[gradsusr] Drawing TC storm track in grads

[Larry Ger Aragon]

Thanks for the response, Jennifer. I understand the concept of the
while loop. But, if I may ask, isn't it that grads sort of overlays
the images as you display, that's why you'll either want to put
'clear' or else (sometimes), you'll have your new displayed image
mashed up with the previous one? I'm afraid that would also be the
case when I apply this while loop, I won't actually 'connect the dots'
for successive time as the next images I would then add would just
cover the one where I'm drawing my tracks. At most, I can only have
two points and a line from the last image I would generate. Anyway, I
haven't tried this but, can I store my drawn points and lines in a
certain variable (container)? and just make some looping so I could
update that when I want? I've only tried storing, say one whole
spatial data at specific time/level in one variable, compare it to
other (e.g. 6hr rainfall -  3hr raindall)
, and display the resulting spatial values. I havent tried it when
attemping to draw lines then store it in a container/variable (I guess
it's not possible? just a wild guess). Anyway, I'd be glad to see your
better idea on this.

And just another topic, I hope you won't mind if I no longer created a
new thread on this, but, Is there a way I could mask out only the
values of say, precipitation, in the landmass (to exclude the ocean?).
I've read this function mask of grads, but from how I understood it,
it's only applicable when (ideally) you have negative values on the
ocean part which could be set to as constant (using the const
function). I've also been trying to find answer on the net, so I could
grasp your ideas well when you respond.

This will be of great help, jennifer, hope to have your consideration
on these. Thank you very much.





On 12/3/14, Jennifer Adams <jma at cola.iges.org> wrote:
> Hi, Larry —
>
> How about something like this:
>
> cmd=‘draw line’
> while (...looping over forecast times...)
>   …your code to determine lat/lon of cyclone center...
>   ‘q w2xy ‘lon’ ‘lat
>   xpos=subwrd(result,3)
>   ypos=subwrd(result,6)
>   cmd=cmd’ 'xpos’ ‘ypos
> endwhile
> cmd    ;* this will send the ‘draw line’ command to GrADS and plot the whole
> cyclone track
>
> —Jennifer
>
>
>
>
> On Dec 3, 2014, at 3:05 AM, Larry Ger Aragon <larrygeraragon30 at gmail.com>
> wrote:
>
>> Greetings Grads users,
>>
>> I'd be very glad to receive some help regarding this problem. I have
>> this algorithm collecting tropical cyclone center at each forecast
>> time, which I record only at two variables (lon and lat). I also print
>> these coordinates (thru say command) in the terminal. After collecting
>> all the values, I plan to make a track from the coordinates I just
>> collected. I can't think of how I would program this in grads (does
>> grads support fortran syntaxing?) with changing the values of the two
>> variables I have so I would not have veeeery long .gs of just
>> copy-pasting "q w2xy" then connect lines. If only  grads support C
>> program/functions or R, it would be easier for me. Just want to ask if
>> anybody have some ideas on this. Thanks.
>> _______________________________________________
>> gradsusr mailing list
>> gradsusr at gradsusr.org
>> http://gradsusr.org/mailman/listinfo/gradsusr
>
> --
> Jennifer M. Adams
> Center for Ocean-Land-Atmosphere Studies (COLA)
> 111 Research Hall, Mail Stop 2B3
> George Mason University
> 4400 University Drive
> Fairfax, VA 22030
>
>
>
>
>
>


-- 
Weather Observer I
Numerical Modelling Section
Research & Development and Training Division
Philippine Atmospheric, Geophysical and Astronomical Services Administration
Quezon City, Philippines
Tel: +632 920 4064