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Mid-Atlantic Severe Weather Climatological Aspects

Mid-Atlantic Severe Weather Climatological Aspects. by Kevin S. Lipton Richard H. Grumm and John LaCorte. Introduction. Creating a Severe Weather Database Climatic Issues Location, type, and Time if severe weather events Local Pennsylvania problems/considerations

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Mid-Atlantic Severe Weather Climatological Aspects

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  1. Mid-Atlantic Severe WeatherClimatological Aspects by Kevin S. Lipton Richard H. Grumm and John LaCorte National Weather Service State College PA

  2. Introduction • Creating a Severe Weather Database • Climatic Issues • Location, type, and • Time if severe weather events • Local Pennsylvania problems/considerations • Improving the forecasting of severe weather events • An example National Weather Service State College PA

  3. Methods and Data • NCDC Storm Data • Has some use issues • Tornado gets counted by every county it impacts • Inflates some numbers • SPC Severe Plot Data • Lowers tornado probabilities • A cleaner data set • Loaded into mySQL and MS-Access • NCEP-NCDC Reanalysis Data • Plot anomalies and show how case looked • Apply to model forecasts for forecasting (GrADS) National Weather Service State College PA

  4. Creating a Severe Weather Database • Prototype with Storm data to get top 20 events in eastern US • Case examples to follow • Severe Plot used for a parallel study • Timing of events • Location of events • Seasonality of events • The Severe Plot data was found to be more reliable National Weather Service State College PA

  5. Climatic Issues • Pennsylvania problems/considerations • Terrain may enhance bow echo climatology • Focus on Pennsylvania Severe Weather • Location, • type (Severe and tornadic) • Seasonality • Diurnal trends National Weather Service State College PA

  6. Enhanced Bow echoesterrain influence National Weather Service State College PA

  7. 13 August 1999Tuscarora valley SLBESRM saw this bow before REF National Weather Service State College PA

  8. Seasonality National Weather Service State College PA

  9. Monthly Occurrences National Weather Service State College PA

  10. Diurnal Trend in Pennsylvania National Weather Service State College PA

  11. 50% occurs between 2PM and 6PM 68% of all Severe Weather occurs between 1PM and 7PM National Weather Service State College PA

  12. # of events in each category National Weather Service State College PA

  13. National Weather Service State College PA

  14. Climatic Examples • Test Climatic Anomalies • Top severe events • Compare to severe weather occurrences • Wind Anomalies • Appear to have some forecast potential • Relate to helicity • Precipitable water • Shear climatology • This was only recently developed (Sep 2002) • Has many potential forecast Applications • Relates to helicity National Weather Service State College PA

  15. Events with most reportsEastern US • 1/21/1999-1/22/1999: 129 Tornadoes, 14 other severe; MS, LA, AR • 11/21/1992-11/23/1992: 84 Tornadoes, unknown severe; GA, AL, MS, LA • 11/23/2001-11/24/2001: 76 Tornadoes, 31 Severe; AL, MS, LA, AR • 5/31/1985: 60 Tornadoes, 30 Severe; OH, NY, PA • 4/16/1998: 48 Tornadoes, 72 Severe; TN, KY, AR, AL • 5/30/1998-5/31/1998: 43 Tornadoes, 300 Severe; NH, MA, NJ, NY, PA, VT, MI, MN • 11/15/1989-11/16/1989: 32 Tornadoes, 3 Severe; NY, NJ, PA, GA, AL • 7/12/1992: 30 Tornadoes, Unknown Severe; OH • 4/14/1999 - 4/15/1999: 25 Tornadoes, 30 Severe; NC, SC, GA, AL, MS • 5/18/2002: 22 Tornadoes, 80 Severe; IL • 5/15/1998: 21 Tornadoes, 184 Severe; IA, MN • 7/19/1996: 20 Tornadoes, Unknown Severe; MD, PA • 4/28/2002: 22 Tornadoes, 137 Severe; KY, TN, MD • 5/16/1999: 14 Tornadoes, 104 Severe; IA • 5/10/2001: 13 Tornadoes, 104 Severe; IA • 4/20/2000: 13 Tornadoes, 101 Severe; IL, KY, TN National Weather Service State College PA

  16. National Weather Service State College PA

  17. National Weather Service State College PA

  18. Integrating Data setsGrADS-reanalysis-Severe plot (SPC) National Weather Service State College PA

  19. Shear ExamplesEastern US tornado Outbreak May 1985 National Weather Service State College PA

  20. Shear ExamplesPA-NY tornado Outbreak May 1998 National Weather Service State College PA

  21. Forecast Applications • Use of ensembles • Climatic anomalies • Shear climatology verse model forecasts • To anticipate a potentially large severe weather outbreak • Example: 10-11 November 2002 • Large shear anomalies • High CAPE for November • Largest severe weather outbreak of 2002 National Weather Service State College PA

  22. The two big events of 2002 • 28 April Eastern US Severe outbreak • LaPlata Tornado • 10-11 November 2002 Severe outbreak • F2 in Pennsylvania…rare in November National Weather Service State College PA

  23. Figure 1. Storm Prediction Center (SPC) plots of severe weather over the eastern United States on a) 27 April and b) 28 April 2002. 28 April 2002severe reports National Weather Service State College PA

  24. Strong Shear Case LaPlata Tornado 28 April 2002 National Weather Service State College PA

  25. Figure 3. As in Figure 2 except forecasts of 850 hPa winds (U and V) and departures from normal. Figure 2 Eta forecast initialized at 0000 UTC 28 April valid at 2100 UTC 28 April 2002. Upper panel shows 700 hPa heights (m) and anomalies (Standard deviations from normal) and lower panel MSLP (hPa). 28 April 2002anomalous low and southwest winds National Weather Service State College PA

  26. Figure 5 NCEP SREF forecasts of CAPE (Jkg-1). Upper panel shows spaghetti plots and dispersion about the mean. Eta members are black and RSM members are red. Lower panel shows the probability of the CAPE greater than or equal to 1200 Jkg-1 and the position of the consensus 1200 and 2400 contours. 28 April 2002SREF CAPEProbabilities and spaghetti National Weather Service State College PA

  27. Figure 6. As in Figure 5 except valid at 2100 UTC. 28 April 2002SREF CAPEProbabilities and spaghetti National Weather Service State College PA

  28. Figure 13. Reflectivity and SRM data from KLWX radar around 2357 UTC 28 April 2002. LaPlataSupercellcomplete with hook and TV National Weather Service State College PA

  29. Figure 12. As in Fig 11 except at 2202 UTC. Columbia County TornadocSplit in line depicts the F1 tornado location National Weather Service State College PA

  30. A Figure 1. Reflectivity and SRM valid at 2207 UTC showing the structure of the thunderstorm which produced a tornado in Lebanon County. The A denotes initial thunderstorm and the arrows refer to points noted in the text. Lebanon County TornadocOh no..its a tornado near RT-22 in Ono! National Weather Service State College PA

  31. 10-11 November 2002 Severe outbreak • Big in Mississippi Valley and east • Strong southerly low-level flow • High CAPE for November • Not uncommon as some big November events like 4 November 1950 • Strong shear • Rare strong tornado in western Pennsylvania in November National Weather Service State College PA

  32. Figure Storm Prediction center storm reports. Color coded by type. Upper panel is 10 November and lower panel is 11 November 2002 National Weather Service State College PA

  33. Figure . Eta shear forecasts initialzed at 1200 UTC 10 November valid from left to right a) 2100 and b) 0000 UTC 10 November and c) 0300 UTC 11 November 2002. Upper panels show the shear and anomalies from the surface to 850 hPa lower panels show the shear anomalies from the surface to 700 hPa. Eta surface based CAPE is plotted on the upper panels and layer CAPE on lower panels. Shear Forecasts with AnomaliesEta Model National Weather Service State College PA

  34. Conclusions • Built a regional Severe Weather Database • Addressed many Climatic Issues • Location, type, and • Time if severe weather events • Local Pennsylvania problems/considerations • Climatic Anomalies show great forecast potential when applied to model and ensemble forecasts • New tools to integrate Data sets National Weather Service State College PA

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