GFS 0-240h is not correct 6 hrs Accumulated Precipitation. Correct is 3 hrs (on diagram)

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sonny.zinn
Posts: 67
Joined: May 8th, 2019, 1:31 pm
Registered HYSPLIT User: Yes

GFS 0-240h is not correct 6 hrs Accumulated Precipitation. Correct is 3 hrs (on diagram)

Post by sonny.zinn »

This is a repost of an email inquiry:

GFS 0-240h.
is not correct 6 hrs Accumulated Precipitation.
Correct is 3 hrs (on metgram is 3 hrs Accumulated Precipitation ).
Am I wrong?
Attachments
5938450_metgram.gif
6 hrs Accumulated Precipitation.png
GFS 0-240h.png
sonny.zinn
Posts: 67
Joined: May 8th, 2019, 1:31 pm
Registered HYSPLIT User: Yes

Re: GFS 0-240h is not correct 6 hrs Accumulated Precipitation. Correct is 3 hrs (on diagram)

Post by sonny.zinn »

Thank you for contacting us about accumulated precipitations. One of our scientists looked into the issue you raised and concluded there is no error. Here is the explanation:

There is no inconsistency. The GFS 1-degree forecast file used here is at 3-hour intervals and the precipitation is a 6 hour accumulation.

For example, for a 00z forecast file, the 1st time period after the forecast start is 03z. At that time the precipitation accumulation has only been over 3-hours (00-03z), but it is still called a 6-hour accumulation. At the next time period, 06z, the accumulation period is 6-hours (00-06z) and this ends the accumulation. At the next time period, 09z, the accumulation is over 3-hours (06-09z). The next time period, 12z it is over 6-hours (06-12z), and so on.

The program that displays the precipitation amounts in 3-hour intervals on the meteorogram does the subtraction to calculate 3-h accumulations for the entire forecast period. Using the above example, at the valid time of 06z, what is displayed on the plot is the precipitation value at 06z minus the value at 03z.
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