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Notes from the Hippy-Dippy Computer Weatherman (1Dec92)
(from KPNO, NOAO Newsletter No. 32, 1 December 1992)

Since the summer of 1991, NOAO/Tucson has had continuously improving
access to a local archive of hourly geosynchronous weather satellite
pictures of the continental United States. These are similar to
pictures that are available over the Internet, but are acquired in a
different format from a source that is closer to the US Government
agency responsible for distributing them.

Three times an hour, 24 hours a day, a new picture is downloaded in one
of three different wavelength bands:  visible, infrared, and water
vapor (narrow band IR sensitive to atmospheric moisture). These are
first processed to translate the obscure native image format into IRAF.
The IRAF images are then registered to the nearest pixel and overlaid
with the North American geo-political boundaries as solid yellow lines.
The pictures are also translated into the popular GIF format.

We archive the last 24 hours worth of pictures for each of the three
bandpasses in the directory /weather on our machine gemini. The archive
also includes GIFs of the Internet surface analysis maps indicating
radar echoes, atmospheric pressure, weather fronts, and local
conditions at cities around the United States and Canada. The downtown
archive is mirrored over the T1 link to a machine on our Kitt Peak
network which is accessible from the Sun workstations at each of the
telescopes.

A local IRAF task, wdisplay, can be used to view the pictures in a
variety of revealing ways.

Display the latest visible light picture:
    wdisplay vis

Display the last four IR pictures in successive imtool frame buffers:
    wdisp ir four+

Display the latest from each of the three bands:
    wdisp all

Or, you can display the surface analysis maps:
    wdisp sa

Type help weather for more examples and for hints for making imtool blink
movies.

An allied facility is supplied by the local Unix nws command, which
will retrieve the current weather forecast and conditions for many
cities around the US and Canada. Some examples:

Retrieve the forecast for Tucson:
    nws tus (or simply nws)

Retrieve the current conditions for Arizona:
    nws az

Retrieve the national weather roundup:
    nws usa

For more examples, type help nws from within IRAF, or type nws -help
from Unix. Folks using X windows can access the same information using
the xforecast client, which will display a North American map and allow
the desired city to be selected with the mouse.

Many incremental improvements have been made to our support for the
weather archive over the past year, and these should continue at a
steady pace.  Future additions will include new sources of data, new
image formats, new display options, and improved networking support.
Only some of the current capabilities have been described here.

Suggestions and inquiries should be directed to rseaman@noao.edu, and
are welcome from outside organizations as well as from NOAO.

The National Weather Service data are provided courtesy of the
NSF-funded Unidata Project, the University of Arizona, the University
of Michigan, and the University of Illinois, Urbana-Champaign.

Rob Seaman

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