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Analysis of the Mountain Wave Down-Slope Wind Event on March 12-13, 2005

This document reviews the meteorological characteristics of a down-slope wind event that occurred on March 12-13, 2005, focusing on its unusual intensity relative to typical spring storms. Winds gusted between 30-50 knots at Fort Bliss, El Paso. The analysis suggests that while conditions were ripe for strong winds, the expected stable layer was absent, complicating the classification of the event. This case demonstrates how down-slope winds can occur without strong upper-level winds, posing challenges for forecasting models.

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Analysis of the Mountain Wave Down-Slope Wind Event on March 12-13, 2005

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  1. Mountain-Wave Down-slope Wind Event Reviewed Meteorology Branch Forecast Section RO-DA-F 505-678-2488/2462 Eric Hatfield APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05

  2. Presentation Highlights APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • What happened 12-13 Mar 05? • Explainable by usual spring storms? • Down-slope wind event • Summary

  3. What Happened? APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • 12-13 Mar 05: • --Winds gusted 30-50kts 16-03L on Main Post. • --’Howled’ all night at forecaster’s house in El Paso blowing garbage can east about 15ft.

  4. Explainable by usual Spring Storms?RT-FDDA 500mb Hgt, Rel Vort & Winds valid 06Z, 13 Mar 05 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • Weak Flow • No Vort max over AZ/SRN CA or Upstream • Pattern over CNTRL Rockies more similar to Spring Storms **Not Here**

  5. Explainable by usual Spring Storms?RT-FDDA 300mb Hgt & Winds valid 06Z, 13 Mar 05 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • Weak Flow • Jet is well North • Weak trof SRN • CA way too • weak **Not Here**

  6. Explainable by usual Spring Storms?RT-FDDA 700mb Hgt, Temp & Winds valid 06Z, 13 Mar 05 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • Gradient is tight • enough • Note 30-40 kts • Main Post area • towards El Paso

  7. Explainable by usual Spring Storms?RT-FDDA 850mb Hgt, Temp & Winds valid 06Z, 13 Mar 05 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • Gradient is tight • enough • Trof is way east • over Texas

  8. Explainable by usual Spring Storms? APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 Conclusion: NO Begs the question, What did cause it?

  9. Enter the Mountain-Wave Down-Slope APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • Classic Characteristics---- • At Night (It did) • Flow nearly perpendicular to mountains (It was) • Negative Wind Shear within 2 km of ridge top • Stable Layer within 2 km of ridge top Can double-triple wind speeds if all are in place!

  10. Upper Air SoundingRT-FDDA Skew-T for Main Post valid 06Z, 13 Mar 05 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • Ridge top is about 750mb • Lowering wind speed up to 600mb • No Stable Layer • **Not Classic**

  11. Mountain-Wave Cross SectionRT-FDDA valid 06Z, 13 Mar 05 APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • Long arrows cascading down the hill • Wave is above the ridge • Critical Point is a little high • **Not Classic**

  12. In Summary APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05 • This non-extreme wind event is a Down-Slope Wind –Event variant. • Elements were present except the stable layer within 2 km of ridge top. • This event also shows you can get warning criteria winds without having very strong winds aloft.

  13. The End

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