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Upper-level Mesoscale Disturbances on the Periphery of Closed Anticyclones

Upper-level Mesoscale Disturbances on the Periphery of Closed Anticyclones. Thomas J. Galarneau, Jr. and Lance F. Bosart University at Albany, State University of New York Albany, NY 12222 USA. Fourth Symposium on Southwest Hydrometeorology 21 September 2007 – Tucson, AZ. Motivation.

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Upper-level Mesoscale Disturbances on the Periphery of Closed Anticyclones

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  1. Upper-level Mesoscale Disturbances on the Periphery of Closed Anticyclones Thomas J. Galarneau, Jr. and Lance F. Bosart University at Albany, State University of New York Albany, NY 12222 USA Fourth Symposium on Southwest Hydrometeorology 21 September 2007 – Tucson, AZ

  2. Motivation • Warm season continental closed anticyclones (CAs) link weather and climate on intraseasonal time scales • Can persist for most of 90-day warm season • Surface temperature/rainfall anomalies with CAs can determine overall seasonal anomalies for a given region • High-impact severe weather on CA periphery associated with mesoscale disturbances

  3. Goals • Examine the CA of July 1995 over the US • Impact on rainfall distribution • Behavior of mesoscale disturbances on periphery of CA and their role in MCS development

  4. Data and Methods • 2.5 NCEP–NCAR Reanalysis • 1.125 ECMWF Reanalysis (ERA-40) • 0.25 NCEP Unified Precipitation Dataset (UPD) • University of Wyoming sounding archive • National Lightning Detection Network (NLDN) • Dynamic tropopause defined at 1.5 PVU surface

  5. July 1995 CA over US

  6. 500 hPa Height (dam) Mean and Anomaly and Wind (m/s) Fig. A1 from Galarneau et al. 2007 2.5 NCEP–NCAR Reanalysis ridge building Height Anomaly 5–10 July 1995 Wind eastward progression Height Anomaly 11–15 July 1995 Wind 11-15 Jul 1995 500 hPa HGHT

  7. 850 hPa 21C Isotherm Continuity Map 0000 UTC 5–15 July 1995 11 12 10 9 7 8 6 13 14 15 5 2.5 NCEP–NCAR Reanalysis Fig. A5 from Galarneau et al. 2007

  8. 00Z/13 +/- DT  (K) and wind (knots) X NLDN CG lightning MCS #1 PV tail mesoscale disturbance X X 1.125 ECMWF Reanalysis

  9. 12Z/13 +/- X DT  (K) and wind (knots) X X X NLDN CG lightning X MCS #1 X X PV tail mesoscale disturbance X X 1.125 ECMWF Reanalysis

  10. 00Z/14 +/- X X DT  (K) and wind (knots) X X X NLDN CG lightning MCS #2 X MCS #1 X PV tail mesoscale disturbance X X 1.125 ECMWF Reanalysis

  11. 12Z/14 +/- X X DT  (K) and wind (knots) X X X NLDN CG lightning X X MCS #2 X PV tail mesoscale disturbance X X X 1.125 ECMWF Reanalysis

  12. 00Z/15 +/- X DT  (K) and wind (knots) X X X X NLDN CG lightning MCS #3 X PV tail X mesoscale disturbance X X 1.125 ECMWF Reanalysis

  13. 12Z/15 +/- DT  (K) and wind (knots) X X X NLDN CG lightning MCS #3 X PV tail X mesoscale disturbance X X 1.125 ECMWF Reanalysis

  14. Schematic for 13–15 July 1995 L Strong Jet X H X X DT flow mesoscale disturbance source region PV Tail

  15. CG Lightning 12–15 July 1995 +/- 12–13 13–14 14–15 +/- +/- NLDN

  16. Storm Reports 12–15 July 1995 MCS #1 MCS #3 MCS #2 tornado/wind reports near persistent trough tornado wind hail Reports associated with PV tail + Generated using SeverePlot v2.5 Source: Storm Prediction Center

  17. 850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1) 00Z/13–15 July 1995 1.125 ECMWF Reanalysis

  18. 850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1) 00Z/13–15 July 1995 1.125 ECMWF Reanalysis 2300 J kg-1 Univ. Wyoming 00Z/13

  19. 850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1) 00Z/13–15 July 1995 1.125 ECMWF Reanalysis 7000 J kg-1 Univ. Wyoming 00Z/13

  20. 850 e (K), 925–500 wind shear (knots), 850–500 lapse rate (K km-1) 1800 J kg-1 Univ. Wyoming 00Z/13–15 July 1995 1.125 ECMWF Reanalysis 00Z/14

  21. % Contribution of JJA to Yearly Precipitation 1948–2003 UPD %

  22. % Contribution of 12–15 Jul to JJA Climo ~25% ~20–30% UPD %

  23. Case Study Summary • Downstream development led to ridge building over the Intermountain West • As CA moved eastward, convection formed on the periphery in association with mesoscale disturbances and a PV tail • Serial severe MCSs formed on poleward side • High CAPE, high shear environment • Scattered convection formed on equatorward side • Moderate CAPE, low-moderate shear environment

  24. Climate Implications • Rainfall • MCSs on periphery contributed ~25% of climatological JJA precipitation • Mesoscale disturbances can produce intense rain events and/or severe weather events • Temperature • Subset of CAs that build over Intermountain West, then move eastward can produce heat waves • Climatologically hot air over Intermountain West must be displaced to “anomalous” regions

  25. Postscript:Upper-level disturbances, PV tails, and tropical systems

  26. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 06Z/16

  27. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 12Z/16

  28. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 18Z/16

  29. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 00Z/17

  30. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 06Z/17

  31. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 12Z/17

  32. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 18Z/17

  33. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 00Z/18

  34. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 06Z/18

  35. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 12Z/18

  36. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 18Z/18

  37. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 00Z/19

  38. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 06Z/19

  39. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 12Z/19

  40. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) Low-level Vorticity center 18Z/19

  41. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) Source: NCDC GIBBS GOES-12 PV tail thinning and breaking 00Z/20

  42. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 06Z/20

  43. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 12Z/20

  44. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) 18Z/20

  45. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) Source: NCDC GIBBS GOES-12 00Z/21

  46. DT  (K), wind (knots), and 925–850 hPa  (10-5 s-1) Jerry? 06Z/21

  47. 1345Z/21 VIS

  48. 1445Z/21 VIS

  49. 1545Z/21 VIS

  50. 1645Z/21 VIS

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