Re: wrf_helicity function

Piotr,

I asked the developer who provided me with the wrf_helicity Fortran code, and he said he'd look into this when he had time.
He said you should be seeing values between 100-500.

Meanwhile, he provided these comments that might help:

C ***************************************************************
C * Storm Relative Helicity (SRH) is a measure of the *
C * streamwise vorticity within the inflow environment of a *
C * convective storm. It is calculated by multiplying the *
C * storm-relative inflow velocity vector (Vh-C) by the *
C * streamwise vorticity (Zh) and integrating this quantity *
C * over the inflow depth (lowest 1-3 km layers above ground *
C * level). It describes the extent to which corkscrew-like *
C * motion occurs (similar to the spiraling motion of an *
C * American football). SRH corresponds to the transfer of *
C * vorticity from the environment to an air parcel in *
C * convective motion and is used to predict the potential *
C * for tornadic development (cyclonic updraft rotation) in *
C * right-moving supercells. *
C * *
C * There is no clear threshold value for SRH when forecasting *
C * supercells, since the formation of supercells appears to be *
C * related more strongly to the deeper layer vertical shear. *
C * Larger values of 0-3-km SRH (greater than 250 m**2/s**2) *
C * and 0-1-km SRH (greater than 100 m**2/s**2), suggest an *
C * increased threat of tornadoes with supercells. For SRH, *
C * larger values are generally better, but there are no clear *
C * "boundaries" between non-tornadic and significant tornadic *
C * supercells. *
C * *
C * SRH < 100 (lowest 1 km): cutoff value *
C * SRH = 150-299: supercells possible with weak tornadoes *
C * SRH = 300-499: very favorable to supercell development and *
C * strong tornadoes *
C * SRH > 450 : violent tornadoes *
C ***************************************************************

On Oct 28, 2010, at 10:38 PM, Piotr Djaków wrote:

> 2010/10/28 Mary Haley <haley@ucar.edu>:
>> Which helicity function in RIP are you using?
>>
>> --Mary
>>
>>
>
> It's function from relh.f file as i think. This function is called in
> fields.f file (attached). In RIP script only thing i must to do, it's
> tell RIP what field i want to draw:
>
> ===========================================================================
> ---------------------- Plot Specification Table ---------------------
> ===========================================================================
> feld=sreh; ptyp=hc; smth=2; cint=50.; cbeg=100.; cmth=fill; nozr; nolb; nohl;>
>
> That's all. "Feld=sreh" draw Storm Relative Helicity map. There is no
> functions in RIP scripts.
>
> Best Regards
> Piotr
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Received on Fri Oct 29 13:04:09 2010