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19991102: Gempak--SFPARM--CBAS

>From: weather <address@hidden>
>Organization: .
>Keywords: 199910181907.NAA15709

>Can you refresh my memory, decoding synoptic data
>using sflist, what is the definition of the CBAS parameter,
>is it the output in meters or feet (10's of feet)..etc?
>
>Thanks,
>Robert Mullenax
>


Robert,

After looking at your question, and the code, I have determined 2 things.
First to answer your question at hand... CBAS is the cloud height in meters.

The first method of the cloud base report comes from the group i(r)i(x)hVV,
where the cloud ceiling "h" is a number from 0 to 9 which refers to a
category in table 1600 as follows:

0 0-50m
1 50-100m
2 100-200m
3 200-300m
4 300-600m
5 600-1000m
6 1000-1500m
7 1500-2000m
8 2000-2500m
9 >2500m
/ unknown

The gempak routine $GEMPAKHOME/src/bridge/rs/rshhde.f stores this value as
the lower of the range values.

There is the possibility of a second 9hh// group in section one as well
which uses a 2 digit cloud height for more precise reporting where

CBASE = 30 * hh     (hh <= 50)
CBASE = 300 * (hh - 50)  (50 > hh <= 80)
CBASE = 1500 * (hh - 74) (80 > hh <= 90)

Now for the second point....

I have found that in group 1, 9GGgg is being confused for 9hh// if that group is
reported. For example, 91153 should be stating that the observation was taken
at 1153Z, but instead, can be interpreted as hh=11 -->CBAS = 330m.

I have fixed this case for 9hh// vs 9GGgg in
$GEMPAKHOME/src/bridge/rs/rsdeco.f and have placed this routine
in ~gbuddy/nawips-5.4/patches/rsdeco.f.

Steve Chiswell