Hi Folks, The jetogenesis discussion that follows is based on Kyle Griffin’s loops appended below….. Impressive jetogenesis is forecast to culminate in the formation of a 110+ m/s jet stream core at 250 hPa over eastern Canada by 22 Dec 2013. The GFS deterministic runs suggest that wind speeds in the 250-hPa jet core will approximately double in the 60 h period ending 1200 UTC 22 Dec. This forecast doubling of the 250-hPa jet core wind speeds occurs in conjunction with ridge amplification over eastern North America in a larger-scale environment that features broad confluent flow. Kyle Griffin’s loops of SLP, 1000-500 hPa thickness, 250-hPa wind speeds, 250-hPa geopotential heights and standardized geopotential height anomalies, and 300-200-hPa layer mean wind speed, PV, irrotational wind, PW and SLP indicate that jetogenesis will occur in conjunction with a strengthening of the meridional geopotential height, temperature and PV gradients in response to negative PV advection by the 300-200 hPa irrotational wind in the equatorward jet-entrance region and surface anticyclogenesis and low-level cold-air advection over eastern Canada in the poleward jet-emntrance region. Negative PV advection by the 300-200 hPa irrotational wind arising from strengthening divergent outflow will be associated with cyclogenesis in a moisture-rich environment over the Ohio Valley (where standardized PW anomalies are forecast to exceed +4 sigma) and very heavy rainfall. Surface anticyclogenesis and low-level cold advection over eastern Canada in the poleward jet-entrance region will occur in conjunction with the passage of a leading, weak short wave trough in the northern branch of the westerlies that makes up the aforementioned confluent flow. This forecast synoptic-scale flow evolution is likely to facilitate a significant ice storm event across portions of northern New York and New England, and adjacent southern Quebec over the weekend. The 54 h GFS 250 hPa geopotential height and standardized height anomaly forecast verifying 1200 UTC 22 Dec nicely illustrates the ridge amplification over eastern North America and the western Atlantic in conjunction with trough passage across eastern Canada that results in an anomalous 5-sigma meridional geopotential height gradient between northern Labrador and eastern New England. How do you spell jetogenesis? Also of possible interest is the deep 250-hPa trough that is forecast to form over the southwestern Atlantic and northeastern Caribbean by 22 Dec in response to anticyclonic wave breaking associated with the aforementioned ridge over eastern North America. Ahead of this trough, a concentrated area of +3 to +4 sigma PW is forecast to develop by 24-25 Dec to the east and northeast of Puerto Rico and the Leeward Islands. Some of this concentrated tropical moisture is then forecast to bleed northeastward as a part of an atmospheric river toward western Europe on 26-27 Dec while the main area of tropical moisture is forecast to move westward toward the Bahamas and the western Caribbean where it may be in a position to cause “trouble” over parts of the southeastern U.S. toward the end of next week and beyond. Does anyone have an updated climatological pdf of 250 hPa jet core wind speeds over eastern North America and the western Atlantic? My impression is that if the jet core wind speeds do reach 110+ m/s as forecast that would be getting close to the highest wind speeds observed in this region. Lance ------------------------------------ ------------------------------------ ------------------------------------ Lance, I accessed the 2.5-degree NCEP-NCAR Reanalysis for 0000 UTC times during 1979-2012 and computed the maximum 250-hPa wind speed in the domain 40-60N and 90W-60W. The histogram of maximum 250-hPa wind speed for these 12,419 dates is attached. There were 10 days that had wind speed values > 100 m/s; see below. 11-Dec-86 100.06 9-Dec-89 101.87 2-Dec-91 105.98 3-Dec-91 109.61 19-Jan-92 100.99 3-Feb-96 101.74 15-Dec-97 108.85 15-Jan-05 101.17 4-Feb-07 105.32 5-Feb-10 100.88 Jay ------------------------------------ ------------------------------------ ------------------------------------ Hi Jay, We have likely broken the maximum upper-air wind speed record over eastern Canada at 1200 UTC 22 Dec 2013. Anton Seimon posted the 1200 UTC 22 Dec soundings from Goose Bay (CYYR) and La Grande (CYAH) to me earlier this morning and I have appended them in turn to this post. The maximum 250 hPa winds at CYYR and CYAH were are 248 kt (127.6 m/s) and 226 kt (116.3 m/s), respectively (max reported wind speed at CYAH was 232 kt or 119.4 m/s at 242 hPa). It’s not every day that you see an observed sounding with “five flags” as was the case at CYYR this morning. Savor and save the plotted sounding. The geese, and the jet planes, over Goose Bay were flocking eastward with record ground speeds this morning. Will the day come when we will see “six flags over" (fill-in-the-blank)? Lance ------------------------------------ ------------------------------------ ------------------------------------ As a follow-up to this discussion solely from a "hi-res" global grid perspective... Looking at the GFS and CFS analyses, these grids were able to analyze the maximum wind speed associated with this jet to be ~129 m/s and 131 m/s, respectively, at the 54˚N and 63.5˚W (for the CFS analysis). Each wind speed maximum was located at the 250 hPa level, although the 225 hPa level was only marginally (~1 m/s) weaker in each. While these are clearly impressive wind speeds, I noticed that they were significantly larger than the values that Jay Cordeira shared from the NCEP/NCAR reanalysis grids, likely due in part to the relatively coarse nature of the NCEP/NCAR grids (2.5˚ horizontal resolution) to the GFS or CFS grids (0.5˚ horizontal resolution). With this in mind, I did a quick comparison of the strongest wind speed maxima across the 0.5˚ CFS-Reanalysis dataset over the 1979-2012 period. Aside from a number of isolated dubious points in these grids, a list of cases with wind speed >120 m/s can be found below. 0000 UTC 25 Nov 2002 250hPa 40N 179.5E 126.611 1200 UTC 5 Feb 2004 250hPa 36N 137E 126.431 1200 UTC 11 Dec 1987 250hPa 48N 153E 126.249 1200 UTC 7 Dec 1985 250hPa 40N 169E 123.304 0600 UTC 15 Dec 1997 250hPa 43.5N -52E 123.29 1200 UTC 17 Jan 1981 250hPa 38N 161E 123.119 0000 UTC 7 Jan 1985 250hPa 36.5N 166.5E 123.006 1800 UTC 3 Jan 2002 250hPa 35N 157.5E 122.772 0000 UTC 3 Dec 1991 250hPa 50.5N -72E 122.538 1800 UTC 21 Jan 2010 250hPa 44N -157E 122.287 0000 UTC 15 Nov 1979 250hPa 58N -52E 122.239 0000 UTC 26 Nov 1979 250hPa 50N 171.5E 121.911 1800 UTC 13 Jan 2010 250hPa 37N 148.5E 121.865 1800 UTC 4 Jan 1994 250hPa 52.5N -46.5E 121.76 1200 UTC 2 Nov 2010 250hPa 42.5N -166E 121.579 0000 UTC 24 Feb 1991 250hPa 39N 153.5E 121.559 0600 UTC 16 Dec 2003 250hPa 42.5N -174.5E 121.382 1800 UTC 14 Jan 2001 250hPa 36N 149.5E 121.361 0000 UTC 15 Feb 1979 250hPa 38N -19E 121.301 0600 UTC 8 Feb 2004 250hPa 39N 173E 121.258 1200 UTC 14 Jan 1988 250hPa 38N -160E 120.856 1800 UTC 12 Dec 2008 250hPa 56N -39E 120.844 1200 UTC 23 Jan 1983 250hPa 35N 169.5E 120.704 0600 UTC 15 Jan 1992 250hPa 42N 166.5E 120.517 1800 UTC 17 Jan 2009 250hPa 48N -47.5E 120.391 0000 UTC 20 Jan 1982 250hPa 37N 151.5E 120.055 Three other local maxima in wind magnitude at other pressure levels (300, 250, 225, and 200) ranked higher than any other speed in the above list, although all three events are also represented on the first list of 250 hPa wind maxima: 1800 UTC 11 Dec 1987 225hPa 48.5N 150.5E 128.753 0600 UTC 15 Dec 1997 300hPa 43N -56.5E 127.883 0000 UTC 7 Jan 1985 225hPa 36.5N 165.5E 126.711 With this in mind, one could say that the 11 Dec 1987 jet is the strongest Northern Hemisphere jet observed over the last 34 years in the gridded CFS-Reanalysis at 128.75 m/s - a full 3 m/s less than has been analyzed by the CFS assimilation system (which, I believe, is what feeds the CFS-Reanalysis v2 data since the beginning of 2011) for the 1200 UTC 22 Dec 2013 jet over Eastern Canada. It is further interesting to note that the GFS did not resolve the full strength of this jet maximum until the Goose Bay observation was assimilated at 12z/22 and short-term forecasts from all prior runs underestimated the strength of the jets by over 5 m/s. The resulting question must be as to whether this jet would have been resolved at a speed >129 m/s without this observation, as nearly all of the events listed above are not within the observational network and are likely not analyzed via the direct observation of extreme jet-level winds as was the case with the Goose Bay sounding. So, while it may be tempting to say that this recent jet over eastern Canada is the strongest in the era of high-resolution global gridded analyses (and it does appear to be the strongest in the gridded reanalyses themselves), the caveats associated with being able to analyze from a direct observation when direct observations are so rare on the global perspective should be a significant consideration when comparing this event to others in the historical record. Kyle ------------------------------------ ------------------------------------ ------------------------------------ Hi Kyle, Many thanks for documenting all occurrences of 250 hPa winds speeds > 120 m/s, all of which have occurred over the western Pacific, in the CFS gridded dataset since 1979. Based on your analysis, it appears that the corridor of 120+ m/s winds at 250 hPa from Goose Bay eastward to Labrador and Newfoundland at 1200 UTC 22 Dec is unique in the North American record (even when allowing for measurement uncertainties….especially in earlier years as noted by Jimmy Correia). I searched online for strong jet stream winds and found many references to 300 mph (260.7 kt; 134.1 m/s) and greater jet stream winds (e.g., http://www.geoffreywildman.eu/page2.html). Alas, I was unable to find any online sources that gave specific evidence (e.g., wind speed, date, flight level) of 300 mph jet stream winds. Presumably, grizzled commercial or military pilots who flew (or currently fly) routes across the North Pacific in winter and/or airline meteorologists responsible for route planning across the North Pacific would have an interesting perspective on the frequency of occurrence and magnitudes of extreme jet stream winds. Input welcome here! Lance ------------------------------------ ------------------------------------ ------------------------------------ Greetings Lance & Kyle, To follow up on Kyle's excellent analysis, I performed a quick find-max on the 0.5° grid-points in the NCEP CFSR + CDASv2 (1979-2013) dataset for wind speed at 200-hPa. To help visualize the geographic locations of historical jet streaks, I'm attaching 3-figures that represent the wind speed maximum analyzed at each grid point using 6-hourly files from 1979-2013. (a) Maximum Wind > 60 m/s (b) Maximum Wind > 100 m/s (c) Maximum Wind > 60 m/s during December 2013 There are a lot of garbage grid-points in the CFSR that make searching for global extreme events in pressure level fields an extra hard task. Nevertheless, I think we've firmly established that a 100 m/s jet streak is rarefied air. Cheers, RYAN