CoastalWx Posted January 17, 2012 Share Posted January 17, 2012 I referenced the 12z GEFS for fair comparison with the 12z EC, but your post illustrates what I described with the GEFS. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 This morning, the PNA had fallen to -0.603. That places the current pattern in an area in which a cluster of 6" or greater snowstorms occurred in Seattle (ENSO Region 3.4 anomalies: -1.0°C to -0.5°C; PNA: -1.25 to -0.50). At this time, I believe it is reasonable to estimate that Seattle will receive total snowfall of 6"-12" for the 1/17-19/2012 timeframe. As the storms responsible for excessive precipitation along the West Coast move eastward, there will be a growing risk of a severe weather outbreak in the warm sector in parts of the central and especially southern Plains. In the meantime, the AO has gone negative. However, it is not sufficiently negative to overwhelm the pattern, so cold shots will remain transient in the East with some hit-or-miss opportunities for snow. The final week of January still looks to be warmer than average as a whole. The ECMWF ensembles continue to forecast the MJO in Phase 4 (low amplitude) toward the end of January. Link to comment Share on other sites More sharing options...
Srain Posted January 17, 2012 Share Posted January 17, 2012 As Don mentioned, the severe weather event potential increases for early next week and the 00Z Euro continues to advertise a more southerly track ~vs~ the GFS that suggests a Central Plains solution. As we have seen since November, the more southerly solution has been the favored track in a zonal flow pattern and my hunch is that will be what we eventually see for next Sunday-Wednesday. It appears we will have a couple of major weather headlines with the heavy rains/snowy pattern along the West Coast and a potential wide spread severe weather event early next week in the warm sector across the Southern Plains and Lower Mississippi Valley. Link to comment Share on other sites More sharing options...
wxmx Posted January 17, 2012 Share Posted January 17, 2012 I am enjoying this current warming: It's an impressive warming in the upper stratosphere, but it looks like a no-propagator (new word): Fig 1. Current analysis (Yesterday's really) Anomalies in the -50s m/s are impressive...but Fig 2. ...they look to weakly propagate in the opposite direction we want. In the meantime, the mid stratosphere PV looks like will be strengthening...though, not as strong as it was earlier in the season...by day 10 the whole column weakens a bit. I still think the warming will help down the road in February, but it will need help from tropical forcing, IMO...and there will probably won't be a sustained period of high latitude ridging...maybe 2-3 weeks tops. The good news is that it will probably coincide with the climo high for snow in the east coast. Link to comment Share on other sites More sharing options...
bluewave Posted January 17, 2012 Share Posted January 17, 2012 The PNA is having a tough time sustaining much of a negative phase for a La Nina year. The GFS is backing off some of it's solutions from last week. La Nina DJF composite Winter so far Last week Today Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 From the National Weather Service Winter Storm Warning for the Seattle Area: URGENT - WINTER WEATHER MESSAGE NATIONAL WEATHER SERVICE SEATTLE WA 500 AM PST TUE JAN 17 2012 .SNOW SHOWERS...LOCALLY HEAVY...WILL CONTINUE TODAY. AFTER A BREAK THIS EVENING...A MAJOR WINTER STORM WILL MOVE INTO WESTERN WASHINGTON FROM THE SOUTH LATE TONIGHT AND WEDNESDAY... * TIMING...TODAY THROUGH WEDNESDAY EVENING. * SNOW ACCUMULATIONS...ANOTHER 1 TO 2 INCHES IS POSSIBLE TODAY IN SHOWERS. SIGNIFICANT SNOW ACCUMULATIONS ARE EXPECTED LATE TONIGHT THROUGH WEDNESDAY EVENING WITH ANOTHER 5 TO 10 INCHES OF NEW SNOW POSSIBLE BY WEDNESDAY EVENING. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 The PNA is having a tough time sustaining much of a negative phase for a La Nina year. The GFS is backing off some of it's solutions from last week. That might well be temporary. Time will tell. Statistically, odds favor a PNA- for February. Since 1950, there were 14 years in which the PDO was -1.000 or below in February: 1950, 1951, 1954, 1955, 1956, 1962, 1965, 1971, 1972, 1974, 1976, 1979, 1989, and 2009. 13/14 (93%) of those cases saw the PNA average < 0. Just one case (1971) saw the PNA average > 0. Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 17, 2012 Share Posted January 17, 2012 That might well be temporary. Time will tell. Statistically, odds favor a PNA- for February. Since 1950, there were 14 years in which the PDO was -1.000 or below in February: 1950, 1951, 1954, 1955, 1956, 1962, 1965, 1971, 1972, 1974, 1976, 1979, 1989, and 2009. 13/14 (93%) of those cases saw the PNA average < 0. Just one case (1971) saw the PNA average > 0. How many of those had a +PNA/+AO avg in December? Link to comment Share on other sites More sharing options...
Lee Posted January 17, 2012 Share Posted January 17, 2012 The PNA is having a tough time sustaining much of a negative phase for a La Nina year. The GFS is backing off some of it's solutions from last week. La Nina DJF composite Winter so far Last week Today Good point. I think it's pretty clear the main reason this winter has been a disappointment for cold/snow lovers in the East is what transpired at the higher Lats.; the +AO/NAO. Not so much La nina as some want to think. Of course, who knows, maybe what went on @ higher lats had an affect on where the HP set up in the Pacific and had the AO not been so rediculously positve a typical La nina setup there may have been the case. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 How many of those had a +PNA/+AO avg in December? 3 of them: 1954-55, 1975-76, and 1988-89. Link to comment Share on other sites More sharing options...
bluewave Posted January 17, 2012 Share Posted January 17, 2012 That might well be temporary. Time will tell. Statistically, odds favor a PNA- for February. Since 1950, there were 14 years in which the PDO was -1.000 or below in February: 1950, 1951, 1954, 1955, 1956, 1962, 1965, 1971, 1972, 1974, 1976, 1979, 1989, and 2009. 13/14 (93%) of those cases saw the PNA average < 0. Just one case (1971) saw the PNA average > 0. It will be interesting to see if the PNA will be able to defy the odds going through February. It's hard to find a La Nina winter without at least one month with a negative PNA on average. My guess is that If the ridge east of the Caspian persists, the PNA will be able to at least break even or be positive for February. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 It will be interesting to see if the PNA will be able to defy the odds going through February. I agree. I suspect that the prolonged strongly negative PDO will take a toll and reduce prospects for a PNA+, but we'll see what happens. Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 17, 2012 Share Posted January 17, 2012 3 of them: 1954-55, 1975-76, and 1988-89. Thanks. Seems like good analogs are hard to come by this year. Judging by the +AO from August onward this year, occuring in a -PDO base phase which is exceedingly rare, do you think the statistical method is viable? I think it might have to do with the lack of a QBO signal until very recently, years that have this QBO signal seem to be 1967/68, 1988/89, 1999/00. 1999/00 and 1967/68 were in -PDO base periods. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 Seems like good analogs are hard to come by this year. Judging by the +AO from August onward this year, occuring in a -PDO base phase which is exceedingly rare, do you think the statistical method is viable? I think it might have to do with the lack of a QBO signal until very recently, years that have this QBO signal seem to be 1967/68, 1988/89, 1999/00. 1999/00 and 1967/68 were in -PDO base periods. For having a sense of probabilities e.g., concerning the February PNA, there's some utility but subject to uncertainty. For some months, the relationship is inconclusive e.g., summer. For trying to pin down a month-by-month forecast for Winter 2011-2012 back from the fall, probably not. The sample size is way too small. Using various scenarios in which key variables are tweaked can help, if there's a consistent theme. Nevertheless, seasonal forecasting is still an exercise with a high degree of error. Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 17, 2012 Share Posted January 17, 2012 For having a sense of probabilities e.g., concerning the February PNA, there's some utility but subject to uncertainty. For some months, the relationship is inconclusive e.g., summer. For trying to pin down a month-by-month forecast for Winter 2011-2012 back from the fall, probably not. The sample size is way too small. Using various scenarios in which key variables are tweaked can help, if there's a consistent theme. Nevertheless, seasonal forecasting is still an exercise with a high degree of error. Thanks. Do you have any thoughts on the GEFS ensembles consistantly pegging a -NAO in the longer range? I don't know much about the GFS and it's biases, but in the relatively short time period I have been tracking wx models I can't recall seeing pressures progged so low over the entire NH on the Ensembles and OP in a weak Nina. Could this be model artifact? I'm not sure if it even means anything to our sensible wx but I found it interesting and it seems to be trending deeper. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 Thanks. Do you have any thoughts on the GEFS ensembles consistantly pegging a -NAO in the longer range? I don't know much about the GFS and it's biases, but in the relatively short time period I have been tracking wx models I can't recall seeing pressures progged so low over the entire NH on the Ensembles and OP in a weak Nina. A sustained period of a negative NAO is plausible in February. The GEFS tends to rush turning points, so one has to be cautious. Having said that, one should not automatically assume that an NAO- means a cold February in the East. One La Niña case that featured warmth in the East and cold in the West was February 1956. Link to comment Share on other sites More sharing options...
JSchwake28 Posted January 17, 2012 Share Posted January 17, 2012 That might well be temporary. Time will tell. Statistically, odds favor a PNA- for February. Since 1950, there were 14 years in which the PDO was -1.000 or below in February: 1950, 1951, 1954, 1955, 1956, 1962, 1965, 1971, 1972, 1974, 1976, 1979, 1989, and 2009. 13/14 (93%) of those cases saw the PNA average < 0. Just one case (1971) saw the PNA average > 0. Don, where do you get all your historical statistics for the PNA, PDO, and such indices? Link to comment Share on other sites More sharing options...
tnweathernut Posted January 17, 2012 Share Posted January 17, 2012 A sustained period of a negative NAO is plausible in February. The GEFS tends to rush turning points, so one has to be cautious. Having said that, one should not automatically assume that an NAO- means a cold February in the East. One La Niña case that featured warmth in the East and cold in the West was February 1956. If there is a winter that could yield warmth in the east with a - NAO, this is probably it. Thanks for all your imput, time will give us an answer shortly. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 Don, where do you get all your historical statistics for the PNA, PDO, and such indices? Monthly and daily statistics for the AO, NAO, and PNA: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml Just click on each index and one can then find references to monthly and daily data PDO: http://jisao.washington.edu/pdo/PDO.latest Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 17, 2012 Share Posted January 17, 2012 Verification: Below is the composite temperature anomaly map posted for the January 8-15, 2012 timeframe (Message #342) based on the following criteria: All cases in the January 5-20 period (1950-2011) during which the ENSO Region 3.4 anomaly was -1.50°C to -0.70°C, the AO was 0 to +2.00, and the PNA was -1.00 to +0.50: The outcome for the January 8-15, 2012 timeframe was: In short, the warmth was fairly widespread for yet another week in January. Alaska remained unseasonably cold. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 18, 2012 Share Posted January 18, 2012 Today and this evening saw more unseasonable warmth in the East after a cold air mass retreated. The following are 10 pm temperatures/daily highs/normal highs for the date for select cities: Albany: 10 pm: 42°; Daily high: 42°; Normal high: 30° Baltimore: 10 pm: 57°; Daily high: 59°; Normal high: 41° Boston: 10 pm: 45°; Daily high: 45°; Normal high: 35° Charleston: 10 pm: 59°; Daily high: 70°; Normal high: 59° Charlotte: 10 pm: 56°; Daily high: 66°; Normal high: 51° Concord: 10 pm: 36°; Daily high: 39°; Normal high: 30° Burlington: 10 pm: 39°; Daily high: 39°; Normal high: 27° Harrisburg: 10 pm: 52°; Daily high: 54°; Normal high: 37° Hartford: 10 pm: 42°; Daily high: 42°; Normal high: 34° New York City: 10 pm: 51°; Daily high: 51°; Normal high: 38° Newark: 10 pm: 49°; Daily high: 49°; Normal high: 38° Norfolk: 10 pm: 62°; Daily high: 69°; Normal high: 48° Philadelphia: 10 pm: 54°; Daily high: 55°; Normal high: 40° Portland, ME: 10 pm: 39°; Daily high: 39°; Normal high: 31° Providence: 10 pm: 47°; Daily high: 47°; Normal high: 37° Richmond: 10 pm: 60°; Daily high: 62°; Normal high: 47° Washington, DC: ...DCA: 10 pm: 57°; Daily high: 59°; Normal high: 43° ...IAD: 10 pm: 55°; Daily high: 58°; Normal high: 42° Wilmington, DE: 10 pm: 55°; Daily high: 55°; Normal high: 40° Link to comment Share on other sites More sharing options...
HM Posted January 18, 2012 Share Posted January 18, 2012 The warming that's progagted down to 500mb, that's causing the ridge to develop over Alletiuans and Bering Straight right now. Instead of spread over the NAO regions, this ridge forecast by the models retrograde into Central Siberia. You're, to some extent, simplifying a more complicated process. However, your point is correct when put into these terms: A stratospheric warming doesn't guarantee a -NAO but it certainly can help when in tandem with something tropospheric, e.g. a MJO wave. This is why everyone thinks the stratosphere is overrated this year but was underrated in 2005-06 (a rarer beast). But the reflection at 500mb that you pointed out is to a degree related to the recent warmings but not directly from "downwelling" per se. It was a more cause/effect chain of events that lead to those 500mb anomalies (also working in tandem with the extended Pacific Jet at the time). Link to comment Share on other sites More sharing options...
Damage In Tolland Posted January 18, 2012 Share Posted January 18, 2012 Euro ensembles destory the Alaskan vortex day 10 and beyond and we have some nice ridging in Greenland. Signs are growing stronger for a colder/strormy end of Jan and Feb for the entire east coast Link to comment Share on other sites More sharing options...
Srain Posted January 18, 2012 Share Posted January 18, 2012 Euro ensembles destory the Alaskan vortex day 10 and beyond and we have some nice ridging in Greenland. Signs are growing stronger for a colder/strormy end of Jan and Feb for the entire east coast The bigger threat in the near term will be the severe potential near the 24th-25th for the S Plains/Lower Mississippi Valley... Link to comment Share on other sites More sharing options...
am19psu Posted January 18, 2012 Author Share Posted January 18, 2012 Not to mention I think it's a bit premature to say "Signs are growing stronger for a colder/strormy end of Jan and Feb for the entire east coast" given the expected EPO regime and the Atlantic ridging being mostly located in the eastern part of the basin in the ensembles. Link to comment Share on other sites More sharing options...
HurricaneJosh Posted January 18, 2012 Share Posted January 18, 2012 Not to mention I think it's a bit premature to say "Signs are growing stronger for a colder/strormy end of Jan and Feb for the entire east coast" given the expected EPO regime and the Atlantic ridging being mostly located in the eastern part of the basin in the ensembles. Heartbreaka. Link to comment Share on other sites More sharing options...
buckeye Posted January 18, 2012 Share Posted January 18, 2012 Not to mention I think it's a bit premature to say "Signs are growing stronger for a colder/strormy end of Jan and Feb for the entire east coast" given the expected EPO regime and the Atlantic ridging being mostly located in the eastern part of the basin in the ensembles. just keep'n it real... Link to comment Share on other sites More sharing options...
am19psu Posted January 18, 2012 Author Share Posted January 18, 2012 Heartbreaka. To be fair (and I know you're just trolling me), I don't have a good feel for the pattern post Feb 1. There will be a MT event at the end of Jan that will disrupt the polar vortex again and tropical forcing appears to be weak at the start of Feb, too. That could end up with a -EPO/+PNA pattern which keeps winter across the Plains, not the East Coast, and is similar to Don S' forecast. On the other hand, if we do see significant ridging up into the Davis Straits, it could portend better chances for the East Coast. It's worth noting that the Euro weeklies have remained warm through Valentine's Day, though Weeks 3 and 4 should always be taken with a grain of salt Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 18, 2012 Share Posted January 18, 2012 Euro ensembles destory the Alaskan vortex day 10 and beyond and we have some nice ridging in Greenland. Signs are growing stronger for a colder/strormy end of Jan and Feb for the entire east coast I hope so, but am skeptical until there is strong run-to-run continuity on this idea. Both the GFS and ECMWF ensembles have forecast a number of pattern changes that didn't work out. Instead, what one saw were short-lived cooler periods. Recent warming in ENSO Region 1+2 while Region 3.4 has remained relatively stable increases the risk of a February 1999 ENSO situation. February 1999 also had a neutral to somewhat positive AO and neutral PNA (monthly averages). Among the dates listed on the GFS ensembles' 11-day objective analogs centered around 1/29/2012 is 1/25/1999. The ECMWF ensembles also show the MJO finally escaping the low amplitude circle and emerging in Phase 5 at the end of January. Phase 5 is typically mild in the East: So my guess at this point is that the ECMWF ensembles might be hinting at some opportunities for cold shots, but much more evidence needs to become available for me to buy into a cold February scenario. Having said that, I do not believe February 2012 will be a February 1999-style disaster. Something similar to February 1956, but with more expansive warm anomalies seems to be more likely, but that's not yet cast in concrete. Again, this is just my opinion. I could well be wrong (and I hope so). Link to comment Share on other sites More sharing options...
usedtobe Posted January 18, 2012 Share Posted January 18, 2012 I'd also be careful about jumping onto a pattern change for the east even if the AO continues to stay negative unless it goes strongly negative like it did last year. February la ninas typically are warmer than normal and a negative AO with a la nina gives you something like this tempwise. Better than we've had but around normal for most of us, if the AO rises to near zero then temps get warm except across the extreme northern plains. Right now I'd lean towards a compromise between the neutral and negative composites even though I think the AO will be negative more than neutral. Link to comment Share on other sites More sharing options...
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