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Pattern February Discussion Part II

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pcbjr said:
Webb - Very informative and thanks! I've been saying that the Pac was the driver and you have provided some in-depth analysis as to the case!
PS - The graphics really assist in understanding - thanks for including those, BTW!
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I really appreciate it, yea I was just trying to forge another connection between how the tropical pacific responded to alterations in the extratropical stratosphere, emphasizing the two-way interaction amongst the two.

You can see this stratosphere - tropical tropospheric/MJO connection in action nicely here.
http://www.cpc.ncep.noaa.gov/products/intraseasonal/temp10anim.shtml

Pay very close attention to the area in/around the Maritime Continent, note how it cooled anomalously several degrees kelvin within several days after the initiation of the sudden stratospheric warming event in the high-latitude arctic.
 

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Webberweather53 said:
I can’t believe I didn’t catch the mid-latitude SSW > tropical convection/MJO connection earlier… An ongoing sudden stratospheric warming event (SSWE) induced via wave 2 polar vortex split, w/ simultaneous upper level ridging over the far North Atlantic and North Pacific is potentially contributing to the initiation of an Madden Julian Oscillation (MJO) event in the Maritime Continent and far western Pacific. The stratospheric warming event aids in triggering the MJO event via enhanced wave driving in the mid-latitudes and a stronger than normal meridional overturning circulation. The invigorated meridional circulation induces large-scale upwelling in the near-equatorial stratosphere and upper troposphere, and is augmented by mass and water-vapor convergence in the lower troposphere. This leads to local cooling in the upper troposphere and stratosphere, thus altering (lowering) the static stability of the upper troposphere such that a kelvin-wave like response with deep convection in the tropics is generated. This Kelvin Wave like response and deep tropical convection triggered in part by the high latitude SSWE can also influence the probability of sudden stratospheric warming events by modulating the placement, intensity, and frequency of mid-latitude rossby waves and wave trains which upwell near the stratospheric surf zone and deposit their momentum onto the mean background flow (which envelopes the wintertime polar vortex). Therefore, although the stratosphere and troposphere are generally referred to as separate entities with their own quasi-independent internal variability, they are actually tightly coupled, and it’s paramount to closely monitor both in order to increase the accuracy and lead time of medium and long range weather forecasts.

You can see the tropical stratosphere respond relatively quickly following the initiation of warming in the mid-upper stratosphere, with fairly significant cooling occurring over the equator... In short, this cooling of the lower stratosphere and upper troposphere induced by the mid-latitude stratospheric warming event and enhanced meridional circulation associated with it decreased the stability of the troposphere, helping to instigate ascent and convection in the troposphere. Hence, a few days later, to no surprise, an MJO event developed in the Maritime Continent and Western Pacific. We also had simultaneous stratospheric warming events in the northern and southern hemispheres earlier this fall aid in the instigation of a series of CCKWs and MJO events over the Maritime Continent and Western Pacific. Interesting huh?...

20S-0S longitudinal average temperature-height cross section time series. Note the downward propagation of negative temperature anomalies from the upper stratosphere to the lower stratosphere and upper troposphere in conjunction with the SSWE occurring simultaneously in the arctic...
View attachment 17

Zonally averaged 100mb (lower stratosphere) latitude-T time series. Note the cooling near the equator that followed the stratospheric warming in the high-latitudes of the northern hemisphere...
View attachment 18


Here's a relatively simple "hand-wavy" depiction of the Brewer-Dobson Circulation so you can visualize some of the physical processes and connections linking the mid-latitude stratospheric warming event to the recent development of an MJO pulse and CCKW couplet in the tropics... Increased descent in the mid-high latitudes needs to be compensated for by increased upwelling from the tropical troposphere, which leads to the excitation of tropical convection...

image001.jpg


For more information on the stratospheric warming - tropical tropospheric convection, see:
http://onlinelibrary.wiley.com/doi/10.1029/2006GL028744/full
https://www.jstage.jst.go.jp/article/sola/7/0/7_0_197/_pdf
http://journals.ametsoc.org/doi/pdf/10.1175/JCLI3251.1
http://www.ann-geophys.net/34/331/2016/angeo-34-331-2016.pdf

The combination of a Pacific MJO event and intrinsic variability within the high latitude north Pacific, wherein classic retrogression of a northeast Pacific blocking ridge, will lead to the formation of an unusually deep Aleutian-Gulf of Alaska vortex by next week and into at least mid-February. Such a pattern is often characterized by an extensive, eastward displaced, and stronger than normal pacific jet with the majority of the North America continent (except perhaps for the southern tier of the US) usually being flooded with mild, pacific air, and a robust western hemisphere subtropical jet.

View attachment 19

Regression of the MEI index onto northern hemisphere geopotential heights in February
View attachment 20

Hence, higher than normal risks for above normal precipitation and seasonable temperatures can be expected in the southeastern US for mid-February. Thereafter uncertainty remains with regards to the downward propagation of anomalous stratospheric circulation anomalies in the northern hemisphere exciting a potentially significant high-latitude blocking episode later in the month of February and into early March. The continuation of the MJO pulse from the central Pacific into the Indian Ocean, and a major reshuffling of the equatorial pacific with the possibility for the formation of a downwelling oceanic kelvin wave in the wake of the ongoing MJO pulse. It’s worth mentioning that, in the past 150 years of the observational record, we have yet to observe an El Nino event in year +2 following the culmination strong-super El Nino event, if an El Nino somehow developed next year it would be unprecedented since at least the early 19th century. Oth, this response shouldn’t be too surprising given AGW is likely allowing the Indo-West Pacific warm pool to recover more quickly than the it used to, and the observational record is too short to observe and analyze the full spectrum of ENSO variability…
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Awesome work! But, for us dumb people, does that mean that Alabama is going to get snow or not? ;)o_O
 
Here's to hoping we can get the mjo into P2...P1 isn't that good

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Yeah p8 is a given but as webber pointed out above there is going to be too much of a GoA low and it's probably going to verify warmer than Feb mjo p8 composites

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SD said:
Yeah p8 is a given but as webber pointed out above there is going to be too much of a GoA low and it's probably going to verify warmer than Feb mjo p8 composites

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absolutely agree (and not just 'cause it's Webb - although as I said somewhere else earlier today - he surely crystallizes my thoughts in a way I never could) - that damn Pac has been a fly in the ointment most of the winter ... other dynamics besides MJO (as Webb better articulates than I ever could)
 
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SD said:
Yeah p8 is a given but as webber pointed out above there is going to be too much of a GoA low and it's probably going to verify warmer than Feb mjo p8 composites

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Why can't we get something to screw up p1 like the Gulf of Alaska low screwing up p8 so mjo p1 could verify colder than composites lol

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Update to GEFS based PNA forecast: the bias adjusted forecast peak is even higher today and one day later. It is near +1.95 for the peak on 2/15! Reminder: there have been only three days in all of met winter since 1950 with a PNA reaching 2.00 meaning that that has been about a one in 2,000 day occurrence in winter!! All three were in either Feb. 1968 or in Feb. 1983.
 
GaWx said:
Update to GEFS based PNA forecast: the bias adjusted forecast peak is even higher today and one day later. It is near +1.95 for the peak on 2/15! Reminder: there have been only three days in all of met winter since 1950 with a PNA reaching 2.00 meaning that that has been about a one in 2,000 day occurrence in winter!! All three were in either Feb. 1968 or in Feb. 1983.
Click to expand...

The mid 80s were cold and dry.


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Next potential threat?? I'm still interested in midmonth due to the combo of an extremely rare +PNA peak (strong PNA's average solidly cold in the SE though a few times they averaged near normal; also, there is a good correlation between +PNA and major SE snowstorms), a very strong Phase 8 MJO (strong phase 8 has averaged cold in the SE though not always cold..sometimes near normal), and waning -AO. Fwiw, (I fully realize very little at this point this far away, especially since I'm talking about the horrendously cold biased GFS suite) the 0Z GFS and more importantly, the 0Z GEFS are suggesting a Miller A threat for ~2/16-7, which would be around the tail end of this trifecta as well as peak climo (2nd week into the 3rd week of Feb). I counted about 6 members having a Miller A crossing FL.

Oddly enough, as cold biased as is the GFS suite, it is actually slightly -PNA biased! So, when it shows a very strong +PNA, it has a very high chance of verifying. So, I can assume with high confidence that we'll have a very strong +PNA 2/13-17. So, knowing that along with the relatively reliable EPS prog for a very strong phase 8 (GEFS agrees) tells me that things are liable to get quite interesting then. We already have the AO plunging. So, the strong -AO prior to then is almost a given. Even if it is already waning, a strong -AO just prior is often enough to do its dirty work.
 
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GaWx said:
Next potential threat?? I'm still interested in midmonth due to the combo of an extremely rare +PNA peak (strong PNA's average solidly cold in the SE though a few times they averaged near normal; also, there is a good correlation between +PNA and major SE snowstorms), a very strong Phase 8 MJO (strong phase 8 has averaged cold in the SE though not always cold..sometimes near normal), and waning -AO. Fwiw, (I fully realize very little at this point this far away, especially since I'm talking about the horrendously cold biased GFS suite) the 0Z GFS and more importantly, the 0Z GEFS are suggesting a Miller A threat for ~2/16-7, which would be around the tail end of this trifecta as well as peak climo (2nd week into the 3rd week of Feb). I counted about 6 members having a Miller A crossing FL.

Oddly enough, as cold biased as is the GFS suite, it is actually slightly -PNA biased! So, when it shows a very strong +PNA, it has a very high chance of verifying. So, I can assume with high confidence that we'll have a very strong +PNA 2/13-17. So, knowing that along with the relatively reliable EPS prog for a very strong phase 8 (GEFS agrees) tells me that things are liable to get quite interesting then. We already have the AO plunging. So, the strong -AO prior to then is almost a given. Even if it is already waning, a strong -AO just prior is often enough to do its dirty work.
Click to expand...
giphy.gif
your such a superhuman, makes me happy
 
GaWx said:
Next potential threat?? I'm still interested in midmonth due to the combo of an extremely rare +PNA peak (strong PNA's average solidly cold in the SE though a few times they averaged near normal; also, there is a good correlation between +PNA and major SE snowstorms), a very strong Phase 8 MJO (strong phase 8 has averaged cold in the SE though not always cold..sometimes near normal), and waning -AO. Fwiw, (I fully realize very little at this point this far away, especially since I'm talking about the horrendously cold biased GFS suite) the 0Z GFS and more importantly, the 0Z GEFS are suggesting a Miller A threat for ~2/16-7, which would be around the tail end of this trifecta as well as peak climo (2nd week into the 3rd week of Feb). I counted about 6 members having a Miller A crossing FL.

Oddly enough, as cold biased as is the GFS suite, it is actually slightly -PNA biased! So, when it shows a very strong +PNA, it has a very high chance of verifying. So, I can assume with high confidence that we'll have a very strong +PNA 2/13-17. So, knowing that along with the relatively reliable EPS prog for a very strong phase 8 (GEFS agrees) tells me that things are liable to get quite interesting then. We already have the AO plunging. So, the strong -AO prior to then is almost a given. Even if it is already waning, a strong -AO just prior is often enough to do its dirty work.
Click to expand...
Don't forget to mention the GFS itself has had a low show up around that time frame as well, but warm and a little too far north for us to get snow. At least it is a sign for the pattern to look better, hopefully.
 
GaWx said:
Next potential threat?? I'm still interested in midmonth due to the combo of an extremely rare +PNA peak (strong PNA's average solidly cold in the SE though a few times they averaged near normal; also, there is a good correlation between +PNA and major SE snowstorms), a very strong Phase 8 MJO (strong phase 8 has averaged cold in the SE though not always cold..sometimes near normal), and waning -AO. Fwiw, (I fully realize very little at this point this far away, especially since I'm talking about the horrendously cold biased GFS suite) the 0Z GFS and more importantly, the 0Z GEFS are suggesting a Miller A threat for ~2/16-7, which would be around the tail end of this trifecta as well as peak climo (2nd week into the 3rd week of Feb). I counted about 6 members having a Miller A crossing FL.

Oddly enough, as cold biased as is the GFS suite, it is actually slightly -PNA biased! So, when it shows a very strong +PNA, it has a very high chance of verifying. So, I can assume with high confidence that we'll have a very strong +PNA 2/13-17. So, knowing that along with the relatively reliable EPS prog for a very strong phase 8 (GEFS agrees) tells me that things are liable to get quite interesting then. We already have the AO plunging. So, the strong -AO prior to then is almost a given. Even if it is already waning, a strong -AO just prior is often enough to do its dirty work.
Click to expand...

Oh the if onlys of this world. Watching last night's game summed up our winter. I counted about the same number of A Millers on the 06z GEFS as well. Until I see the white stuff falling from the sky I trust no model but it is good to see the +PNA showing up.


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