could someone please send me a link to a good weather site. its looking pretty good for hrp tonight, i think i might try and crack off my first 11 second pass. tia joey

 

www.weather.com
www.weatherunderground.com

and a DA calculator...

http://rshelq.home.sprynet.com/calc_da.htm

 

Thanks for the info Colonel.OK guys I used the calculator but dont really know what numbers Im looking for when it comes to DA. Whats yalls opinion of perfect weather for the best ET possible. Thanks again

 

The lower the DA the better for HP. A cold track doesn't hook as well.

So, the perfect weather would be -5000ft DA with a track surface temp of 125 degrees! <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> (That will never happen, BTW.)

 

Well from what im getting, it looks like it will be around 46 degrees tonight with a DA around -1400. Hows that?

 

That's pretty good! I consider any DA below sea level to be good.

 

Anyone know a good place to get elevations from??

Thanks!

Mark

 

Post or PM to me the street address, city and state or at least the Zip code and i will look it up for you.

John

 

DA is a concept using a "standard" column of air. Its a measure of air quality in this standard column, so altitude is irrelevent <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

J.

 

John:
I'll do that! Thanks! It would be nice to have a site where we could pull this up for the various tracks.

Crazyquik:
The calculator above asks for altitude as one of its entries.

Mark

 

Ahh, didn't realize that. Rockingham is pretty close to sea level so thats the only one I'm familiar with .

J.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Bob Cosby:
<strong> </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">DA is a concept using a "standard" column of air. Its a measure of air quality in this standard column, so altitude is irrelevent</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is true IF, and only if the barometer reading you are getting is the actual pressure at the station - not corrected to 'Sea Level Pressure' or 'Altimeter Setting' like almost every place does....including the stuff you see on Wunderground and the Weather Channel. For example....go get the pressure right now for Houston and Denver. Denver is over 5000 ft higher, yet the pressure given by Wunderground is actually more than what is reported for Houston.

Why is that? Meteorologist correct all pressure readings to what they WOULD BE at sea level, based on the station elevation. Otherwise, on a weather chart, you'd always have lower pressure over the mountains (higher elevations = less atmosphere = less air pressure) and higher pressure near the coasts.

This isn't a big deal for near sea-level tracks like HRP, E-town, VMP, etc - but will make a significant difference for anything else.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Completely true, verified by a meteorologist (me). There is actually a bit more to it than this, which I will fill in:

Because pressure in the atmosphere decreases logarithimically (sp?) with height, meteorologists needed a way to identify meteorological systems at the surface that was not distorted by altitude pressure changes. To do this, actual station pressure is corrected to so-called sea-level pressure. This correction depends upon an assumed temperature profile that the atmosphere would have going from the station to sea-level. Strangely enough, this means that literally atmospheric temperatures are being assumed *below* the earth's surface.

What does this mean to the drag racer? If you live near the ocean (like at HRP), then station pressure and sea-level pressure are about the same. At elevation, however, sea level pressure is extrapolated, and *how* it is extrapolated depends upon current station temperature. Do not use sea-level pressures at elevation - find out the actual pressure.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">DA is a concept using a "standard" column of air. Its a measure of air quality in this standard column, so altitude is irrelevent</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">This is true IF, and only if the barometer reading you are getting is the actual pressure at the station - not corrected to 'Sea Level Pressure' or 'Altimeter Setting' like almost every place does....including the stuff you see on Wunderground and the Weather Channel. For example....go get the pressure right now for Houston and Denver. Denver is over 5000 ft higher, yet the pressure given by Wunderground is actually more than what is reported for Houston.

Why is that? Meteorologist correct all pressure readings to what they WOULD BE at sea level, based on the station elevation. Otherwise, on a weather chart, you'd always have lower pressure over the mountains (higher elevations = less atmosphere = less air pressure) and higher pressure near the coasts.

This isn't a big deal for near sea-level tracks like HRP, E-town, VMP, etc - but will make a significant difference for anything else.

 

Bob Cosby –

You are correct!! I learned something new today. Thanks.

At MMP in Montgomery, Alabama the elevation is 185ft so it is not a big deal for me but for others it could be substantial.

John

<small>[ May 02, 2002, 12:44 PM: Message edited by: JNorris ]</small>

 

WeatherGuy:

Ok, I thought I had a handle on this, let's make sure I do!

Using the DA calc link above, I enter:
Altitude: the actual elevation in feet.
Air Temp: the actual reported temperature.
Altimeter Setting: Exactly what do I enter here? The weatherunderground site just says "pressure"? What kind is it? Weather.com just says barometer? What's that?

Thanks!

Mark

<small>[ May 03, 2002, 04:26 PM: Message edited by: Sparky ]</small>