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Mountain-Wave Down-slope Wind Event
Reviewed
Mountain-Wave Down-slope Wind Event
ReviewedMeteorology Branch Forecast Section
RO-DA-F505-678-2488/2462
Eric Hatfield
Meteorology Branch Forecast SectionRO-DA-F
505-678-2488/2462Eric Hatfield
APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. OPSEC REVIEW CONDUCTED ON 9 AUG 05
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Presentation Highlights
•What happened 12-13 Mar 05?
•Explainable by usual spring storms?
•Down-slope wind event
•Summary
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What Happened?
•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.
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Explainable by usual Spring Storms?RT-FDDA 500mb Hgt, Rel Vort & Winds valid 06Z, 13 Mar 05
•Weak Flow
•No Vort max over AZ/SRN CA or Upstream
•Pattern over CNTRL Rockies more similar to Spring Storms
**Not Here**
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Explainable by usual Spring Storms?RT-FDDA 300mb Hgt & Winds valid 06Z, 13 Mar 05
•Weak Flow
•Jet is well North
•Weak trof SRNCA way too weak
**Not Here**
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Explainable by usual Spring Storms?RT-FDDA 700mb Hgt, Temp & Winds valid 06Z, 13 Mar 05
•Gradient is tightenough
•Note 30-40 kts Main Post areatowards El Paso
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Explainable by usual Spring Storms?RT-FDDA 850mb Hgt, Temp & Winds valid 06Z, 13 Mar 05
•Gradient is tightenough
•Trof is way east over Texas
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Explainable by usual Spring Storms?
Conclusion: NO
Begs the question,What did cause it?
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Enter the Mountain-Wave Down-Slope
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!
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Upper Air SoundingRT-FDDA Skew-T for Main Post valid 06Z, 13 Mar 05
•Ridge top is about 750mb
•Lowering wind speed up to 600mb
•No Stable Layer
**Not Classic**
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Mountain-Wave Cross SectionRT-FDDA valid 06Z, 13 Mar 05
•Long arrows cascading down the hill
•Wave is above the ridge
•Critical Point is a little high
**Not Classic**
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In Summary
•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.
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The EndThe End