[gradsusr] Probability precipitation map using ensemble forecast

[Miquel Bernis]

Thank you very much Hosmay, I really appreciate your help. That was just
what I needed, there's still a lot to learn using grads.

Miquel

2015-06-19 16:05 GMT+02:00 Hosmay Lopez <hlopez at rsmas.miami.edu>:

>  Hi Miguel,
>
>  This is straightforward in GrADS if you use a combination of functions.
> It goes like this:
>
>  If you have a variable for precipitation named *precip *and let say, 100
> ensemble members. You do:
>
>  set e 1 100
> define prec5mm = const( const( maskout( precip, precip - 5), 1), 0.0, -u)
>
>  The *maskout* function sets the values to undefined where precip < 5
> The inner *const* function sets the remaining defined values to ones.
> And the outer *const* function sets the undefined values to zeros.
> So the new variable prec5mm is made of 1 wherever precip > 5 and 0
> otherwise.
>
>  Now you average for all your ensemble members and multiply the results
> by 100 to get % of ensemble members with precipitation above 5mm .
>
>  set e 1
> define percentage5mm = 100 * ave( prec5mm, e=1, e=100)
>
> Hope this helps.
>
>   Hosmay Lopez
> UM/CIMAS/RSMAS NOAA/AOML/PHOD
> 4301 Rickenbacker Causeway,
> Miami, FL 33149, USA
> Phone: (305) 361-4329
>
>    ------------------------------
> *From:* gradsusr-bounces at gradsusr.org [gradsusr-bounces at gradsusr.org] on
> behalf of Miquel Bernis [bernisfeina at gmail.com]
> *Sent:* Friday, June 19, 2015 3:26 AM
> *To:* GrADS Users Forum
> *Subject:* [gradsusr] Probability precipitation map using ensemble
> forecast
>
>   Hi everyone,
>
>  Do you think is there any way to plot a forecast probability
> precipitation map, using an ensemble forecast? I mean, calculating which
> forecasts of the ensemble give, for example, an amount of rain > 5 mm and
> which not, for an specific moment of time, and displaying a contour map of
> the % you can take from that. Watching to the grads functions it seems not
> possible, but maybe some of you, with more experience on grads than me, can
> imagine a way to do that.
>
>  Thanks a lot!
> Miquel
>
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