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Weather briefing – Thursday 11 June 2009

Weather briefing – Thursday 11 June 2009. NCSU – team members… Note: Data from many of our usual forecast tools (e.g., Bufkit , SREF , high-resolution simulated radar , SPC mesoanalysis page , etc.) were not available in this retrospective mode… would show other/additional plots.

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Weather briefing – Thursday 11 June 2009

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  1. Weather briefing – Thursday 11 June 2009 NCSU – team members… Note: Data from many of our usual forecast tools (e.g., Bufkit, SREF, high-resolution simulated radar, SPC mesoanalysis page, etc.) were not available in this retrospective mode… would show other/additional plots

  2. 5 Ops Objectives

  3. Decisions/Things to Keep in Mind(as a forecaster) • Mission has to decide where to fly and what category of objective they’re fulfilling • The ER-2 needs 24 hours’ notice to fly • The ER-2 crew has strict rest policies • 12 hours after missions • 14 if mission is 8 hours • No more than 3 days without a down day • Calls need to be made about current missions with past and future missions in mind (for the above reasons) • The Citation should stay out of >35 dBZ • ER-2 takeoff no go if: • 25 knots maximum steady or 35 gusts regardless of dir. • 15 knot maximum crosswind • 1/4 mile minimum visibility • Lightning within 5 NM

  4. Overview • Day -1 (W 10th): Stationary front to north, zonal flow aloft. Humid & unstable with moderate shear. Organized convective storms in afternoon, some severe • Day 0 (Th 11th): Instability and shear appear to have increased somewhat this morning, ingredients in place for organized convection. MCV to W this morning • Day 1 (F 12th): Weak front drops southward during the day, possibly enhanced, organized convection over area • Day 2 (Sa 13th) and beyond: Weak front to south of area, & weaker shear: Weaker, less organized convection. Potential for offshore convection with stalled front.

  5. Day -1 surface analysis: 15 Z 10 June 2009

  6. Day -1 (10 June) • MCS move east, passed to south of study area, dissipated over GA • New convection developed ahead of MCV, some severe (hail, wind) with these cells

  7. Day -1 (10 June, 12-21 UTC)

  8. NAM 500-mb Z analysis: 00 Z 11 June 2009

  9. Nashville sounding, 00 Z 11 June 2009

  10. Analysis, Day 0 (11 June) • Shear and instability have increased this morning (e.g,. ~2400 J/kg BNA at 12Z); MCV to west • One MCS to our north this morning as well, in addition to MCV to west • Diurnal heating possible this morning, further increasing severe threat • Timing: MCS/MCV over TN, moving east. Storms in area by 18 Z? Severe threat increased

  11. GOES-13 IR, 1215 Z 11 June

  12. GOES-13 VIS, 1330 Z 11 June

  13. NAM 500-mb Z,  analysis: 12 Z 11 June 2009

  14. HPC surface analysis: 12 Z 11 June 2009

  15. NAM SLP, theta-e1000, 500Z valid: 12 Z 11 June

  16. Nashville sounding, 12 Z 11 June 2009

  17. SPC Day 1 outlook, valid 13Z 11th – 12Z 12th Primary: Hail, wind

  18. SE Radar Mosaic, 0-14 UTC 11 June

  19. SE Radar Mosaic, 14 UTC 11 June

  20. SE Radar Mosaic, with NLDN, 14 UTC 11 June

  21. Day 0 Forecast (11 June) • Organized convection, MCV to west will approach study area today; MCV in NAM initial condition • New convection could fire ahead of MCV currently over western TN (similar to yesterday) • Timing: Convective storms likely to develop between 17-20Z across study region (from west) • Aircraft threats: Lightning, hail @Robins afternoon, Convection (winds, hail, lightning) KAVL after 17Z

  22. NAM 12-h CAPE, CIN valid 12 Z 11 June

  23. NAM 18-h fcst, 6-h QPF, valid 18 Z 11 June

  24. NAM 18-h fcst sounding, valid 18 Z 11 JuneKAVL WBZ: ~9200 ft Freezing level ~11,000 Sfc-6 km shear ~ 30 kt

  25. Day 1 Forecast (Fri 12 June) • Weak cold front approaches, opportunity for organized convection ahead of front • Timing of weak front difficult to establish; merges with lee trough late in day (by 00Z Sat) • Now appears that passage will be around mid-day • Only weak drying, stabilization behind front, more so in wake of any organized convection that forms • As front stalls along coast, offshore convection potential increases early morning Sat and Sun (Day 2,3)

  26. F36 NAM SLP, theta-e, 12Z 12 June

  27. F48 NAM SLP, theta-e, 00Z 13 June

  28. Days 2-3 (Sat, Sun) • Following weak cold front passage day 1, focus for convection shifts southward, and to offshore waters • Shear, instability will weaken, but sufficient instability to support diurnal orographic showers • Frontal boundary advances northward again towards study area, potential for more showers Days 2, 3 (Sat, Sun) • GFS shows MCV-type feature bringing strong storms to area Sun, but skeptical given convective origin of forcing in model forecast

  29. 60-h NAM SLP, theta-e, 500 Z 12 Z 13 June

  30. Days 4+ • NW flow storms possible, shortwave passes north of area Saturday (model variability) • With ridge axis to west (aloft), NW flow regime becomes established • Longer term: Ensemble indicates very strong ridge developing over central US, study area in NW flow but dry with synoptic subsidence

  31. 60-h GFS 500-mb Z, SLP valid 12Z Sat 13 June

  32. 84-h GFS 500-mb Z, SLP valid 12Z Sun 14 June Spurious system?

  33. 120-h GFS 500 Z, SLP valid 00Z Tue 16 June

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