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  1. 4 points
    Hi Matt, some good observations there and well constructed . True what you say regarding the AAM changes and increased westerly flow across the N Atlantic next week - but now, the falling phase is starting to look too brief for the Atlantic trough to push right across to the UK longitudes (thankfully, I’d you prefer it warm) before AAM cycles back around and the ridge builds back in. With the Pacific El Niño event underway, even though it’s weak, its reasonable to assume further positive AAM cycles going forward. The main uncertainty is the time spent in each phase, as the case for next week has shown. Got to rush off now - I’ll see if I can find time to expand on this later.
  2. 4 points
    Tomorrow is going to be a day to remember. Virtually every parameter is showing a significant severe episode
  3. 3 points
  4. 3 points
    As an addition to the above, find below a few extra graphics and plots. This seems to tie in nicely and is seemingly a good example of how the AAM and 500mb anoms can clearly be connected with regards to either +AAM through the mid-lats, say 40-60N, as what occurred during the first half of March or more. This N Hem pattern is clearly a distinctly +NAO regime too and, as I highlighted yesterday, brought a particularly unsettled and disturbed period of weather to the British Isles. The opposite has seemingly been occurring since early April mind, with -AAM through a similar latitude range, but clearly note the completely different N Hem pattern and especially so across the N Atlantic domain. This has, essentially meant that the first half of March compared with the first half of April, for the UK and NW Europe are completely opposite and this seems to be a superb example and connection to me. I think the main question of interest, which no doubt has a very complicated answer is; how can one predict the likely evolution of the AAM, whether +ve or -ve looking forward, especially so within than 40-60N latitude range?...As we found out this winter mind, this link isn't always clear cut and can vary, but still.
  5. 3 points
  6. 3 points
    The final snowfall in Chicago on Sunday was 5.4". That tied the record set on April 16, 1961 for the greatest daily snowfall after April 10.   The ENSO Region 1+2 anomaly was 0.1°C and the Region 3.4 anomaly was +0.9°C for the week centered around April 10. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.20°C and the ENSO Region 3.4 anomaly has averaged +0.98°C. Conditions consistent with El Niño should persist through April in Region 3.4.   The SOI was -4.04 today.   Today's preliminary value of the Arctic Oscillation (AO) was -0.066.   Over the next 4-5 days, variable temperatures can be expected. Several days of generally cooler than normal readings are possible, along with several warmer days. The closing 7-10 days of the month could be warmer than normal with perhaps a turn toward normal as the month comes to a close. There remains uncertainty concerning the risk of a possible turn to near normal readings near the end of the month.   Since 1950, there have been 6 cases where the AO dropped to -2.500 or below during the April 1-10 period, as happened on April 7. The mean April 16-30 temperature was 56.3° with a standard deviation of 2.3°. The latest guidance shows an estimated mean temperature of 57.6° for that period this year. The implied probability of a warmer than normal April is currently 78%.   On April 14, the MJO was in Phase 1 at an amplitude of 0.444 (RMM). The amplitude was above the April 13-adjusted figure of 0.377. The MJO has now had an amplitude below 1.000 for 32 consecutive days. That's the longest such stretch since the MJO was at a low amplitude for 39 consecutive days from April 21, 2015 through May 29, 2015.   Within 2-6 days, the MJO could emerge into an amplitude of 1.000 or above, likely in Phase 2.
  7. 3 points
    Just thought I'd drop a quick message in here, it's a shame discussion have fallen away. While winter is over there's still be some interesting connections and links with how the weather so far this spring has progressed, or so it seems from over here in the UK. Apologies if this is brief and with some rather 'rusty comments' perhaps, it's been a good few months since I've sat down and properly looked at any AAM/GWO stuff and linked it to current/recent synoptics and how things may evolve... What seems to have been of particular interest here in the UK is how, finally, some more significant blocking patterns have materialized over the last 2 weeks, or essentially the first half of April even though the strat vortex has been in a particularly strong late-winter phase, so no help from there I would suggest and the MJO has been particularly 'quiet' too. March was, overall, noticeably cyclonic and wet, very wet for some areas of the UK, but this transition to blocking patterns at more northern latitudes is what was clearly hoped for during most of the winter. While we all know that the blocking regimes were there, at times, the lack of ability, if that's the right word, to set up at more northern latitudes was clearly a major failure, with the NAO in particular very reluctant to get -ve in any shape or form. However, I would surmise that the -ve values of total AAM since late March and through into April above 40N initially and then above 50N is surely related to the large and dominant Scandinavian blocking pattern, with a very much reduced W'ly component to the atmosphere at these latitudes. Indeed, if this had been 2 or 3 months back then much of N Europe would have been in the freezer, it has been quite cold here in association with the block anyway, but clearly not to the same extremes that would have been possible back in the winter months. However, does that pattern now look set to change?...It does to me, there has clearly been a progression towards the tendency to fall more negatively in recent days, nearing the values of late February. 500mb anom plots from the EC, GFS and the CMC all signal quite an abrupt change and removal of the blocking pattern through next week, not before however bringing a very pleasant Easter weekend to the UK with rising temperatures as a much warmer air mass becomes entrained into the overall block. However, could this be a good example of the links and connections between the AAM and blocking patterns or, indeed, more cyclonic weather at times. Perhaps one for one of the more knowledgeable to answer... Mountain torque has trended negative of late and while the GWO has been loitering in P5, 6, 7 and 8 it hasn't really been on the move or with any significant amplification. But could that be about to change, in association with this more pronounced trend away from such a strong blocking pattern across Scandinavia? There may well be someone out there who may be able to make a more distinct prediction of how the AAM may evolve over the next few weeks, perhaps drifting into phase 8, so more of neutral or even La Nina regime, but I would suggest that after the last 2 weeks of -ve anoms at 40, 50 and 60N, with a much reduced W'ly momentum, that pattern may well reverse with the more N Lats seeing an injection of W'ly momentum looking forward. Regards to all, Matt.
  8. 3 points
    Maybe the SPC should change the shape of the enhanced just a bit .
  9. 3 points
    Now that's what I call a flip 24.37 down to -23.80 in 4 days, almost a 50.00 point flip.
  10. 2 points
    When you say "further positive AAM cycles" I presume you mean through the sub-tropical regions, as we have had over the last couple of weeks, so roughly 10N to 30N, as opposed to +ve AAM regimes like back in early March at more northern lats? If this is what you're implying then I can see how the -ve AAM regime may well continue then at more northern latitudes as per the last couple of weeks, meaning that further blocking episodes are likely. I would imagine with the breakdown of the strat vortex too over the next few days this will only reinforce the lack of any W'ly momentum at more northern latitudes; Clearly May is often the driest month of the year across the UK, on average, for a reason(s), this certainly being one each year no doubt. The latest GWO plot seems to have done just that, from a few days ago it has suddenly 'jumped' back around to phase 5 so a relatively high/+AAM state still which ties in with what you mention as well... The charts are now 72hrs old, so hopefully should update today, but even back on the 15th the relative AAM tendency has quickly bounced back up, perhaps related to some mountain torque activity. Again, tying this in with what you've mentioned, could this well be the sign that +AAM will return through the sub-tropical regions, while more northern lats maintain more of a -ve regime. Apologies for the crude colouring (on the right image) but perhaps the prediction then, in terms of a total AAM through the next week would be something like below, this mirroring or at least being similar to that of the first half of April as we approach late April and early May. The end result, or prediction, is a continued risk or a greater propensity for blocking regimes within the N Atlantic/N Europe domain (?) Regards, Matt.
  11. 2 points
    A strong storm will likely bring 1.00" or more rain across parts of the Gulf Region Thursday into Saturday. The heaviest amounts could be focused on northern Mississippi, northern Alabama, Tennessee, Kentucky, and parts of North Carolina. That region could also see severe thunderstorms. Excessive rainfall figures of 2.00" or more are likely along the Appalachians. Afterward, a general 0.50"-1.00" rain is likely in the New York City area.   The ENSO Region 1+2 anomaly was 0.1°C and the Region 3.4 anomaly was +0.9°C for the week centered around April 10. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.20°C and the ENSO Region 3.4 anomaly has averaged +0.98°C. Conditions consistent with El Niño should persist through April in Region 3.4.   The SOI was -7.14 today.   Today's preliminary value of the Arctic Oscillation (AO) was -0.655.   Over the next 3-4 days, variable temperatures can be expected. Several days of generally cooler than normal readings are possible, along with several warmer days. The closing 7-10 days of the month could be warmer than normal with perhaps a turn toward normal as the month comes to a close. There remains uncertainty concerning the risk of a possible turn to near normal readings near the end of the month.   Since 1950, there have been 6 cases where the AO dropped to -2.500 or below during the April 1-10 period, as happened on April 7. The mean April 16-30 temperature was 56.3° with a standard deviation of 2.3°. The latest guidance shows an estimated mean temperature of 58.2° for that period this year. The implied probability of a warmer than normal April is currently 82%.   On April 15, the MJO moved into Phase 2 at an amplitude of 0.553 (RMM). The amplitude was above the April 14-adjusted figure of 0.444. The MJO has now had an amplitude below 1.000 for 33 consecutive days. That's the longest such stretch since the MJO was at a low amplitude for 39 consecutive days from April 21, 2015 through May 29, 2015.   Within 1-5 days, the MJO could emerge into an amplitude of 1.000 or above, likely in Phase 2. Historic data with the very long duration periods of low amplitude favors a return to higher amplitude at Phases 8, 1, or 2 (Phase 2 accounts for 6/14 or 43% cases). Typically, additional days at low amplitude then follow during the subsequent 30 days.
  12. 2 points
  13. 2 points
    Why yet another sea breeze tomorrow? Can't this sh*t end already?
  14. 2 points
    Get ready for another quick round of tstorms for parts of NJ/NYC in 30 min..,
  15. 2 points
    Umm, okay, I know this most likely won't verify for my area, but it is a good indication that it is going to be a rough Sunday night and early Monday morning for many areas of the upper mid-Atlantic and Northeast.
  16. 2 points
    https://www.spc.noaa.gov/products/outlook/day1otlk.html
  17. 2 points
  18. 2 points
  19. 2 points
  20. 2 points
    00z HRRR has what would amount to a full-blown tornado outbreak over LA/AR/MS tomorrow afternoon. I'm still sticking to my guns about maintaining the MOD at least until 16:30 UTC
  21. 2 points
    Wind shear is crazy high my goodness
  22. 2 points
    Good grief this spells trouble to no end
  23. 1 point
  24. 1 point
    Marginal moved north on the new Day 2 Outlook. Have to see what happens in subsequent outlooks. https://www.spc.noaa.gov/products/outlook/day2otlk.html
  25. 1 point
    A strong storm will likely bring 1.00" or more rain across parts of the Gulf Region tomorrow into Saturday. The heaviest amounts could be focused on northern Mississippi, northern Alabama, Tennessee, Kentucky, and parts of North Carolina. That region could also see severe thunderstorms. Excessive rainfall figures of 2.00" or more are likely along the Appalachians. Afterward, a general 0.50"-1.50" rain is likely in the New York City area.   The ENSO Region 1+2 anomaly was 0.1°C and the Region 3.4 anomaly was +0.9°C for the week centered around April 10. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.20°C and the ENSO Region 3.4 anomaly has averaged +0.98°C. Conditions consistent with El Niño should persist through April in Region 3.4.   The SOI was -11.03 today.   Today's preliminary value of the Arctic Oscillation (AO) was -0.700.   The closing 7-10 days of the month will likely be generally warmer than normal. Since 1950, there have been 6 cases where the AO dropped to -2.500 or below during the April 1-10 period, as happened on April 7. The mean April 16-30 temperature was 56.3° with a standard deviation of 2.3°. The latest guidance shows an estimated mean temperature of 59.1° for that period this year. The implied probability of a warmer than normal April is currently 88%.   On April 16, the MJO was in Phase 2 at an amplitude of 0.666 (RMM). The amplitude was above the April 15-adjusted figure of 0.540. The MJO has now had an amplitude below 1.000 for 34 consecutive days. That's the longest such stretch since the MJO was at a low amplitude for 39 consecutive days from April 21, 2015 through May 29, 2015.   Within the next 4 days, the MJO could emerge into an amplitude of 1.000 or above, likely in Phase 2. Historic data with the very long duration periods of low amplitude favors a return to higher amplitude at Phases 8, 1, or 2 (Phase 2 accounts for 6/14 or 43% cases). Typically, additional days at low amplitude then follow during the subsequent 30 days.
  26. 1 point
    Latest from SPC for the east coast Friday into Saturday.
  27. 1 point
  28. 1 point
  29. 1 point
    Given the obs I'm guessing the storms will weaken near the coast? Marine layer seems strong.
  30. 1 point
    Through 4 pm, Chicago had picked up 4.8" snow. That set a new daily record snowfall amount for April 14. The previous record was 2.2", which was set back in 1980. This was only Chicago's second daily snowfall of 4" or above after April 10. The only other such daily snowfall occurred on April 16, 1961 when 5.4" accumulated (6.7" was the storm total from April 15-17, 1961). To date, Chicago has received 46.4" snow for the 2018-19 snowfall season, which ranks the current season as Chicago's 34th snowiest on record.   Tonight into tomorrow morning, a cold front associated with the storm responsible for Chicago's snowfall will bring periods of rain and thunderstorms. That system will likely bring a general 0.25"-0.75" rain to the New York City area with some locally higher amounts (especially to the north and west of New York City and Newark). The potential for strong to severe thunderstorms is somewhat elevated across southeastern New York State and more so south and westward.   Across central and Upstate New York, a widespread 1.00"-2.00" rainfall is likely with some locally higher amounts. As a result, flooding is possible in parts of that area, especially Upstate where above normal seasonal snowfall has occurred.   As the storm pulls away, the clouds will break. However, the wind could gust past 40 mph.   The ENSO Region 1+2 anomaly was 0.0°C and the Region 3.4 anomaly was +0.9°C for the week centered around April 3. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.27°C and the ENSO Region 3.4 anomaly has averaged +1.02°C. Conditions consistent with El Niño should persist through April in Region 3.4.   The SOI was -15.14 today.   Today's preliminary value of the Arctic Oscillation (AO) was +0.488. That ends the stretch of 10 consecutive days during which the AO was negative.   Over the next 5-6 days, variable temperatures can be expected. Several days of generally cooler than normal readings are possible, along with several warmer days. The closing 7-10 days of the month could be warmer than normal with perhaps a turn toward normal as the month comes to a close. There remains uncertainty concerning the risk of a possible turn to near normal readings near the end of the month.   Since 1950, there have been 6 cases where the AO dropped to -2.500 or below during the April 1-10 period, as happened on April 7. The mean April 16-30 temperature was 56.3° with a standard deviation of 2.3°. The latest guidance shows an estimated mean temperature of 58.0° for that period this year. The implied probability of a warmer than normal April has increased to 78%.   At this point in time, the EPS hints at a cooler than normal May. However, the CFSv2 favors warm anomalies in the region. Model skill from this point in time is generally poor, but current ENSO conditions suggest warm anomalies may be somewhat more likely than not.   On April 13, the MJO moved into Phase 1 after having spent 3 days at Phase 2. The MJO's amplitude was 0.375 (RMM). The amplitude was above the April 12-adjusted figure of 0.162. Within 3-7 days, the MJO could emerge into an amplitude of 1.000 or above, likely in Phase 2.
  31. 1 point
  32. 1 point
    Three-quarters of the state of Pennsylvaniay is under a tornado watch basically from Lancaster West
  33. 1 point
    https://www.spc.noaa.gov/products/outlook/day1otlk.html
  34. 1 point
    I didn't know they had such low highs forecast out there. That's just a stupid forecast.
  35. 1 point
    My forecast high was 61 as of an hour ago and it’s 68. That’s a bust
  36. 1 point
  37. 1 point
  38. 1 point
  39. 1 point
  40. 1 point
    Looks like models are portending the Final Warming to downwell to the surface...
  41. 1 point
    SPC holds steady with their PM Update Some lingering questions about the tornado risk remain due in part to some conditional factors yet to occur. However, it appears the tornado risk may maximize in 2 corridors. First, a diurnally focused tornado risk (primarily supercellular) across northern LA into far southern AR vicinity between 3-9pm. A second area of potential concern may focus from northeast LA near the MS River east-northeast across central and into parts of northeast/east MS during the evening into the overnight. A mix mode of supercell/QLCS or hybridization of the two within a convective line are possible. Along with damaging gusts, strong tornadoes may also occur with a few of the most intense storms. While the pre-frontal, cellular convection should diminish overnight, a semi-organized band of storms -- with embedded rotating updrafts and continued severe/tornado potential -- will move across the central Gulf Coast states through the end of the period.
  42. 1 point
  43. 1 point
    I agree, November and April are my least favorite months
  44. 1 point
  45. 1 point
    April is a horrible month for weather. Useless cold and lots of wind. Today is a good example, high around 50 and cloudy. pass
  46. 1 point
  47. 1 point
  48. 1 point
  49. 1 point
    Below is a map link that displays the NWS forecast discussion layer on top of the watches and warnings. To read the discussion, click the map and then follow the link. Open GISsurfer map: https://mappingsupport.com/p2/gissurfer.php?center=42.520973,-99.219142&zoom=6&basemap=ESRI_streets&overlay=Weather_watch_warning,Forecast_discussion&txtfile=https://mappingsupport.com/p2/special_maps/disaster/USA_rain_flood.txt
  50. 1 point
    To 1. - I don't believe any changes that NCEP has made to FV3 to address the documented issues have been pushed to public acceptance testing as of yet. The work is underway though and various members of the working group have noted publicly clear progress is being made. In the meantime TT, WB, WM etc that are providing FV3 are still running the same ol flawed release point from a few months ago, so to us nothing has changed - yet. I'd argue it would basically be better if they just pulled it for now.
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