Krymsk Flood of 6-7 July 2012-Draft

Transcription

1 1. Overview Krymsk Flood of 6-7 July 2012-Draft A flood ripped through the Russian town of Krymsk overnight on 6-7 July The flood killed 172 people and people were injured or suffered losses due to the flooding. The floods were caused by a slow moving upper low which pushed moisture from the Black Sea into the coastal hills which are 400 to 500 m high. This resulted in torrential rains in the higher terrain to the southwest of Krymsk which resulted in flash flooding. Satellite imagery (Fig. 2 &3) showed showers over the region after 0000 UTC 06 July 2012 with an enhanced region of cold cloud tops indicative of deep convection by 0800 UTC. A second round of deep convection, as indicated by satellite, developed over the region around 2000 UTC and the coldest cloud tops evolved around 2300 UTC 6 July and persisted through 0200 UTC 7 July when the system began to weaken and warm. By 0600 UTC 7 July most of the significant rainfall had likely ended. Figure 1. Google map with terrain along the northeast shore of the Black Sea showing the location of Krymsk, to the lee of a chain of hills. A road runs up a valley from Krymsk to the valley west of these hills. A stream appears to follow the road. The convection developed near an 850 hpa cyclone (Fig. 4). The cyclone was relatively strong for the time of year and location with height anomalies on the order of -1 to -2σ below normal. North of the Black Sea the 850 hpa heights were above normal, indicating a large anticyclone over Russia. The 850 hpa low moved westward over time, retrograding over the Black Sea. The southwesterly flow southeast of the cyclone center brought moist Black Sea air into the terrain along the shore of Black Sea, west of Krymsk (Fig. 1). It will be shown that forecasts from ensemble forecasts systems and deterministic models predicted the potential for rain in the region where satellite imagery indicated rainfall and in close proximity to Krymsk, where the deadly flash flood was observed. Furthermore, high resolution model data indicated that the flow favored some heavy rainfall in the hills near Krymsk. These data suggest that this event was relatively predictable.

2 It is unknown whether local forecasters had radar and whether these data are accessible to examine the short-term information potentially available in the warning decision process. At this time satellite data provides the insights as to when the rain most likely fell, based on cloud top temperatures and features. There were indications for the potential for rainfall and perhaps above normal rainfall. It is unlikely that there was sufficient information to warn-on-forecast. Forecasts can aid in heightening situational awareness. This paper will document the tragic and deadly flow in Krymsk, Russia. The focus is on the pattern associated with heavy rainfall and forecasts related to the rainfall. The goal is to see if this event was predictable or had signals which would have allowed a longer lead-time to alert people to the threat of heavy rainfall and flooding. 2. Data and Methods GFS 00-hour forecasts were used to diagnose the pattern over central Europe and the Black Sea. The GFS was also used to initialize the workstation WRF model to make high resolution runs. The GFS, GEFS, and EC model data were used to examine the forecasts of the pattern (not shown) and the potential quantitative precipitation forecasts. The NCEP models were retrieved and archived in real-time. The EC models and ensembles were retrieved from the European Center for Medium-Range Weather Forecasts (ECMWF) TIGGE site. Satellite data where taken from the Climate Prediction Center (CPC) CMORPH site. The 3-hourly version of the CMORPH data were used here. All data were displayed using GrADS. 3. The large scale pattern associated with the flood The 500 hpa pattern over the region from 05/0000 UTC through 1200 UTC 7 July 2012 (Fig. 5) showed a ridge north of the Black Sea with above normal heights over Russia. The low over the eastern Black Sea (Fig. 5b-e) had the appearance of a Rex Block (Rex 1950a;1950b) with a high north of the low. The 850 hpa cyclone (Fig. 2) was beneath the 500 hpa cyclone. The flow about the 850 hpa cyclone (Fig. 6) advected moisture (Fig. 7) into the region near Krymsk. The 850 hpa winds into the terrain were about 10ms-1 which is about 1σ above normal. The precipitable water (PW) values were around 40mm over the region, about 2-3σ above normal. The relatively high PW values persisted over and near Krymsk approximately the entire period of heavy rainfall, from 06/0600 UTC through 07/1200 UTC. The combination of strong winds and above normal PW values produced strong moisture flux in the region. The 925 hpa moisture flux (Fig. 8) was stronger than the moisture flux at 850 hpa and 700 hpa (not shown). The 925 hpa moisture flux implied a strong low-level circulation (not shown) advecting the warm moist air into the terrain along the shores of the Black Sea. The local terrain feature likely added in the enhanced rainfall. The low-level flow or inflow of

3 moisture off the Black Sea likely explains the relative back building convection which was observed when looping the METEOSAT data. This back building effect can be seen in the mesoscale convective complex in Figure 2 between 06/2100 and 07/0130 UTC. Though the 925 hpa moisture flux anomalies were modestly above normal, in a favorable convective environment they often indicate the potential for convective development and maintenance. 4. Quantitative Precipitation forecasts The NCEP GFS QPF from the four successive runs from 05/0600 UTC through 06/0000 UTC (Fig. 8) show the potential for QPF over the region in each run. There were clear run-to-run inconsistencies indicating uncertainty. The two latter runs from 06/1800 and 07/0000 UTC showed higher QPF amounts, farther to the east suggesting predictability issues and a relatively short predictability horizon. The latest run, initialized just 5-6 hours before the heavy rains began predicted over 80mm of QPF. The model indicated the potential for 50 mm or more QPF from the GFS initialized at 06/1800 and 07/0000 UTC. The GFS forecast the period of heaviest rainfall from 06/0600 UTC and 07/0900 UTC. The European Center high resolution model (EC) forecasts in 12-hour increments from 05/0000 through 06/0000 UTC (Fig. 9) show that the EC had a better location for the axis if heavy rainfall. The relative position and axis of the heavy rainfall was more consistent than the NCEP GFS forecasts. The EC produced similar total QPF amounts, about 80mm from the forecast issued at 06/0000 UTC. Similar to the GFS, higher amounts were forecast at shorter forecast ranges 5. Satellite QPE and observations The 3-hour CMORPH rainfall in 6-hour periods for 6 July (Fig. Q1) implies that the heaviest rainfall was from 06/1800 through 07/0000 UTC (Fig. Q1-d) with 6-hour periods of upto 24 mm of estimated rainfall along the shore of the Black Sea for the 6-hour period ending at 06/0600 UTC and about 16mm at 06/1200 UTC. Inland rainfall estimates peaked at 06/1800 and 07/0000 UTC. The best 3-hour rainfall was from July, UTC 6 July and UTC 7 July (not shown) which affected the total 12-hour QPE (Fig. Q2-d). Synoptic surface observations confirmed the satellite data with reports of CB clouds and showers along and east of the Sea of Azov to the city of Novorossiysk. Similar to the CMORPH QPE the showers were reported in the region from after 06/1200 through 07/0600 UTC at several stations. Krymsk had CB and showers from 06/1500 through 07/0300 UTC based on the 3- hourly synoptic plots. Several time periods are shown in Figure Q3. 6. Summary A cut-off low beneath a strong ridge over Russia tapped moisture from the Black Sea, pushing warm moist air into the terrain in southern Russia. Based on satellite data, a cold cloud shield indicative of mesoscale convective system (MCS) developed in the hills near Krymsk. The

4 resulting convection near the 850 hpa cyclone produced locally heavy rainfall, resulting in flash flooding in Krymsk killing 172 people. The proximity to the 850 hpa low and closed 500 hpa low suggest that this event has some of the characteristics of a subtle heavy rainfall event (SHARS:Spayd and Scofield 1983). Model forecasts showed some ability to predict the potential rainfall. Though only higher resolution local area models at 4 and 8 km resolution appeared to be capable of predicting rainfall amounts in excess of 150 to 225 mm of QPF. Deterministic models and global ensembles appeared to predict the potential for rainfall in the region where the rain was observed. However, most forecasts suggested 25 to 75 mm of rainfall. Though it is unclear how if 75 to 80mm of rainfall would be an extremely heavy rainfall event in the region in and around Krymsk. This would be important information as well as information as to whether numerical guidance was predicting a high end rainfall event. The EC forecasts were more consistent relative to the NCEP GFS forecasts, implying higher variability in the initial conditions in the GFS relative to the EC. Despite this, both models produced similar QPF amounts and general locations from forecast initialized at 06/0000 UTC. The ability to predict and anticipate the potential for heavy rainfall is critical in the decision making process. It is irrelevant if the rain could have been forecast or not if there is no mechanism to communicate the information and take actions to avoid the loss of life and property. It is difficult to warn-on-forecast and to get decision makers to act on forecasts. It is unknown whether real-time radar was available and monitored to estimate the threat of extremely heavy rainfall and flooding. There is considerable missing hydrologic information to include what rainfall amounts are know or estimated to cause flash flooding in the region, how fast the streams respond to extreme rainfall in the headwater regions, and how much time is available to warn once it is known that heavy rainfall is falling in the basins. 7. References Craven, J. P., and H. E. Brooks, 2004: Baseline climatology of sounding-derived parameters associated with deep moist convection. Natl. Wea. Dig., 28, Doty, B.E. and J.L. Kinter III, 1995: Geophysical Data Analysis and Visualization using GrADS. Visualization Techniques in Space and Atmospheric Sciences, eds. E.P. Szuszczewicz and J.H. Bredekamp, NASA, Washington, D.C., Davies, J. M., 2006a: Tornadoes in Environments with Small Helicity and/or High LCL Heights. Wea. Forecasting, 21, doi: Davies, J.M.. (2006b) Tornadoes with Cold Core 500-mb Lows. Weather and Forecasting 21:6, Online publication date: 1-Dec Abstract. Full Text. PDF (1512 KB)

5 Grams,J.S, R. L. Thompson, D. V. Snively, J. A. Prentice, G. M. Hodges, L. J. Reames. (2012) A Climatology and Comparison of Parameters for Significant Tornado Events in the United States. Weather and Forecasting 27:1, Online publication date: 1-Feb Grams, J. S.,W.A.Gallus Jr., S. E.Koch, L. S.Wharton,A. Loughe, and E. E. Ebert, 2006: The use of a modified Ebert McBride technique to evaluate mesoscale model QPF as a function of convective system morphology during IHOP Wea Forecasting, 21, Markowski, P. M., J. M. Straka, and E. N. Rasmussen, 2002: Direct surface thermodynamic observations within rear-flank downdrafts of nontornadic and tornadic supercells. Mon.Wea. Rev., 130, Rutledge, G.K., J. Alpert, and W. Ebuisaki, 2006: NOMADS: A Climate and Weather Model Archive at the National Oceanic and Atmospheric Administration. Bull. Amer. Meteor. Soc., 87, Markowski, P, Y. Richardson, E. Rasmussen, J. R. Davies-Jones, R. J. Trapp, 2008: Vortex Lines within Low-Level Mesocyclones Obtained from Pseudo-Dual-Doppler Radar Observations. Mon. Wea. Rev., 136, doi: Rex, D. F., 1950a: Blocking action in the middle troposphere and its effect upon regional climate. I. An aerological study of blocking action. Tellus, 2, , 1950b: Blocking action in the middle troposphere and its effect upon regional climate. II. The climatology of blocking action. Tellus, 2, Shapiro, Melvyn, and Coauthors, 2010: An Earth-System Prediction Initiative for the Twenty-First Century. Bull. Amer. Meteor. Soc., 91, doi: Schoen, J.M W. S. Ashley. 2011: A Climatology of Fatal Convective Wind Events by Storm Type. Weather and Forecasting 26:1, Online publication date: 1-Feb Abstract. Full Text. PDF (1569 KB) Spayd, L.E. Jr and R.A. Scofield: 1983: Operationally detecting flash flood producing thunderstorms which have subtle heavy rainfall signatures in GOES imagery. Fifth Conference on Hydrometeorology, Tulsa, OK, Amer. Meteor. Soc., Trapp, R. J., S. A. Tessendorf, E. S. Godfrey, H. E. Brooks, 2005: Tornadoes from Squall Lines and Bow Echoes. Part I: Climatological Distribution. Wea. Forecasting, 20, doi:

6 Figure 2. METEOSAT9 IR imagery at (clockwise from top left) 6 July 0200 UTC, 6 July 0730 UTC 6 July 2100 UTC and 7 July 0130 UTC. Images courtesy of Dan Lindsey. Return to text.

7 Figure 3. As in Figure 2 except for 7 July at 0700 and 1100 UTC. Return to text.

8 Figure 4. GFS 00-hour forecasts of 850 hpa heights and 850 hpa height anomalies in 6-0hour periods from a) 0600 UTC 6 July 2012 through f) 1200 UTC 7 July Heights every 150 m and anomalies in standard deviations from normal as in the color bar. Return to text.

9 Figure 5. NCEP GFS 00-hour forecasts of 500 hpa heights (m) and 500 hpa height anomalies in 12-hour periods from a) 0000 UTC 5 July through f) 1200 UTC 7 July Return to text.

10 Figure 6. As in Figure 3 except for GFS 850 hpa winds and wind anomalies. Return to text.

11 Figure 7. As in Figure 6 except for precipitable water and precipitable water anomalies.

12 Figure 8. NCEP GFS forecasts of total accumulated precipitation from 0000 UTC 06 July 2010 through 1200 UTC 7 July 2012 from GFS initialized at a) 0600, b) 1200 UTC, and c) 1800 UTC 7 July 2012 and d) 0000 UTC 06 July Contours are every 25mm and shading as in the color bar to the right of each image. Return to text.

13 Figure 9. As in Figure 8 except for European Center forecasts of QPF (mm) from 3 EC forecast cycles initialized at a) 0000 UTC 5 July, b) 1200 UTC 5 July and c) 0000 UTC 6 July Return to text.

14 Figure Q1. CMORPH estimated rainfall (mm) summed from 3-hour data showing estimated precipitation for the 6 hour periods ending at a) 0600 UTC 6 July 2012, b) 1200 UTC 6 July 2012, c) 1800 UTC 6 July 2012, and d) 0000 UTC 7 July Return to text.

15 - Figure Q2. As in Figure Q1 excepted summer over 12 hour periods showing 12-hour estimates for the periods ending a) 1200 UTC 6 July, b) 0000 UT C7 July, c) 1200 UTC 7 July and d) 0000 UTC 8 July Return to text.

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17 Figure Q3. Synoptic observations showing the report and plot at (clockwise from top) 0000 UTC 6 July, 0600 UTC 6 July, 21 UTC 6 July and 0000 UTC 7 July. Data courtesy of Tim Hewson, ECMWF. Return to text.

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19 - Figure 2. 8km WRF nested within a 24km WRF using the 0000 UTC 06 July 2012 GFS as IC and BCs.