Of Capping Lids, Drylines, and Alberta Thunderstorms*

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Of Capping Lids, Drylines, and Alberta
Thunderstorms and Support to UNSTABLE G.S.
Strong - Ardrossan, AB Susan Skone - UofC,
Calgary, AB Craig Smith - EC, Saskatoon, SK

geoff.strong_at_shaw.ca
All things are connected like the blood which
unites one family. Chief
Seattle, 1854.
A developing storm over Rocky Mountain House, 16
July 2003
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To acknowledge all(?) our Sponsors Contributors
. . . .
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The basic large-scale Conceptual Model

• What to Look for
• 1) Synoptic conditions 6-18 hours preceding
• - subsidence preceding upper ridge
• - ascent preceding upper trough
• - orographic subsidence/ascent
• - location - location - location
• (where/when cyclogenesis?)
• Whats going on between the synoptic
• and meso-? scales?

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cm s-1
Storm formation 1830Z
Pre-storm period)
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Critical changes occur in the BL during
late-morning (1400-1600 UTC) . . .HOW?
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Major Topographic Features to Consider
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Proposed Modification to the Multi-scale Conceptu
al Model of Alberta Thunderstorms to account for
dryline initiation of storms.
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Surface Transect across Dryline
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GPS Precipitable Water Trend on 20 July 2003
Storm peak moves by 2200Z
Earliest radar echoes 2030Z
1730Z
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How important is local evapotranspiration to
storm formation?

• Some background for this from a study of
  moisture contrast between
• prairie grass and a wheat field in St. Denis,
  SK, July-August, 1992
• (previously unpublished data).

St. Denis, SK Fieldsite, July-August, 1992
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St. Denis, SK Crop/Grass ET Field Tests,
July-Aug., 1992 (18-day average for each half
hour)

• grass
• transition
• wheat

- after Hrynkiw Strong (1992)
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Conclusions/Recommendations for UNSTABLE

• Preceding (6-18 hours) synoptic conditions.
• Whats going on between scales?
• 2a) Everyone Documented cloud
  photography and manual observations!!
• 3) Document mesoscale conditions over foothills
  2-6 hours preceding storm initiation.
• 4) Note foothills topography.
• 5) Need high temporal resolution soundings
  (2-hour intervals recommended during morning)
• tethered balloons and/or instrumented
  towers (100-m) would be great assets.
• 6) Document storm initiation life cycle
  (radar/satellite).
• 7) Mobile surface transects deep into the
  foothills (late morning and mid-afternoon).
• 8) High spatial/temporal resolution GPS PW
  data, concentrate on -4 to 2 hours of storm
  initiation.
• 9) Need reliable soil moisture (and ET) data in
  major soil zones regions.
• Analyses
• Precedent synoptic conditions, 6-18 hours.
• Precedent mesoscale conditions, 2-6 hours.
• Everything for storm initiation period (-1 to
  hours)!
• Storm-scale (meso-gamma) for storm life cycle.
• Diurnal trends in all variables.

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UNSTABLE Proposal to CFCAS, Feb 2002

• To investigate synoptic to micro-scale
  interactions with thunderstorms at
• three interfaces as indicated,
• - Focus on the pre-storm to storm initiation
  periods.

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Sundre (WAV) (Skew-T) Soundings 20 July 03 at
1530Z 2352Z
Precipitable Water 1530Z - 19.9 mm 2352Z - 20.9 mm
EA3 18Z - 15.9 mm EA2 00Z - 15.7 mm EF4 12Z -
15.6 mm EF4 17Z - 16.2 mm
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Analyses of surface MIXING RATIO
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Climatological Trend of Mixing Ratio (YXD, YXE,
YWG)
- after Strong (2005)