Gedday,

In some ways this discussion is becoming a little "Victoria-centric"  Part of the reason is that we in Head-Office/BMRC live here in Vic, and so we experience the joys of the summer cool changes and that wonderful tropical-style thunderstorm that went through last Friday night.

Part of the reason, though, is that we have on the Victorian RFC web page, a nice weather browser.  One of the features of this is the map-tool displays of the current wind-temperature plots over various regions (Western Vic, Central vic, Eastern Vic, Melbourne) and we have 24-hour animated gifs of the past 24 images for each region.  This makes it easy to follow the weather here, and to go over the past situation, see what happened, compare it to the model, etc.
 I'll show by example in a tick... but the point of this is some sort of a plea, to whoever sets these things up, to put similar handy displays on their regional web-pages.  then we will be able to easily follow what is going on in the other states.

My example is up on my web page.  The front that went through central Victoria last Friday/Saturday is an interesting one, with some complexities in the wind change, as is always the case with summertime fronts.

On my web page, I have put up gifs of the mesolaps 1m wind forecast, and the maptool display for Victoria for 08 GMT 1 Feb (the timer of the 2 cm hailstones in my backyard in North Melbourne), 14 GMT, 20 GMT, 02 GMT 2 Feb and 08 GMT 2 Feb.
--- where I note, as per earlier discussions, the model forecast is mislabeled by 1 hr (i.e. the forecast for 08Z is labeled 09Z)

08 GMT 1 Feb

                                    Prog                                                                                            Obs (AWS)
14 GMT

 

20 GMT

02 GMT 2 Feb

08 GMT  2 Feb

Looking at the evolution through the 24 hours, there are a number of interesting features.
At 08Z, the model has put a southerly stream across all of western Victoria, whereas in the atmosphere, the southerly inflow at this time seems to be largely associated with the sea breeze and has penetrated only about 150 km inland.  Despite that the north-south confluence line that generated the thunderstorms is well represented in the model, extending from central Port Phillip Bay up to the NSW border.

At 14 Z the complex structure in eastern Victoria and south eastern NSW is well represented.  Features include a confluence between southeasterlies and northeasterlies down in Bass Strait, strong northeasterlies in eastern Bass Strait that weaken considerably over land (i.e. in Gippsland), southerly flow across the entire western Vic, easterlies in southern NSW and north easterlies in eastern Vic/Gippsland

At 20 GMT, a nice feature is the surging of the westerly flow across Wilsons Promontory, with easterlies overland directly to the north.  Jumping to the final set (08 GMT 2 Feb) we have a good strong southerly stream over Western Vic in both forecast and obs, whereas in eastern Vic we have weak southerlies and southeasterlies, with westerlies to the south over eastern Bass Strait.

One could go on for some time analyzing this in terms of idealized model runs in the literature, and some of the work of Graham Mills (Guru Murrumbidgee) in recent years and by the CSIRO-Atmospheric Research Group a decade or so back.

My point, though, is that these fronts go through Adelaide before they visit us; and after they have been here, they shoot on up to Sydney.  It would be good to have some observation plots, some analyses and some discussion of their behavior in those areas.

Hmmm.. another long essay.

cheers

John mcb