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•  > What was the origin of the air that contributed to the rainfall sample we measured on 12/15/99 in Front Royal, Virginia?

Could you tell us the origin of the air that contributed to the rainfall sample we measured on 12/15/99 in Front Royal, Virginia?

Yes I could, but then you wouldn't learn how to find out using the online HYSPLIT trajectory model. Here is what you do...

1. go to the READY HYSPLIT page at:
   http://www.arl.noaa.gov/HYSPLIT.php
2. click on the link called "Run HYSPLIT with archived data"
3. Click on the link "Compute Trajectories"
4. Choose the EDAS data set.
5. Choose the file "edas.subgrd.dec99.001" which has data from Dec 1-15, 1999
6. Enter the latitude and longitude of Front Royal (I guess about 39.00 and -78.4).
7. Click on Backward (to see where the air came from).
8. Make the day 15 and the hour 12.
9. Make the starting heights1500 and 3000 meters agl to start the trajectory near the cloud height (where the rain is made).
10. You can change the duration if you want longer than 24 hours back.
11. Click "Request trajectory"
12. Click "HYSPLIT RUN RESULTS" (remember the green number if you want to look at the trajectories again within the next 24 hours.)
13. Wait until the links for the trajectories show up, then click on them to see your results.

Glenn Rolph