National Weather Service-Pennsylvania State University Weather Events

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1 National Weather Service-Pennsylvania State University Weather Events The high latitude Eurasian Anticyclone of January-February 2012 by Richard H. Grumm National Weather Service State College PA Abstract:. A strong blocking anticyclone developed over northern Russia in late January As the anticyclone strengthened, a closed 5640m ridge with near 3σ above normal height anomalies developed over northern Russia. At the surface an anticyclone developed with a closed 1060 hpa and at times a closed 1064 hpa contour. This massive deep anticyclone transported warm moist air into the Arctic, producing warm conditions and rain in the Spitsbergen Islands to near 80 degrees north latitude. But the high impact, if not historic, weather event occurred to the south where the strong easterly flow on the southern flank of the anticyclone pushed arctic air into eastern, central and eventually Western Europe. The cold air resulted in over 150 weather related deaths by 2 February The winter of had been relatively mild for most of Europe. As the cold air surged westward, it brought snow and temperatures fell to near normal then to well below normal. The mild conditions were rapidly replaced by harsh winter conditions. As the cold weather swept into Western Europe it brought snow to Rome, Italy for the first time in 26 years. Temperature fell below -32C (-26F) over portions of Eastern Europe. This paper will document the anticyclone and the cold episode that affected much of Europe over the period of 30 January through 3 February 2012.and its impacts. The focus is on the use of anomalies to analyze this and similar high impact weather events. Forecasts from the NCEP GFS and GEFS are presented to show the value of using climate data in the forecast process to better anticipate extreme weather events.

2 1. INTRODUCTION A massive anticyclone developed over the higher latitude of Eurasia toward the end of January The National Centers for Environmental Predictions (NCEP) Global Forecast System (GFS) showed a closed 1060 hpa contour at 0000 UTC on 30 and 31 January (Fig. 1) with mean sea level pressure anomalies in the 3 to 4σ above normal range. As impressive as this anticyclone may have been, a record pressure of hpa was recorded on 31 December 1968 at Agata, Evenhiyskiy, Russia (ASU) and surface pressure over Russia in excess of 1060 hpa though not common, does occur periodically over Russia during the winter months. The strong surface anticyclone was associated with a strong mid-tropospheric anticyclone (Fig. 2) at 500 hpa. Similar too many strong anticyclones, there often surges of deep moisture and warm air on the western flanks of these systems (Grumm 2011). This event too had a surge of warm moist air along its western flank. This produced warm weather and rain over Spitsbergen in late January The high impact weather with these events often occurs to the south where strong easterly flow can transport cold air over Siberia westward into Europe. Strong anticyclones over Russia ridging into Western Europe are historically linked to record cold episodes in central and Western Europe. Similar to previous massive anticyclones over Russia, this anticyclone pushed arctic air into eastern, central, eventually into Western Europe. This abruptly brought cold air and snow into Europe (AP 2012; MailOnline 2012a & 2012b) which had been experiencing a relatively mild winter until this outbreak of cold air. The Siberian anticyclone (Britannica) is a semi permanent system of high pressure beneath which extremely cold air develops. As this system extends westward, it can cause arctic outbreaks over Eastern and Western Europe. The cold weather was blamed for over 70 deaths from Russia to Poland and southward into the Balkans (AP 2012). In the Ukraine the cold weather reportedly killed 101 people with 38 deaths reportedly killed overnight 2-3 February 2012 (MailOnline 2012b). Portions of Turkey and the Balkans were also hit by heavy snow and blizzard conditions. For a region of the world known for cold weather, the impact was severe. The severity was attributed to the general lack of cold weather and the relatively mild winter until the abrupt change to colder weather in late January. The cold weather spread into Western Europe and Rome reported measurable snow for the first time since Climatologies of northern hemisphere anticyclones (Galarneau et al. 2008;Bell and Bosart 1989, and Barriopedro 2006) suggest this event occurred in region where closed 500 hpa anticyclones and surface anticyclones typically form during the winter months. Unfortunately, most studies focused on strong ridges, using a closed contour such as 5880 m. Thus studies such as Galarneau et al. (2008) were more likely to identify ridges associated with summer time heat events and warm episodes than winter anticyclones associated with arctic outbreaks. Many studies approach the problem associated with large anticyclones from the perspective of blocking (Wiedenmann et. al. 2002; Lupo et. al 1995). Interestingly, northern hemispheric blocking events were found to be stronger and more frequent during La Niña year than El Niño years. Additionally, Wiedenmann et al. (2002) showed

3 that a large number of northern hemispheric blocking events are observed between about -40 and +40 degrees longitude (see their Fig. 3). This event appeared to occur within that longitudinal band during a La Niña winter. The winter of was extremely cold 20 th century winter over Europe (Lejeñas 1989) and it was characterized by blocking and cut-off lows which peaked during the months of January and February 1942 This paper will document the massive high latitude anticyclone over northern Europe in late January and early February The system will be examined from using standardized anomalies to characterize the event, including the cold and the surge of warm air into the arctic on its western flanks. The focus is on the standardized anomalies as a tool to both analyze and predicted this and similar events. The forecast section of this paper will show the value of using climate data and internal ensemble prediction system climate data to better anticipate and predict extreme weather events. 2. Methods and Data The NCEP GFS is used to re-produce the conditions associated with the event to include the large scale pattern. The standardized anomalies are displayed in standard deviations from normal as in Hart and Grumm (2001) and are computed using the climatology from the NCEP/NCAR global reanalysis data (Kalnay et al. 1996). The focus is on the pattern and anomalies associated with the storm. The value of EFS and anomalies with EFS data are presented. Ensemble data shown here are from the NCEP Global Ensemble forecast system which is run at 75km in horizontal resolution. The emphasis here is on products which may aid in predicting the potential for extreme or high impact weather events. The overall pattern is described using the 27.5km NCEP GFS 00-hour forecasts. The pattern and standardized anomalies followed the methods outlined in Hart and Grumm (2001) and the GFS 00-hour forecasts were used to establish the pattern and standardized anomalies. The term R-Climate is used in reference to analysis and forecast which use re-analysis climate data to diagnose or forecast the departures from normal. The NCEP/NCAR reanalysis data was used to find the occurrence of mean sealevel pressures above 1064 hpa from 1 January December These data were also used to find 500 hpa heights over 5640 m over the region during the winter season. For brevity times are presented as day and hour in the format 31/1200 UTC and 01/0000 UTC which would be 1200 UTC 31 January 2012 and 0000 UTC 1 February 2012 respectively. Fully qualified dates are limited to comparative data from times outside of January and February Results i. The large scale pattern The evolution of the 500 hpa pattern (Fig. 2a) showed the 500 hpa ridge over Asia at 22/0000 UTC and another 500hPa ridge over Spitsbergen. The key feature was the retrograding 500 hpa anticyclone (Figs. 2a-e). This feature strengthened as it moved eastward across Russia into Eastern Europe. A closed 5640 m contour is evident at 01/0000 UTC with over +3σ height anomalies implying a strong mid-tropospheric anticyclone. Examining these data in 6, 12 and 24 hour increments (not shown) implied

4 that the 5640 m contour developed on 31 January around 1200 UTC. The key features with the ridge include the strong easterly flow over Eurasia south of the ridge and the strong west to southwestern flow north of the ridge. The former would bring cold air into Europe while the later would flood the arctic north of Europe with warm moist air. The surface pattern showing the evolution of the surface anticyclone from 26/0000 UTC through 31/0000 UTC (Fig. 1) and from 27/1200 UTC through 01/1200 UTC (Fig. 3) indicated a massive surface anticyclone which had a central pressure over 1060 hpa (Figs. 1e&f and Fig. 3d-f) and at times had a closed 1064 hpa contour (Figs 3ef). Mean sea-level pressure anomalies over 1σ above normal dominated most of Eurasia with +3 to +4σ anomalies located near the anticyclone center (Figs. 3c-f). As shown by Graham and Grumm (2011) and Grumm and Hart (2001), significant weather events (SWE) are often associated with features associated with large standardized anomalies. This case was no exception. Based on the NCEP/NCAR re-analysis data, surface pressure greater than 1064 hpa occur have occurred been observed 941 times since 1948 of the time periods available. Values greater than 1080 hpa have been observed 6 times with the winter of 1958 dominating the list occurring on 12, 13 and 28 January Large anticyclones in January 1955, 1960, and 2010 rounded out the list with pressure values over 1080 hpa. The 850 hpa temperatures over the region initially showed that the 850 hpa temperatures were close to normal (Fig. 4). The plume of warm moist air moving over the ridge (Figs. 4a-f) was the most anomalies feature in the early stages of the anticyclones evolution (Figs. 1 &3). The surge of warm air brought 2 to 3σ above normal 850 hpa temperatures into the Arctic Ocean. By 29/1200 UTC (Fig. 4c) a surge of cold air, with a -20C contour could be seen moving westward out of Asia toward Europe. This second surge of cold air would flood most of Europe with below normal 850 hpa temperatures (Fig. 4e) by 31/1200 UTC and 850 hpa temperatures would fall below 20C over the Balkans with -3 to -4σ 850 hpa temperatures by 01/1200 UTC. The plume of anomalous moisture (Fig. 5) moved into the arctic north of the ridge (Fig. 2). Plumes of deep moist warm air on the western flanks are commonly found in mid-latitude anticyclones (Grumm 2011). The precipitable water (PW) values of 5 to 15 mm present anomalously high values of PW in the arctic. These 24 hour increment data show the surge of +5 to +6σ PW values into the arctic and over Spitsbergen where warm air and rain affected an extremely poleward region 1. ii. Regional pattern and key anomalies The surge of high PW air (Fig. 6), which brought rain to Spitsbergen at 78N on 29 January 2012 brought 3-4s PW anomalies to the region by 29/1800 UTC (Fig. 6b) and a 12-hour period where PW anomalies were in excess of 6s above normal (Fig. 6c-d). Interestingly, at such high latitude that PW values near 15mm produced a 6σ event. This clearly represented an anomalously warm moist air mass for such a poleward latitude. These high PW values were accompanied by strong winds which produced relatively large values of 850 hpa moisture flux (MFLUX) and high MFLUX anomalies. 1 Reports of temperatures of 5C with rain on the permafrost reportedly turned the town of Svalbard at N (ENSB) into a skating rink on 29 January METAR observations showed rain and 5C temperatures from 2000 UTC through 2300 UTC 29 January.

5 MFLUX anomalies in excess of 6σ were present over Spitsbergen from 29/1200 UTC through 30/1200 UTC (Fig. 7). The surge of cold air across western portions of Eurasia into central Europe is depicted with 850 hpa temperatures (Fig. 8). These data show the first surge of cold air over the Turkey and southeastern Europe (Fig. 8a) and the western edge of an even colder air mass moving westward south of the 500 hpa anticyclone. This second colder air mass brought -3 to 4σ 850 hpa temperature anomalies to Eastern Europe by 01/1200 UTC (Fig. 8f). Clearly, the anticyclone was able to tap cold air from Siberia and advect it westward and this second air mass was considerable colder than the initial news worthy air mass which affected the region on January iii. GFS Forecasts For brevity a few select GFS 850 hpa temperature forecasts are shown to compare to the analysis of the event presented in the previous sections. The GFS initialized at 25/1200 and 30/1200 UTC are presented in Figures 9 & 10 respectively. Forecasts are in 12-hour increments from 31/1200 UTC through 02/1200 UTC. Both cycles predicted a surge of cold air with below normal 850 hpa temperatures into eastern and central Europe. Bucharest (red dot) was forecast to be considerably colder from the more recent 30/1200 UTC forecasts than from the 25/1200 UTC forecasts. Note the large -3 to -4σ anomalies valid 02/0000 UTC (Fig. 10F) verse the 25/1200 UTC forecasts which did not bring the cold Siberian air as far west. This general trend toward colder 850 hpa temperatures was present in all GFS forecasts (Fig. 11) over the 6 day period. The longer range forecasts were cold, but not as cold as shorter range forecasts. The differences and errors related to a weaker 500 hpa ridge aloft (not shown) and a weaker surface anticyclone (Fig. 12) in the longer range forecasts. iv. GEFS Forecasts Two GEFS forecasts are shown to compliment the forecast shown above. The projection has been shifted to show the impact of the 500 hpa and surface anticyclones. GEFS initialized at 25/1200 and 28/1200 UTC valid at 02/0000 UTC are shown. The 25/1200 UTC grossly underestimated the probability of a +2s 500 hpa height anomaly and a +2s mean sea-level pressure anomaly (Figs. 13a&b). The results were lower probabilities of -2s temperature anomalies at 850 hpa and 2m relative to the forecasts initialized at 28/1200 UTC (Fig. 14a&b). The shorter range forecasts from the NCEP GEFS initialized at 28/1200 UTC showed that nearly all members were predicting +2s height and pressure anomalies with the anticyclone over northern Russia (Fig. 14a&b). The stronger anticyclone forecasts produced higher probabilities of colder 850 hpa temperatures and 2m temperatures (Figs. 14c-d). Similar trends were found in the GEFS forecasts initialized on 26, 27, 29 and 30 January. It was critical to get the anticyclone correct in order to get the magnitude of the cold air. v. Historical and meteorological perspective

6 . This event was characterized by a massive anticyclone at the surface and a blocking pattern over Eurasia. At 500 hpa the heights over northern Russia exceed 5580m at time and the surface pressure exceeded 1060 hpa. Large anticyclones over Russia typically form in the Siberia and the region about Lake Baikal. The massive anticyclone of December 1968 when Agata, Evenhiyskiy, Russia (ASU) set a record pressure of hpa is shown in Figure 15. Despite the high pressure the NCEP/NCAR data only depicted a 1068 hpa contour (Figs. 15e&f). During December 1968 the 500 hpa block had an anomalous ridge of Siberia and cut-off low over China (not shown) and the anomalously cold air at 850 hpa affected Asia. The anticyclone associated with the 2012 event formed with the block over central Russia and the anticyclone pushed cold air into Europe. The cold air arrived on the heels of a relatively warm period over Eastern Europe. In the Ukraine temperatures were above normal most of December through mid-january (Fig. 16). Initially, temperatures fell below normal around the 16 th and then fell well below normal after the 24 th of January. Farther west, over Germany, there was clearly a prolonged period of above normal warm weather from late November though late January. The truly cold air did not arrive in Germany until late January Conclusions A strong blocking anticyclone developed over northern Russia in late January As the anticyclone strengthened a closed 5640m ridge with near 3σ above normal height anomalies developed over northern Russia. At the surface an anticyclone developed with a closed 1060 hpa and at times a closed 1064 hpa contour. Strong easterly flow south of the surface anticyclone brought cold Siberian air into Eastern, Central and eventually into Western Europe. The cold arrived with devastating effect. As of 3 February 2012 the cold and snow were attributed with causing over 150 deaths. The primary cause was due to hypothermia. The deaths began to appear in the media around 30 January 2012 several days before the deep arctic air arrived in central Europe (Fig. 4). The winter of was atypically warm over much of Western and Eastern Europe (Fig. 16). The period of prolonged warmth before the arrival of the arctic air may have contributed to the significant societal impacts. Despite a region of the world generally use to cold air, the warmth may have left individuals and municipalities in a low state of readiness for the impacts of a record cold event. Meteorologically, the large closed 500 hpa anticyclone center (Fig. 2) was close to the position where winter season anticyclones were often observed the 15-year study of northern hemisphere 500 hpa closed anticyclone centers (Fig. 5: Bell and Bosart 1989). Unfortunately, there are no comprehensive studies of anticyclones and their impacts over Eurasia. Most studies of this nature focus on blocking and blocking indices. These indices provide useful information as they relate to events where above normal heights is present at high latitudes and lower heights are found at lower latitudes. Blocking studies suggest these situations relate to the Arctic Oscillation (AO) and can be instrumental in bringing cold air into lower latitudes. During the winter of the AO was strongly positive but rapidly fell to negative around 20 January 2012 and

7 lowered to -3 by then of January. The blocking episode over Russia clearly changed the sign of the AO in mid-january which lined up well with the end of the warm weather in the Ukraine (Fig. 16) in mid-january and over Germany by late January In addition to pushing arctic or Siberian air into Europe, large high latitude ridges can push warm moist air into high latitudes on their western flanks. Such plumes of deep moist warm air on the western flanks are commonly found in mid-latitude anticyclones (Grumm 2011) during the warm season. The so-called ring-of-fire is common warm season feature. This case demonstrates the more general nature of large mid-tropospheric anticyclones to transport warm moist air poleward on their western flanks. To the south, these large features can transport cool air into lower latitudes. The plume of moisture which moved about the western flanks of the massive 500 hpa and surface anticyclone brought rain well into the arctic north of Norway. The rain was accompanied by 6σ PW anomalies. Observations implied that the city of Svalbard reached 5C during a period of rainfall, which fell on the permafrost. This created icy conditions on the Island and in the city. To the south, the anticyclone effectively brought extreme winter conditions to lower latitudes. The data shown here imply that this extreme cold outbreak was relatively well predicted by the NCEP GFS and GEFS. Though not shown forecasts implied that the cold conditions in Europe would continue through at least the middle of February. It is tragic to note that despite these relatively successful forecasts, many people lost their lives. It should be noted that 5-6 days out the NCEP models underestimated the cold air and the intensity of both the 500 hpa anticyclone and the surface anticyclone. 5. Acknowledgements The Albany Map of information related to the event. Ryan Maue and Lance Bosart for information on the event and for providing references. 6. References Associated Press, 2012: Death Toll from Europe Cold Spell Hits 79 (and similar stories published 30 January through 1 February 2012.) Bell, Gerald D., Lance F. Bosart, 1989: A 15-Year Climatology of Northern Hemisphere 500 mb Closed Cyclone and Anticyclone Centers. Mon. Wea. Rev., 117, Barriopedro, David, Ricardo García-Herrera, Anthony R. Lupo, Emiliano Hernández, 2006: A Climatology of Northern Hemisphere Blocking. J. Climate, 19, Galarneau, Thomas J., Lance F. Bosart, Anantha R. Aiyyer, 2008: Closed Anticyclones of the Subtropics and Midlatitudes: A 54-Yr Climatology ( ) and Three Case Studies. Meteorological Monographs, 33, Graham, Randall A., and Richard H. Grumm, 2010: Utilizing Normalized Anomalies to Assess Synoptic-Scale Weather Events in the Western United States. Wea. Forecasting, 25,

8 Grumm, R.H 2011: The Central European and Russian Heat Event of July-August 2010.BAMS, 92, Grumm, R.H. and R. Hart. 2001: Standardized Anomalies Applied to Significant Cold Season Weather Events: Preliminary Findings. Wea. and Fore., 16, Hart, R. E., and R. H. Grumm, 2001: Using normalized climatological anomalies to rank synoptic scale events objectively. Mon. Wea. Rev., 129, Junker, N.W, M.J.Brennan, F. Pereira,M.J.Bodner,and R.H. Grumm, 2009:Assessing the Potential for Rare Precipitation Events with Standardized Anomalies and Ensemble Guidance at the Hydrometeorological Prediction Center. Bulletin of the American Meteorological Society,4 Article: pp Junker, N. W., R. H. Grumm, R. Hart, L. F. Bosart, K. M. Bell, and F. J. Pereira, 2008: Use of standardized anomaly fields to anticipate extreme rainfall in the mountains of northern California. Wea. Forecasting,23, Jones, Justin E., Judah Cohen, 2011: A Diagnostic Comparison of Alaskan and Siberian Strong Anticyclones. J. Climate, 24, Lalaurette, F. 2003: Early Detection of abnormal weather conditions using a probabilistic extreme forecast index. QJRMS,129, Lejañas, H.,1989: The Severe Winter in Europe The large scale-circulation, cut-off lows, and blocking. BAMS,70, Lupo,A.R, and P. J. Smith, 1995a: Climatological features of blocking anticyclones in the Northern Hemisphere. Tellus, 47A, Mail Online 2012a Deep Freeze death toll rises to 48 as Eastern Europe is battered by heavy snow. (and similar stories 31 January 2012). + Mail Online 2012b Snow falls in Rome for the first time in 26 Years as -36C temperatures across eastern Europe send death toll to 150. (and similar stories 2-3 February 2012). Root, B., P. Knight, G.S. Young, S. Greybush, R.H. Grumm, R. Holmes, and J. Ross, 2007: A fingerprinting technique for major weather events. Journal of Applied Meteorology and Climatology, 46, Wiedenmann, Jason M., Anthony R. Lupo, Igor I. Mokhov, Elena A. Tikhonova, 2002: The Climatology of Blocking Anticyclones for the Northern and Southern Hemispheres: Block Intensity as a Diagnostic. J. Climate, 15,

9 Figure 1. NCEP GFS 00-hour forecasts of mean sea level pressure (hpa) and pressure standardized anomalies (standard deviations) in 24- hour increments from a) 0000 UTC 26 January 2012 through f) 0000 UTC 31 January Contours are every 4 hpa and anomalies are as as in the color bar. Return to text.

10 Figure 2. As in Figure 1 except for 500 hpa heights (m) and 500 hpa height standardized anomalies in 48 hour increments from a) 0000 UTC 22 January 2012 through f) 0000 UTC 01 February Contours every 60m. Return to text.

11 Figure 3. As in Figure 1 except for surface pressure in 24-hour increments from a) 1200 UTC 27 January through f) 1200 UTC 1 February Green dot is near Svalbard in the Spitsbergen Islands. Return to text.

12 Figure 4. As in Figure 3 except for 850 hpa temperatures and 850 hpa temperature standardized anomalies. Isotherms every 2C. Return to text.

13 Figure 5. Precipitable water (mm) and precipitable water anomalies over Eurasia in 24 hour increments from a) 1200 UTC 27 January 2012 through f) 1200 UTC 01 February PW contours every 5mm. The green dot is near Svalbard in the Spitsbergen Islands. Return to text.

14 Figure 6. As in Figure 5 except for PW focused over northern Europe in 6-hour increments from a) 1200 UTC 29 January through f) 1800 UTC 30 January Return to text.

15 Figure 7. As in Figure 6 except for 850 hpa moisture flux and moisture flux anomalies. Return to text.

16 Figure 8. GFS 850 hpa temperatures and temperature anomalies over central Europe in 12 hour increments from a) 1200 UTC 30 January 2012 through f) 1200 UTC 2 February Return to text.

17 Figure 9. NCEP GFS 850 hpa temperature forecasts initialized at 1200 UTC 25 January 2012 showing forecasts valid in 12-hour increments from a) 1200 UTC 30 January through f) 0000 UTC 02 February Isotherms are every 2C and anomalies in standard deviations from normal as in the color bar. The red dot is Bucharest, Romania. Return to text.

18 Figure 10. As in Figure 9 except for forecasts initialized at 1200 UTC 30 January Return to text.

19 Figure 11. GFS 850 hpa temperatures forecasts valid at 0000 UTC 2 February 2012 from GFS forecasts initialized at 1200 UTC a) 30 January, b) 29 January, c) 28 January, d) 27 January, e) 26 January and f) 25 January Return to text.

20 Figure 12. As in Figure 11 except for mean sea-level pressure (hpa) and pressure anomalies valid at 0000 UTC 02 February Return to text.

21 Figure 13. NCEP GEFS initialized at 1200 UTC 25 January 2012 showing ensemble mean a) 500 hpa heights and the probability of 500 hpa heights exceeding 2s above normal, b) mean sea-level pressure and the probability of sea level pressure anomalies in excess of 2s above normal, c) 850 hpa temperatures and the probability of 850 hpa temperature anomalies less than -2s below normal, and d) 2m temperatures and the probability of 2m temperatures being -2s below normal. The 500 hpa heights are every 120m, isotherms 8 hpa, 850 hpa temperatures 4C, and 2m temperatures are powers of 2 with intervening 12 and 24 contours. Return to text.

22 Figure 14. As in Figure 13 except GEFS initialized at 1200 UTC 28 January Return to text.

23 Figure 15. NCEP/NCAR re-analysis of mean sea-level pressure and pressure anomalies in 24 hour increments from a) 1200 UTC 28 December 1968 through f) 1200 UTC2 January Return to text.

24 Figure 16. Climate Prediction Center data showing daily average temperature anomalies, daily temperature departures and daily temperatures for Zaporozhe, Ukraine, and Berlin, Germany. Return to text.