1

Of Capping Lids, Drylines, and Alberta Thunderstorms** and Support to UNSTABLE

G.S. Strong - Ardrossan, AB Susan Skone - UofC, Calgary, ABCraig Smith - EC, Saskatoon, SK

geoff.strong@shaw.ca

A developing storm over Rocky Mountain House, 16 July 2003

All things are connected like the blood which unites one family. Chief Seattle, 1854.

2

To acknowledge all(?) our Sponsors & Contributors . . . .

3

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?)

2) What’s going on between the synoptic and meso-γ scales?

4Storm formation ~ 18:30ZPre-storm period)

cm s-1

5

Critical changes occur in the BL during late-morning (1400-1600 UTC) . . .HOW?

6

Major Topographic Features to Consider

7

ProposedModification

to theMulti-scaleConceptual

Model ofAlberta

Thunderstormsto account for

dryline initiationof storms.

8

9

Surface Transect across Dryline

10

GPS Precipitable Water Trend on 20 July 2003

Storm peak moves by ~ 2200Z

Earliest radar echoes 2030Z

1730Z

11

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a study of moisture contrast between prairie grass and a wheat field in St. Denis, SK, July-August, 1992 (previously unpublished data).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

12

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

- after Hrynkiw & Strong (1992)

- grass- transition- wheat

13

Conclusions/Recommendations for UNSTABLE:1. Preceding (6-18 hours) synoptic conditions.2. What’s 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:1. Precedent synoptic conditions, 6-18 hours.2. Precedent mesoscale conditions, 2-6 hours.3. Everything for storm initiation period (-1 to + hours)!4. Storm-scale (meso-gamma) for storm life cycle.5. Diurnal trends in all variables.

14

15

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.

16

17

Sundre (WAV)

(Skew-T)Soundings20 July 03

at 1530Z& 2352Z

Precipitable Water1530Z - 19.9 mm2352Z - 20.9 mm

EA3 18Z - 15.9 mmEA2 00Z - 15.7 mm

EF4 12Z - 15.6 mmEF4 17Z - 16.2 mm

18

Analyses of surface MIXING RATIO

19- after Strong (2005)

Climatological Trend of Mixing Ratio (YXD, YXE, YWG)