donsutherland1 Posted February 10, 2015 Author Share Posted February 10, 2015 Severe Cold Returning to the East... Part 1 of 2: So far, the warmth in the West, cold in the East paradigm has generally prevailed through the first nine days of February During the 2/8-9 period, temperatures peaked at 70° in Albuquerque (2/8), 70° in Denver (2/9), and 83° in Phoenix (2/9). Month-to-date anomalies for select cities include: The latest guidance suggests that this paradigm will likely be sustained through at least the next 7-10 days. In fact, the East may be facing the coldest readings of the winter this coming weekend and early next week (see OHWeather's post above for some additional details). The GFS ensembles suggest that temperatures could be 2-3 standard deviations below normal in parts of the region. Below are temperatures associated with the standardized anomalies: Afterward, as the EPO- regime eases and the PNA possibly goes neutral, the cold could ease in the East with reduced warmth in the West. However, it remains to be seen if this would be a temporary situation, as the PDO+ continues to favor a positive PNA. Link to comment Share on other sites More sharing options...
donsutherland1 Posted February 10, 2015 Author Share Posted February 10, 2015 Part 2 of 2: In addition, the AO will likely remain predominantly positive over the next 7-14 days. Hence, significant snowstorm threats will likely favor New England rather than the Mid-Atlantic region, though the possible transitional period between the severe cold and moderation might present an opportunity for a more widespread winter storm. At this point in time, it is very likely that the AO will wind up having had a positive average for the winter. Just to achieve a December-February average of 0, the AO would need to average -2.403 for the remainder of February. The ensembles argue against such an outcome. In contrast, the AO would need to average +0.097 for the remainder of February for a winter average of +0.5. An winter average between +0.50 and +0.75 appears likely. At most, if every remaining day of February were negative (not forecast by the ensembles), 44% of the days during the December-February period would wind up negative. Through today, 31% of the days were negative and 10% of the days had a reading of -1 or below. In contrast, 69% of the days have been positive, 39% had readings of +1 or above and 14% had readings of +2 or above. Finally, from a forecasting standpoint, what will now be a pair of winters where the Snow Advance Index (SAI) and October Pattern Index (OPI) did not perform well, indicates a growing possibility that forecasting the predominant state of the winter AO remains challenging. The EPO-/PNA+ combination has produced sustained cold in the East during January and at least the first half of February in the East (and warmth in the West). The AO+ has resulted in skewed snowfall totals with high amounts across the Great Lakes region into New England and sharply lower amounts south of there. Link to comment Share on other sites More sharing options...
donsutherland1 Posted February 11, 2015 Author Share Posted February 11, 2015 Morning thoughts... With respect to the height of the cold centered around 2/16, the 2/11 0z GFS MEX MOS shows the following coldest readings for select cities: Boston: -3° Bridgeport: -3° New York City: 0° Newark: -1° Philadelphia: 3° Poughkeepsie: -10° White Plains: -5° Link to comment Share on other sites More sharing options...
SnoSki14 Posted February 11, 2015 Share Posted February 11, 2015 Those would be impressive readings for mid January let alone mid February. I wonder if temps will moderate a bit though as they often tend to but the source region favors very cold air. The wind chills could be very impressive as well. Windchills near zero for Sunday during the day are possible. Link to comment Share on other sites More sharing options...
Mike.Ventrice Posted February 13, 2015 Share Posted February 13, 2015 Hi all, thought I'd share some of my thoughts on what could be driving the Feb-early March pattern: http://www.wsi.com/blog/aviation/the-eastern-pacific-ocean-is-now-in-cooling-state-that-should-last-roughly-a-month-or-so-shades-of-winter-2013-2014/ Link to comment Share on other sites More sharing options...
Harry Posted February 14, 2015 Share Posted February 14, 2015 Cannot wait to get rid of that +PNA! That need not show up again for a decade! Link to comment Share on other sites More sharing options...
donsutherland1 Posted February 14, 2015 Author Share Posted February 14, 2015 Morning thoughts... A graph through February 13 to illustrate just how extraordinary the recent snowfall has been in Boston. On January 23, the City had only a paltry 5.5" snowfall for the winter. The following 21 days saw 74.0" fall, bringing seasonal snowfall to 79.5". That makes Winter 2014-15 Boston's 8th snowiest on record. At the same time, Boston's seasonal snowfall surged past the figure to date for 1995-96 when a record 107.6" fell. Link to comment Share on other sites More sharing options...
Isotherm Posted February 18, 2015 Share Posted February 18, 2015 The key for those further south is getting a wave to eject from the southern stream. February 2003 had a +AO/+NAO/+PNA pattern overall. Significant snows can occur in this regime, but it's tough to accomplish with Miller B's at our longitude without downstream blocking. However, Miller A's would work given the amount of cold air available. Often times these features aren't detected until < 5-6 days, and the MJO currently in phase 8 tends to increase the probability of something ejecting, so we'll see. It's a possibility. Both significant February events in 2003 were Miller A's (Feb 7th and 17th). We haven't had much of those this winter, and that is connected to the weaker Nino and poor tropical forcing. However, the MJO now in phase 8 for the first time this season lends some credence to the idea of a potential sern stream wave. As I posted last week, we did in fact see the southern stream wave eject for the 17th, and as a result, much of the Southern US into the Mid and north Atlantic region experienced a significant snowfall. There were totals upwards of 6-8" from central NJ southward through Virginia. This was exactly what needed to happen for the Mid-atlantic to receive a significant snowfall, namely a southern stream wave propagating into a frigid antecedent airmass. This can occur in dominate +NAO / +AO / +PNA regimes as we saw. Link to comment Share on other sites More sharing options...
Isotherm Posted February 19, 2015 Share Posted February 19, 2015 Thoughts on medium-long term pattern: Highlights- [1] An anomalously cold pattern over the next 7-10 days in the Central and Eastern US [2] Transient Eastern warm-up in the beginning of March w/ the development of a more zonal / gradient flow for the first 10 days of March as the tropical forcing worsens, and the +PNA retrogrades into a predominately -WPO/-EPO [3] The maintenance of at least slightly -EPO with blocking poleward up into Alaska will ensure the continuation of cross polar flow into the CONUS. This is probable through at least early March. However, once the +PNA reverses, there should be a tendency for more SE-ridge resistance, and thus a greater probability of warm surges in the Northeast, as well as mixed / rain events. [4] The potential for a complete breakdown of the pattern into a +EPO/+AO/NAO/-PNA regime by mid March; however, this point has low confidence as it's still about 3-4 weeks away. Either way, at that time, mid March is climatologically the end of winter for most of the United States. The tropical forcing pattern over the past 30 days suggests the significant influence that the eastward propagation of tropical convection has had on the mid latitude pattern. Convection has been centered closer to the dateline since late January, and we have seen more eastward progression of MJO waves. These factors have permitted the development and maintenance of a favorable Pacific / NPAC regime for sustained troughiness in the Eastern US, regardless of the AO state. NAO has shown transient perturbations to the negative modality via east based ridging, but the powerful stratospheric vortex has and will continue to prevent the initiation of a prolonged -AO/NAO period through early (and probably mid) March. 200hpa velocity potential in the Pacific indicates a conducive D 1-7 pattern, but we see progressive trends toward worsening tropical forcing in the week 2 and especially week 3 time frame, as convection once again returns to the far western Pacific. This change in tropical forcing will allow the +PNA ridge to collapse, probably by the beginning of March, and we should see a gradual retrogression of the mid level ridge axis in the Pacific. Thus, week 2-3 should be mostly -EPO/-WPO driven, with a cold northern tier of the United States and warmth / spring trying to run up into the Mid Atlantic. Right now, I'm not seeing an "end" to winter (below normal temps and wintry pcpn chances) in the northern and northeastern US through March 10th. It appears the potential pattern collapse for the entire CONUS could be the second week / middle of March. The polar vortex should continue to be strong in the stratosphere, so I see no change to the dominant +NAO/AO states through March. Confidence is fairly high on that front. My main concern is how quickly does the Pacific ridge retrograde, and do we lose the -EPO entirely by March 10th? That is a question that will need to be addressed in a week or so. Until then, there are a few opportunities for wintry precip along w/ cold temperatures. There is a threat this weekend for light-mdt accumulation in the North, and another period to watch later next week. Watch for any phasing opportunities. Overall, the period Feb 19th-Mar 1st looks very cold for the entire Central / Eastern US. The period March 1st-10th should be cold from the Pac NW eastward to the Northeast, with warming in the Southern US. By mid March, most of the nation could turn warm but that is very far out. Link to comment Share on other sites More sharing options...
donsutherland1 Posted February 20, 2015 Author Share Posted February 20, 2015 Record Low Temperatures for Select Cities (2/20): Atlantic City: -1° (Old record: 0°, 1966) Baltimore: 1° (Old record: 4°, 1979) Charleston, SC: 18° (Old record: 22°, 1968) Cleveland: -17° (Old record: -3°, 1968): February monthly record Danbury: -3° (Old record: -2°, 1978) Detroit: -13° (Old record: -8°, 1934) Flint: -25° (Old record: -21°, 1929): February monthly record Islip: 2° (Old record: 10°, 1993) Jacksonville: 24° (Old record: 28°, 1958) New Haven: 2° (Old record: 3°, 1950) New York City: ...JFK: 3° (Old record: 7°, 1950) ...LGA: 3° (Old record: 7°, 1950) ...NYC: 2° (Old record: 7°, 1950) Newark, NJ: 1° (Old record: 5°, 1936) Norfolk: 9° (Old record: 13°, 1896): Latest single-digit reading on record Pittsburgh: -9° (Old record: -2°, 1968) Raleigh: 7° (Old record: 13°, 1979) Savannah: 21° (Old record: 22°, 1958) Toledo: -19° (Old record: -5°, 1978): February monthly record Trenton: 0° (Old record: 6°, 1936) Washington, DC (DCA): 5° (Old record: 8°, 1896) Westhampton: -7° (Old record: 7°, 2005) White Plains: -1° (Old record: 5°, 1966) Wilmington, NC: 13° (Old record: 19°, 1896) Youngstown: -16° (Old record: -5°, 1968): Tied February monthly record Notes: 1. This list is not all-inclusive. 2. Bridgeport, CT broke the record for its current location with a 1° reading (Old record: 2°, 1968). However, if the earlier site is included, the existing record is -7° from 1936. Link to comment Share on other sites More sharing options...
iceman56 Posted February 20, 2015 Share Posted February 20, 2015 Record Low Temperatures for Select Cities (2/20): Baltimore: 1° (Old record: 4°, 1979) Charleston, SC: 18° (Old record: 22°, 1968) Cleveland: -17° (Old record: -3°, 1968): February monthly record Danbury: -3° (Old record: -2°, 1978) Detroit: -12° (Old record: -8°, 1934) Flint: -25° (Old record: -21°, 1929): February monthly record Islip: 2° (Old record: 10°, 1993) Jacksonville: 24° (Old record: 28°, 1958) New Haven: 2° (Old record: 3°, 1950) New York City: ...JFK: 3° (Old record: 7°, 1950) ...LGA: 3° (Old record: 7°, 1950) ...NYC: 2° (Old record: 7°, 1950) Newark, NJ: 1° (Old record: 5°, 1936) Norfolk: 9° (Old record: 13°, 1896): Latest single-digit reading on record Pittsburgh: -9° (Old record: -2°, 1968) Raleigh: 7° (Old record: 13°, 1979) Savannah: 21° (Old record: 22°, 1958) Toledo: -17° (Old record: -5°, 1978): February monthly record Trenton: 0° (Old record: 13°, 1945) Washington, DC (DCA): 5° (Old record: 8°, 1896) Westhampton: 2° (Old record: 7°, 2005) White Plains: -1° (Old record: 5°, 1966) Wilmington, NC: 13° (Old record: 19°, 1896) Youngstown: -14° (Old record: -5°, 1968) Notes: 1. This list is not all-inclusive. 2. Bridgeport, CT broke the record for its current location with a 1° reading (Old record: 2°, 1968). However, if the earlier site is included, the existing record is -7° from 1936. Don, I believe TTN record was 6 in 1936, still broken though. Thanks for the update, amazing how many records were smashed. Link to comment Share on other sites More sharing options...
donsutherland1 Posted February 20, 2015 Author Share Posted February 20, 2015 Don, I believe TTN record was 6 in 1936, still broken though. Thanks for the update, amazing how many records were smashed. You are correct, Iceman56. The daily low maximum record is 20° (1959). Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 2, 2015 Author Share Posted March 2, 2015 Preliminary AO Numbers for the December 2014-February 2015 Period: Average: +0.791 Days > 0: 74% Days +1 or above: 43% Days +2 or above: 18% Days +3 or above: 2% Days < 0: 26% Days -1 or below: 8% Days -2 or below: 0% Highest: +3.096 Lowest: -1.622 There's really no way to sugarcoat it, but after last winter's difficulties with the Snow Advance Index and October Pattern Index (both overstating the positive AO in that case), this winter witnessed a catastrophic failure of both indices when it came to forecasting the predominant winter state of the AO. These outcomes represent a likely setback when it comes to winter seasonal forecasting. Even as the AO, alone, does not determine the outcome of a winter (the predominant EPO-/PNA+ defined the 2014-15 winter), it is still an important contributor, especially as it relates to storm tracks (particularly for the Middle Atlantic region). Link to comment Share on other sites More sharing options...
RCNYILWX Posted March 2, 2015 Share Posted March 2, 2015 Preliminary AO Numbers for the December 2014-February 2015 Period: Average: +0.791 Days > 0: 74% Days +1 or above: 43% Days +2 or above: 18% Days +3 or above: 2% Days < 0: 26% Days -1 or below: 8% Days -2 or below: 0% Highest: +3.096 Lowest: -1.622 There's really no way to sugarcoat it, but after last winter's difficulties with the Snow Advance Index and October Pattern Index (both overstating the positive AO in that case), this winter witnessed a catastrophic failure of both indices when it came to forecasting the predominant winter state of the AO. These outcomes represent a likely setback when it comes to winter seasonal forecasting. Even as the AO, alone, does not determine the outcome of a winter (the predominant EPO-/PNA+ defined the 2014-15 winter), it is still an important contributor, especially as it relates to storm tracks (particularly for the Middle Atlantic region). The poor performance of the SAI and OPI is disappointing, but the very cold temperatures again in the eastern half of the US this winter, particularly during a very strong +AO February, is another sign that the AO is not of utmost importance to cold air supply in the east. It seems clear that the biggest driver was the strongly +PDO and the persistent -EPO/+PNA that resulted from it in much of January and February, which also demonstrates that the Pacific pattern is often can be more important than the AO/NAO when it comes to winter temperatures, as long as there isn't a strong El Nino like in 1997-98. But going back to Eurasian snow cover, maybe the role played was by overall snow extent (SCE), and we're finding that SAI is more flawed. October 2013 had slow advance but above average snow extent, while October 2014 had rapid advance and extent. But both Octobers having above average SCE and both winters going on to produce well below normal cold seems to be a good sign for that correlation. This is part of an excellent post from millwx on the Mid Atl subforum copied onto the And We Begin thread regarding SAI vs. SCE and winter temperatures in the eastern half of the US: " Moreover, while I said that the correlations support the SAI proponents, I'm not totally sold on the increase being most important anyway. The correlation between AO and just the total snow cover in a given week (not the increase) barely comes in under the peak increase correlation. The top correlation to raw snow cover values is -0.5259 (in Week 43 ...not coincidentally, I'm sure, the end-week on the peak increase correlation... indicating that the first week that you're subtracting off is of almost negligible importance). Furthermore, the AO is not a perfect harbinger of U.S. winter temps anyway. The correlation between Eurasian snow cover and population-weighted U.S. temperatures (which is what we use in my industry... but the population in the U.S. leans heavily to the East... so, this is VERY relevant to this board) actually does NOT peak on a snow increase value. It peaks on an absolute snow cover value. And, in fact, it's not even remotely close. The highest correlation you get between U.S. winter temps and Eurasian snow increase is a putrid +0.1673 (correlation is positive because it's on U.S. heating degree days, not temperature)... that's on Week 43 minus Week 37. But whatever... that's a pretty poor correlation. The BEST correlation is on the absolute snow cover value... NOT on the increase! The top correlation (still modest, lower than the AO correlation itself, but MUCH better than the HDD correlation with the snow increase), is +0.3024. That is the correlation of the U.S. winter temps with Week 42 (10/15 - 10/21). So, for U.S. (mainly Eastern U.S.) temperatures what matters most in Eurasian snow cover is the absolute amount by mid or mid-to-late October. It's really as simple as that. Sometimes I think we over-complicate matters. If Eurasian snow cover is high in mid-October, that's a positive sign for a cold winter (not a guarantee... a 0.3 correlation is far, far from a home run... just a good indicator). Simple as that. (And, as an aside, if the GFS ends up even in the rough ballpark of correctness, snow cover by mid-Oct should be above normal... but that's pretty far out there... and it's the GFS... so, we'll see.) " Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 8, 2015 Author Share Posted March 8, 2015 Some record low temperatures from today (3/7): Atlantic City: 8° (old record: 10°, 1890) Baltimore: 6° (old record: 10°, 1960) Sterling, VA: 2° (old record: 14°, 1985) Westhampton, NY: -9° (old record: 2°, 2007) ***Lowest March Temperature*** Link to comment Share on other sites More sharing options...
icebreaker5221 Posted March 8, 2015 Share Posted March 8, 2015 Some record low temperatures from today (3/7): Atlantic City: 8° (old record: 10°, 1890) Baltimore: 6° (old record: 10°, 1960) Sterling, VA: 2° (old record: 14°, 1985) Westhampton, NY: -9° (old record: 2°, 2007) ***Lowest March Temperature*** Hey Don, how about the fact that the AO currently stands above +5? It's interesting because heights aren't even insainley low over the arctic. Seems to just be that the current height pattern, especially the heigher heights over the Alutians and western Europe and lower heights in the NAO region, projects almost perfectly onto the AO loading pattern. Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 8, 2015 Author Share Posted March 8, 2015 Hey Don, how about the fact that the AO currently stands above +5? It's interesting because heights aren't even insainley low over the arctic. Seems to just be that the current height pattern, especially the heigher heights over the Alutians and western Europe and lower heights in the NAO region, projects almost perfectly onto the AO loading pattern. new.ao.loading.gif f0_gefs.gif I completely agree with you. It's probably as close to a perfect fit as there could be. FWIW, today's preliminary AO reading of +5.660 is the highest ever recorded in March (previous record: +4.917, March 16, 1968) and 2nd highest all-time (record: +5.911, February 26, 1990). Interestingly enough, one of the years when the AO rose to exceptional levels (+4.5) or above in early March was 1956. Just over two weeks later, blocking developed and predominated through much of April. Some of the ensemble guidance is hinting at the development of blocking in the medium-term. While the kind of substantial snows that occurred during the 3/12-4/8/1956 period is an extreme outlier, the notion that parts of the Great Lakes region, Mid-Atlantic states, and New England could see at least some additional accumulations of snow before winter is finished for good is probably an above climatological probability. The 1990 case cited above also saw the AO above +4.5 in early March. Two snow events occurred in parts of the aforementioned region around 3/24 and 4/7. The 1968 case saw the extreme AO+ set in later and general springlike conditions prevailed. It will be interesting to see what happens before spring takes hold. Even if the additional snowfall doesn't materialize, it has been a fun winter out here. It's highly unfortunate, though, that the West has suffered through more abnormal warmth and lack of snowfall in areas. Barring changes in the weeks ahead, one has to wonder about agricultural and fire season implications. Hopefully, those adverse outcomes can be avoided. Link to comment Share on other sites More sharing options...
snowman19 Posted March 9, 2015 Share Posted March 9, 2015 I completely agree with you. It's probably as close to a perfect fit as there could be. FWIW, today's preliminary AO reading of +5.660 is the highest ever recorded in March (previous record: +4.917, March 16, 1968) and 2nd highest all-time (record: +5.911, February 26, 1990). Interestingly enough, one of the years when the AO rose to exceptional levels (+4.5) or above in early March was 1956. Just over two weeks later, blocking developed and predominated through much of April. Some of the ensemble guidance is hinting at the development of blocking in the medium-term. While the kind of substantial snows that occurred during the 3/12-4/8/1956 period is an extreme outlier, the notion that parts of the Great Lakes region, Mid-Atlantic states, and New England could see at least some additional accumulations of snow before winter is finished for good is probably an above climatological probability. The 1990 case cited above also saw the AO above +4.5 in early March. Two snow events occurred in parts of the aforementioned region around 3/24 and 4/7. The 1968 case saw the extreme AO+ set in later and general springlike conditions prevailed. It will be interesting to see what happens before spring takes hold. Even if the additional snowfall doesn't materialize, it has been a fun winter out here. It's highly unfortunate, though, that the West has suffered through more abnormal warmth and lack of snowfall in areas. Barring changes in the weeks ahead, one has to wonder about agricultural and fire season implications. Hopefully, those adverse outcomes can be avoided. Don, it's obvious that if we had not had the +PDO/+PNA/-EPO combo in the Pacific this winter the outcome would have been completely different, my question is this, what do you think was the cause of the persistently +AO and +NAO all winter. We are nearing the end of the +AMO in the Atlantic and I read that +AMO strongly favors -NAO/-AO more than -AMO does, the Siberian snow cover in October theory pretty much got debunked this year, but I'm at a loss to explain the AMO correlation, can we throw that theory out the window too? Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 9, 2015 Author Share Posted March 9, 2015 Don, it's obvious that if we had not had the +PDO/+PNA/-EPO combo in the Pacific this winter the outcome would have been completely different, my question is this, what do you think was the cause of the persistently +AO and +NAO all winter. We are nearing the end of the +AMO in the Atlantic and I read that +AMO strongly favors -NAO/-AO more than -AMO does, the Siberian snow cover in October theory pretty much got debunked this year, but I'm at a loss to explain the AMO correlation, can we throw that theory out the window too? A lot of variables influence the AO. Not all are well-understood. At the same time, the relationship is complex. The poor performance of the SAI may provide a hint that not only is the snowcover link weaker than had first been thought, but perhaps there is no single dominant variable that drives the AO. Given the ocean/land-atmosphere relationship (including feedbacks/second order effects), some of those variables are bottom-up e.g., the changes in Eurasian snowcover (and probably AMO), and others are top-down e.g., a downwelling response from a sudden stratospheric warming (SSW). However, SSWs are currently poorly understood. Some literature presents the argument that SSWs are largely the result of Rossby waves (especially with an easterly or negative QBO), however that line of argument is undercut by the fact that predictive accuracy for SSWs even in the near-term is low when such waves develop. Winter 2014-15 provides a good example. Despite the development of several strong upward-propagating Rossby waves during a QBO- state that led to predictions of imminent SSW events, none materialized. There were some more modest warmings, but nothing of a magnitude sufficient to induce a sustained period of strong blocking. Almost certainly, something else needs to be present/happen for such a wave to kick off an SSW event. I haven't seen literature that identifies or discusses what that factor or set of factors might be. What is clear is that most such waves do not trigger SSW events. In short, while such waves can play a role, SSWs have materialized as a response to episodes of severe blocking that preceded the warming (sometimes, but not always, leading to renewed strong blocking). At other times, such warmings have occurred leading to a strong blocking response. My guess is that variables beyond Eurasian snowcover developments during October and meaningful improvements in understanding of the stratospheric warming phenomenon will be needed before one can predict the predominant state of the AO with reasonable accuracy. The NAO is more of a local phenomenon, so predicting its predominant winter state may be even more challenging than that of the AO. Link to comment Share on other sites More sharing options...
Isotherm Posted March 10, 2015 Share Posted March 10, 2015 We could be looking at one of the sharpest drops in AO values in quite some time; +5 SD to possibly -1SD or lower. Link to comment Share on other sites More sharing options...
bigtenfan Posted March 10, 2015 Share Posted March 10, 2015 We could be looking at one of the sharpest drops in AO values in quite some time; +5 SD to possibly -1SD or lower. Too little too late? Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 15, 2015 Author Share Posted March 15, 2015 Through today, Boston's seasonal snowfall remains stuck at 105.7". That is the second highest seasonal figure on record, surpassed only by Winter 1995-96's total of 107.6". Even as Boston has seen no accumulating snowfall since March 3, odds still likely favor Boston's setting a new record by the time the last snow has accumulated. First, since 1950, Boston has seen a 4" or greater snowstorm after March 15 approximately once every 1.8 winters. The last such snowfall occurred on March 18-19, 2013 when 7.2" snow fell. The point here is that the kind of snowstorm that would easily bring this winter's total past the current record is not all that uncommon. Second, the most common teleconnections setup for such snowstorms is an AO-/PNA+ pattern (30%). The March 18-19, 1956 snowstorm, which dumped 13.2" snow at Boston is the biggest for that setup during the 1950-2014 timeframe. The AO is currently +1.206 and falling while the PNA has risen to +0.984. An AO-/PNA+ pattern is forecast to develop on the GFS ensembles and will likely remain in place through at least March 24. Third, the latest ECMWF ensemble 500 mb height anomalies forecast at 168 hours is not too dissimilar from the pattern that was in place during the March 18-19, 1956 snowstorm, except that the trough is forecast to be somewhat farther to the north this time around. In the meantime, both the 3/14 18z GFS and RGEM suggest 1" to perhaps 2" of snow could fall in Boston tomorrow. Given how narrow the area of heaviest snow is forecast to be, one should probably err on the side of caution when looking at amounts. Hence, a 0.5"-1.0" snowfall might be a reasonable guess right now until one sees how things are developing tomorrow. In sum, the pause in Boston's snowfall appears poised to end tomorrow. Afterward, Winter 2014-15 will likely set a new seasonal snowfall mark in Boston, even if there is no 4" or greater snowfall for the remainder of the 2014-15 snow season. Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 15, 2015 Author Share Posted March 15, 2015 Afternoon thoughts... 1. Boston still looks to pick up 0.5" to 1.0" snow and possibly a little more. In fact, the 12z RGEM shifted the heaviest accumulations somewhat farther east than its earlier runs, and is now showing about 2" for Boston. So if the snow can come down heavily enough and the temperature can fall quickly enough to allow for maximum accumulations, there's a chance that Boston could reach its record today. 2. The pattern discussed above continues to look favorable for snowfall chances afterward, particularly the 3/20-24 period. In sum, things appear to remain on track for Boston's setting a new seasonal snowfall record. Link to comment Share on other sites More sharing options...
TalcottWx Posted March 19, 2015 Share Posted March 19, 2015 Don, thoughts heading forward? Link to comment Share on other sites More sharing options...
QcSevereWx Posted March 19, 2015 Share Posted March 19, 2015 Link to comment Share on other sites More sharing options...
donsutherland1 Posted March 21, 2015 Author Share Posted March 21, 2015 Don, thoughts heading forward? Near the end of March into the first week of April (3/27-4/3) could offer another opportunity, especially for New England. Link to comment Share on other sites More sharing options...
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