Convert HOURLYPressureTendency variable to be categorical

[Edward Leardi]

HOURLYPressureTendency is actually a categorical variable. From the NOAA LCD documentation:

Press. Tend: Pressure tendency (In general a 0 through 3 here indicates an increase in pressure over previous 3 hours and a 5 through 8 indicates a decrease over the previous 3 hours and 4 indicates no change during the previous 3 hours). See ISD Documentation (under Atmospheric-Pressure-Change) for further details.

We can convert it to 9 dummy variables or bucket into 3 dummy variables using the buckets discussed above. This will alter model inputs, preprocessing, postprocessing, testing, and model files.