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[GEMPAK #NAT-847496]: GEMPAK - NARR Model Sounding Max Temp / Conv. Temp Bug

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  • Subject: [GEMPAK #NAT-847496]: GEMPAK - NARR Model Sounding Max Temp / Conv. Temp Bug
  • Date: Thu, 27 Sep 2007 12:51:09 -0600
> Institution: Plymouth State University
> Package Version: NSHARP 4.0
> Operating System: Linux
> Hardware Information: Dell Server
> Inquiry: Hi,
> 
> Just pointing out a possible bug.  When generating NARR model proximity 
> (lat/lon) soundings in the latest version of NSHARP, it appears that Max Temp 
> and Conv Temp values are flipped.
> 
> Max Temp is actually Conv Temp and vice versa. The values are correct but 
> flipped.
> 
> Attached is a postscript example taken from 20030708_0900 at 43.64, -70.63.
> 
> Evan Lowery
> 
> --------
> Plymouth State University
> Applied Meteorology M.S. Program
> 
> 
> 

Evan,

The Max Temp being computed is:
        /*  Calculates a maximum temperature forecast based on       */
        /*  depth of mixing level and low level temperatures.        */

Looking at your postscript file, a miximg down of the air at the top
opf the inversion dry adiabatically would result graphically of 26X which is
close to the Max Temp of 84F shown in your plot.


The Convective temperature is:
        /*  Computes convective temperature, assuming no change in   */
        /*  moisture profile.  Parcels are iteratively lifted until  */
        /*  only (mincinh) j/kg are left as a cap.  The first guess  */
        /*  is the observed surface temperature.                     */

The mincinh specified for this output is "-50 j/kg". Note that the dashed line
shown in the plot is the default most unstable level, and not surface which
can be specified using the PARCEL button on the page. Again, frlm ispection of 
your plot,
the value of 20C would be pretty close to the moist adiabat of most of the 
atmosphere brought
down to the surface, so that is ~68F. The value shown of 65F in your plot is 
that which
contains a cap of -50 j/kg, so again, based on what is shown in your plot, the 
values
seem to match.

My inperpretation is that with a convective temperature lower than the 
theoretical max temp,
you would expect cloudcover to begin after convetctive mixing begins which would
therefore be a counteractive force to the expected max tempBut, were you 
expecting something
different?.

Steve Chiswell
Unidata User Support

Ticket Details
===================
Ticket ID: NAT-847496
Department: Support GEMPAK
Priority: Normal
Status: Closed