TPP6

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croc
Posts: 6
Joined: January 22nd, 2015, 10:25 am
Registered HYSPLIT User: Yes

TPP6

Post by croc »

Hi,
I would like to plot 3h total precipitation from forecast date in files hysplit.t00z.gfsf.
Looks like they have every 3rd hour a 6-hour accumulated total precipitation. If I have understood
correctly, the first of such values (0Z, I guess) refers to the rainfall of the last 6 hours, right?
I could subtract each value from the next one but still I would have left in each result the term from
-6Z to -3Z.
I can't think of a way to extract 3-hours resolved total precipitation from such parameter.
Of course I could collect just parameters for 6Z, 12Z, etc and divide by 2 but I feel a
little frustrated to have in some way a higher resolved value without being able to extract it.
Thank you for the help,

Stefano
barbara.stunder
Posts: 421
Joined: November 9th, 2012, 4:23 pm
Registered HYSPLIT User: Yes

Re: TPP6

Post by barbara.stunder »

Yes, in hysplit.t00z.gfsf, the 00z, 06z, 12z, and 18z valid time precipitation values give the amount for the last 6 hours. At valid times 03z, 09z, 15z, and 21z, they give the amount for the last 3 hours. To get the series of 3-hourly precipitation, directly use the values at 03z, 09z, 15z, 21z, and for the other hours subtract the 3-hourly from the next 6-hourly. For example to get the precip from 03z to 06z, take the the 06z value minus the 03z value.
croc
Posts: 6
Joined: January 22nd, 2015, 10:25 am
Registered HYSPLIT User: Yes

Re: TPP6

Post by croc »

Wow, so while 00z, 06z, 12z, .... are true TPP6, 03z, 09z, 15z, and 21z are actually TPP3?
I haven't found this description anywhere in the GFS and ARL site. Is this an undocumented
feature or could you give me a link to a document where this and the other in depth structures of gfsf
files are presented? I wish to avoid ignoring basic documentation.
Thank you very much for your help and the prompt answer. I appreciate it.
Regards,

Stefano
barbara.stunder
Posts: 421
Joined: November 9th, 2012, 4:23 pm
Registered HYSPLIT User: Yes

Re: TPP6

Post by barbara.stunder »

At http://ready.arl.noaa.gov/READYflddesc.php it says TPP6 is 6-hour accumulated precipitation.

TPP6 means there is a 6-hour accumulating 'bucket'. Imaging a bucket outside collecting rain. At 00z the bucket is empty. At 3 hours, you measure the depth, it is 1 inch. Then at 6 hours you measure again and it is 3 inches, and you empty the bucket to start again for the next 6 hours. That means from hour 0 to 3 it rained 1 inch and from 3 to 6 it rained 2 inches (3-1). Analogously, in the GFS the TPP6 at hour 3 is 1 inch, and at hour 6 it is 3 inches. The precipitation is accumulating with time over the 6-hour period. At hour 3 TPP6=TPP3.

This TPP6 is in the GFS grib files output from NCEP. These are converted to make the HYSPLIT-formatted file.
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