[Chaos-l] [Medoc-mountain-men] Weather forecasting-- great article in S&T
rfitzgerald1 at nc.rr.com
rfitzgerald1 at nc.rr.com
Tue Mar 2 12:48:16 EST 2010
Great information! Yes, I've largely been disappointed with CSC and have been relying on AccuWeather. They have a few astronomy folks on staff, update forecast more often and have been quick to respond to my questions concerning specific-area forecasts.
Rule from your email:
<70 @300 /700 mb RH = OK
Wind Data @300 mb, Jet Stream Impacts Seeing
Wind The Most When Isobars Are Close!
---- Mark South <md_south at mac.com> wrote:
> Sky and Telescope Feb 2010 issue has a great article on Astronomy
> Weather forecasting that goes beyond the Clear sky clock.
> The supplement to the issue online with some great links is here:
> The big idea in this article is that we should cross check with
> multiple weather models, starting with a general forcast and CSC, then
> moving to more complex models for more fine tuning such as the Global
> Forecast System (GFS) . GFS is a great modeling system and predictor
> for the week (in addition to CSC and Accu-weather) for info on
> clouds, rain, etc. and is updated four times a day unlike CSC which
> is updated only twice a day. The author says regarding the CSC,
> "...that's good but not ideal; a lot can change in 12 hours."
> Click here for GFS and NAM (North American Mesoscale)
> Quoting the article:
> "The GFS map...shows predicted precipitation and mean sea level
> pressure (MSLP). Rainy areas are best avoided while high-pressure
> systems are most likely to have cloudless skies. But if the isobars
> (lines of equal pressure) are squeezed tight together, expect high
> winds and poor seeing.
> Diffrent layers in the atmosphere are labeled by pressure at
> that altitude. The map showing relative humidity @ 700 millibars
> (about 10,000 feet) is labeled "700 mb RH." Cloud cover is likely if
> this value is above 70%. High humitity at 300 mb (30,000 feet) is
> likely to cause cirrus clouds. If you see high winds at 300mb, it
> meas that the jet stream is overhead, which usually causes poor seeing."
> Great stuff. I'm going to start looking at these sites in the future
> to make better decisions. For example, it looks like Friday is going
> to be a quite clear according to NWS and the GFS. GFS says at 84
> hours out from today that 700 mb RH is "0" and 300mb is "0" so it
> apears that it will be quite clear and some good seeing. I'm just
> learning this.... does anyone agree with my findings or disagree for
> Friday's weather? :)
> Kind regards,
> Mark South
> Medoc-mountain-men mailing list
> Medoc-mountain-men at rapideye.us
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