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donsutherland1

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  1. donsutherland1
  2. donsutherland1
    Overnight, the guidance began to consolidate toward a scenario where snowfall is limited in the New York City area with appreciable amounts (4"+) occurring only well north and west of the City. The 1/4 6z GFS soundings were brutal. A meaningful share of the precipitation e.g., between 72 hours-75 hours would fall as rain. The 1/4 12z NBE's estimated snowfall for the City was 1.4" at Central Park, 1.1" at LaGuardia Airport, and 0.6" at JFK Airport. Temperatures are currently forecast to remain above freezing throughout the storm in New York City leading to very low ratios. Historic data for January 1-15, 1869-2023 with low temperatures above freezing highlighted the issue of low ratios. With some of the guidance now showing a low of 35° or above, a wider look at all cases revealed that just 26% of such cases saw 1" or more snowfall while 74% saw less than 1" of snow (Mean: 0.8"; Median: 0.5"). The mean figure was skewed by April 9, 1907 (5.0") and November 9, 1892 (2.3") snowfalls. In both cases the snow fell very heavily over a short period of time. Such dynamics are not likely this time around. With the strong short wave digging into the Southwest, this kind of solution was a danger. There was more downside risk than upside risk. Unfortunately, even at this point in time, there still remains somewhat more downside risk than upside risk, namely that the 1" of slushy snow to perhaps 3", if everything went well, could evolve into a coating to an inch-type scenario. The low ratios (high confidence assumption given the consistently forecast temperatures) rendered 10:1 snowfall maps irrelevant. That included individual ensemble maps based on 10:1 ratios. In both cases, the operational and ensemble maps overstated what was likely. For an illustrative example, maps assessing the probability of 4" or more snowfall were actually assessing the probability of 2" or more snow in and around NYC and along the coastal plain, because their 10:1 ratios were not realistic. As a result of the overnight guidance, the probability that New York City's streak without 1" or more daily snowfall, which will reach 690 days today, will continue has increased. However, even as the New York City area will have to wait for another storm for the opportunity for a moderate or significant snowfall, it should be noted that 75% of seasonal snowfall during strong El Niño winters falls after January 15th and around 50% falls on or after February 1st. Therefore, it is likely that there will be additional opportunities as the current winter progresses deeper into January and then beyond.
  3. donsutherland1
    Latest EPS and NBE information: Note: EPS amounts are based on 10:1 ratios. The actual ratios in NYC could be closer to 4:1 to 6:1 given that readings could remain several degrees above freezing throughout most or even all of the storm. In fact, the NBE shows < 0.5" at JFK Airport. WPC's probabilistic Winter Storm Severity Index: Probability of a moderate impact: It is possible that the 1"+ daily snowfall droughts could continue in parts of the region. Baltimore and Philadelphia are at highest risk, but there is a non-negligible risk at Central Park. The overnight 0z model runs or tomorrow's model cycles could begin to converge toward a consensus. Uncertainty remains higher than usual given the marginal air mass involved and impact that small changes in the track could have on where the precipitation is predominantly liquid or predominantly frozen.
  4. donsutherland1
    Generally cool, dry weather will continue through the remainder of the week. A few locations could see a rain or snow shower tomorrow morning. Overall, the first week of January remains in line for somewhat above normal temperatures. A storm could bring measurable snowfall to parts of the region Saturday afternoon into Sunday. There are currently two leading scenarios. The first involves significant snow (6" or more) falling well north and west of an area that includes Philadelphia and New York City. The second involves significant snowfall extending south and east into the area that includes New York City and Philadelphia. The first scenario is currently more likely than the second. The probability of such an outcome has increased over the past 24 hours. Details remain to be worked out. However, this appears to be the kind of storm that could bring a general 1" to perhaps 3" of slushy snow to New York City (lowest amounts in Queens, Brooklyn, and Staten Island and highest amounts in the Bronx) with 3"-6" of snow well north and west of New York City. Afterward, a major storm could bring a heavy windswept rain to much of the region during the middle of next week. The potential exists for a 1"-3" rainfall with locally higher amounts. Temperatures could surge toward or into the 50s. The ENSO Region 1+2 anomaly was +0.8°C and the Region 3.4 anomaly was +2.0°C for the week centered around December 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +1.55°C and the ENSO Region 3.4 anomaly has averaged +2.00°C. A basinwide El Niño event is ongoing. The SOI was +0.81 today. The preliminary Arctic Oscillation (AO) was -1.127 today. Strong blocking in the final week of November, as occurred this year, has often been followed by frequent blocking in December and January. On January 1 the MJO was in Phase 2 at an amplitude of 1.959 (RMM). The December 31-adjusted amplitude was 1.894 (RMM).
  5. donsutherland1
    From NWS-New York:
  6. donsutherland1
    From NWS Boston:
  7. donsutherland1
    And some wind up posting exaggerated snowfall totals from such maps on Social Media which creates real headaches for the professional community. It creates perceptions that the professional community of private- and public-sector meteorologists are "wrong" when the exaggerated amounts don't verify, as is typically the case for extreme solutions that have little support. Such maps are starting to be called out more frequently on social media. But there is no sign yet that the pushing of reckless speculation is slowing. One such map: If everything went right, Allentown would have a shot at 6"-12", but right now 4"-8" seems likely (downside risk is greater than upside risk). The latest NBE forecast is for just under 6" there.
  8. donsutherland1
    This page explains it and has some links to more detailed discussions: https://home.pivotalweather.com/guides/snowfall
  9. donsutherland1
    The EPS is better and there could be some degree of dynamic cooling. I suspect that once one gets 30 miles or so outside of NYC, there will be 3"-6" amounts.
  10. donsutherland1
    The importance of recognizing that the upcoming event will be a low- to very low-ratio event in New York City cannot be overstated. Most of the guidance keeps NYC above freezing throughout the storm. While model solutions showing 6"+ snow appear attractive, the early surface temperature forecasts and early soundings suggest that such figures based on a 10:1 ratio will likely be far off the mark. Since 1869, there have been 9 storms during January 1-15, 1869-2023 that had minimum temperatures above freezing and measurable snowfall. The ratios for such storms were exceptionally low: Notice also that the highest ratios, which occurred with systems that produced less than 0.50" precipitation occurred during the 19th century when New York City's heat island was less formidable than it is today. Even as the 0z ECMWF upped its snowfall totals (10:1 ratios), the share of ensemble members showing 10" or more snow did not increase and those showing 4" or more decreased. That could be an early indication that the range is starting to narrow toward a lighter snowfall event. Given the early sounding forecasts and the historic data from above, I believe NYC remains in line for 1" of snowfall with perhaps up to 3" if things come together. IMO, 6" or more is out of the question for New York City and its surrounding area within at least 30 miles. There could also be more downside risk than upside risk. Things that could lead to a snowier outcome: 1. A stronger high in eastern Canada 2. A deeper, colder air mass 3. A weaker shortwave in the Southwest In short, be wary of 10:1 snowfall maps. The upcoming storm will be coming into a marginal air mass. Such maps offer very little guidance with such air masses.
  11. donsutherland1
    Early morning thoughts... The operational ECMWF was far more aggressive than its ensembles. The share of ensemble members with 10" or more snow remained constant at around 10%. The share of ensemble members showing 4" or more declined somewhat. It's still early, but that might be the first indication that the realistic range for snowfall is beginning to narrow. Of concern remains surface temperatures that will be above freezing for most or all of the event. Soundings will become increasingly important as the event draws closer, but this still looks to be a wet, low ratio snowfall for NYC and its nearby suburbs. At least some rain remains a risk, especially for NYC, Long Island, coastal Westchester County, and perhaps coastal Fairfield County.
  12. donsutherland1
    Latest snowfall outlook with EPS ensemble members and the NBE for NYC: The forecast pattern is an AO-/NAO-/PNA- one. Since 1950, there were 26 days during January 1-15 that saw measurable snowfall. 50% saw less than 1" while 50% saw 1" or more (daily snowfall not storm total snowfall). Nearly one-third (31%) saw 2" or more while 8% saw 4" or more (both cases were 6.3" and 6.4" respectively). However, there was a single case that saw the low temperature remain at or above 30° (33° low). That case had just 0.1". This data provides a rough picture of what may lie ahead keeping in mind the importance of details such as the soundings during the storm, etc. This will very likely be a relatively low ratio snowfall for the NYC area. For now, based on the above data, there remains a realistic chance that NYC could pick up an inch or more of snow (whether 1" or more falls on one day to break the record 688-day streak without such snowfall remains to be seen). It remains unlikely that NYC will pick up 6" or more snowfall, which would also fit historic experience for January 1-10 following cases where the AO reached +3..000 or above during December 15-25.
  13. donsutherland1
    Cool, dry weather will continue through the remainder of the week. A few locations could see a rain or snow shower on Thursday morning. Overall, the first week of January remains in line for near normal to somewhat above normal temperatures. That is quite a contrast from the much greater warmth that had prevailed through most of December. A storm could bring measurable snowfall to the region during January 7-8. There are currently two leading scenarios. The first involves significant snow (6" or more) falling well north and west of an area that includes Philadelphia and New York City. The second involves significant snowfall extending south and east into the area that includes New York City and Philadelphia. The first scenario is currently more likely than the second. Nevertheless, details remain to be worked out. Afterward, a major storm could bring a heavy windswept rain to much of the region during the middle of next week. The potential exists for a 1"-3" rainfall with locally higher amounts. Temperatures could surge toward or into the 50s. The ENSO Region 1+2 anomaly was +0.8°C and the Region 3.4 anomaly was +2.0°C for the week centered around December 27. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +1.55°C and the ENSO Region 3.4 anomaly has averaged +2.00°C. A basinwide El Niño event is ongoing. The SOI was +0.10 today. The preliminary Arctic Oscillation (AO) was -1.468 today. Strong blocking in the final week of November, as occurred this year, has often been followed by frequent blocking in December and January. On December 31 the MJO was in Phase 2 at an amplitude of 1.894 (RMM). The December 30-adjusted amplitude was 2.047 (RMM).
  14. donsutherland1
    Hopefully, the storm won’t be as wet as currently appears.
  15. donsutherland1
    Even as attention is focused on the possible snowfall for late Saturday into Sunday, perhaps the bigger story for the first half of January will be the potential rainstorm for January 9-10. Already, there is an impressive signal on the ECMWF's Extreme Forecast Index (EFI) guidance:
  16. donsutherland1
    Afternoon thoughts: Lengthy streaks during which Atlantic City, Baltimore, New York City, and Philadelphia have not seen 1" or more daily snowfall continue today. Today, the streak will reach 703 days at Atlantic City (2nd longest). The streaks will reach a record 688 days at New York City (Central Park), 703 days at Philadelphia, and 704 days at Baltimore. But there is some possibility that these streaks could be nearing their end in a number of these locations. Although there are now early indications that a trough in the West will influence the track of a storm that will impact the region from late Saturday into Sunday, prospects for at least a measurable snowfall are higher than they have been this winter on a regionwide basis. At present, a 1" to perhaps 3" snowfall still seems plausible for Baltimore, New York City, and Philadelphia. Temperatures will likely remain above freezing for much of the storm in those areas. Atlantic City will likely fall short of 1" daily snowfall, allowing its ongoing streak to continue to advance toward that City's record (715 days). There continue to be more downside risks than upside ones. The two leading scenarios involve the storm's passing close enough to the coast to bring abundant warm air in along the coastal plain resulting in low snowfall amounts for the big cities. The other meaningful scenario involves the storm's taking a track farther south and east, allowing for a moderate snowfall even in the big cities. Taking into consideration the trough that will be anchored in the Southwest, a suppressed solution appears unlikely. The timing of the storm is sufficiently far out that the models can have errors of 25-50 miles. Such an error could make the difference between little or no accumulating snow or a moderate snowstorm.
  17. donsutherland1
    Climate change is likely playing an important role through the impact of a warming North Pacific Ocean. There was a paper on this in 2021: https://www.nature.com/articles/s41558-020-00966-8
  18. donsutherland1
    I felt nothing but heard the rumbling.
  19. donsutherland1
    Some NYC residents saw the 12z GEFS and what it portends: They reacted strongly. The result: Notification issued 01-02-2024 at 11:26 AM. The United States Geological Survey (USGS) reports that a 1.7 magnitude earthquake has occurred near Astoria, Queens. The earthquake has reportedly been felt in the New York City area, but there are no reports of injuries or damage in New York City at this time.
  20. donsutherland1
    Both the NAO and EPO were predominantly positive during December.
  21. donsutherland1
    From the WPC's Probabilistic Winter Storm Severity Index tool: Moderate Impact
  22. donsutherland1
    Even as there remains considerable uncertainty, it is unlikely that Allentown will see 12"-18" of snow. The potential exists for 6"-12" if things come together. Select Data: 1/2 0z NBE: 6.2" (the 2z increased the snowfall to 9.0") 1/1 12z EPS Members: 12" or more: 20%; 18" or more: 2% WPC Probabilistic Winter Storm Severity Index for Major Impact: < 5% (around 20% for a moderate impact)
  23. donsutherland1
    2024 kicked off with benign weather. The temperature rose into the middle 40s as the clouds broke for a time. The first week of January will likely feature generally near normal to somewhat above normal temperatures. Severe cold is unlikely. Some snow flurries and snow showers are possible Thursday morning. There is the possibility that a significant storm could bring measurable snowfall to the region during January 7-8. Details remain to be worked out. The ENSO Region 1+2 anomaly was +1.6°C and the Region 3.4 anomaly was +2.0°C for the week centered around December 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +1.75°C and the ENSO Region 3.4 anomaly has averaged +1.98°C. A basinwide El Niño event is ongoing. The SOI was -2.63 today. The preliminary Arctic Oscillation (AO) was -1.779 today. Strong blocking in the final week of November, as occurred this year, has often been followed by frequent blocking in December and January. On December 30 the MJO was in Phase 2 at an amplitude of 2.047 (RMM). The December 29-adjusted amplitude was 1.993 (RMM).
  24. donsutherland1
    As has become increasingly common in recent years, the New Year begins with a range of flowers in bloom in the NYC area. Cherry blossoms are in bloom in Central Park. Camelia, Mahonia, and Witch Hazel are in bloom in the New York Botanical Garden.
  25. donsutherland1
    Nice jump on the 15z NBE for NYC (3.8"). Let's see where things are in a few days. There may be some basis to increase confidence in a 1"-3"/2"-4" snowfall (a "great storm" by winter 2022-23 standards). Interior sections appear most likely to see a significant (6"+) snowfall.
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