blizzard1024 Posted January 18, 2013 Share Posted January 18, 2013 So far, as of yesterday in Binghamton NY we are in the top 5 warmest winters. If you look at the indices like the AO, and NAO you don't see anything that is strikingly warm for the northeast. The PNA has been mostly negative especially in December which explains the warmth but it switches right at the time when we turned cold in late December and remained so until the warm up in January. But, it really didn't get that cold during this "colder" period. This morning we had our second day below 10F as a minimum at Binghamton NY!!! That is nuts! We have been constantly above normal in our minimums. I know the models at present are finally predicting bitter cold, but for all the blocking we have had, this winter still reminds me a lot of last year's so far temperature-wise. We have managed more snow thank god. But the persistent feature has been the "La-Nina-ish" southeast ridge that just seems to be popping up anytime a storm comes into the Pacific coast. The EPO for December was at .12 which is slightly positive. What is causing this southeast ridge like last winter? I brought this up back in late November and pretty much ticked off a lot of people. One member wanted my MET tag removed!! But I was correct in my analysis that if the southeast ridge remained, no matter what happens to our north, blocking vs no blocking, this would kill winter unless it breaks down. Below is the graph of some of the indices and a map of the 500 mb height anomalies from December 1-January 14. Notice how the positive height anomalies in the southeast connect to the positive anomalies around Greenland where there has been blocking. This is a massive reverse PNA pattern!!! Anyone know what forces a reverse PNA? I suspect tropical convection but am not 100% up on this stuff. This is a winter killer in the east no matter what the EPO, NAO, or AO does. I hope it changes and this upcoming cold shot is not transient! Link to comment Share on other sites More sharing options...
uncle W Posted January 18, 2013 Share Posted January 18, 2013 The pna was brought up a few days ago and I started looking at the coldest January's for NYC and what the pna was... 1957...-pna all month... 1961...+pna all month... 1963...-/+ colder second half... 1965...-/+/mixed 1968...-/+/- 1970...m/+/- 1971...-pna all month... 1976...-/+ colder second half... 1977...+pna all month... 1978...+pna all month... 1981...+pna all month... 1982...+pna most of the month... 1984...+/-/+ 1985...+pna 1988...+pna most of the month... 1994...-pna most of the month...ends+... 1996...+/- 2000...-pna most of the month...ends+... 2003...+pna all month... 2004...+pna most of the month...Starts-... 2005...-/+ 2009...-/+/- 2011...+pna most of the month... 1957 and 1971 had a minus pna all month and we had two very cold January's...Some of the years like 2005 and 1963 had colder second halfs when the pna went +...1996 was cold the first half when the pna was + but thawed the second half when the pna went-...there are many more + months that were cold... Link to comment Share on other sites More sharing options...
icebreaker5221 Posted January 18, 2013 Share Posted January 18, 2013 Anyone know what forces a reverse PNA? I suspect tropical convection but am not 100% up on this stuff. This is a winter killer in the east no matter what the EPO, NAO, or AO does. I hope it changes and this upcoming cold shot is not transient! No matter what the EPO, NAO or AO does? You're making it sound like the indices have been great yet we've still had a persistent southeast ridge. That has not been the case. The only stretch of significant blocking, i.e. NAO<-1.0 was Dec 10-12, but this was also accompanied by a PNA<0. The only period of PNA>1.0 was during the 1st week in Jan, but this week featured a NAO>0. While it's true that you traditionally get the strongest southeast ridge with -PNA, +NAO, you'll often still get a southeast ridge slightly displaced to the east that still comes into play during a +/+ or a -/-. You also mentioned that the WPO was only slightly positive during Dec, with periods of positive and periods of negative. A -WPO can overcome the southeast ridge, but is much more effective at doing so when accompanied by a negative NAO. That also didn't happen. So, to be honest, this less-than-stellar winter so far is not all that surprising when looking back at the indices. Link to comment Share on other sites More sharing options...
blizzardof96 Posted January 18, 2013 Share Posted January 18, 2013 The negative PDO plays a big part in the long lasting -PNA regime as well as phases 3-6 of the MJO which favour an eastern ridge and western trough. Link to comment Share on other sites More sharing options...
blizzard1024 Posted January 18, 2013 Author Share Posted January 18, 2013 No matter what the EPO, NAO or AO does? You're making it sound like the indices have been great yet we've still had a persistent southeast ridge. That has not been the case. The only stretch of significant blocking, i.e. NAO<-1.0 was Dec 10-12, but this was also accompanied by a PNA<0. The only period of PNA>1.0 was during the 1st week in Jan, but this week featured a NAO>0. While it's true that you traditionally get the strongest southeast ridge with -PNA, +NAO, you'll often still get a southeast ridge slightly displaced to the east that still comes into play during a +/+ or a -/-. You also mentioned that the WPO was only slightly positive during Dec, with periods of positive and periods of negative. A -WPO can overcome the southeast ridge, but is much more effective at doing so when accompanied by a negative NAO. That also didn't happen. So, to be honest, this less-than-stellar winter so far is not all that surprising when looking back at the indices. If we have a persistent reverse PNA it does not matter what the other indices show...ridge on the east coast = bad for winter no matter how you slice it. this is obvious. Link to comment Share on other sites More sharing options...
OSUmetstud Posted January 19, 2013 Share Posted January 19, 2013 we haven't had a lot of real blocking this winter. I mean the AO was negative...but it was mainly ineffective. Seems like a weird thread to start when we are in some real winter weather now lol. We do currently have an -EPO which is mainly responsible for the cold. Also, the PNA is positive currently. Link to comment Share on other sites More sharing options...
OSUmetstud Posted January 19, 2013 Share Posted January 19, 2013 If we have a persistent reverse PNA it does not matter what the other indices show...ridge on the east coast = bad for winter no matter how you slice it. this is obvious. no it's not. We've had plenty of periods in the record where there was cold and snowy conditions during a -EPO/-PNA pattern. See Jan 1994. Link to comment Share on other sites More sharing options...
WXeastern Posted January 19, 2013 Share Posted January 19, 2013 NAO blocking so far this winter has been rather bleh. Look no further than that for the SE ridging Link to comment Share on other sites More sharing options...
blizzard1024 Posted January 19, 2013 Author Share Posted January 19, 2013 no it's not. We've had plenty of periods in the record where there was cold and snowy conditions during a -EPO/-PNA pattern. See Jan 1994. That ridge was well off the east coast with a very strong hudson bay vortex. That also does not look like a reverse PNA to me either. see plot. Link to comment Share on other sites More sharing options...
blizzard1024 Posted January 19, 2013 Author Share Posted January 19, 2013 NAO blocking so far this winter has been rather bleh. Look no further than that for the SE ridging yes. concur. Link to comment Share on other sites More sharing options...
ORH_wxman Posted January 19, 2013 Share Posted January 19, 2013 The most negative PNA December on record was December 2010: Here were the temperature anomalies that month: Link to comment Share on other sites More sharing options...
blizzard1024 Posted January 19, 2013 Author Share Posted January 19, 2013 The most negative PNA December on record was December 2010: Here were the temperature anomalies that month: The most negative PNA December on record was December 2010: Here were the temperature anomalies that month: I guess I need to go back and look at the loading pattern again. I always thought that the heights were higher in the east with a reverse PNA. Nevertheless the ridging in the southeast this year sucks and has kept us mild so far. Link to comment Share on other sites More sharing options...
OSUmetstud Posted January 19, 2013 Share Posted January 19, 2013 I guess I need to go back and look at the loading pattern again. I always thought that the heights were higher in the east with a reverse PNA. Nevertheless the ridging in the southeast this year sucks and has kept us mild so far. The PNA has no calculation of heights across the east in it's calculation. It does of course lead to higher heights in the east, disregarding other factors that can overwhelm it. I just think you're putting way too much stake in it. It's a significant factor, among others. When you have no blocking to go all with a -PNA...it's going to be pretty warm. Link to comment Share on other sites More sharing options...
OSUmetstud Posted January 19, 2013 Share Posted January 19, 2013 The real hardcore dynamical guys would tell you the -PNA and other indices is a result of other more holistic factors, anyway. Link to comment Share on other sites More sharing options...
blizzard1024 Posted January 19, 2013 Author Share Posted January 19, 2013 The real hardcore dynamical guys would tell you the -PNA and other indices is a result of other more holistic factors, anyway. I agree. Indices are a convenient way to put atmospheric patterns into neat "boxes" which we know the atmosphere does not behave that way. good point. Link to comment Share on other sites More sharing options...
cbmclean Posted January 19, 2013 Share Posted January 19, 2013 This looks like a thread with lots of Mets hashing it out with nary a weenie to be seen. I am an interested layman who tries to soak up knowledge on this board. I try not to annoy the Mets with too many questions I know that it is not your job to educate me personally. But I figure you guys/gals might be interested to see the perspective that educated laypeople have and some of the questions that intrigue us. So I am just going to put a few of my questions out there. If any of you feel like answering any of them, then knock yourselves out. In my perceptions there here has been a great expansion in the last 15 years or so in the use by Mets to explain temp anomalies (especially winter temp anomalies) in terms of the various indices mentioned in this thread. At first mostly the AO/NAO, then later the PNA, EPO QBO SO etc. 1. Are these indices "causes" or simply "measurements"? In order to better indicate what I mean, let me use an example from the AO/NAO: Does a negative AO/NAO "cause" blocking, or is it simply the result when you "measure" certain parameters in an atmosphere that is displaying blocking? 2. The AO/NAO have been represented to the public as related, sometimes almost even the same thing. I know that hey are usually, but not always in phase. Are they related in that they measure two aspects of the same phenomenon, or do they measure two separate phenomena that are related in some deeper way? 3. What is the relationship between the PNA and the EPO? I get the impression that they are related, but its not something that is widely disseminated to a public audience. If they are related, then question #2 can be extended to them. 4. Assuming that the PNA and EPO are related, is the AO/NAO couplet related to the PNA/EPO couplet? Of course I know that "related" is somewhat of a broad word. If you go deep enough, everything is related to everything else What I mean is are they strongly coupled in some fashion. To me, they seem to vary with each other somewhat randomly. Sometimes they are both positive, sometimes they are both negative, sometimes they are split one way or the other. 5. I have seen hints this year that the PNA/EPO couplet may be related to the PDO. Would it be accurate (or at least not completely inaccurate) to say that the PNA/EPO and the PDO are manifestations of the same phenomenon, but on different timescale? If so, what about the AMO and the AO/NAO? 5. I don't believe that I have ever heard of the "WPO". I suspect from context that the WPO is an "West Pacific Oscillation". What are its significant effects on North America if any ? Link to comment Share on other sites More sharing options...
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