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Stratosphere Discussion 2012-13


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Warming of the Asian stratosphere is already evident, although it remains slightly cold overall. It looks like some major warming is forecasted.

Anybody know what is causing this? Mountain torque? Ozone? HM?

Sudden stratospheric warmings (what some are calling a vortex split here) are forced by large amplitude planetary scale Rossby waves propagating from the lower troposphere to the stratosphere, where they are absorbed and decelerate the mean westerly flow, sometimes to the point that the flow reverses and you end up splitting the stratospheric polar vortex.

These large amplitude planetary scale Rossby waves generally arise from mountain range forcing or the difference between land and ocean (like the east coast for example, where you get persistent ridging over the warm ocean and persistent troughing over land so you end up with a large amplitude). Sudden stratospheric warmings are rare to non-existent in the southern hemisphere during winter since there aren't any significant meridonal land/ocean boundaries or mountain ranges near the polar vortex, and thus Rossby waves don't have a big enough amplitude to break the polar vortex.

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Yeah - that's the future, but let's talk about what we've seen so far the month of November, and that's a very cold stratosphere from 1mb down through 70mb.

According to the correlations, this would argue for a +AO Dec (based upon only the stratosphere). Not saying that'll happen, but the stratosphere right now is one indicator that's not conducive to sustained blocking.

70mb9065.gif

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Yeah - that's the future, but let's talk about what we've seen so far the month of November, and that's a very cold stratosphere from 1mb down through 70mb.

According to the correlations, this would argue for a +AO Dec (based upon only the stratosphere). Not saying that'll happen, but the stratosphere right now is one indicator that's not conducive to sustained blocking.

70mb9065.gif

Jeeze, it's worse than last year, if only slightly.

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Yeah - that's the future, but let's talk about what we've seen so far the month of November, and that's a very cold stratosphere from 1mb down through 70mb.

According to the correlations, this would argue for a +AO Dec (based upon only the stratosphere). Not saying that'll happen, but the stratosphere right now is one indicator that's not conducive to sustained blocking.

70mb9065.gif

I think we're at a point though where we have to combine those observations with the actual patterns we are seeing. And it's clear that this fall has shown a much greater tendency towards high latitude blocking than last fall, and there is often a correlation between blocky falls and the following winter.

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The "top-down" processes are even more favorable for a cold stratosphere this winter compared to last. However, the bottom-up processes are way different and that's why we're going to see a wave 2 response and possible (probable?) vortex split next week.

while I believe the stratsophere sometimes leads the AO phase. The correlation is only in the .40 to .50 range which when squared says way more of the variance is explained by other factors than merely the stratosphere. If a warming event takes place and the ep flux is pointed in the right direction, then the correlation is probably much higher but the bottom up approach certainly works at time.

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Warming of the Asian stratosphere is already evident, although it remains slightly cold overall. It looks like some major warming is forecasted.

Anybody know what is causing this? Mountain torque? Ozone? HM?

Spike in the GLAAM due mainly to North American sourced mountain torque. Currently traversing phase 5 of the GLAAM phase diagram and headed for some of the highest AAM anomalies in quite some time. This usually translates to a period of cold weather for the eastern 2/3 of the CONUS...which is forecasted. This might spill unto the stratosphere and allow for a period of high latitude ridging.

gwo_40d.gif

gltaum.90day.gif

glaam.sig1-21.seascyc.90day.gif

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Winds in the 30-50mb zone are progged to weaken some as we head into the beginning of December, possibly owing to the wave 2 stuff going on right now. A nice split also progged at 70mb, although EP flux while less equatorial...still point in that direction.

Stratospheric EP flux is probably still equatorial, but that's to be expected since it's a bottom-up event unraveling...tropospheric EP flux is probably averaging into the poleward end of things lately.

ep_12z_tr_nh.gif

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Stratospheric EP flux is probably still equatorial, but that's to be expected since it's a bottom-up event unraveling...tropospheric EP flux is probably averaging into the poleward end of things lately.

ep_12z_tr_nh.gif

Those have looked better as of late. There are still some mixed signals, but it does appear we are trying to at least give it a good punch to the gut from the bottom up. I noticed the euro ensembles swing around some very warm anomalies at 50mb right over the north pole and practically split the vortex into two.

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North Atlantic blocking will occur next week bringing below average temps first to western Europe (UK, western France, Spain) then the cold will spread east into central and eastern Europe during the first week of DEC. Could even have some wintery weather across the UK and parts of northern Europe during the upcoming cold snap... it's likely the North Atlantic remains blocked into the second week of DEC... the forecast of the AO index continues to plunge in the coming days as well...could be lots of interesting weather upcoming across the northern hemisphere as the tropospheric polar vortex (jet stream) weakens... it would also appear we're starting the onset of stratospheric warming and a disruption of the stratospheric polar vortex, however, it's also likely the impacts of a SSW event won't be felt at the surface for several weeks down the road...

ao.sprd2.gif

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You mean the final 2 months of winter. The lag is apparent.

No, the first 2 months. The lag is only a couple weeks which takes us to Dec 7, and the AO is already negative anyways and forecasted to remain negative. There's very little correlation between the late November stratosphere and the February AO. The vortex often reestablishes before then. The correlation is to Dec and Jan.

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