East Coast Heavy Rainfall of January 2010 By Richard H. Grumm National Weather Service

Transcription

1 1. INTRODUCTION A strong storm moved across the United States from 21 January through 25 January 2010 (Fig. 1). This storm produced record rainfall and snowfall in the western United States from January before moving eastward. As the storm approached the eastern United States on the 23 rd and 24 th of January it produced heavy rainfall in the eastern United States (Fig. 2) and 37 reports of severe weather in the southeastern United States. Most of the severe weather was on the 24 th (Fig. 3). In the northeastern United States the key impact was heavy rainfall and minor flooding along rivers and streams. East Coast Heavy Rainfall of January 2010 By Richard H. Grumm National Weather Service As the surface cyclone tracked into the Great Lakes (Fig. 1), a surge of unseasonably warm moist air moved into the eastern United States. This pattern indicated a Maddox Synoptic event type (Maddox 1979). Heavy rains were observed in the strong southerly flow with a widespread 25 to 50mm rainfall event over much of the Mid-Atlantic region and northeastern United States. In the Mid- Atlantic region, over 182 reporting stations reported over 50 mm of rainfall and over 30 stations received in excess of 75 mm of rainfall on over the two day period from January 2010 (Table 1). The rainfall amounts set records in many locations and were clearly a meteorologically and climatologically significant event. The 24-hour rainfall in State College broke the old record for the date and was the second largest 24 hour value since 19 January Williamsport Pennsylvania set a record with 73 mm ( 2.90 inches) of rainfall ending at 1200 UTC on 25 January and an event total of 92 mm (3.65 inches). The latter value represents a month s worth of rainfall in the Figure 2. Unified precipitation data showing the total accumulated rainfall ending on 1200 UTC 25 January Figure 3. Storm Prediction Center summary of severe weather reports on 24 January Data from Storm Prediction Website.

2 Figure 1. GFS 00-hour forecasts of mean sea level pressure (hpa) and pressure anomalies (standard deviations) from (a-i) 0000 UTC 22 January through 1200 UTC 25 January Interval between images changes with more images at shorter time ranges. span of 48 hours. The use of standardized anomalies to identify significant weather events were by Grumm and Hart (2001) and Hart and Grumm (2001). Studies using anomalies associated with heavy rainfall were presented by Grumm and Hart (2003). These studies showed that standardized anomalies can help identify potentially significant rainfall events and help identify the event type. One of the primary heavy rainfall event types identified was the Maddox Synoptic type associated with strong v-wind and precipitable water anomalies. Most of the extreme precipitation events of this type often had 2 to 3 SD above normal or larger PW and low-level v-wind anomalies. A wide range of studies have examined the use of climatological data to gauge the intensity of an event. Examples include Lackmann and Gyakum (1999) and Junker et al. (2008) both showed anomaly patterns associated with heavy rain in the Pacific Northwest and Northern California. Junker et al. (2008) used standardized anomalies which helped

3 Figure 4. As in Figure 1 except showing GFS 00-hour forecasts of 250 hpa winds (kts) and total wind anomalies. characterize many events in the western United States which produced over 100 mm of rainfall. Grumm and Stuart (2006) and Grumm and Holmes (2007) showed the anomalies associated with winter storms and heavy rain in the Northeast and Mid-Atlantic states. Winter storms producing heavy snowfall typically had strong easterly flow, characterized by significant negative u-wind anomalies at 850 and 925 hpa. Stuart and Grumm (2006) showed the value of negative u-wind anomalies in predicted winter storms. From a forecasting perspective, Junker et al. (2009) showed the value of using standardized anomalies derived from ensemble data to assess the potential for significant precipitation events. In each case, the anomalies provided a coherent signal which aided in identifying the prospective rare event. This technique of using patterns and anomalies can be used operationally to aid forecasters in the prediction of potentially extreme precipitation amounts. The connection between significant anomalies based on key forecast parameters (Doswell et al. 1996) when used in conjunction with ensemble probabilities of heavy rainfall can provide confidence in a significant event.

4 Figure 5. As in Figure 1 except showing NCEP GFS 00-hour forecasts of precipitable water and precipitable water anomalies. Previous studies using standardized anomalies suggest that when the models and ensemble forecast systems (EFS) predict a known heavy precipitation pattern the potential for a significant event is possible. When this pattern is associated with significant standardized anomalies, both a meteorologically and climatologically significant event is possible. This paper will provide an overview of the heavy rainfall event of January 2010 in the eastern United States. The focus is on the patterns and the anomalies used to identify the pattern. Forecasts from the NCEP EFS are provided to show the value of using EFS probabilities and standardized anomalies to anticipate meteorologically and climatologically significant rain events. 2. METHODS AND DATA The 500 hpa heights, 850 hpa temperatures and winds, other standard level fields were derived from the NCEP GFS, GEFS, and the NCEP/NCAR (Kalnay et al. 1996) reanalysis data. The means and standard deviations used to compute the standardized anomalies were from the NCEP/NCAR data as described by Hart and Grumm (2001). Anomalies were displayed in

5 standard deviations from normal, as standardized anomalies. All data were displayed using GrADS (Doty and Kinter 1995). The standardized anomalies computed as: SD = (F M)/σ ( ) Where F is the value from the reanalysis data at each grid point, M is the mean for the specified date and time at each grid point and σ is the value of 1 standard deviation at each grid point. Model and ensemble data shown here were primarily limited to the GFS and GEFS. The 1.25x1.25 degree JMA data may be used when it becomes available. The NAM and SREF data were also available for use in this study. Displays will focus on the observed pattern and some forecast issues associated with the pattern. For brevity, times will be displayed in day and hour format such at 24/0000 UTC signifies 24 January 2010 at 0000 UTC. 3. RESULTS i. Synoptic scale pattern The evolution of the surface pattern was shown in Figure 1. The evolution of the upper-level flow pattern as described by the 250 hpa winds are shown in Figure 4. These data show the strong 250 hpa winds over western North America at 21/0000 UTC (Fig. 4a) and the implied Pacific Jet moving eastward. The winds show a more cyclonic pattern and curvature as the jet moves through the mountains of the southwestern United States from January. By 25/0000 UTC the stronger winds and anomalies are on the eastern side of the high amplitude trough which developed as the storm moved eastward (Figs. 4h-i). The surge of high PW air into the eastern United States is shown in Figure 5a-i. The initial high PW air 2-3SD PW anomalies entered the western United States with the storm system and Pacific Jet. This plume of high PW crossed the Rockies and then tapped additional moisture from the Gulf of Mexico. This evolution is evident when examining a loop and by inspection of Figures 5d-g. Note there is an atmospheric river (AR: Neiman et 2002 and Neiman et al 2008) effect with a plume of high PW air moving over the eastern Pacific across Mexico and from the Gulf of Mexico into the eastern United States. East of the Rockies the strong north-south oriented PW plume is indicative of Maddox (1979) Synoptic event type. ii. Regional pattern and anomalies Figure 6-8 show the 6-hourly evolution of the pattern over the eastern United States. The 850 hpa winds and v-wind anomalies (Fig. 6) showed strong southerly winds with 3 to 4 SD anomalies over the Ohio Valley and moving eastward. Between 25/0600 and 25/1800 UTC a broad area of 4-5 SD anomalies were present and there were isolated areas (Fig. 6i) where the v-wind anomalies topped 5SDs above normal. The PW field and attendant anomalies (Fig. 7) showed the surge of high PW air with the strong low-level southerly flow. PW anomalies of 2 to 3 SDs above normal were common until the system began to cross the Appalachian Mountains. Clearly, after 25/0000 UTC the frontal zone strengthened and sharpened (Fig. 5f-g) and the PW anomalies increased with a broad area of 4-5SD anomalies and a few areas in southern Quebec where PW anomalies exceeded 5SDs above normal (Fig. 5h-i). The frontal sharpening was associated (not shown) with sharp north-south rain bands on regional radar. The 250 hpa winds and v-wind anomalies are shown in Figure 8. These data showed a strong south to north jet with 2-3SD v-wind anomalies. The split in the anomalies implies a jet streak around 25/1200 UTC (Fig. 8h). Though not shown, a secondary pressure minimum moving up the implied north-south front in Figure 6 was visible in the sea-level pressure pattern at this time.

6 Figure 6. As in Figure 1 except GFS 00-hour forecasts of 850 hpa winds (kts) and v-wind anomalies a-i for the period of 1800 UTC 23 January through 1800 UTC 25 January Figure 9 shows the 24-hour precipitation totals ending at 1200 UTC January These data show the north-south oriented bands of precipitation aligned with the low-level jet and PW plumes Figures 6a-b & 7a-b line up incredibly well with the precipitation maximum in the Mississippi Valley from Arkansas to Wisconsin ending at 24/1200 UTC (Fig. 9b). This clear alignment with the low-level jet and PW surge is evident when comparing Figures 9c & 9d to the appropriate times in Figures 6 & 7. The surge of strong low-level winds and high PW outlined the rainfall area and the heavy rainfall are extremely well. iii. Ensemble Forecasts The displays in this section do not fully exploit the value of EFS data in the forecast process, however, they facilitate telling the story and showing the overall forecasts of the pattern quickly. A few probabilistic forecasts are offered at the end to address the obvious uncertainty in terms of when and where the heavy rainfall would fall during this event.

7 Figure show the GEFS forecasts from 9 cycles of the larger scale pattern over the eastern United States all valid at 25/0000 UTC. The ensemble mean and the standardized anomalies are shown for each forecast and thus no direct measure of uncertainty is provided. These data show a relatively consistent forecast of the large scale pattern. The wind fields show a stronger low-level jet with larger anomalies at the shorter range forecast (Fig. 11i) which suggest as the spread decreases the size of anomalies increased. This effect can be seen in the PW fields too. The larger scale pattern implied a classic Maddox Synoptic event type over the eastern United States. The anomalies implied a potentially significant precipitation event was possible from this pattern. Clearly, there were run-to-run inconsistencies, clearly discernable in the pressure patterns and anomalies. The deeper and more anomalous cyclone at the shorter ranges (Figs. 10g-i) imply more agreement and more emphasis on a southern stream wave that was clearly weaker in earlier forecasts. The spread, not shown, was larger in the longer range forecasts. The display method selected here somewhat obfuscates the uncertainty until the anomalies are tied back in. The total accumulated QPF from these forecasts is shown in Figure 13. These data too are the ensemble mean values. These run-to-run comparisons show a steady progression of heavier QPF amounts to the west. A comparison to Figure 1 reveals that the shorter range forecasts were more accurate. Forecasts initialized on January (Figs. 13a-e) were generally too far west with the QPF. SREF were similar to those produced by the GEFS and for brevity only one comparative image the QPF is shown in Figure 14. These data show that the SREF too initially predicted the heavier QPF too far east and slowly moved the QPF maximum to the west with time. Though not shown, but implied by the QPF shield, the SREF predicted a Maddox Synoptic like pattern. The finer resolution SREF predicted stronger winds and higher PW anomalies. Figures 15 & 16 show the GEFS and SREF probabilities of 2 inches of rainfall in 24 hours for the period ending at 25/1200 UTC. These forecasts show considerably uncertainty as to where the heaviest rainfall would fall. Selecting other valid times, such as 25/1800 UTC would have shown heavier rainfall to the east. Choosing different intervals, for example 36 hours also would have changed the outcomes. The key point here is that the location and probability of heavy rainfall changed with time in both the GEFS and SREF. Thus both models got the pattern correct but uncertainty issues limited the ability to get the exact heavy rainfall areas correct. iv. Impacts and weather This event was a high impact event. As shown in Figures 2 & 3 and Table 1. The event produced heavy rainfall over a large portion of the eastern United States and it produced severe weather in the southeast. The event also produced synoptic scale wind gusts in the 50 to 70kt range from eastern Pennsylvania to the coast and northward into southern New England. The winds produced power outages. The high winds were not widespread. The warm temperatures associated with the event, temperatures were in the 50s and 60s as far north as Pennsylvania and southern New England, produced snow melt. The snow melt and the widespread 1 to 3 inch rainfall event produced flooding along many creeks, streams, and rivers. Most of the flooding was characterized as minor flooding along the rivers and most streams. However, the Loyalsock Creek in Lycoming County, were 3 inches of rain fell around Williamsport and snow melt contributed to the run-off, the creek briefly reached major flooding. The 1 to 3 inches of rainfall with higher amounts suggests that this event was meteorologically significant and climatologically significant. Many locations in the eastern United States received 33 to 133% of the monthly January rainfall with this event. 4. CONCLUSIONS

8 A relatively well predicted storm of Pacific origin brought heavy rain to the eastern United States. In portions of the Mid-Atlantic and Northeastern United States, the locally heavy rainfall and snow melt produced flooding along rivers and streams. Most of the flooding was categorized as minor flooding. Farther south, the storm system produced severe weather. The large scale pattern as shown in Figures 1,4-6 suggest that the storm originated in over the Pacific Ocean. It was the same general system that produced the record rains, snows, and severe weather in the southwestern United States from January As the system moved eastward, it became more amplified allowing a surge of well above normal PW air into the eastern United States. A Maddox Synoptic system was set up. These data clearly imply that a strong Pacific System crossed the United States and producing a transcontinental high impact event. High impact transcontinental events can occur frequently during the winter. A recent high impact transcontinental event would include the Transcontinental Express of 8-10 December The Presidents Day storm of February 2003 was another example of a Pacific Storm which produced heavy rain in southern California and 3 days later produced heavy snow in the eastern United States. The NCEP GEFS and SREF predicted the pattern quite well (Figs ) and thus had the general area to receive heavy rainfall relatively well predicted. The details on where the heaviest rainfall would fall remained elusive in both EFS s. Both systems, only the GEFS was shown, predicted anomalous PW, pressure, and v-winds with large anomalies, often good indicators of a significant event. Thus, the models correctly predicted a Maddox Synoptic pattern associated with anomalous values in the key fields often associated with heavy rainfall. The sharp north-south alignment of the PW and PW anomalies along with the 2-4SD above normal low-level v-winds implied and identified a Maddox synoptic heavy rain event type (Figs.4-5). Additionally, the anomalies of these two critical fields implied that a known heavy rainfall pattern would be associated with anomalies values of key forecast parameters. This information provided confidence in a meteorologically significant event. The fact that the NCEP EFS s predicted them led to confidence in a heavy rainfall event several days in advance. The pattern and the anomalies were relatively well predicted by the GEFS (Figs.10-13) and the SREF. But the location of the heaviest rainfall was difficult to determine as there was considerable uncertainty due to minor differences in the timing and intensity of the frontal system. The probabilities of heavy rainfall in the GEFS and SREF (Figs ) and the high QPF values in multiple runs of the GEFS (Fig. 13) and SREF (Fig. 14) combined with the pattern and anomalies in that pattern further reinforced confidence in a heavy rainfall event. However, as stated earlier, the details as to where the heaviest rain would fall were hard to quantify. Ultimately, this was as high impact event in both a meteorological and climatological context. Meteorologically, the event had extreme values in PW and v-winds associated with a defined heavy rainfall. The heavy rainfall was observed and impacted rivers and streams. The overall rainfall was climatologically significant in that many locations received 33 to 133% of the totally monthly precipitation. Many locations in Pennsylvania set daily 24-hour rainfall records. In State College, this event was the second alltime highest 19 January 1996 event, which also was a Maddox Synoptic type event (Fig. 17). Grumm and Holmes (2007) demonstrated that the Maddox Synoptic type was the primary event type associated with many of the extreme rainfall events in the eastern United States, thus the fact that this event and the 19 January 1996 events were of the same time is not surprising. The event of November 1995, another heavy rain event with a similar Synoptic pattern look is presented in Figure 19. Grumm (2000) showed how one of these events, on 8 November 1996 (Fig. 20) appeared on radar and how this narrow cold frontal rain band (NCFRB) event produced over 25mm of rainfall in an hour and

9 locally over 100 mm of rainfall. Due to the strong frontal forcing, this event was considered to have been relatively well forecast by the NCEP Eta at 29 km horizontal resolution. 5. Acknowledgements Ned Pryor of the MARFC for 2 day rainfall data in plot able and tabular formats. Thanks to Theodore Ted Rogers for inputs about the event and QPF issues prior to and after the event. A thanks to Matthew Matt Steinbugl for inputs and forcing the implementation of the comparative SREF forecast page. 6. REFERENCES Doswell,C.A.,III, H.E Brooks and R.A. Maddox, 1996: Flash flood forecasting: An ingredients based approach. Wea. Forecasting, 11, Doty, B. E., and J. L. Kinter III, 1995: Geophysical data and visualization using GrADS. Visualization Techniques Space and Atmospheric Sciences, E. P. Szuszczewicz and Bredekamp, Eds., NASA, Grumm, R.H. and R. Hart. 2001: Standardized Anomalies Applied to Significant Cold Season Weather Events: Preliminary Findings. Wea. and Fore., 16, Grumm, R.H., and R. Hart, 2001a: Anticipating Heavy Rainfall: Forecast Aspects. Preprints, Symposium on Precipitation Extremes, Albuquerque, NM, Amer. Meteor. Soc., Grumm, R.H., and R. Holmes, 2007: Patterns of heavy rainfall in the mid-atlantic. Pre-prints, Conference on Weather Analysis and Forecasting,Park City, UT, Amer. Meteor. Soc., 5A.2. Grumm, Richard H. 2000, "Forecasting the Precipitation Associated with a Mid-Atlantic States Cold Frontal Rainband", NWA Digest,24, 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., R.H. Grumm,R.H. Hart, L.F Bosart, K.M. Bell, and F.J. Pereira, 2008: Use of normalized anomaly fields to anticipate extreme rainfall in the mountains of northern California.Wea. Forecasting, 23, , 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. Bull. Amer. Meteor. Soc., 90, Lackmann, G. M., and J. R. Gyakum, 1999: Heavy cold-season precipitation in the northwestern United States: Synoptic climatology and an analysis of the flood of January Wea. Forecasting, 14, Neiman, P.J., F.M. Ralph, A.B. White, D.E. Kingsmill, and P.O.G. Persson, 2002: The Statistical Relationship between Upslope Flow and Rainfall in California's Coastal Mountains: Observations during CALJET. Mon. Wea. Rev., 130,

10 ,, G.A. Wick, J.D. Lundquist, and M.D. Dettinger, 2008: Meteorological Characteristics and Overland Precipitation Impacts of Atmospheric Rivers Affecting the West Coast of North America Based on Eight Years of SSM/I Satellite Observations. J. Hydrometeor., 9, Forecasting, 21, Stuart, N.A., and R.H. Grumm, 2006: Using Wind Anomalies to Forecast East Coast Winter Storms. Wea. Figure 7. As in Figure 6 except for PW and PW anomalies.

11 Figure 8. As in Figure 6 except for 250 hpa winds and 250 hpa v-wind anomalies.

12 Figure 9. As in Figure 1 except showing 24 hour accumulated precipitation (mm) for the periods ending at a) 23 January, b) 24 January, c) 25 January and d) 26 January 2010.

13 Figure 10. As in Figure 1 except GEFS mean sea-level forecasts and anomalies valid at 0000 UTC 25 January from forecasts initialized at a) 0000 UTC 2 January, b) 1200 UTC 22 January, c) 0000 UTC 23 January, d) 0600 UTC 23 January, e) 1200 UTC 23 January, f) 1800 UTC 23 January, g) 0000 UTC 2 January, h) 0600 UTC 24 January, and i) 1200 UTC 24 January 2010.

14 Figure 12. As in Figure 11 except showing GEFS mean 850 hpa winds and v-wind anomalies.

15 Figure 13. As in Figure 10 except for GEFS mean precipitable water (mm) and precipitable water anomalies.

16 Figure 14. As in Figure 10 except showing GEFS mean accumulated precipitation (mm) for the period ending at 1200 UTC 25 January 2010.

17 Figure 14. As in Figure 13 except showing the SREF mean QPF valid at 1200 UTC 25 January 2010 from forecasts initialized at a) 0900 UTC 22 January, b) 1500 UTC 22 January, c) 2100 UTC 22 January, d) 0300 UTC 23 January, e) 0900 UTC 23 January, f) 1500 UTC 23 January, g) 2100 UTC 23 January, h) 0300 UTC 24 January, and i) 0900 UTC 24 January 2010.

18 Figure 15. GEFS forecast of precipitation (inches) showing, in the upper panels, the probability of 2 inches or more precipitation in the 24 hours ending at 1200 UTC 25 January and the ensemble mean 2 inch contour. Lower panels show the ensemble mean 24 hour QPF and each member 2 inch contour. Forecast initialized for each 2 panel chart at left) 0600 UTC 22 January, center) 0600 UTC 23 January, and right) 0600 UTC 24 January Note these data are from the soon to operational 75km GEFS not the older 105km version of the GEFS.

19 Figure 16. As in Figure 14 except 32km SREF forecasts from SREF initialized at left) 0900 UTC 23 January, center) 0300 UTC 24 January, and right) 0900 UTC 24 January 2010.

20 Figure 17. JMA data showing the pattern over the eastern United States at 0600 UTC 1996 fields shown include a) 500 hpa heights (m) and height anomalies, b) mean sea level pressure (hpa) and anomalies, c) 850 hpa winds (kts) and v-wind anomalies, and d) precipitable water and anomaleis.

21 Figure 18. As in Figure 17 except for 0000 UTC 12 November 1995.

22 Location State Precip BLCV2 VA 5.95 MONV2 VA 5.12 GLAV2 VA 4.46 JWTN6 NY 4.33 USLV2 VA 4.31 CROV2 VA 4.15 SFTV2 VA 4.04 BBRP1 PA 3.80 IPT PA 3.65 WLFP1 PA 3.64 LAPP1 PA 3.61 LAPP1L PA 3.60 LHTP1 PA 3.46 FAYP1 PA 3.40 AFTV2 VA 3.39 BGIV2 VA 3.37 MLCV2 VA 3.36 GETP1 PA 3.33 MNYP1 PA 3.33 SHEV2 VA 3.32 EBVP1 PA 3.30 LAKN4 NJ 3.28 LOYP1 PA 3.28 CTVV2 VA 3.22 GLEP1 PA 3.20 KQ60 NJ 3.20 GLEV2 VA 3.15 ROXP1 PA 3.06 VABD06 VA 3.05 ELIP1 PA 3.03 BLAP1 PA 3.02 LBGP1 PA 3.02 LRRV2 VA 3.00 SLGP1 PA Table 1 Points with 2-day rain totals of 3 or more inches of rainfall period is January Return to text.

23 Figure 20. As in Figure 18 except valid at 1200 UTC 8 November 1996.