The newer computer output pages are better than the old synoptic chart because you can predicted changes in a 3 hourly basis or the next 3 days and 6 hours for a week. Remember to take less notice of small scale features as the prediction goes out. The big highs move fairly predictably; small and transient lows will be swamped by inaccuracies in the model initial data further out. These charts can be animated. They don't show fronts - you have to gauge them yourself . eg Australia http://www.bom.gov.au/australia/charts/viewer/index.shtml?domain=combinedA&type=mslp-precip SE aust: http://www.bom.gov.au/australia/charts/viewer/index.shtml?type=mslp-precip&tz=AEDT&area=Vic&model=A
You can also look at the 500mb predictions to see where things are going. As a verrrrrry loose approximation you might say the surface systems are "blown along" by the 500mb winds. http://www.bom.gov.au/australia/charts/viewer/index.shtml?type=pressureHgt&level=500hPa&tz=AEDT&area=Au&model=R&chartSubmit=Refresh+View Also worth a look is the new MetEye product, lots of weather data with 3 hour predictions for a few days. http://www.bom.gov.au/australia/meteye/ The Zehr-enhanced satellite loop show where the action is by highlighting cold clouds. These are clouds that extend vertically up into the cold parts of the atmosphere, thus producing rain and storms. http://www.bom.gov.au/australia/satellite/?tz=AEST&unit=p23&domain=1&view=33&satSubmit=Refresh+View Hadley cells: The cells are kind of theoretical concepts. Air can't travel in straight lines on the earth because the earth is rotating. In the ground frame of reference, air gets pushed sideways so tends to move around in circles and wavy shapes. The result is that the theoretical cells break up into the messy migrating and interacting patterns we actually see on weather maps. The net effect averaged over time is air moving in Hadley patterns but at any time you have a bunch of stuff going in any direction. Jetstreams It's hard to get an intuitive picture of what is going on here. I've tried. We just don't think in three dimensional rotating fluids! One thing to notice is that the asymmetries of the horizontal circulation patterns will result in net north-south momentum transfers. This obviously will result somehow in a balancing mechanism that balances this the momentum flow; this is the jet stream. However, this is probably an unsatisfying explanation. It the end, the fluid flow equations make the jet streams. As far as I've seen there's no good simple intuitive explanation. There are nice pictures on jet streams circling the earth in waxy bands but, like the Hadley cells, these are idealisations: actual jet streams appear and disappear just like other meteorological features. - Jim On 19 December 2013 12:42, Robin Whittle <[email protected]> wrote: > Here is a new addition to my collection of weather URLs: > > http://earth.nullschool.net/ > > I read about it at http://www.universetoday.com. It is a > javascript-driven, apparently very fluid, display of wind direction > anywhere on Earth, with data updated from various models every 3 hours. > There is also the ability to look back in time and to look forwards by > up to 24 hours. > > The "earth" thingo at the bottom opens up a menu from which various > settings can be selected, with the "about" link providing an > explanation. Settings can be stored in a URL: > > > > http://earth.nullschool.net/#current/wind/isobaric/1000hPa/orthographic=-225.44,-36.35,416 > > It is evident that the jetstream at about 10km (250hPa) is very > different from winds at the surface. I don't understand how the > jetstream makes sense in terms of what I understand about Hadley cells: > > https://en.wikipedia.org/wiki/Hadley_cell > > On a day like today in Melbourne, at the western edge of a high pressure > system, I understand a significant amount of the heat we feel (predicted > maximum 40C) is due to hotter than normal, very dry, air piling up in > the troposphere after being transported there from the tropics. This is > in addition to air arriving from the inland north. This somehow > displaces air on the ground with dryer, hotter, air. If that's the > case, I am not sure how it works with the jetstream winds doing > something apparently unrelated (to my eyes) with the anticlockwise winds > at ground level which result from the high pressure system. > > My other weather links are: > > http://www.bom.gov.au/australia/charts/synoptic_bw.shtml > http://www.bom.gov.au/vic/forecasts/melbourne.shtml > http://www.bom.gov.au/vic/observations/melbourne.shtml > > > http://www.bom.gov.au/products/IDR023.loop.shtml?looping=1&reloaded=0&topography=true&locations=true&range=true#skip > http://www.bom.gov.au/australia/satellite/ > > http://www.bom.gov.au/jsp/watl/weather/obs.jsp?graph=all_obs&station=86068 > > The last one is for the nearby Viewbank weather station. This shows the > last few days of temperature and other measurements, including the dew > point. The dew point is a measure of the moisture content of the air. > When this drops suddenly, as it did a few hours ago, I understand (from > an explanation by a meteorologist) this is the dry Hadley cycle air > descending to ground level and somehow (I have no idea how) displacing > the more moist air which was previously at ground level. > > A final link, which is only for the Melbourne area is: > > http://www.baywx.com.au/melbtemp.html > > This page, one of several, shows the predicted minimum and maximum > temperatures with the observations filled in as the day progresses. > There's an archive of the graphs, which enabled me to generate > temperature graphs of the heatwave associated with the 2009 bushfires: > > https://en.wikipedia.org/wiki/Black_Saturday_bushfires > > https://commons.wikimedia.org/wiki/File:Melbourne-temp-2009-02-10.png > > > https://commons.wikimedia.org/wiki/File:Melbourne-temp-2009-02-10-compact.png > > > I understand those dramatic peaks in temperature are driven largely by > Hadley cells. > > - Robin > > > > > > _______________________________________________ > Link mailing list > [email protected] > http://mailman.anu.edu.au/mailman/listinfo/link > _______________________________________________ Link mailing list [email protected] http://mailman.anu.edu.au/mailman/listinfo/link
