to get going across the SE US and stretching up our way a bit. It is still almost a little less than a week out but we will get a taste of what may be coming by this thursday friday saturday period where some places may experience their first heat wave.
The GFS after this time period really wants to get the ridge strengthening after a few shortwaves run along the top of this. We may be on the battle grounds in this region between some cooler air and extreme heat but that is to be determined what is everyones thoughts on this?
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Thanks for the birthday wishes accubrother lol
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I think you deserve more than three stars! Maybe we can start a petition!
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