tasmanian springtime frontal events n.
Skip this Video
Loading SlideShow in 5 Seconds..
Tasmanian springtime frontal events PowerPoint Presentation
Download Presentation
Tasmanian springtime frontal events

Loading in 2 Seconds...

play fullscreen
1 / 31

Tasmanian springtime frontal events - PowerPoint PPT Presentation

  • Uploaded on

Tasmanian springtime frontal events. Origins of dry air. Background. Increase in severity of springtime events in the last several decades Objectively verified Why?. (Recent) Approaches to frontal case studies. Mills 2008 (a, b). (and 2002, 2003, 2005a,b, 2006, 2007, 2010).

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

Tasmanian springtime frontal events

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript


  • Increase in severity of springtime events in the last several decades
  • Objectively verified
  • Why?
recent approaches to frontal case studies
(Recent) Approaches to frontal case studies

Mills 2008 (a, b)

(and 2002, 2003, 2005a,b, 2006,

2007, 2010)

Dry slots, and short-term sfc dryings assw frontal circulations

  • Parallel strand of research in US:
    • Zimet et al 2007
    • Kaplan et al 2008
    • Huang et al 2009
  • 2 high-end spring fire weather days:
    • 7 November 2002 (40+ scrub fires Hobart area)
    • 12 October 2006 (800 Ha burnt Hobart eastern shore. FFDI 100+ for several hours.)
300 hpa
300 hPa

Trough increasingly tilted as it approaches Tasmania

ir imagery
IR Imagery

Development evident in period from 06/2030 to 07/0530

meanwhile hobart ap 06 2300 utc
Meanwhile…Hobart Ap 06/2300 UTC

Dry aloft, unstable, 50 kt at 850 hPa

airmass origins
Airmass Origins

Courtesy of

Alan Wain

1500m less

“cluttered” than


what s going on in eucla
What’s going on in Eucla?

Very dry

around 2000m

moisture from bight
Moisture from Bight…?
  • Maybe not!
  • Strong MBL inversion (for model)

Model vertical sounding

near 38S 136E ,

from 24 hour forecast of

mesoLAPS, initialised at

0000 UTC 05 November


Cross-section through line at left

Hobart at arrow location above

Cross-section displays RH (black, %)

and PVOR (red, PVU)


MBL north coast

Foehn effect

Decreased, but not unusual,



Again, N coast MBL

Lee downslide winds

Low (but not exceptional)


compare events
Compare events…

Both reveal effects of Tasmanian orography – foehn effect/MBL north coasts

  • 12 October 2006 – no evidence of intrusion of drier air from aloft. Airmass is very dry anyway

But… what’s different? Both have approaching change, jet streak nearby

  • Isentropes essentially horizontal
  • While tropopause depression is evident, intrusion doesn’t extend to low levels
  • Axis of trough well west of Tasmania

MesoLAPS resolved dynamics well in both cases, it seems - scope for using xn to diagnose possible dry air descent

But low level moisture fields not well-resolved (take note GFE regions!)

Variety (>=2!) of mechanisms possible for dry air to occur ahead of Tas fronts

Some common features