WMOD00286 ‎(3)‎

• Project Name: Colorado River Basin Pilot Project
• Title: Comprehensive Atmospheric Data Report 1974-75 Season - Volume I
• Date: 8/31/1975
• Weather Modification - Doc Type: Report

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share computer system. It was an additional near real time precipi-
tation monitoring system along with the four real time telemetered
precipitation gages the seeding contractor had available.

As with the previous operating season, the operational
decision was not locked to the 0900 MST evaluation, but could be
adjusted as the weather movl9d in. A storm system which was distant
at 0500 MST, but nevertheless threatened to produce precipitation
before 1100 MST of the following day, could be more closely examined
for timing of the onset of precipitation and the suitability of the cloud
system for modification. The experimental day call could be postponed
until after the 1700 MST synoptic data had been analyzed. However, no
experimental day calls could be made after 2300 MST on any day. Sub-
sequently, a forecast of 30 hours in advance of initial data was reduced
to 18 hours or less. The forecasters' goal was to declare an experi-
mental day at least three hO\llrs prior to the existence of modification
potential.

3. 4. 1 Forecast Procedures for Experimental Day Recognition
The daily operational procedure and decision making routine
(see Figure 3-1) began by hand plotting and analysis of the 700 and 500
mb charts and the surface charts for the 0500 MST data. Upon com-
pletion of this effort, an analysis was made of forecast guidance material
from the NAFAX circuit, and a brief descriptive prognoses chart of the
500 mb level was then made for a 24- hour and 48- hour period. This
chart included an assessment of the precipitation probability and the
experimental day potential, and was detailed (on the form shown in
Figure 3-2) for a forecast period of five days. Following the completion
of the above 5-day forecast chart, a detailed picture of criteria para-
meters was prepared as shown in Figure 3-3 and 3-4 to include the 500
mb temperature (as a guide to temperature change), the 700 mb wind
and a two-dimensional time-(~ross section of the cloud picture and
precipitation. With this detailed picture, the specific parameters and
the criteria of the recognition forecast were then summarized on the
Forecast Work Sheet (Figure 3-5) which included a discussion on the
synoptic features and their eUects during the forecast period. Finally,
having the summarized forecast parameters and with the experimental

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